MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Medical Engineering and Physics' source. Sat, 20 Mar 2010 16:33:34 +0100 http://www.medworm.com/index.php?rid=3366024&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453310000366%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366024 Mon, 15 Mar 2010 17:02:19 +0100 3366024 http://www.medworm.com/index.php?rid=3366016&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453310000329%2Fabstract%3Frss%3Dyes Full integration of wheelchair users into our communities and societies is key to maximizing their potential to live productive and fulfilling lives. Transportation plays an important role in meeting this goal. Many wheelchair users travel seated in their wheelchairs and do so using a variety of transport modes; these include private vehicles, fixed-route transit vehicles and demand-responsive vehicles. Wheelchair users travel as both wheelchair-seated drivers and passengers. Safe transportation for these individuals is dependent upon a structurally sound wheelchair, securement of the wheelchair to the vehicle, and use of an appropriately positioned crashworthy occupant restraint system. Moreover, the transportation process, which includes boarding and alighting from the vehicle requires t... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366016 Mon, 15 Mar 2010 17:02:18 +0100 3366016 http://www.medworm.com/index.php?rid=3366015&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453310000342%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366015 Mon, 15 Mar 2010 17:02:18 +0100 3366015 http://www.medworm.com/index.php?rid=3251035&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453310000135%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251035 Mon, 08 Feb 2010 17:00:05 +0100 3251035 http://www.medworm.com/index.php?rid=3251020&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453310000111%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251020 Mon, 08 Feb 2010 17:00:03 +0100 3251020 http://www.medworm.com/index.php?rid=3251033&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002641%2Fabstract%3Frss%3Dyes Abstract: An understanding of aortic root biomechanics is pivotal for the optimisation of surgical procedures aimed at restoring normal root function in pathological subjects. For this purpose, computational models can provide important information, as long as they realistically capture the main anatomical and functional features of the aortic root.Here we present a novel and realistic finite element (FE) model of the physiological aortic root, which simulates its function during the entire cardiac cycle. Its geometry is based on magnetic resonance imaging (MRI) data obtained from 10 healthy subjects and accounts for the geometrical differences between the leaflet-sinus units. Morphological realism is combined with the modelling of the leaflets’ non-linear and anisotropic mechanical resp... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251033 Mon, 11 Jan 2010 00:00:00 +0100 3251033 http://www.medworm.com/index.php?rid=3251032&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900263X%2Fabstract%3Frss%3Dyes Abstract: Anterior lumbar interbody fusion (ALIF) with cylindrical cages and supplemental posterior fixation has been widely used for internal disc derangement. However, most researchers have focused on single-level ALIF. Therefore, the biomechanical performance of various fixation constructs after two-level ALIF is not well characterized. This research used three-dimensional finite element models (FEM) with a nonlinear contact analysis to evaluate the initial biomechanical behavior of five types of fixation devices after two-level ALIF (L3/L4, L4/L5) under six loading conditions. These fixation constructs included a three-level pedicle screw and rod, a two-level translaminar facet screw, a two-level transfacet pedicle screw, a bisegmental pedicle screw and rod, and a bisegmental pedicle s... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251032 Mon, 11 Jan 2010 00:00:00 +0100 3251032 http://www.medworm.com/index.php?rid=3124442&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002550%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124442 Mon, 28 Dec 2009 16:14:53 +0100 3124442 http://www.medworm.com/index.php?rid=3124428&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002537%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124428 Mon, 28 Dec 2009 16:14:48 +0100 3124428 http://www.medworm.com/index.php?rid=3251034&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002513%2Fabstract%3Frss%3Dyes This study expands and supplements the limited data available in the literature. Furthermore, it provides biomechanical data (closed-form moment–angle functions) that can be directly integrated into spine-ribcage models. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251034 Fri, 25 Dec 2009 00:00:00 +0100 3251034 http://www.medworm.com/index.php?rid=3251031&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002501%2Fabstract%3Frss%3Dyes Abstract: The exact role of fluid mechanics in the patho-physiological process of atherosclerosis has been a research topic over many years, yet without clear conclusive result. One has observed that morphological manifestations of the disease are found at some well-defined locations: certain vessel bifurcations and in curvatures. The flow in these regions is characterized by unsteadiness and often separation. Currently there are no complete theories that can explain the process since the different components in the process are not fully understood. Here we carry out detailed computations of the unsteady flow in an arterial segment typical to location of early appearance of arterial lesions. We study the wall shear stress (WSS) field variations near a junction with the purpose of identifyi... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251031 Fri, 25 Dec 2009 00:00:00 +0100 3251031 http://www.medworm.com/index.php?rid=3251030&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002495%2Fabstract%3Frss%3Dyes Abstract: In a chamber of the heart, large-scale vortices are shown to exist as the result of the dynamic blood flow and unique morphological changes of the chamber wall. As the cardiovascular flow varies over a cardiac cycle, there is a need for a robust quantification method to analyze its vorticity and circulation. We attempt to measure vortex characteristics by means of two-dimensional vorticity maps and vortex circulation. First, we develop vortex component analysis by segmenting the vortices using an data clustering algorithm before histograms of their vorticity distribution are generated. The next stage is to generate the statistics of the vorticity maps for each phase of the cardiac cycle to allow analysis of the flow. This is followed by evaluating the circulation of each segmente... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251030 Mon, 21 Dec 2009 00:00:00 +0100 3251030 http://www.medworm.com/index.php?rid=3251029&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002483%2Fabstract%3Frss%3Dyes Conclusion: Obtaining good quality MLR data in awake subjects is challenging. Data quality improves during clinical anaesthesia and with advanced stimulation methods, but reliable detection of changes in the MLR for clinical monitoring remains a challenge. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251029 Wed, 16 Dec 2009 00:00:00 +0100 3251029 http://www.medworm.com/index.php?rid=3251028&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002471%2Fabstract%3Frss%3Dyes This study presents a novel parameter, tone–entropy (T–E) that analyses heart rate variability (HRV) of 20min lead II ECG recordings. Tone (T) represents sympatho-vagal balance and entropy (E) the autonomic regularity activity. Thirteen normal subjects without (CAN−) and 21 with CAN (CAN+) participated in this study. Among 21 CAN+ subjects, 13 are early CAN+ (eCAN+), eight are definite CAN+ (dCAN+) according to autonomic nervous system function tests as described by Ewing. The results showed that tone was higher and the entropy was lower in the dCAN+ group (T=−0.033 to −0.010 and E=1.73–2.24) compared with the eCAN+ (T=−0.0927 to −0.0311 and E=2.0–2.65) and normal (T=−0.128 to −0.0635 and E=2.64–3.15) group. The research verified that T–E is a suitable method to d... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251028 Wed, 09 Dec 2009 00:00:00 +0100 3251028 http://www.medworm.com/index.php?rid=3251022&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900229X%2Fabstract%3Frss%3Dyes Abstract: Arteriovenous fistula (AVF) pathologies related to blood flow necessitate valid calculation tools for local velocity and wall shear stress determination to overcome the clinical diagnostic limits. To illustrate this issue, a reconstructed patient-specific AVF was investigated, using computational fluid dynamics (CFDs) and particle image velocimetry (PIV). The aim of this study was to validate the methodology from medical images to numerical simulations of an AVF by comparing numerical and experimental data. Two numerical grids were presented with a refinement difference of a factor of four. A mold of the same volume was created and mounted on an experimental bench with similar boundary conditions. The patient's acquired echo D006Fppler flow waveform was injected at the arterial i... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251022 Mon, 07 Dec 2009 00:00:00 +0100 3251022 http://www.medworm.com/index.php?rid=3251024&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900232X%2Fabstract%3Frss%3Dyes Abstract: This paper presents a discriminant bispectrum (DBS) feature extraction approach to surface electromyogram (sEMG) signal classification for prosthetic control. The proposed feature extraction method involves two steps: (1) the bispectrum matrix integration, and (2) the Fisher linear discriminant (FLD) projection. We compare DBS with other conventional features, such as autoregressive coefficients, root mean square, power spectral distribution and time domain statistics. First, the separability of the features is investigated by the visualization of feature distribution in the FLD subspace and quantitative measurement (Davies–Boulder clustering index). Then four linear and non-linear classifiers are used to evaluate the discriminative powers of the features in terms of classifica... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251024 Thu, 03 Dec 2009 00:00:00 +0100 3251024 http://www.medworm.com/index.php?rid=3251027&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002367%2Fabstract%3Frss%3Dyes Abstract: Aims of the present study were to test the hypotheses that (1) the compressive properties of articular cartilage are affected more by changes in the medium ionic concentration than the tensile properties, (2) collagen network controls the compression–tension nonlinearity of articular cartilage, and (3) proteoglycan (PG) and collagen contents are primary determinants of the compressive and tensile properties of cartilage, respectively. These hypotheses were experimentally tested by axial compressive and tensile tests (perpendicular to the cartilage surface) of bovine articular cartilage samples immersed in 0.005M (n=6), 0.15M (n=12) and 1.0M (n=6) saline solutions. Compressive and tensile behaviour was analyzed by a nonlinear fibril-reinforced poroelastic model. Tissue PG and co... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251027 Wed, 02 Dec 2009 00:00:00 +0100 3251027 http://www.medworm.com/index.php?rid=3251025&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002331%2Fabstract%3Frss%3Dyes Abstract: Instead of extracting the abnormal intra-QRS potentials (AIQP) waveform, this study proposes the analysis of the unpredictable intra-QRS potentials (UIQP) based on an autoregressive moving average (ARMA) prediction model to detect the signals with sudden slope change within the QRS complex for the diagnosis of high-risk patients with ventricular tachycardia (VT). The UIQP is detected as the slope changes at slope discontinuities by the prediction error of the ARMA prediction model. Because of the linearity of the ARMA prediction model, the UIQP is also proportional to the amplitude of the QRS complex if the input QRS waves have the same shapes. Hence this study further defines the UIQP-to-QRS ratio to normalize the UIQP by the root-mean-square (RMS) value of the QRS complex. The ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251025 Tue, 01 Dec 2009 00:00:00 +0100 3251025 http://www.medworm.com/index.php?rid=3251026&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002355%2Fabstract%3Frss%3Dyes Abstract: The present study aims to the design of a finite-element model simulating accurately the pullout behaviour of cylindrical pedicle screws and predicting their pullout force. Three commercial pedicle screws, subjected to pure pullout from synthetic bone, were studied experimentally. The results were used for the design, calibration and validation of a finite-element model. Special attention was paid to the accurate simulation of the failure inside the host material under shear. For this purpose, a bilinear cohesive zone material model was adopted, controlling the mode-II debonding of neighbouring elements in the vicinity of the screw. Comparison between experimental and numerical results proved that the implementation of this approach can significantly enhance the accuracy of the n... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251026 Mon, 30 Nov 2009 00:00:00 +0100 3251026 http://www.medworm.com/index.php?rid=3124440&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002343%2Fabstract%3Frss%3Dyes Abstract: Effects of collagen digestion have been defined up to the fibril level. However, the question remains as to whether the alteration of skeletal muscle extracellular matrix (ECM) affects a muscle's passive elastic response. Various elastography methods have been applied as tools for evaluating the mechanical properties and ECM content of skeletal muscle. In an effort to develop an ECM altered skeletal muscle model, this study determined the effect of collagen digestion on the passive elastic properties of skeletal muscle. Passive mechanical properties of rat diaphragms were evaluated in various degrees of collagen digestion. Between cyclic loading tests, muscle strips were immersed in various concentrations of clostridium histolyticum derived bacterial collagenase. All samples were... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124440 Mon, 30 Nov 2009 00:00:00 +0100 3124440 http://www.medworm.com/index.php?rid=3124437&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900215X%2Fabstract%3Frss%3Dyes This study describes the development and validation of a computer model simulating an adult wheelchair-seated occupant subjected to a rear impact event. The model was developed in MADYMO™ and validated rigorously using the results of three similar sled tests conducted to specifications provided in the draft ISO/TC 173 standard. Outcomes from the model can provide critical wheelchair loading information to wheelchair and tiedown manufacturers, resulting in safer wheelchair designs for rear impact conditions. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124437 Mon, 30 Nov 2009 00:00:00 +0100 3124437 http://www.medworm.com/index.php?rid=3251023&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002318%2Fabstract%3Frss%3Dyes We examined 17 patients with PD (Hoehn and Yahr score: 2.7±0.7; ON state) and 15 age-matched healthy controls; mean ages were 66.8±5.9 years, 67.6±9.6 years, respectively. Subjects wore a 3D-accelerometer (ADXL330, Analog Devices) on the lower back while performing the TUG test. Sit-to-Stand and Stand-to-Sit times were extracted from the anterior–posterior (AP) signal. Parameters included Sit-to-Stand, Stand-to-Sit durations, amplitude range (Range) and slopes (Jerk). Acceleration median and standard deviation (SD) were also calculated.Results: Stopwatch-based TUG duration tended to be higher for the PD patients compared to the control group, although not significantly (p=0.08). In contrast, the TUG duration that was extracted from the acceleration signal was significantly (p (Source:... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251023 Fri, 27 Nov 2009 00:00:00 +0100 3251023 http://www.medworm.com/index.php?rid=3124436&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002148%2Fabstract%3Frss%3Dyes This study illustrates a methodology with the potential to generate femur models incorporating material properties for large scale multi-femur finite element studies. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124436 Mon, 23 Nov 2009 00:00:00 +0100 3124436 http://www.medworm.com/index.php?rid=3012179&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002380%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012179 Fri, 20 Nov 2009 16:27:21 +0100 3012179 http://www.medworm.com/index.php?rid=3251021&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002288%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to determine the use and feasibility of accelerometry-based monitoring and to examine a discrete multi-resolution signal analysis technique to determine motoric subtypes in patients with DSM-IV delirium. Forty consecutive patients receiving palliative care (23 male, 17 female, mean age±standard deviation 68.4±11.9 years) were assessed using 24-h accelerometer-based monitoring. The total amount of time spent per activity of sitting/lying, standing and stepping were calculated. This was achieved through the multilevel decomposition and reconstruction of the accelerometer signals by means of the discrete wavelet transform. Both the reconstructed approximations and details of the discrete transform were used for motoric subtyping. This was compared to ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3251021 Fri, 20 Nov 2009 00:00:00 +0100 3251021 http://www.medworm.com/index.php?rid=3124439&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002276%2Fabstract%3Frss%3Dyes This article is concerned with soft computing-based noninvasive screening for malignant disorders in human larynx. The suitability of two types of data for the analysis is explored. The questionnaire data and the digital voice recordings of the sustained phonation of the vowel sound /a/ are the data types considered in this study. The screening is considered as a task of data classification into the h ealthy, cancerous, and noncancerous classes. To explore data and decisions a nonlinear mapping technique exhibiting the property of local data ordering is applied. The classification accuracy of over 92% was obtained for unseen questionnaire data collected from 240 subjects. The experimental investigations have shown that, concerning the three classes, the questionnaire data carry much more d... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124439 Thu, 19 Nov 2009 00:00:00 +0100 3124439 http://www.medworm.com/index.php?rid=3124438&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002161%2Fabstract%3Frss%3Dyes Conclusion: The better understanding of how these tissues mechanically behave is essential for a correct modeling of the human trachea, a better simulation of its response under different loading conditions, and the development of strategies for the design of new endotracheal prostheses. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124438 Wed, 18 Nov 2009 00:00:00 +0100 3124438 http://www.medworm.com/index.php?rid=3124435&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002136%2Fabstract%3Frss%3Dyes Abstract: This work aims at investigating seven morphological parameters in distinguishing malignant and benign breast tumors on ultrasound images. Linear discriminant analysis was applied to sets of up to five parameters and then the performances were assessed using the area Az (± standard error) under the ROC curve, accuracy (Ac), sensitivity (Se), specificity (Sp), positive predictive value and negative predictive value. The most relevant individual parameters were the normalized residual value (nrv) and overlap ratio (RS), both calculated from the convex polygon technique, and the circularity (C). When nrv and C were taken together with roughness (R), calculated from normalized radial length (NRL), a performance slightly over 83% in distinguishing malignant and benign breast tumors wa... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124435 Wed, 18 Nov 2009 00:00:00 +0100 3124435 http://www.medworm.com/index.php?rid=3124429&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002045%2Fabstract%3Frss%3Dyes Abstract: The conventional zero-heat-flow thermometer, which measures the deep body temperature from the skin surface, is widely used at present. However, this thermometer requires considerable electricity to power the electric heater that compensates for heat loss from the probe; thus, AC power is indispensable for its use. Therefore, this conventional thermometer is inconvenient for unconstrained monitoring. We have developed a new dual-heat-flux method that can measure the deep body temperature from the skin surface without a heater. Our method is convenient for unconstrained and long-term measurement because the instrument is driven by a battery and its design promotes energy conservation. Its probe consists of dual-heat-flow channels with different thermal resistances, and each heat-f... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124429 Wed, 11 Nov 2009 00:00:00 +0100 3124429 http://www.medworm.com/index.php?rid=3124434&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002124%2Fabstract%3Frss%3Dyes Abstract: In the present paper it is investigated how anisotropic resolution, typical for clinical imaging devices like computed tomography, influences detection of principal directions of test structures. The gray-level intensity is derived as a function of position in 3D space for network-like objects under an assumption of anisotropic blurring and then three tensors of structural anisotropy are calculated for the computed gray-level image of the object. The three approaches to compute the tensor of structural anisotropy are based on zero, first and second order derivatives of the gray-level intensity. It is shown that detection of principal directions is biased under anisotropic resolution if zero and first order approaches are used. The computation of principal values is biased for all... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124434 Mon, 09 Nov 2009 00:00:00 +0100 3124434 http://www.medworm.com/index.php?rid=3124431&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002082%2Fabstract%3Frss%3Dyes Abstract: Concerns over accelerated damage to the untreated compartment of the knee following unicompartmental knee arthroplasty (UKA), as well as the relatively poor success rates observed for lateral as opposed to the medial arthroplasty, remain issues for attention. Finite element analysis (FEA) was used to assess changes to the kinematics and potential for cartilage damage across the knee joint in response to the implantation of the Oxford Mobile Bearing UKA. FE models of lateral and medial compartment arthroplasty were developed, in addition to a healthy natural knee model, to gauge changes incurred through the arthroplasty. Varus–valgus misalignments were introduced to the femoral components to simulate surgical inaccuracy or over-correction. Boundary conditions from the Stanmore k... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124431 Mon, 09 Nov 2009 00:00:00 +0100 3124431 http://www.medworm.com/index.php?rid=3124441&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002094%2Fabstract%3Frss%3Dyes Abstract: A new instrumented hip joint prosthesis was developed which allows the in vivo measurement of the complete contact loads in the joint, i.e. 3 force and 3 moment components. A clinically proven standard implant was modified. Inside the hollow neck, 6 semiconductor strain gauges are applied to measure the deformation of the neck. Also integrated are a small coil for the inductive power supply and a 9-channel telemetry transmitter. The neck cavity is closed by a titanium plate and hermetically sealed by electron beam welding. The sensor signals are pulse interval modulated (PIM) with a sampling rate of about 120Hz. The pulses are transmitted at radio frequencies via a small antenna loop inside the ceramic head, which is connected to the electronic circuit by a two-pin feedthrough. I... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124441 Wed, 04 Nov 2009 00:00:00 +0100 3124441 http://www.medworm.com/index.php?rid=3124433&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002112%2Fabstract%3Frss%3Dyes Abstract: Measures of postural steadiness – known as posturography – are commonly used for balance assessment during quiet standing. Although quiet sitting balance may be studied via posturography as well, this has not been done to date. As such, the purpose of this study was to characterize the posturography during quiet sitting in comparison with quiet standing and to provide a benchmark for future studies investigating differences in balance regulation and execution. Twelve young and healthy people agreed to quietly sit and stand on a force platform with their eyes open and closed. For each condition, one trial of 2min was executed and the anterior–posterior, medial–lateral, and resultant distance fluctuations of the body's center of pressure (COP) were calculated. Finally, time... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124433 Mon, 02 Nov 2009 00:00:00 +0100 3124433 http://www.medworm.com/index.php?rid=3124432&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002100%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to predict time-dependent biomechanics of bone around cylindrical screw dental implants with different macrogeometric designs under simulated immediate loading condition. The remodeling of bone around a parallel-sided and a tapered dental implant of same length was studied under 100N oblique load by implementing the Stanford theory into three-dimensional finite element models. The results of the analyses were examined in five time intervals consisting loading immediately after implant placement, and after 1, 2, 3 and 4 weeks following implantation. Maximum principal stress, minimum principal stress, and strain energy density in peri-implant bone and displacement in x-(implant lateral direction with a projection of the oblique force) and y-(implant lo... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124432 Mon, 02 Nov 2009 00:00:00 +0100 3124432 http://www.medworm.com/index.php?rid=3012195&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002069%2Fabstract%3Frss%3Dyes Abstract: The paper presents a theory of fixation failure and loosening in cemented total hip prostheses and proceeds to investigate this using an experimentally validated finite element model and two prosthesis types, namely the Charnley and the C-Stem. The study investigates the effects of retroversion torque occurring at heel-strike in combination with a loss of proximal cement/bone support and distal implant/cement support with a good distal cement/bone interface. A 3D finite element model was validated by comparison of femoral surface strains with those measured in an in vitro experimental simulation using an implanted Sawbone femur loaded in the heel-strike position and including a simplified representation of muscle forces. Results showed that the heel-strike position applies a high... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012195 Mon, 02 Nov 2009 00:00:00 +0100 3012195 http://www.medworm.com/index.php?rid=2950551&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002185%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950551 Sun, 01 Nov 2009 00:00:00 +0100 2950551 http://www.medworm.com/index.php?rid=3124430&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002070%2Fabstract%3Frss%3Dyes Conclusion: Time-to-loading of single-tooth implants may not differ in terms of load distributions in neighboring peri-implant bone. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3124430 Fri, 30 Oct 2009 00:00:00 +0100 3124430 http://www.medworm.com/index.php?rid=3012196&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309002057%2Fabstract%3Frss%3Dyes Abstract: The crosstalk phenomenon consists in recording the volume-conducted electromyographic activity of muscles other than that under study. This interference may impair the correct interpretation of the results in a variety of experiments. A new protocol is presented here for crosstalk assessment between two muscles based on changes in their electrical activity following a reflex discharge in one of the muscles in response to nerve stimulation. A reflex compound muscle action potential (H-reflex) was used to induce a silent period in the muscle that causes the crosstalk, called here the remote muscle. The rationale is that if the activity recorded in the target muscle is influenced by a distant source (the remote muscle) a silent period observed in the electromyogram (EMG) of the remo... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012196 Fri, 30 Oct 2009 00:00:00 +0100 3012196 http://www.medworm.com/index.php?rid=3012197&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900188X%2Fabstract%3Frss%3Dyes Abstract: To determine the reliability, stability, validity and precision of a stereophotogrammetry (SP) system for use in quantifying the complex three-dimensional structure of the human torso, we performed assessments of the system using images of geometric solids and a human-form mannequin. Analysis of geometric solids revealed excellent intra- and interrater reliability of the system for linear, surface area and volume measurements (r>0.99, P0.06). The system exhibited excellent stability in images of the mannequin over time (r>0.99). The limit of precision (error>5%) of the system to detect objects on the surface of the mannequin was estimated at an object size of 23.5cm2 for surface area and 32mL for volume. These results demonstrate the capability of SP of the torso to be used as a ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012197 Mon, 12 Oct 2009 00:00:00 +0100 3012197 http://www.medworm.com/index.php?rid=3366018&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001891%2Fabstract%3Frss%3Dyes Abstract: In-depth investigations of motor-vehicle crashes involve detailed inspection, measurement, and photodocumentation of vehicle exterior and interior damage, evidence of belt-restraint use, and evidence of occupant contacts with the vehicle interior. Results of in-depth investigations thereby provide the most objective way to identify current and emerging injury problems and issues in occupant safety and crash protection, and provide important feedback on the real-world performance of the latest restraint-system and vehicle crashworthiness technologies. To provide an objective understanding of real-world transportation safety issues for wheelchair-seated travelers, the University of Michigan Transportation Research Institute (UMTRI) has been conducting and assembling data from in-de... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366018 Mon, 05 Oct 2009 00:00:00 +0100 3366018 http://www.medworm.com/index.php?rid=3012194&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900191X%2Fabstract%3Frss%3Dyes Abstract: In this paper it is studied how three methods of quantifying structural anisotropy are related. Mean intercept length (MIL) method has been designed for the analysis of binary images. Autocorrelation function and the covariance matrix of the gray-level intensity gradient (GST method) are approaches designed for the analysis of gray-level data. It is shown here that the autocorrelation function and the MIL methods are not related in a general case. In contrast, an analytical proof is provided to show that MIL and GST methods are strictly equivalent. The standard definition of MIL is expressed in terms of a gradient field. Next it is shown that eigenvectors of the MIL fabric tensor are also eigenvectors of the GST fabric tensor and eigenvalues of the MIL fabric tensor can be determ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012194 Mon, 05 Oct 2009 00:00:00 +0100 3012194 http://www.medworm.com/index.php?rid=2862229&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001933%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862229 Wed, 30 Sep 2009 23:00:00 +0100 2862229 http://www.medworm.com/index.php?rid=3366020&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001908%2Fabstract%3Frss%3Dyes Abstract: Previous research has pointed out that non-collision injuries occur among wheelchair users in Special Transportation Services (STS – a demand-responsive transport mode). The organization of such modes is also quite complex, involving both stakeholders and key personnel at different levels. Our objective was therefore to qualitatively explore the state of safety, as perceived and discussed within a workplace context. Focus groups were held with drivers of both taxi companies and bus companies.The results indicated that passengers run the risk of being injured without being involved in a vehicle collision. The pertinent organizational and corporate culture did not prioritize safety. The drivers identified some relatively clear-cut safety threats, primarily before and after a ride... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366020 Mon, 28 Sep 2009 00:00:00 +0100 3366020 http://www.medworm.com/index.php?rid=3366021&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001866%2Fabstract%3Frss%3Dyes Abstract: ANSI/RESNA WC19 (i.e., WC19) is a voluntary standard that specifies design and performance requirements for wheelchairs that are suitable for use as seats in motor vehicles. The guiding principles for the standard originate from automotive crash-protection principles that are effective in reducing occupant injuries and fatalities. In addition to frontal-impact testing of wheelchairs, the standard includes tests for securement-point accessibility, tiedown-strap clear paths, lateral stability, and accommodation of vehicle-anchored belt restraints. Results from testing wheelchairs to WC19 reveal that the most common wheelchair problems include: a lack of structural integrity during frontal-impact loading; sharp rigid edges; and wheelchair structures that interfere with achieving pro... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366021 Sun, 27 Sep 2009 00:00:00 +0100 3366021 http://www.medworm.com/index.php?rid=2950568&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001611%2Fabstract%3Frss%3Dyes Abstract: As the needs for various kinds of body surface information are wide-ranging, we developed an imaging-sensor integrated system that can synchronously acquire high-resolution three-dimensional (3D) far-infrared (FIR) thermal and true-color images of the body surface. The proposed system integrates one FIR camera and one color camera with a 3D structured light binocular profilometer. To eliminate the emotion disturbance of the inspector caused by the intensive light projection directly into the eye from the LCD projector, we have developed a gray encoding strategy based on the optimum fringe projection layout. A self-heated checkerboard has been employed to perform the calibration of different types of cameras. Then, we have calibrated the structured light emitted by the LCD project... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950568 Sun, 27 Sep 2009 00:00:00 +0100 2950568 http://www.medworm.com/index.php?rid=2950561&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001532%2Fabstract%3Frss%3Dyes This study is one step towards the modeling of soft tissue mechanics using a meshless finite element approach to be applied in real-time haptic feedback of soft-tissue models in virtual reality simulation. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950561 Wed, 23 Sep 2009 00:00:00 +0100 2950561 http://www.medworm.com/index.php?rid=3012193&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001878%2Fabstract%3Frss%3Dyes Abstract: Large implants for vertebral body replacement (VBR) have a large footprint, and are normally supported by stronger bone at the rim of the vertebral body. But they also necessitate a greater corpectomy defect in the vertebral body concerned. In order to study the effect of implant size on contact pressure on the adjacent vertebral bodies and thus the risk of implant subsidence, an osseoligamentous finite element model of the lumbar spine was employed. The VBR was inserted at the level of L4 and additionally stabilized by posterior spinal instrumentation. Flat and curved vertebral endplates, small and large corpectomy defects, different implant positions and axial preloads as well as normal and osteoporotic vertebral bodies were simulated. Contact pressures in the vertebral body ar... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012193 Tue, 22 Sep 2009 00:00:00 +0100 3012193 http://www.medworm.com/index.php?rid=3012192&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001854%2Fabstract%3Frss%3Dyes Abstract: The truCCOMS™ cardiac output monitor system provides a continuous and instantaneous measurement of cardiac output, derived from the amount of energy required for heating a filament to maintain a fixed 2°C blood temperature difference between two thermistors located distally on a pulmonary artery catheter. Clinical studies, however, reported relatively poor accuracy of the cardiac output estimation, possibly due to linearly assumed power–cardiac output relationship used for calibration of the catheters. We experimentally studied the shape of the truCCOMS™ calibration relationship (i) in a hydraulic bench model of the right heart and (ii) in vivo intact animal model. The results showed a nonlinear relationship between the power input into the heating element and the cardiac ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012192 Tue, 22 Sep 2009 00:00:00 +0100 3012192 http://www.medworm.com/index.php?rid=3012189&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001829%2Fabstract%3Frss%3Dyes We present single fibre heart activity model (SFHAM) based on the current flow through the five bunches of fibres of the cardiac muscle (CM). The five effective fibres are identified and assigned to the appropriate segments of CM. Analytical functions describing ionic flows along the fibres are derived and proposed. The parameters determining the shapes and amplitudes of the functions proposed are obtained on the basis of standard 12-lead ECG measurements after numerical fitting procedures concentrating on the QRS-waves. As a consequence, five independent courses of partial, transient potentials are obtained representing: anterior, inferior, lateral, posterior walls, and interventricular septum activities, respectively. Moreover, to check our theoretical results we compare the potentials c... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012189 Thu, 17 Sep 2009 00:00:00 +0100 3012189 http://www.medworm.com/index.php?rid=3012187&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001799%2Fabstract%3Frss%3Dyes Abstract: The earthworm (Lumbricus terrestris) is presented as an in vitro model of a peripheral nerve containing only two fibers each with distinctly different conduction velocities, the median and lateral giant fibers (MGF and LGF). The worm model is used with a multi-contact cuff electrode to validate the spatial–temporal filtering effect of different electrode contact configurations and the effect of applying a delay adder and matched filter tuned to either the MGF or LGF action potential (AP) to extract conduction direction and velocity from the recording. The results confirmed the known effect of inter-electrode spacing and bipolar and tripolar recording configuration on the AP amplitude. It also demonstrates a crossover point where the amplitude of the tripolar recording is larger... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012187 Thu, 17 Sep 2009 00:00:00 +0100 3012187 http://www.medworm.com/index.php?rid=3012191&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001842%2Fabstract%3Frss%3Dyes Abstract: Microvolt T-wave alternans (TWA), consisting of every-other-beat changes in ECG T-wave morphology, is an index of susceptibility to malignant ventricular arrhythmias, requiring automatic techniques to be identified. Five of these, namely, fast-Fourier-transform spectral method (FFTSM), complex-demodulation method (CDM), modified-moving-average method (MMAM), Laplacian-likelihood-ratio method (LLRM) and adaptive-match-filter method (AMFM), were applied here to simulated and sample clinical data. The aim was to compare individual methods ability to properly identify stationary and time-varying TWA, avoiding false-positive detections. The MMAM provided false-positive TWA when applied to simulated ECGs affected by amplitude variability, but TWA. Stationary TWA was properly quantified... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012191 Wed, 16 Sep 2009 00:00:00 +0100 3012191 http://www.medworm.com/index.php?rid=3012198&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001817%2Fabstract%3Frss%3Dyes This study presents a new computational system for modeling the upper airway in rats that combines tagged magnetic resonance imaging (MRI) with tissue material properties to predict three-dimensional (3D) airway motion. The model is capable of predicting airway wall and tissue deformation under airway pressure loading up to airway collapse. The model demonstrates that oropharynx collapse pressure depends primarily on ventral wall (tongue muscle) elastic modulus and airway architecture. An iterative approach that involves substituting alternative possible tissue elastic moduli was used to improve model precision. The proposed 3D model accounts for stress–strain relationships in the complex upper airway that should present new opportunities for understanding pathogenesis of airway collapse... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012198 Fri, 11 Sep 2009 00:00:00 +0100 3012198 http://www.medworm.com/index.php?rid=3012190&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001830%2Fabstract%3Frss%3Dyes Abstract: Wrist pulse signal contains important information about the health status of a person and pulse signal diagnosis has been employed in oriental medicine for thousands of years. In this research, a systematic approach is proposed to analyze the computerized wrist pulse signals, with the focus placed on the feature extraction and pattern classification. The wrist pulse signals are first collected and pre-processed. Considering that a typical pulse signal is composed of periodically systolic and diastolic waves, a modified Gaussian model is adopted to fit the pulse signal and the modeling parameters are then taken as features. Consequently, a feature selection scheme is proposed to eliminate the tightly correlated features and select the disease-sensitive ones. Finally, the selected ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012190 Fri, 11 Sep 2009 00:00:00 +0100 3012190 http://www.medworm.com/index.php?rid=3012184&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001714%2Fabstract%3Frss%3Dyes Abstract: Finite element (FE) analysis of the effect of implant positioning on the performance of cementless total hip replacements (THRs) requires the generation of multiple meshes to account for positioning variability. This process can be labour intensive and time consuming as CAD operations are needed each time a specific orientation is to be analysed. In the present work, a mesh morphing technique is developed to automate the model generation process. The volume mesh of a baseline femur with the implant in a nominal position is deformed as the prosthesis location is varied. A virtual deformation field, obtained by solving a linear elasticity problem with appropriate boundary conditions, is applied. The effectiveness of the technique is evaluated using two metrics: the percentages of m... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012184 Thu, 10 Sep 2009 00:00:00 +0100 3012184 http://www.medworm.com/index.php?rid=3012186&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001787%2Fabstract%3Frss%3Dyes Abstract: A structural model of skeletal muscle based on the bone–muscle lever system is proposed to describe the relationship between wrist angle and thickness of the extensor carpi radialis muscle during the process of wrist flexion–extension. This model applied the cosine theorem to the expression for muscle length, in order to relate wrist angle to muscle thickness by the invariance of muscle volume, which was used to calculate the length of the extensor carpi radialis muscle from the muscle thickness. To validate the proposed model, wrist angles were also computed by other models based on regression, such as linear regressions, an artificial neural network, and a support vector machine. The results show that wrist angles are predicted well at different extension rates by our propo... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012186 Wed, 09 Sep 2009 00:00:00 +0100 3012186 http://www.medworm.com/index.php?rid=3012188&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001805%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to investigate the effect of bone marrow stromal cells (BMSCs) on tendon healing in a canine ex vivo model. Bone marrow was harvested and BMSCs were isolated and cultured according to established protocols. Cells were seeded into 0.5mg/ml collagen gels and cultured for 24h to allow gel contraction, and then implanted between the lacerated ends of repaired flexor digitorum profundus tendons. Tendons repaired with a gel patch alone and without a gel patch served as control groups. After 2 and 4 weeks in culture, the repaired tendons were evaluated for breaking strength and stiffness. Cell viability was assessed by labeling the cells with PKH26 red fluorescent cell linker. The maximal strength and stiffness of repaired tendons with the BMSC-seeded patch... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012188 Mon, 07 Sep 2009 00:00:00 +0100 3012188 http://www.medworm.com/index.php?rid=3012185&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001775%2Fabstract%3Frss%3Dyes Abstract: The purpose of this study was to evaluate the effects of three different control methods on driving speed variation and wheel slip of an electric-powered wheelchair (EPW). A kinematic model as well as 3D dynamic model was developed to control the velocity and traction of the wheelchair. A smart wheelchair platform was designed and built with a computerized controller and encoders to record wheel speeds and to detect the slip. A model based, a proportional-integral-derivative (PID) and an open-loop controller were applied with the EPW driving on four different surfaces at three specified speeds. The speed errors, variation, rise time, settling time and slip coefficient were calculated and compared for a speed step-response input. Experimental results showed that model based contro... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012185 Mon, 07 Sep 2009 00:00:00 +0100 3012185 http://www.medworm.com/index.php?rid=3366019&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001726%2Fabstract%3Frss%3Dyes Abstract: Previous research has shown that wheelchair-seated passengers using special transportation services (STS) have been injured without being involved in a vehicle crash. In order to estimate incident rate and societal costs for these vehicle-related injuries, the focus needs to be adjusted towards a traveler/incident-oriented perspective. The aim of the project was to utilize such a perspective, related to travelers using STS in Sweden.In order to address the chosen perspective, a mixed method approach was used, involving quantitative as well as qualitative research techniques applied on four different sets of data: one hospital-based record, two sets of STS incident report databases, and interviews with wheelchair-seated STS passengers.The results showed that the injury incidence r... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366019 Tue, 01 Sep 2009 00:00:00 +0100 3366019 http://www.medworm.com/index.php?rid=2950565&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900157X%2Fabstract%3Frss%3Dyes In this study, transitional and turbulent flow within an asymmetric bifurcating model of the upper airway during HFOV are studied using large eddy simulation (LES) methods. The flow, characterized by a peak Reynolds number of 8132, is analysed using a validated LES model of a three-dimensional branching geometry. The pressures, velocities, and vorticity within the flow are presented and compared with prior models for branching flow systems. The results demonstrate how pendelluft occurs at asymmetric branches within the respiratory system. These results may be useful in optimising treatments using HFOV methods. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950565 Fri, 28 Aug 2009 00:00:00 +0100 2950565 http://www.medworm.com/index.php?rid=3012183&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001659%2Fabstract%3Frss%3Dyes Abstract: The mechanical properties of the femoral head are known to play an important role in the athletic performance of animals. In this paper, the full-field displacement and strain distributions of beagle femoral head samples in the U and V fields under loading were measured using the digital speckle correlation method (DSCM), and some deformation characteristics were analyzed. Young's modulus and Poisson's ratio were calculated to demonstrate the notable axial anisotropy of the femoral head. The axial compressive Young's modulus varies from 361MPa to 583MPa, and the transverse one is 213MPa. The Poisson's ratio in the axial–transverse direction ranges from 0.14 to 0.29, and the one in the transverse–axial direction is 0.07. Experimental results validated the accuracy of this meas... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012183 Thu, 27 Aug 2009 00:00:00 +0100 3012183 http://www.medworm.com/index.php?rid=2950566&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001581%2Fabstract%3Frss%3Dyes In conclusion, the configuration of the constructed device provided reliable measurements of the electrocardiogram, BCG, heart sound, and carotid and ankle pulse wave signals. Attached EMFi sensor strips on the neck and limbs yield completely new applications of the EMFi sensors aside from the conventional seat and supine recordings. Higher sensitivity, ease of utilization, and minimum discomfort of the EMFi sensor compared with acceleration sensors strengthen the status of the EMFi sensor for accurate and reliable BCG and PWV measurements, providing novel evaluation of the elastic properties of the cardiovascular system. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950566 Thu, 27 Aug 2009 00:00:00 +0100 2950566 http://www.medworm.com/index.php?rid=3012181&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001635%2Fabstract%3Frss%3Dyes Abstract: The interaction between the handle and operator’s hand affects the comfort and safety of tool and machine operations. In most of the previous studies, the investigators considered only the normal contact forces. The effect of friction on the joint moments in fingers has not been analyzed. Furthermore, the observed contact forces have not been linked to the internal musculoskeletal loading in the previous experimental studies. In the current study, we proposed a universal model of a hand to evaluate the joint moments in the fingers during grasping tasks. The hand model was developed on the platform of the commercial software package AnyBody. Only four fingers (index, long, ring, and little finger) were included in the model. The anatomical structure of each finger is comprised o... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012181 Tue, 25 Aug 2009 00:00:00 +0100 3012181 http://www.medworm.com/index.php?rid=3012180&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001623%2Fabstract%3Frss%3Dyes In this study, nanocomposite of 50wt% calcium sulfate and 50wt% nanocrystalline apatite was produced and its biocompatibility, physical and structural properties were compared with pure calcium sulfate (CS) cement. Indomethacin (IM), a non-steroidal anti-inflammatory drug, was also loaded on both CS and nanocomposite cements and its in vitro release was evaluated over a period of time. The effect of the loaded IM on basic properties of the cements was also investigated. Biocompatibility tests showed a partial cytotoxicity in CS cement due to the reduced number of viable mouse fibroblast L929 cells in contact with the samples as well as spherical morphologies of the cells. However, no cytotoxic effect was observed for nanocomposite cement and no significant difference was found between the ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012180 Fri, 21 Aug 2009 00:00:00 +0100 3012180 http://www.medworm.com/index.php?rid=2950562&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001544%2Fabstract%3Frss%3Dyes Abstract: A multi-technique approach to modelling artificially ventilated patients on the adult general intensive care unit (ICU) is proposed. Compartmental modelling techniques were used to describe the mechanical ventilator and the flexible hoses that connect it to the patient. 3D CFD techniques were used to model flow in the major airways and a Windkessel style balloon model was used to model the mechanical properties of the lungs. A multi-compartment model of the lung based on bifurcating tree structures representing the conducting airways and pulmonary circulation allowed lung disease to be modelled in terms of altered ratios within a lognormal distribution of values and it is from these that gas exchange was determined. A compartmental modelling tool, Bathfp, was used to integrate th... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950562 Fri, 21 Aug 2009 00:00:00 +0100 2950562 http://www.medworm.com/index.php?rid=3012182&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001647%2Fabstract%3Frss%3Dyes Abstract: A robust multi-lead ECG wave detection-delineation algorithm is developed in this study on the basis of discrete wavelet transform (DWT). By applying a new simple approach to a selected scale obtained from DWT, this method is capable of detecting QRS complex, P-wave and T-wave as well as determining parameters such as start time, end time, and wave sign (upward or downward). First, a window with a specific length is slid sample to sample on the selected scale and the curve length in each window is multiplied by the area under the absolute value of the curve. In the next step, a variable thresholding criterion is designed for the resulted signal. The presented algorithm is applied to various databases including MIT-BIH arrhythmia database, European ST-T Database, QT Database, CinC... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3012182 Wed, 19 Aug 2009 00:00:00 +0100 3012182 http://www.medworm.com/index.php?rid=2708905&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001672%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708905 Tue, 18 Aug 2009 11:56:49 +0100 2708905 http://www.medworm.com/index.php?rid=2950570&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001593%2Fabstract%3Frss%3Dyes This study presented a simple force plate method that can be used to determine subject-specific segment masses and COM locations and compared it to other well-known methods. The proposed method was tested in individuals with different body mass index (i.e., lean, normal, and obese) to verify its sensitivity. All the segmental mass and COM values obtained from the force plate method were within the range of those of the other methods for the entire sample. Significant differences were identified between the morphological groups in relative segmental masses at the upper arm and leg and foot, and COM locations at the leg and foot and head and trunk as obtained from the force plate method (p (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950570 Mon, 17 Aug 2009 00:00:00 +0100 2950570 http://www.medworm.com/index.php?rid=2950564&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001568%2Fabstract%3Frss%3Dyes Abstract: Cortical bone is a compact tissue with anisotropic macroscopic mechanical properties determined by a microstructure and the quality of a mineralised collagen matrix. Anisotropic elastic properties and strength are usually measured on different groups of sample which can hardly be pooled; as a consequence little is known on the relationships between strength and elasticity in the different anatomical directions. A method is presented to measure on a same cortical bone sample: (1) Young's modulus and strength (σmax) in the longitudinal direction; (2) stiffness (C11) in the transverse direction. Longitudinal and transverse direction are taken along and perpendicular to the diaphysis axis, respectively. Ultrasonic techniques yield Young's modulus (Ea) and C11; three-point bending te... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950564 Mon, 17 Aug 2009 00:00:00 +0100 2950564 http://www.medworm.com/index.php?rid=2950552&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900143X%2Fabstract%3Frss%3Dyes This study begins the development of a patient-specific model for femur fracture risk assessment and prediction based on individuals’ gait analysis data, bone geometry from imaging and material properties from nanoindentation (Young's modulus=19GPa, Poisson's ratio=0.3). Finite element models of the femur were developed to assess fracture risk of the femur in a pediatric patient with OI type I. Kinetic data from clinical gait analysis was used to prescribe loading conditions on the femoral head and condyles along with muscle forces on the bone's surface. von Mises stresses were analyzed against a fracture strength of 115MPa.The patient with OI whose femur was modeled showed no risk of femoral fracture during normal gait. The highest stress levels occurred during the mid-stance and loadin... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950552 Mon, 17 Aug 2009 00:00:00 +0100 2950552 http://www.medworm.com/index.php?rid=2950571&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001520%2Fabstract%3Frss%3Dyes Abstract: The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system [Stonebridge PA, Brophy CM. Spiral laminar flow in arteries? Lancet 1991; 338: 1360–1]. We investigate the effects of the spiral blood flow in a model of three-dimensional arterial stenosis with a 75% cross-sectional area reduction at the centre by means of computational fluid dynamics (CFD) techniques. The standard k–ω model is employed for simulation of the blood flow for the Reynolds number of 500 and 1000. We find that for Re=500 the spiral component of the blood flow increases both the total pressure and velocity of the blood, and some significant differences are found between the wall shear stresses of the spiral and non-spiral induced flow downstream of the steno... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950571 Wed, 12 Aug 2009 00:00:00 +0100 2950571 http://www.medworm.com/index.php?rid=2950556&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001477%2Fabstract%3Frss%3Dyes Abstract: Needle insertion is performed in many clinical and therapeutic procedures. Tissue displacement and needle bending which result from needle–tissue interaction make accurate targeting difficult. For performing physicians to gain essential needle targeting skills, needle insertion simulators can be used for training. An accurate needle bending model is essential for such simulators. These bending models are also needed for needle path planning.In this paper, three different models are presented to simulate the deformations of a needle. The first two models use the finite element method and take the geometric nonlinearity into account. The third model is a series of rigid bars connected by angular springs. The models were compared to recorded deformations during experiments of appl... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950556 Wed, 12 Aug 2009 00:00:00 +0100 2950556 http://www.medworm.com/index.php?rid=2950567&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900160X%2Fabstract%3Frss%3Dyes Abstract: The aim of this study is to highlight the relationship between muscle motion, generated by whole body vibration, and the correspondent electromyographic (EMG) activity and to suggest a new method to customize the stimulation frequency. Simultaneous recordings of EMG and tri-axial accelerations of quadriceps rectus femoris from fifteen subjects undergoing vibration treatments were collected. Vibrations were delivered via a sinusoidal oscillating platform at different frequencies (10–45Hz). Muscle motion was estimated by processing the accelerometer data. Large EMG motion artifacts were removed using sharp notch filters centred at the vibration frequency and its superior harmonics. EMG–RMS values were computed and analyzed before and after artifact suppression to assess muscula... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950567 Tue, 11 Aug 2009 00:00:00 +0100 2950567 http://www.medworm.com/index.php?rid=2950563&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001556%2Fabstract%3Frss%3Dyes The objective of this study was (1) to confirm whether or not differences in bone strength are reflected in the proximal femur finite element (FE) model constructed from CT images of healthy subjects and osteoporosis patients, and (2) to investigate the effect of loading angle direction on bone fractures. The results from comparison of bone strength between the fracture group, fragile group (osteoporosis patients with no fracture after falling), and healthy group showed that differences in bone strength were definitely reflected in this FE model. Furthermore, the relationship between the loading direction and fracture load value was significant in all groups in the age-adjusted general linear model, and the model made from the trochanteric fracture patients was more sensitive to loading di... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950563 Mon, 10 Aug 2009 00:00:00 +0100 2950563 http://www.medworm.com/index.php?rid=2950560&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001519%2Fabstract%3Frss%3Dyes Abstract: A new constitutive equation is presented to describe the damage evolution process in parallel-fibered collagenous tissues such as ligaments. The model is formulated by accounting for the fibrous structure of the tissues. The tissue’s stress is defined as the average of the collagen fiber’s stresses. The fibers are assumed to be undulated and straightened out at different stretches that are randomly defined according to a Weibull distribution. After becoming straight, each collagen fiber is assumed to be linear elastic. Damage is defined as a reduction in collagen fiber’s stiffness and occurs at different stretches that are also randomly defined by a Weibull distribution. Due to the lack of experimental data, the predictions of the constitutive equation are analyzed by varyi... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950560 Mon, 10 Aug 2009 00:00:00 +0100 2950560 http://www.medworm.com/index.php?rid=2950559&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001507%2Fabstract%3Frss%3Dyes This study presents a whole-head finite element model of deep brain stimulation to examine the effect of electrical grounding, the finite conducting volume of the head, and scalp, skull and cerebrospinal fluid layers. The impedance between the stimulating and reference electrodes in the whole-head model was found to lie within clinically reported values when the reference electrode was incorporated on a localized surface in the model. Incorporation of the finite volume of the head and inclusion of surrounding outer tissue layers reduced the magnitude of the electric field and activating function by approximately 20% in the region surrounding the electrode. Localized distortions of the electric field were also observed when the electrode was placed close to the skull. Under bipolar conditio... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950559 Wed, 05 Aug 2009 00:00:00 +0100 2950559 http://www.medworm.com/index.php?rid=2950557&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001489%2Fabstract%3Frss%3Dyes Abstract: Regional body composition measurements may be achieved in a single operation with impedancemeters equipped with four plantar and four hand electrodes. By measuring sequentially the resistances of five current lines connecting the hands and feet and solving a system of five linear equations, it is possible to calculate the resistances of each limb and the trunk. The impedancemeter used in this study was a prototype with four plantar electrodes and four additional contact electrodes for the hands. Its electronic hardware was identical to that of a Tefal commercial foot-to-foot impedancemeter (FFI). The Tefal FFI was used for measuring weight, whole body fat-free mass (FFM) and fat tissue mass (FM). Impedance and DXA measurements were taken sequentially on a 1st cohort of 170 health... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950557 Wed, 05 Aug 2009 00:00:00 +0100 2950557 http://www.medworm.com/index.php?rid=2950558&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001490%2Fabstract%3Frss%3Dyes Abstract: According to the guidelines the indication for Implantable Cardioverter Defibrillator (ICD) implantation is based on the ejection fraction. However, only a fraction of patients with implanted ICD shows live threatening arrhythmic events followed by adequate shocks. For this reason, further research is needed to find a more sensitive risk stratificator for patients prone to ventricular tachycardia or fibrillation. Unfortunately, standard prospective studies are time consuming.An alternative approach is to perform retrospective studies on patients with already implanted ICDs. So far, an implanted ICD is an exclusion criterion for Magnetic Field Imaging (MFI) studies. To overcome this problem several Blind Source Separation (BSS) algorithms have been tested to find out whether it is... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950558 Mon, 03 Aug 2009 00:00:00 +0100 2950558 http://www.medworm.com/index.php?rid=2950554&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001453%2Fabstract%3Frss%3Dyes Abstract: The aim of the present work is to propose an approach to the biomechanical analysis of oesophagus by defining an appropriate constitutive model and the associated constitutive parameters. The configuration of the different tissues and layers that compose the oesophagus shows very complicated internal anatomy, geometry and mechanical properties. The coupling of these tissues adds to the complexity. The constitutive models must be capable of interpreting the highly non-linear mechanical response. This is done adopting a specific hyperelastic anisotropic formulation. Experimental data are essential for the investigation of the tissues’ biomechanical behaviour and also represent the basis for the definition of constitutive parameters to be adopted within the constitutive formulatio... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950554 Mon, 03 Aug 2009 00:00:00 +0100 2950554 http://www.medworm.com/index.php?rid=2950553&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001441%2Fabstract%3Frss%3Dyes Abstract: Swallow segmentation is a critical precursory step to the analysis of swallowing signal characteristics. In an effort to automatically segment swallows, we investigated artificial neural networks (ANN) with information from cervical dual-axis accelerometry, submental MMG, and nasal airflow. Our objectives were (1) to investigate the relationship between segmentation performance and the number of signal sources and (2) to identify the signals or signal combinations most useful for swallow segmentation. Signals were acquired from 17 healthy adults in both discrete and continuous swallowing tasks using five stimuli. Training and test feature vectors were constructed with variances from single or multiple signals, estimated within 200ms moving windows with 50% overlap. Corresponding ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950553 Fri, 31 Jul 2009 00:00:00 +0100 2950553 http://www.medworm.com/index.php?rid=2862246&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001404%2Fabstract%3Frss%3Dyes Abstract: The paper presents the development of a new measurement system based on acoustic emission (AE) for assessing the dynamic integrity of knee joints, and the evaluation of its efficacy, through an exploratory study using healthy and osteoarthritic knees. For the former, the paper describes the system implemented to acquire joint angle-based AE and the protocol developed to obtain repeatable results. For the latter, the paper reports significant differences between healthy and osteoarthritic knees using statistical analysis of AE occurrence and distribution of AE features in different movement phases. Osteoarthritic knees are found to produce 6–10 times more acoustic emissions than healthy knees, with amplitudes which can be 20dB higher, and durations which can be 10 times longer. ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862246 Wed, 29 Jul 2009 23:00:00 +0100 2862246 http://www.medworm.com/index.php?rid=2862232&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001428%2Fabstract%3Frss%3Dyes Abstract: With developments in software and micro-measurement technology, a three-dimensional middle ear finite element (FE) model can now be more easily constructed to study sound transfer function. Many FE models of the middle ear have been constructed to date, and each has its own particular advantages and disadvantages. In this article, we review the latest developments and technologies in the field of the FE models of the middle ear, and the use of FE in the study of middle ear pathology. Proposals are made for future developments in the field of finite element analysis of middle ear transfer function. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862232 Wed, 29 Jul 2009 23:00:00 +0100 2862232 http://www.medworm.com/index.php?rid=2950555&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001465%2Fabstract%3Frss%3Dyes Abstract: The definition of spinal instability is still controversial. For this reason, it is essential to better understand the difference in biomechanical behaviour between healthy and degenerated human spinal segments in vivo. A novel computer-assisted instrument was developed with the objective to characterize the biomechanical parameters of the spinal segment. Investigation of the viscoelastic properties as well as the dynamic spinal stiffness was performed during a minimally invasive procedure (microdiscectomy) on five patients. Measurements were performed intraoperatively and the protocol consisted of a dynamic part, where spinal stiffness was computed, and a static part, where force relaxation of the segment under constant elongation was studied. The repeatability of the measuremen... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950555 Fri, 24 Jul 2009 00:00:00 +0100 2950555 http://www.medworm.com/index.php?rid=2950569&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001271%2Fabstract%3Frss%3Dyes This article describes a simple custom-made thermoelectrically cooled freeze clamp. The effectiveness of the clamp to transmit loads without tissue slippage was evaluated on 10 canine quadriceps femoris myo-tendinous junctions in both load-to-failure and cyclic loading settings. Dynamic cyclic loading during an extensive period of time was successfully achieved. Loads up to 4.84kN were applied in quasi-static conditions without evidence of clamp slippage or failure. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2950569 Thu, 23 Jul 2009 00:00:00 +0100 2950569 http://www.medworm.com/index.php?rid=2862248&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001386%2Fabstract%3Frss%3Dyes Abstract: Surface Functional Electrical Stimulation (FES) requires high stimulation voltages. A step-up transformer in the output stage of the stimulation circuit is often used. In the present technical paper a voltage controlled current source (VCCS) is presented as an alternative to the transformer coupling. Two (master–slave) coupled transconductance amplifiers (TAs)—in series with pre-charged capacitors—are used to drive the output current. After each stimulation pulse the capacitors are recharged to a high voltage by a switch mode power supply (SMPS). A multiplexer in the output stage is used to provide biphasic output. Output rise-time (10–90%) was less than 2μs at 100mA output. Biphasic charge balanced stimulation current can be produced with a net current to ground of less... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862248 Mon, 20 Jul 2009 23:00:00 +0100 2862248 http://www.medworm.com/index.php?rid=2862247&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001283%2Fabstract%3Frss%3Dyes We present a practical method to select the input parameters of the SampEn algorithm. We show that the computed SampEn successfully discriminates two sensory conditions (eyes-open and eyes-closed) in a group of healthy young adults. We also perform surrogate data tests to investigate the nature of the underlying dynamics of our experimental data. Finally, the results of the proposed approach are compared to those obtained with the multiscale entropy algorithm. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862247 Wed, 15 Jul 2009 23:00:00 +0100 2862247 http://www.medworm.com/index.php?rid=2862245&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001295%2Fabstract%3Frss%3Dyes Abstract: A range of silicone rubbers were created based on existing commercially available materials. These silicones were designed to be visually different from one another and have distinct material properties, in particular, ultimate tensile strengths and tear strengths. In total, eleven silicone rubbers were manufactured, with the materials designed to have a range of increasing tensile strengths from approximately 2 to 4MPa, and increasing tear strengths from approximately 0.45 to 0.7N/mm. The variations in silicones were detected using a standard colour analysis technique. Calibration curves were then created relating colour intensity to individual material properties. All eleven materials were characterised and a 1st order Ogden strain energy function applied. Material coefficients... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862245 Sun, 12 Jul 2009 23:00:00 +0100 2862245 http://www.medworm.com/index.php?rid=2862231&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001398%2Fabstract%3Frss%3Dyes Abstract: In vitro systems provide a powerful means to evaluate the efficacy of total knee arthroplasty (TKA) in restoring normal knee kinematics. The Oxford knee rig (OKR) and the robotic knee testing system (RKTS) represent two systems that have been extensively used to study TKA biomechanics. Nonetheless, a frequently asked question is whether in vitro simulations can capture the in vivo behavior of the knee. Here, we compared the flexion–extension kinematics of intact knees and knees after TKA tested on the OKR and RKTS, to results of representative in vivo studies. The goal was to determine if the in vitro systems could capture the key kinematic features of knees in healthy subjects and TKA patients. Results showed that the RKTS and the OKR can replicate the femoral rollback and ‘... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862231 Sun, 12 Jul 2009 23:00:00 +0100 2862231 http://www.medworm.com/index.php?rid=2862230&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900126X%2Fabstract%3Frss%3Dyes This article provides an overview of the technological aspects of ATF in laparoscopic surgery, gives background information on principles of human perception of related feedback information, and reviews current research attempts in the field of ATF systems in laparoscopic surgery, broken down into three main system components: tactile sensor, display, and data processing.Tactile sensors have been developed to measure tissue compliance, reveal hidden structures or foreign bodies in tissue through measurement of pressure distribution, and to identify and locate arteries by detecting their pulsation. Furthermore, different solutions for presenting tactile data to the surgeon have been developed. Visual and auditory displays are easy to implement into the operating room equipment, while tactil... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862230 Sun, 12 Jul 2009 23:00:00 +0100 2862230 http://www.medworm.com/index.php?rid=2862241&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001246%2Fabstract%3Frss%3Dyes Abstract: The aim of this study is to assess the utility of traditional statistical pattern recognition techniques to help in obstructive sleep apnoea (OSA) diagnosis. Classifiers based on quadratic (QDA) and linear (LDA) discriminant analysis, K-nearest neighbours (KNN) and logistic regression (LR) were evaluated. Spectral and nonlinear input features from oxygen saturation (SaO2) signals were applied. A total of 187 recordings from patients suspected of suffering from OSA were available. This initial dataset was divided into training set (74 subjects) and test set (113 subjects). Twelve classification algorithms were developed by applying QDA, LDA, KNN and LR with spectral features, nonlinear features and combination of both groups. The performance of each algorithm was measured on the t... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862241 Thu, 09 Jul 2009 23:00:00 +0100 2862241 http://www.medworm.com/index.php?rid=2862249&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001210%2Fabstract%3Frss%3Dyes In this study, current model systems have been improved by working with the intact cartilage in real time. An indentation system was designed on a confocal microscope that allows for simultaneous loading and observation of chondrocytes in their native environment. Cell mechanics were then measured under precisely controlled loading conditions. The indentation system is based on a light transmissible cylindrical glass indentor of 0.17mm thickness and 1.64mm diameter that is aligned along the focal axis of the microscope and allows for real time observation of live cells in their native environment. The system can be used to study cell deformation and biological responses, such as calcium sparks, while applying prescribed loads on the cartilage surface. It can also provide novel information ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862249 Tue, 07 Jul 2009 23:00:00 +0100 2862249 http://www.medworm.com/index.php?rid=2862244&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001258%2Fabstract%3Frss%3Dyes This study aims at developing a femoral stem which maintains appropriate mechanical properties for clinical use and provides enough medullary space for revascularization. Hollow and drilled stems were designed to gain sufficient medullary space. Three-dimensional finite element models of the hollow stems were built including the hollow parameters of different wall thicknesses, bore depths and transverse hole patterns. The effects of these parameters on stress under load bearing were investigated. The results indicated that the effects of thickness on the stem depended on their location along the stem. The hollow depth should be designed as deep as possible to ensure a smooth change of cross-sectional area and avoid unexpected stress concentrations. The transverse hole pattern must be arran... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862244 Tue, 07 Jul 2009 23:00:00 +0100 2862244 http://www.medworm.com/index.php?rid=2862243&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001222%2Fabstract%3Frss%3Dyes Abstract: A numerical 3-D fluid–structure interaction (FSI) model of a prosthetic aortic valve was developed, based on a commercial computational fluid dynamics (CFD) software program using an Arbitrary Eulerian Lagrangian (ALE) formulation. To make sure of the validity of this numerical model, an equivalent experimental model accounting for both the geometrical features and the hydrodynamic conditions was also developed. The leaflet and the flow behaviours around the bileaflet valve were investigated numerically and experimentally by performing particle image velocimetry (PIV) measurements. Through quantitative and qualitative comparisons, it was shown that the leaflet behaviour and the velocity fields were similar in both models. The present study allows the validation of a fully coupl... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862243 Sun, 05 Jul 2009 23:00:00 +0100 2862243 http://www.medworm.com/index.php?rid=2862242&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001234%2Fabstract%3Frss%3Dyes Abstract: Regularization is an effective method for the solution of ill-posed ECG inverse problems, such as computing epicardial potentials from body surface potentials. The aim of this work was to explore more robust regularization-based solutions through the application of subspace preconditioned LSQR (SP-LSQR) to the study of model-based ECG inverse problems. Here, we presented three different subspace splitting methods, i.e., SVD, wavelet transform and cosine transform schemes, to the design of the preconditioners for ill-posed problems, and to evaluate the performance of algorithms using a realistic heart-torso model simulation protocol. The results demonstrated that when compared with the LSQR, LSQR-Tik and Tik-LSQR method, the SP-LSQR produced higher efficiency and reconstructed mor... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862242 Sun, 28 Jun 2009 23:00:00 +0100 2862242 http://www.medworm.com/index.php?rid=2862240&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001180%2Fabstract%3Frss%3Dyes Abstract: Quantifying the regional frequency variation in ventricular fibrillation (VF) may lead to focal strategies in treating human VF. We hypothesized that during human VF there are quantifiable regional frequency variations in the ventricles and they relate to underlying fixed myocardial substrate. In eight myopathic human hearts, we studied 35 VF episodes. The electrograms during VF were acquired simultaneously from the epicardium and endocardium using 2 electrode arrays each consisting of 112 electrodes. Regional characterization was performed using a ratio parameter derived from the dominant frequency analysis of the electrograms. The findings were related to the anatomical substrate using bipolar voltage maps. The results of the analysis indicate that LV had a larger dominant freq... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862240 Sun, 28 Jun 2009 23:00:00 +0100 2862240 http://www.medworm.com/index.php?rid=2522413&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001313%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2522413 Fri, 26 Jun 2009 15:37:09 +0100 2522413 http://www.medworm.com/index.php?rid=2862237&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900112X%2Fabstract%3Frss%3Dyes Abstract: Array electrodes are a promising technology that is likely to bring transcutaneous electrical stimulation (TES) a step forward. The dynamic adaptation of electrode size and position helps to simplify the use of electrical stimulation systems and to increase their clinical efficacy. However, up to now array electrodes were built by trial and error and it is unclear how, for example, the gaps between the array elements or the resistivity of the electrode–skin interface material influence the current distribution. A TES model that comprises a finite element model and a nerve model has been used to analyze the influence of array electrode gaps and gel resistivities on nerve activation. Simulation results indicate that the resistivity of the electrode–skin interface layer should b... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862237 Sun, 21 Jun 2009 23:00:00 +0100 2862237 http://www.medworm.com/index.php?rid=2862239&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001192%2Fabstract%3Frss%3Dyes Abstract: The bio-impedance technique provides a safe, low-cost and non-invasive alternative for lung fluid level monitoring. Here we have investigated the feasibility of a novel bio-impedance system in measuring pulmonary congestion in elderly patients suffering from congestive heart failure (CHF). The system employed a parametric reconstruction algorithm to assess mean lung resistivity. Fourteen patients were studied before and following treatment to reduce lung congestion. Significant correlation was found between the changes of radiographic scores and resistivity values following treatment (R=0.57, p (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862239 Thu, 18 Jun 2009 23:00:00 +0100 2862239 http://www.medworm.com/index.php?rid=2862238&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001209%2Fabstract%3Frss%3Dyes In this study a new approach based on time-scale analysis of signals obtained from piezoelectric transducers (PZT) is reported. A post-mortem human subject was instrumented with four PZT on ribs 3 and 7 bilaterally and exposed to lateral blunt impacts to the shoulder and the chest. The fractures were documented after each test, and a criterion was developed to process the PZT signals. The criterion consists in detecting in the PZT signal the onset of a high frequency transient generated by the fracture of a rib using the continuous wavelet transform. Two thresholds were successfully determined to detect fractures that occurred (1) on an instrumented rib, and (2) on the adjacent rib. Further development of this method should allow the detection of all rib fractures using only a few PZT. (So... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862238 Thu, 18 Jun 2009 23:00:00 +0100 2862238 http://www.medworm.com/index.php?rid=2862236&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001167%2Fabstract%3Frss%3Dyes Abstract: Physical whole-body vibration (WBV) exercises become available at various levels of intensity. In a first series of measurements, we investigated 3-dimensional platform accelerations of three different WBV devices without and with three volunteers of different weight (62, 81 and 100kg) in squat position (150° knee flexion). The devices tested were two professional devices, the PowerPlate and the Galileo-Fitness, and one home-use device, the PowerMaxx. In a second series of measurements, the transmission of vertical platform accelerations of each device to the lower limbs was tested in eight healthy volunteers in squat position (100° knee flexion). The first series showed that the platforms of two professional devices vibrated in an almost perfect vertical sine wave at frequenci... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862236 Thu, 11 Jun 2009 23:00:00 +0100 2862236 http://www.medworm.com/index.php?rid=2862235&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001179%2Fabstract%3Frss%3Dyes Abstract: Two-stage reimplantation using an interval hip prosthesis (spacer) of antibiotic-impregnated bone cement has become a well-accepted method to eradicate infection and prevent limb shortening. However, custom made as well as prefabricated spacers share a weakness of limited strength and hence several fractures of spacers have been observed, even for partial weight bearing. The purpose of this study was therefore to improve the strength of the custom made spacer, used at the Orthopaedic Department of the Saarland University Hospital (Germany). As the material strength of bone cement is limited, several reinforced spacers with a metal core consisting of titanium grade two have been developed and investigated. Loading procedure was close to the ISO 7206/4, though small adaptation was ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862235 Thu, 11 Jun 2009 23:00:00 +0100 2862235 http://www.medworm.com/index.php?rid=2862234&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001143%2Fabstract%3Frss%3Dyes Abstract: This paper presents the first systematic characterisation of a new electroretinographic (ERG) electrode, recently described. The new ‘wet’ electrode uses a conducting liquid as a distributed electrical interface between the eye and a solid electronic conductor; the latter detects the ERG potential without any direct contact with the ocular surface. This technique avoids the contact-induced discomfort of both corneal and conjunctival standard electrodes. The wet electrode was tested on 10 volunteers, in comparison with a conjunctival electrode (HK loop), as the most comfortable standard. It was also compared with a cutaneous (cup) electrode, which is even more comfortable, although not standard. Results showed the efficacy of the wet electrode for detecting morphologically acc... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862234 Sun, 07 Jun 2009 23:00:00 +0100 2862234 http://www.medworm.com/index.php?rid=2862233&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001118%2Fabstract%3Frss%3Dyes Abstract: Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. In the first stages of the disease, AF may terminate spontaneously and it is referred as paroxysmal atrial fibrillation (PAF). In this respect, the prediction of PAF termination or maintenance could avoid unnecessary therapy and contribute to take the appropriate decisions on its management. The aim of this work is to predict non-invasively the spontaneous termination of PAF episodes by analyzing the variation of atrial activity (AA) organization. The organization increases as a consequence of the decrease in the number of reentries wandering the atrial tissue before termination. The analysis has been carried out by applying sample entropy, which is a non-linear organization estimator, to surface electro... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2862233 Sun, 07 Jun 2009 23:00:00 +0100 2862233 http://www.medworm.com/index.php?rid=2708924&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309001131%2Fabstract%3Frss%3Dyes Abstract: A combination of lagged Poincaré plots and spectral characteristics were used to investigate the effect of cigarette smoking on the autonomic nervous system (ANS). Heart rate variability (HRV) was determined from pulse-to-pulse intervals (PPI) of ear photoplethysmography (PPG) waveforms. Spectral power analysis of the pulse rate variability (PRV) was performed to determine low frequency (LF) and high frequency (HF) components, and a lagged Poincaré plot was introduced to evaluate the nonlinear characteristics of PRV. The correlations between lagged Poincaré plot and spectral power indices were studied in a group of apparently healthy habitual cigarette smokers and compared to non-smokers. The width (SD1m) and the length (SD2m) of lagged Poincaré plots significantly shrunk in ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708924 Sun, 07 Jun 2009 23:00:00 +0100 2708924 http://www.medworm.com/index.php?rid=2708923&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000976%2Fabstract%3Frss%3Dyes Abstract: Translation of electroencephalographic (EEG) recordings into control signals for brain–computer interface (BCI) systems needs to be based on a robust classification of the various types of information. EEG-based BCI features are often noisy and likely to contain outliers. This contribution describes the application of a fuzzy support vector machine (FSVM) with a radial basis function kernel for classifying motor imagery tasks, while the statistical features over the set of the wavelet coefficients were extracted to characterize the time–frequency distribution of EEG signals. In the proposed FSVM classifier, a low fraction of support vectors was used as a criterion for choosing the kernel parameter and the trade-off parameter, together with the membership parameter based solel... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708923 Sun, 31 May 2009 23:00:00 +0100 2708923 http://www.medworm.com/index.php?rid=2708922&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000964%2Fabstract%3Frss%3Dyes Abstract: Objective: The incidence of pulmonary complaints, severe tracheitis and lung function deterioration is increased during wintertime in laryngectomized individuals. We analyzed how a heat and moisture exchanger (HME) performs in cold and dry ambient circumstances, and how its efficiency in this environmental climate might be improved.Study design: Randomized crossover.Methods: Intra-tracheal temperature and humidity were measured in 10 laryngectomized patients with and without HME, in a cold (mean, 4.7°C) and dry (mean, 4.5mgH2O/L) room.Results: Presence of an HME causes the intra-tracheal mean humidity minima and maxima to increase with 4.2mgH2O/L (95%CI: 3.3–5.0mgH2O/L; p (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708922 Thu, 28 May 2009 23:00:00 +0100 2708922 http://www.medworm.com/index.php?rid=2708925&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000952%2Fabstract%3Frss%3Dyes Abstract: This work studied whether a blind source separation (BSS) and component selection procedure could increase the differences between Alzheimer's disease (AD) patients and control subjects’ spectral and non-linear features of magnetoencephalogram (MEG) recordings. MEGs were acquired with a 148-channel whole-head magnetometer from 62 subjects (36 AD patients and 26 controls), who were divided randomly into training and test sets. MEGs were decomposed using the algorithm for multiple unknown signals extraction (AMUSE). The extracted AMUSE components were characterised with two spectral – median frequency and spectral entropy (SpecEn) – and two non-linear features: Lempel-Ziv complexity (LZC) and sample entropy (SampEn). One-way analysis of variance with age as a covariate was ap... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708925 Sun, 24 May 2009 23:00:00 +0100 2708925 http://www.medworm.com/index.php?rid=2416190&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900099X%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2416190 Tue, 19 May 2009 03:27:26 +0100 2416190 http://www.medworm.com/index.php?rid=2708921&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000940%2Fabstract%3Frss%3Dyes Abstract: Numerous studies have assessed lumbar interbody fusion, but little data from direct interbody load measurements exists. This manuscript describes an interbody fusion cage with integrated 4-axis load cell that can simulate implant heights of 13, 15, 17, 19 and 21mm. The calibrated load cell was accurate to within 7.9% for point compressive loads over the central 8mm×8mm region, but up to 26.8% for eccentric loads on the outer 16mm×16mm rim of the device (although typically errors were less than half). Anterior–posterior shear and lateral shear loads did not affect compressive load measurement ( (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708921 Sun, 17 May 2009 23:00:00 +0100 2708921 http://www.medworm.com/index.php?rid=2522429&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000939%2Fabstract%3Frss%3Dyes We really appreciate the comments made in reference to our published article, as we believe they can improve its content. The purpose of the above mentioned article was to provide a review of concepts in Biotribology based on data referred in specific test methods, available through international peer-reviewed journals. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2522429 Thu, 14 May 2009 23:00:00 +0100 2522429 http://www.medworm.com/index.php?rid=2708919&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000915%2Fabstract%3Frss%3Dyes Abstract: Clinical studies show an association between changed load patterns both in the disc and its adjacent vertebral body, with painful degenerated discs. This suggests that failure to restore the normal loading pattern on implantation of a disc replacement could be a cause of lower clinical success rate. In the present study the variations of load patterns in the vertebra after disc implantation was studied using a simplified finite element models of natural and artificial discs. The effect of implant size and presence of voids at the implant–bony endplate interface were studied, for the worst case scenario of no bone remodelling. An altered stress pattern was observed in the vertebrae of implanted segments. The use of smaller size implants and presence of voids at the interface cau... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708919 Thu, 07 May 2009 23:00:00 +0100 2708919 http://www.medworm.com/index.php?rid=2708920&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000927%2Fabstract%3Frss%3Dyes Abstract: This paper presents a sensor for monitoring and controlling the volume of the cerebrospinal fluid-filled ventricles of the brain. The measurement principle of the sensor exploits electrical conductivity differences between the cerebrospinal fluid and the brain tissue. The electrical contrast was validated using dog brain tissue. Experiments with prototype sensors accurately measured the volume content of elastically deformable membranes and gel phantoms with conductivity properties made to match human brain. The sensor was incorporated into a fully automatic feedback control system designed to maintain the ventricular volume at normal levels. The experimental conductivity properties were also used to assess the sensor performance in a simulated case of hydrocephalus. The computer... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708920 Tue, 05 May 2009 23:00:00 +0100 2708920 http://www.medworm.com/index.php?rid=2708918&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000897%2Fabstract%3Frss%3Dyes Abstract: A new protocol for cryopreservation of arteries frozen at −80°C was compared to the reference protocol for cryopreservation at −150°C and to freshly harvested arteries. The aim of the study is to evaluate both protocols as global procedures to freeze and thaw arteries commonly used in tissue banks. Changes in mechanical properties of rabbit common carotid arteries were studied. Vascular segments were tested in vitro under dynamics loading conditions. Pressure and diameter were recorded simultaneously by a high fidelity transducer and an echotracking device, respectively. The pressure–diameter relationship was fitted by the arctangent Langewouters’ model and the arterial thickness was derived from histological measurements. Histological sections showed that the fresh and... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708918 Sun, 03 May 2009 23:00:00 +0100 2708918 http://www.medworm.com/index.php?rid=2708926&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000903%2Fabstract%3Frss%3Dyes Abstract: Body segment moments of inertia (MOI) are estimated from data obtained from cadavers or living individuals. Though these methods can be valid for the general population, they usually are limited when applied to special populations (e.g., obese). The effect of two geometric methods, photogrammetry and two new methods, namely, inverse dynamics and angular momentum on the estimations of MOI in individuals of different body mass index (BMI) were compared to gain insight into their relative accuracy. The de Leva (1996) method was chosen as a criterion to determine how these methods behaved. MOI methods were not different in individuals with a normal BMI. On the average, MOI values obtained with inverse dynamics and angular momentum were respectively 13.2% lower for lean participants a... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708926 Wed, 29 Apr 2009 23:00:00 +0100 2708926 http://www.medworm.com/index.php?rid=2367303&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002154%2Fabstract%3Frss%3Dyes Abstract: In total hip replacement (THR) a good initial stability of the prosthetic stem in the femur, which corresponds to a good overall initial contact, will help assure a good long-term result. During the insertion the implant stability increases and, as a consequence, the resonance frequencies increase, allowing the assessment of the implant fixation by vibration analysis. The influence of changing contact conditions on the resonance frequencies was however not yet quantitatively understood and therefore a finite element analysis (FEA) was set up.Modal analyses on the hip stem–femur system were performed in various contact situations. By modelling the contact changes by means of the contact tolerance options in the finite element software, contact could be varied over the entire hip... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367303 Sat, 25 Apr 2009 21:14:48 +0100 2367303 http://www.medworm.com/index.php?rid=2367299&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002099%2Fabstract%3Frss%3Dyes In this study we use an approach based on a combined strain/damage algorithm to simultaneously predict both bulk and interfacial peri-prosthetic bone adaptation around a non-cemented hip prosthesis. The influence of stem stiffness is investigated; a flexible iso-elastic stem (20GPa), an titanium alloy stem (110GPa), and a stiff cobalt chrome (CoCrMo) stem (210GPa). The results predict that an iso-elastic stem reduces proximal bone loss because stress shielding is prevented but it increases proximal interface resorption due to damage-stimulated resorption. On the other hand, a stiff cobalt chrome stem increases proximal strain-stimulated resorption but does not induce proximal interfacial damage-stimulated resorption; however damage-stimulated resorption surrounding the distal tip is predic... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367299 Sat, 25 Apr 2009 21:14:03 +0100 2367299 http://www.medworm.com/index.php?rid=2367294&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000368%2Fabstract%3Frss%3Dyes Abstract: This paper describes the application of probabilistic design methods to the analysis of the behaviour of an uncemented total hip replacement femoral component implanted in a proximal femur. Probabilistic methods allow variations in factors which control the behaviour of the implanted femur (the input parameters) to be taken into account in determining the performance of the construct. Monte Carlo sampling techniques were applied and the performance indicator was the maximum strain in the bone. The random input parameters were the joint load, the angle of the applied load and the material properties of the bone and the implant. Two Monte Carlo based simulations were applied, direct sampling and latin hypercube sampling. The results showed that the convergence of the mean value of ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367294 Sat, 25 Apr 2009 21:10:56 +0100 2367294 http://www.medworm.com/index.php?rid=2367289&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002075%2Fabstract%3Frss%3Dyes This study tested the in vivo performance of novel FRC implants made of unidirectional glass fibers (E-glass fibers in Bis-GMA and TEGDMA polymeric matrix). The implant surface was covered with bioactive glass granules. Control implants were made of surface-roughened titanium. Stress-shielding effects of the implants were predicted by finite element modelling (FEM). Surgical stabilization of bone metastasis in the subtrochanteric region of the femur was simulated in 12 rabbits. An oblong subtrochanteric defect of a standardized size (reducing the torsional strength of the bones approximately by 66%) was created and an intramedullary implant made of titanium or the FRC composite was inserted. The contralateral femur served as the intact control. At 12 weeks of healing, the femurs were harve... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367289 Sat, 25 Apr 2009 21:09:11 +0100 2367289 http://www.medworm.com/index.php?rid=2367284&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002026%2Fabstract%3Frss%3Dyes Abstract: The goal of this research is to develop a 3D finite element (FE) model of a left ventricular assist device (LVAD) to predict stresses in the blood sac. The hyperelastic stress–strain curves for the segmented poly(ether polyurethane urea) (SPEUU) blood sac were determined in both tension and compression using a servo-hydraulic testing system at various strain rates. Over the range of strain rates studied, the sac was not strain rate sensitive, however the material response was different for tension versus compression. The experimental tension and compression properties were used in a FE model that consisted of the pusher plate, blood sac and pump case. A quasi-static analysis was used to allow for nonlinearities due to contact and material deformation. The 3D FE model showed tha... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367284 Sat, 25 Apr 2009 21:07:05 +0100 2367284 http://www.medworm.com/index.php?rid=2367278&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002105%2Fabstract%3Frss%3Dyes In this study, a finite element based modelling strategy is proposed to investigate and optimize the mechanics of braided stents. First a geometrical and finite element model of a braided Urolume endoprosthesis was built with the open source pyFormex design tool. The results of the reference simulation of the Urolume stent are in close agreement with both analytical and experimental data. Subsequently, a simplex-based design optimization algorithm automatically adjusts the reference Urolume geometry to facilitate precise positioning by reducing the foreshortening with 20% while maintaining the radial stiffness. Therefore, the proposed modelling strategy appears to be a promising optimization methodology in braided stent design. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367278 Sat, 25 Apr 2009 21:04:29 +0100 2367278 http://www.medworm.com/index.php?rid=2367274&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330800204X%2Fabstract%3Frss%3Dyes This study compares the mechanical effects of the expansion of five different designs of balloon-expandable stents in a coronary artery by means of numerical models based on the finite element method. An index for the evaluation of the tissue prolapse based on the expanded configuration reached by the stent cells is proposed. The effects of the balloon inflation and deflation are included in the present study. Wall stresses and tissue prolapse of the vessel wall within the stent cells are evaluated and compared among the different stent designs. Results show that the printed area does not predict prolapse, and that the proposed index (PI) does correlate with tissue prolapse. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367274 Sat, 25 Apr 2009 21:02:54 +0100 2367274 http://www.medworm.com/index.php?rid=2367270&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002038%2Fabstract%3Frss%3Dyes In this study, one of the currently applied techniques is analysed which involves the implantation of a stent in the main branch, followed by subsequent inflation of a balloon through the side of the stent. This improves the side branch patency and provides access to the side branch for later stent implantations. The impact of using different balloon sizes and stent designs was investigated. The stent cell through which the balloon is inflated increases considerably and as intuitively expected, using a larger balloon results in a larger opening. Furthermore, it was observed that this procedure may compromise the downstream main branch lumen. These observations correspond well with previously reported results, which were based on in vitro studies. The added value of the proposed numerical m... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367270 Sat, 25 Apr 2009 21:01:31 +0100 2367270 http://www.medworm.com/index.php?rid=2367265&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002063%2Fabstract%3Frss%3Dyes Abstract: Intracoronary stent implantation is a mechanical procedure, the success of which depends to a large degree on the mechanical properties of each vessel component involved and the pressure applied to the balloon. Little is known about the influence of plaque composition on arterial overstretching and the subsequent injury to the vessel wall following stenting. An idealised finite element model was developed to investigate the influence of both plaque types (hypercellular, hypocellular and calcified) and stent inflation pressures (9, 12 and 15atm) on vessel and plaque stresses during the implantation of a balloon expandable coronary stent into an idealised stenosed artery. The plaque type was found to have a significant influence on the stresses induced within the artery during sten... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367265 Sat, 25 Apr 2009 20:59:48 +0100 2367265 http://www.medworm.com/index.php?rid=2367260&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453308002051%2Fabstract%3Frss%3Dyes Abstract: Tissue-engineered bone shows promise in meeting the huge demand for bone grafts caused by up to 4 million bone replacement procedures per year, worldwide. State-of-the-art bone tissue engineering strategies use flow perfusion bioreactors to apply biophysical stimuli to cells seeded on scaffolds and to grow tissue suitable for implantation into the patient's body. The aim of this study was to quantify the deformation of cells seeded on a collagen-GAG scaffold which was perfused by culture medium inside a flow perfusion bioreactor. Using a μCT scan of an unseeded collagen-GAG scaffold, a sequential 3D CFD-deformation model was developed. The wall shear stress and the hydrostatic wall pressure acting on the cells were computed through the use of a CFD simulation and fed into a line... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367260 Sat, 25 Apr 2009 20:57:27 +0100 2367260 http://www.medworm.com/index.php?rid=2367258&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000733%2Fabstract%3Frss%3Dyes Society expects effective and reliable medical devices. Clinical trials are the ultimate test, but engineers need to test devices before they are ever implanted in patients . Such pre-clinical tests include computational modelling, animal experimentation, and bench testing with physical models and cadavers. It is computational modelling that is undergoing the most rapid growth at the moment; increasing computational power is becoming available; imaging allows the creation of patient-specific models; and the algorithms behind mechano-regulated processes are being discovered. Indeed, combining these aspects to create ‘virtual environments’ as platforms for testing medical devices has set new goals for bioengineering of medical devices . (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367258 Sat, 25 Apr 2009 20:56:24 +0100 2367258 http://www.medworm.com/index.php?rid=2367256&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000800%2Fabstract%3Frss%3Dyes (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2367256 Sat, 25 Apr 2009 20:56:16 +0100 2367256 http://www.medworm.com/index.php?rid=3366023&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000770%2Fabstract%3Frss%3Dyes This study characterizes pediatric wheelchair kinematic responses and wheelchair tiedown and occupant restraint system (WTORS) loading during rear impact. It also examines the kinematic and loading effects of wheelchair headrest inclusion in rear impact. In two separate rear-impact test scenarios, identical WC19-compliant manual pediatric wheelchairs were tested using a seated Hybrid III 6-year-old anthropomorphic test device (ATD) to evaluate wheelchair kinematics and WTORS loading. Three wheelchairs included no headrests, and three were equipped with slightly modified wheelchair-mounted headrests. Surrogate WTORS properly secured the wheelchairs; three-point occupant restraints properly restrained the ATD. All tests used a 26km/h, 11g rear-impact test pulse. Headrest presence affected wh... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366023 Fri, 24 Apr 2009 00:00:00 +0100 3366023 http://www.medworm.com/index.php?rid=3366017&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000381%2Fabstract%3Frss%3Dyes Conclusions: WhMD users have a greater chance of incurring injury during ingress/egress than during transit. Research is needed to objectively assess real world transportation experiences of WhMD passengers, and to assess the adequacy of existing federal legislation/guidelines for accessible ramps used in public transportation. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=3366017 Thu, 23 Apr 2009 00:00:00 +0100 3366017 http://www.medworm.com/index.php?rid=2708916&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000757%2Fabstract%3Frss%3Dyes Conclusion This study showed that the anisotropic behaviour of bone cannot be neglected in the numerical simulations. The actual design of the prosthesis is not optimal concerning the capacity of all metallic parts to support loads. Finally, it was demonstrated that the tilting of implants induced a high stress level at bone-implant interface. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708916 Wed, 22 Apr 2009 23:00:00 +0100 2708916 http://www.medworm.com/index.php?rid=2708915&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000745%2Fabstract%3Frss%3Dyes Abstract: Clinical and experimental studies indicate that structural and functional changes in the microvasculature can predate or accompany risk factors for cardiovascular disease at the earliest stages in the disease process. In the current work, both simulated and actual Doppler ultrasound maximum blood velocity waveform envelopes recorded from the ophthalmic artery were analysed using a root-MUSIC and least squares fitting approach to determine amplitude frequency spectra. Both amplitude and frequency components of noise contaminated simulated waveforms were reliably determined indicating the robustness of the technique. The technique was then used to compare the spectral content of the ophthalmic artery blood velocity waveforms of normal controls in three test states: at baseline, fol... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708915 Thu, 16 Apr 2009 23:00:00 +0100 2708915 http://www.medworm.com/index.php?rid=2708907&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000782%2Fabstract%3Frss%3Dyes This article reviews the role of cavitation in the therapeutic applications of ultrasound and laser surgery, and the cavitation effects in mechanical heart valves. Whenever laser pulses are used to ablate or disrupt tissue in a liquid environment, cavitation bubbles are produced which interact with the tissue. The interaction between cavitation bubbles and tissue during pulsed laser surgery may cause collateral damage to sensitive tissue structures in the vicinity of the laser focus, and it may also contribute in several ways to ablation and cutting. Cavitation is also one of the most exploited bioeffects of ultrasound for therapeutic advantage. In both cases, the violent implosion of cavitation bubbles can lead to the generation of shock waves, high-velocity liquid jets, free radical spec... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708907 Wed, 08 Apr 2009 23:00:00 +0100 2708907 http://www.medworm.com/index.php?rid=2708917&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000769%2Fabstract%3Frss%3Dyes Abstract: The sensitivity of shear stress over smooth muscle cells (SMCs) to the deformability of media layer due to pressure is investigated in thoracic aorta wall using three-dimensional simulations. A biphasic, anisotropic model assuming the radius, thickness, and hydraulic conductivity of vessel wall as functions of transmural pressure is employed in numerical simulations. The leakage of interstitial fluid from intima to media layer is only possible through fenestral pores on the internal elastic lamina (IEL). The media layer is assumed a heterogeneous medium containing SMCs embedded in a porous extracellular matrix of elastin, proteoglycan, and collagen fibers. The applicable pressures for the deformation of media layer are varied from 0 to 180mmHg. The SMCs are cylindrical objects of... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708917 Tue, 07 Apr 2009 23:00:00 +0100 2708917 http://www.medworm.com/index.php?rid=2300941&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19329044%26dopt%3DAbstract Authors: Prendergast PJ, Lally C, Lennon AB PMID: 19329044 [PubMed - in process] (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2300941 Fri, 03 Apr 2009 07:29:47 +0100 2300941 http://www.medworm.com/index.php?rid=2708914&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000708%2Fabstract%3Frss%3Dyes Abstract: The aims of this study were to predict and explain the patterns of ligament forces in the stump of a left trans-tibial amputee during walking, and to study the effects of the prosthetic alignment. Musculoskeletal modeling and computer simulation were combined to calculate ligament forces. The prosthesis was aligned to be in optimal position for the subject and then changed by ±6° in the sagittal plane. The results showed most ligaments bearing the maximum tension forces around both heel-strike and toe-off. The PT force was the biggest in all of the ligaments which were studied. The load patterns of ACL and PCL were opposite in the gait cycle, but the load patterns of MCL and LCL appeared similar. The above results showed that the ligament forces increased at the incorrect align... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708914 Thu, 02 Apr 2009 23:00:00 +0100 2708914 http://www.medworm.com/index.php?rid=2522428&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000721%2Fabstract%3Frss%3Dyes I recently read the article from Affatato S. et al., which was aimed to give a review of the actual and up-to-date concepts in biotribology. I paid particular attention to the part that addressed the different joint simulators available as I do represent one of them: AMTI (Advanced Mechanical Technology, Inc.). (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2522428 Thu, 02 Apr 2009 23:00:00 +0100 2522428 http://www.medworm.com/index.php?rid=2708913&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900071X%2Fabstract%3Frss%3Dyes Abstract: The first objective of this study was to determine the kinematic variability of the lower extremity joints using methods from the mathematical chaos theory in a normal walking environment in conjunction with a large population of healthy young adults. The second objective was to test the hypothesis that variability characteristics are different between joints and to further investigate differences between male and female and right and left subgroups. A total of forty young healthy subjects (20 males: 24.1±3.1 years; 20 females: 22.5±3.2 years) volunteered, and their joint motions were captured while walking on a treadmill for 90s in order to estimate Lyapunov Exponent (LE) values. Means and standard deviations of the LEs ranged from 0.035±0.016 (right ankle) to 0.073±0.023 (l... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708913 Fri, 27 Mar 2009 00:00:00 +0100 2708913 http://www.medworm.com/index.php?rid=2300942&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19328033%26dopt%3DAbstract Authors: Son K, Park J, Park S The first objective of this study was to determine the kinematic variability of the lower extremity joints using methods from the mathematical chaos theory in a normal walking environment in conjunction with a large population of healthy young adults. The second objective was to test the hypothesis that variability characteristics are different between joints and to further investigate differences between male and female and right and left subgroups. A total of forty young healthy subjects (20 males: 24.1+/-3.1 years; 20 females: 22.5+/-3.2 years) volunteered, and their joint motions were captured while walking on a treadmill for 90s in order to estimate Lyapunov Exponent (LE) values. Means and standard deviations of the LEs ranged from 0.035+/-0.016 (rig... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2300942 Wed, 25 Mar 2009 04:00:00 +0100 2300942 http://www.medworm.com/index.php?rid=2708911&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000691%2Fabstract%3Frss%3Dyes In this study, we propose the use of the BI technique for the evaluation of gastric motility considering global features of the fast FFT spectra. The study was performed in eleven healthy subjects who were evaluated in fasting and postprandial conditions. The results indicate that the use of the median of the area under the FFT spectra is equivalent to the use of the main peak of the spectra to determine the changes in gastric motility from the fasting to the postprandial state. This demonstrates that BI is a valid technique for gastric motility evaluation in short time recordings. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708911 Mon, 23 Mar 2009 00:00:00 +0100 2708911 http://www.medworm.com/index.php?rid=2300943&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19303803%26dopt%3DAbstract In this study, we propose the use of the BI technique for the evaluation of gastric motility considering global features of the fast FFT spectra. The study was performed in eleven healthy subjects who were evaluated in fasting and postprandial conditions. The results indicate that the use of the median of the area under the FFT spectra is equivalent to the use of the main peak of the spectra to determine the changes in gastric motility from the fasting to the postprandial state. This demonstrates that BI is a valid technique for gastric motility evaluation in short time recordings. PMID: 19303803 [PubMed - as supplied by publisher] (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2300943 Thu, 19 Mar 2009 04:00:00 +0100 2300943 http://www.medworm.com/index.php?rid=2708912&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS135045330900068X%2Fabstract%3Frss%3Dyes Abstract: The detailed quantitative characterization of soft-tissue in-growth into highly porous artificial implants is critical to understanding the biophysical processes that will lead to the best structural scaffolding construct. Previous studies have performed mechanical peel tests and mostly qualitative histological analyses of soft-tissue. The goal of this paper is to report the results obtained from applying two image analysis algorithms to quantify the morphological structure found in histological images of stained soft-tissue in-growth into alumina ceramic foam metal implants using a canine model. Three different pore sizes were used and three different post-operative time points were considered. Using the 2D Wavelet Transform Modulus Maxima method and 2D Fourier Transform analysi... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708912 Wed, 18 Mar 2009 00:00:00 +0100 2708912 http://www.medworm.com/index.php?rid=2708910&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000551%2Fabstract%3Frss%3Dyes Abstract: Stability of dental implants is measured by means of the Osstell® device using a method of resonance frequency analysis. The aim of the study was to evaluate the role of direction-dependence of the Osstell® transducer. For this purpose, a set of parametrical finite element analyses has been used.When rotating the transducer around the vertical axis the crucial phenomenon is the change in behavior of the system, which occurs in positions between 30° and 80° to the long axis of the alveolar crest. It seems from the presented results that, when measuring approximately perpendicularly to this long axis, the deviation from the ideal perpendicular position must not exceed 30°. In this case, the first resonance frequency is recorded. When measuring in the approximately parallel pos... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708910 Wed, 18 Mar 2009 00:00:00 +0100 2708910 http://www.medworm.com/index.php?rid=2285279&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19297232%26dopt%3DAbstract Authors: Capek L, Simunek A, Slezak R, Dzan L Stability of dental implants is measured by means of the Osstell((R)) device using a method of resonance frequency analysis. The aim of the study was to evaluate the role of direction-dependence of the Osstell((R)) transducer. For this purpose, a set of parametrical finite element analyses has been used. When rotating the transducer around the vertical axis the crucial phenomenon is the change in behavior of the system, which occurs in positions between 30 degrees and 80 degrees to the long axis of the alveolar crest. It seems from the presented results that, when measuring approximately perpendicularly to this long axis, the deviation from the ideal perpendicular position must not exceed 30 degrees . In this case, the first resonance frequ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2285279 Mon, 16 Mar 2009 04:00:00 +0100 2285279 http://www.medworm.com/index.php?rid=2285278&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19297233%26dopt%3DAbstract Authors: Khalil A, Aponte C, Zhang R, Davisson T, Dickey I, Engelman D, Hawkins M, Mason M The detailed quantitative characterization of soft-tissue in-growth into highly porous artificial implants is critical to understanding the biophysical processes that will lead to the best structural scaffolding construct. Previous studies have performed mechanical peel tests and mostly qualitative histological analyses of soft-tissue. The goal of this paper is to report the results obtained from applying two image analysis algorithms to quantify the morphological structure found in histological images of stained soft-tissue in-growth into alumina ceramic foam metal implants using a canine model. Three different pore sizes were used and three different post-operative time points were considered. ... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2285278 Mon, 16 Mar 2009 04:00:00 +0100 2285278 http://www.medworm.com/index.php?rid=2708906&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000538%2Fabstract%3Frss%3Dyes Abstract: According to “Wolff's Law”, bone is deposited and reinforced at areas of greatest stress. From a clinical perspective, this “law” is supported by the strong association between bone density and physical activity. From a mechanistic standpoint, however, the law presents a challenge to scientists seeking to understand how osteocytes and osteoblasts sense the mechanical load. In the 1960s, collagen piezoelectricity was invoked as a potential mechanism by which osteocytes could detect areas of greater stress but piezoelectricity diminished in importance as more compelling mechanisms, such as streaming potential, were identified. In addition, accumulating evidence for the role of fluid-related shear stress in osteocyte's mechanosensory function has made piezoelectricity seemin... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708906 Mon, 16 Mar 2009 00:00:00 +0100 2708906 http://www.medworm.com/index.php?rid=2275175&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19286413%26dopt%3DAbstract Authors: Ahn AC, Grodzinsky AJ According to "Wolff's Law", bone is deposited and reinforced at areas of greatest stress. From a clinical perspective, this "law" is supported by the strong association between bone density and physical activity. From a mechanistic standpoint, however, the law presents a challenge to scientists seeking to understand how osteocytes and osteoblasts sense the mechanical load. In the 1960s, collagen piezoelectricity was invoked as a potential mechanism by which osteocytes could detect areas of greater stress but piezoelectricity diminished in importance as more compelling mechanisms, such as streaming potential, were identified. In addition, accumulating evidence for the role of fluid-related shear stress in osteocyte's mechanosensory function has made piezoe... Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2275175 Fri, 13 Mar 2009 04:00:00 +0100 2275175 http://www.medworm.com/index.php?rid=2708908&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000575%2Fabstract%3Frss%3Dyes This study has demonstrated that there is a large increase in strain, antero-medially on the proximal tibia, following implantation with a unicompartmental knee replacement. This may be the cause of antero-medial pain. As the bone remodels over time this strain will decrease, which probably explains why the pain usually settles within 12 months after surgery. However, certain errors in implantation result in strain values that might lead to degenerative remodelling and/or increased micro-damage of the bone; this may explain why the pain progressively worsens in some cases. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708908 Thu, 12 Mar 2009 00:00:00 +0100 2708908 http://www.medworm.com/index.php?rid=2261195&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19278893%26dopt%3DAbstract This study has demonstrated that there is a large increase in strain, antero-medially on the proximal tibia, following implantation with a unicompartmental knee replacement. This may be the cause of antero-medial pain. As the bone remodels over time this strain will decrease, which probably explains why the pain usually settles within 12 months after surgery. However, certain errors in implantation result in strain values that might lead to degenerative remodelling and/or increased micro-damage of the bone; this may explain why the pain progressively worsens in some cases. PMID: 19278893 [PubMed - as supplied by publisher] (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2261195 Mon, 09 Mar 2009 04:00:00 +0100 2261195 http://www.medworm.com/index.php?rid=2708909&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000563%2Fabstract%3Frss%3Dyes Conclusion: Strains on the cortical bone around two implant supported, 3-unit screw- or cement-retained fixed prostheses, fabricated either by direct or indirect impression techniques on Straumann dental implants, are similar under a 150N static load. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2708909 Mon, 09 Mar 2009 00:00:00 +0100 2708909 http://www.medworm.com/index.php?rid=2522427&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.medengphys.com%2Farticle%2FPIIS1350453309000526%2Fabstract%3Frss%3Dyes This study suggested the lubrication performance especially the film thickness distribution should vary greatly under different operating conditions and the time and location that potential wear may occur was very sensitive to specific loading and motion conditions. This may provide some explanation to the large variations in wear from hip simulators and clinical studies, and also stress the importance of using more realistic loading and motion conditions in the tribological study of MOM hip prostheses. (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2522427 Mon, 09 Mar 2009 00:00:00 +0100 2522427 http://www.medworm.com/index.php?rid=2261197&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19269878%26dopt%3DAbstract CONCLUSION: Strains on the cortical bone around two implant supported, 3-unit screw- or cement-retained fixed prostheses, fabricated either by direct or indirect impression techniques on Straumann dental implants, are similar under a 150N static load. PMID: 19269878 [PubMed - as supplied by publisher] (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2261197 Fri, 06 Mar 2009 05:00:00 +0100 2261197 http://www.medworm.com/index.php?rid=2261196&cid=s_35854_169_f&fid=35854&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19269879%26dopt%3DAbstract This study suggested the lubrication performance especially the film thickness distribution should vary greatly under different operating conditions and the time and location that potential wear may occur was very sensitive to specific loading and motion conditions. This may provide some explanation to the large variations in wear from hip simulators and clinical studies, and also stress the importance of using more realistic loading and motion conditions in the tribological study of MOM hip prostheses. PMID: 19269879 [PubMed - as supplied by publisher] (Source: Medical Engineering and Physics) Medical Engineering and Physics journals http://www.medworm.com/rss/comments.php?id=2261196 Fri, 06 Mar 2009 05:00:00 +0100 2261196