MedWorm: Biomedical Engineering Top 20

Assessment of Crohn’s Disease Lesions in Wireless Capsule Endoscopy Images

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:08 +0100

Capsule endoscopy (CE) provides noninvasive access to a large part of the small bowel that is otherwise inaccessible without invasive and traumatic treatment. However, it also produces large amounts of data (approximately 50 000 images) that must be then manually reviewed by a clinician. Such large datasets provide an opportunity for application of image analysis and supervised learning methods. Automated analysis of CE images has only focused on detection, and often only for bleeding. Compared to these detection approaches, we explored assessment of discrete disease for lesions created by mucosal inflammation in Crohn’s disease (CD). Our work is the first study to systematically explore supervised classification for CD lesions, a classifier cascade to classify discrete lesio...

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Research4Life

Elsevier Updates: Engineering — Sat, 04 Feb 2012 12:00:12 +0100

Elsevier is a founding partner and leading contributor to Research4Life, a public private partnership, providing developing countries with low or low cost access to academic and peer reviewed content online for four programs HINARI, AGORA, OARE and ARDI. (Source: Elsevier Updates: Engineering)

Online Tissue Discrimination for Transcutaneous Needle Guidance Applications Using Broadband Impedance Spectroscopy

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

This paper reports on a novel system architecture for measuring impedance spectra of a biological tissue close to the tip of a hollow needle. The measurement is performed online using fast broadband chirp signals. The time domain measurement raw data are transformed into the transfer function of the tissue in frequency domain. Correlation technique is used to analyze the characteristic shape of the derived tissue transfer function with respect to known “library functions” for different types of tissue derived in earlier experiments. Based on the resulting correlation coefficients the exact type of tissue is determined. A bipolar coaxial needle is constructed, simulated by finite element method and tested during various in vitro and in vivo experiments. The results show a good...

Cross Validation for Selection of Cortical Interaction Models From Scalp EEG or MEG

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

A cross-validation (CV) method based on state-space framework is introduced for comparing the fidelity of different cortical interaction models to the measured scalp electroencephalogram (EEG) or magnetoencephalography (MEG) data being modeled. A state equation models the cortical interaction dynamics and an observation equation represents the scalp measurement of cortical activity and noise. The measured data are partitioned into training and test sets. The training set is used to estimate model parameters and the model quality is evaluated by computing test data innovations for the estimated model. Two CV metrics normalized mean square error and log-likelihood are estimated by averaging over different training/test partitions of the data. The effectiveness of this method of model selecti...

Automated Algorithm for Generalized Tonic–Clonic Epileptic Seizure Onset Detection Based on sEMG Zero-Crossing Rate

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:10 +0100

Patients are not able to call for help during a generalized tonic–clonic epileptic seizure. Our objective was to develop a robust generic algorithm for automatic detection of tonic–clonic seizures, based on surface electromyography (sEMG) signals suitable for a portable device. Twenty-two seizures were analyzed from 11 consecutive patients. Our method is based on a high-pass filtering with a cutoff at 150 Hz, and monitoring a count of zero crossings with a hysteresis of $pm 50,mu hbox{V}$ . Based on data from one sEMG electrode (on the deltoid muscle), we achieved a sensitivity of 100% with a mean detection latency of 13.7 s, while the rate of false detection was limited to 1 false alarm per 24 h. The overall performance of the presented generic algorith...

DiBa: A Data-Driven Bayesian Algorithm for Sleep Spindle Detection

IEEE Transactions on Biomedical Engineering — Wed, 01 Feb 2012 05:00:00 +0100

Although the spontaneous brain rhythms of sleep have commanded much recent interest, their detection and analysis remains suboptimal. In this paper, we develop a data-driven Bayesian algorithm for sleep spindle detection on the electroencephalography (EEG). The algorithm exploits the Karhunen–Loève transform and Bayesian hypothesis testing to produce the instantaneous probability of a spindle’s presence with maximal resolution. In addition to possessing flexibility, transparency, and scalability, this algorithm could perform at levels superior to standard methods for EEG event detection. (Source: IEEE Transactions on Biomedical Engineering)

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Investigation of Standing-Wave Formation in a Human Skull for a Clinical Prototype of a Large-Aperture, Transcranial MR-Guided Focused Ultrasound (MRgFUS) Phased Array: An Experimental and Simulation Study

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number. (Source: IEEE Transactions on Biomedical Engineering)

Accurate Automatic Analysis of Cardiac Cine Images

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

Acquisition of noncontrast agent cine cardiac magnetic resonance (CMR) gated images through the cardiac cycle is, at present, a well-established part of examining cardiac global function. However, regional quantification is less well established. We propose a new automated framework for analyzing the wall thickness and thickening function on these images that consists of three main steps. First, inner and outer wall borders are segmented from their surrounding tissues with a geometric deformable model guided by a special stochastic speed relationship. The latter accounts for Markov-Gibbs shape and appearance models of the object-of-interest and its background. In the second step, point-to-point correspondences between the inner and outer borders are found by solving the Laplace equation an...

Switchable Faraday Shielding With Application to Reducing the Pain of Internal Cardiac Defibrillation While Permitting External Defibrillation

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:08 +0100

In this study, electrostatic finite element modeling was used to assess the effect of different shield geometries on the leakage of an internally applied field and penetration of an externally applied field. “Switching OFF” the shield by electrically disconnecting shield faces from each other was shown to significantly increase external field penetration. Applying this model to defibrillation, we looked at the effect of spacing and size of shield panels to maximize the ability to deliver an external defibrillation shock to the heart when shield panels are disconnected while providing acceptably low leakage of internal defibrillation shocks to avoid painful skeletal muscle capture when shield panels are connected. This analysis may be useful for designing internal defibrillato...

A Direct Dynamic Dose-Response Model of Propofol for Individualized Anesthesia Care

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:10 +0100

In an effort to open up new opportunities in individualized anesthesia care, this paper presents a dynamic dose-response model of propofol that relates propofol dose (i.e., infusion rate) directly to a clinical effect. The proposed model consists of a first-order equilibration dynamics plus a nonlinear Hill equation model, each representing the transient distribution of propofol dose from the plasma to the effect site and the steady-state dose-effect relationship. Compared to traditional pharmacokinetic-pharmacodynamic (PKPD) models, the proposed model has structural parsimony and comparable predictive capability, making it more attractive than its PKPD counterpart for identifying an individualized dose-response model in real-time. The efficacy of the direct dynamic dose-response model ove...

Automated Detection of Dual p16/Ki67 Nuclear Immunoreactivity in Liquid-Based Pap Tests for Improved Cervical Cancer Risk Stratification.

Annals of Biomedical Engineering — Wed, 04 Jan 2012 05:00:00 +0100

In this study, an automated technique for the evaluation of dual p16/Ki67 immunoreactivity in cervical cell nuclei is introduced. Smears stained with p16 and Ki67 antibodies were digitized, and analyzed by algorithms we developed. Gradient-based radial symmetry operator and adaptive processing of symmetry image were employed to obtain the nuclear mask. This step was followed by the extraction of features including pixel data and immunoreactivity signature from each nucleus. The features were analyzed by two support vector machine classifiers to assign a nucleus into one of four types of immunoreactivity: p16 positive (p16(+)/Ki67(-)), Ki67 positive (p16(-)/Ki67(+)), dual p16/Ki67 positive (p16(+)/Ki67(+)) and negative (p16(-)/Ki67(-)), respectively. Results obtained by our method correlate...

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Deep-Tissue Dynamic Monitoring of Decubitus Ulcers: Wound Care and Assessment

IEEE Engineering in Medicine and Biology — Thu, 01 Jan 1970 00:00:00 +0100

The use of deep-tissue multiwavelength imaging is of paramount importance in clinical settings as a noninvasive solution to identify andmonitor the progression of decubitus ulcers. A point-of-care multiwavelength imager is being developed, whose utility results from the provision of important physiological characteristics and blood flow metrics via analysis of deep-tissue response to light. The noninvasive real-time monitoring and analysis of tissue focusing on wound imaging is integral, because it allows for quantitative in situ measurements that characterize tissue to assess the progress of either tissue healing or necrosis. (Source: IEEE Engineering in Medicine and Biology)

Modeling the Slow Wave Shapes of Spreading Depression in a Rat Cortex: A Methodology for Seeking Physiological Parameters

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

Spreading depression (SD) consists of a transient significant suppression of the spontaneous neural electrical activity that spreads slowly across regions of the gray matter in a wave form. Nowadays, this phenomenon is being studied by means of mathematical and computational models to reproduce the main characteristics of SD. Given the high number of parameters and their unknown ranges of variation, the setting of parameters for current SD models is usually a hard task that must be addressed in order to make such models reproduce real data. In this paper, we present a 1-D model which is able to reproduce the most important characteristics of SD waves observed in laboratory experiments: the slow extracellular potential shift and extracellular ionic concentration variations regarding speed, ...

A coupled biventricular finite element and lumped-parameter circulatory system model of heart failure.

Computer Methods in Biomechanics and Biomedical Engineering — Mon, 16 Jan 2012 05:00:00 +0100

Authors: Wenk JF, Ge L, Zhang Z, Soleimani M, Potter DD, Wallace AW, Tseng E, Ratcliffe MB, Guccione JM Abstract Numerical modelling of the cardiovascular system is becoming an important tool for assessing the influence of heart disease and treatment therapies. In the current study, we present an approach for modelling the interaction between the heart and the circulatory system. This was accomplished by creating animal-specific biventricular finite element (FE) models, which characterise the mechanical response of the heart, and by coupling them to a lumped-parameter model that represents the systemic and pulmonic circulatory system. In order to minimise computation time, the coupling was enforced in a weak (one-way) manner, where the ventricular pressure-volume relationships were...

How the blood pool properties at onset affect the temporal behavior of simulated bruises

Medical and Biological Engineering and Computing — Fri, 20 Jan 2012 07:46:58 +0100

In conclusion, bruise behavior depends non-intuitively on the initial blood pool properties; hence, a model that includes shape, area and concentration distribution at onset is indispensable. Future age determination, including inhomogeneous hemoglobin distributions, will likely be based on the presented method for gaussian distributions. Content Type Journal ArticleCategory Original ArticlePages 1-7DOI 10.1007/s11517-012-0860-5Authors Barbara Stam, Biomedical Engineering and Physics, Academic Medical Centre, P.O. Box 22660, 1100 DD Amsterdam, The NetherlandsMartin J. C. van Gemert, Biomedical Engineering and Physics, Academic Medical Centre, P.O. Box 22660, 1100 DD Amsterdam, The NetherlandsTon G. van Leeuwen, Biomedical Engineering and Physics, Academic Medical Centre, P.O. Box...

Sparse-Grid-Based Adaptive Model Predictive Control of HL60 Cellular Differentiation

IEEE Transactions on Biomedical Engineering — Wed, 25 Jan 2012 14:46:09 +0100

This study develops a sparse-grid-based adaptive model predictive control (MPC) strategy to direct HL60 cellular differentiation. Sparse-grid sampling and interpolation support a computationally efficient adaptive MPC scheme in which multiple data-consistent regions of the model parameter space are identified and used to calculate a control compromise. The algorithm is evaluated in silico with structural model mismatch. Simulations demonstrate how the multiscenario control strategy more effectively manages the mismatch compared to a single scenario approach. Furthermore, the controller is evaluated in vitro to differentiate HL60 cells in both normal and perturbed environments. The controller-derived input sequence successfully achieves and sustains the specified target level of granulocyte...

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IEEE Transactions on Signal Processing Edics

IEEE Transactions on Signal Processing — Thu, 19 Jan 2012 13:01:45 +0100

(Source: IEEE Transactions on Signal Processing)

A Novel Hierarchical Bayesian Approach for Sparse Semisupervised Hyperspectral Unmixing

IEEE Transactions on Signal Processing — Thu, 19 Jan 2012 13:01:43 +0100

In this paper the problem of semisupervised hyperspectral unmixing is considered. More specifically, the unmixing process is formulated as a linear regression problem, where the abundance's physical constraints are taken into account. Based on this formulation, a novel hierarchical Bayesian model is proposed and suitable priors are selected for the model parameters such that, on the one hand, they ensure the nonnegativity of the abundances, while on the other hand they favor sparse solutions for the abundances' vector. Performing Bayesian inference based on the proposed hierarchical Bayesian model, a new low-complexity iterative method is derived, and its connection with Gibbs sampling and variational Bayesian inference is highlighted. Experimental results on both synthetic and real hypers...

Upregulation of SDF-1 is Associated with Atherosclerosis Lesions Induced by LDL Concentration Polarization.

Annals of Biomedical Engineering — Wed, 04 Jan 2012 05:00:00 +0100

In this study, ten rabbits were treated with gel-silica loop to develop a defined local stenosis in the straight segment of the left carotid artery. Both numerical simulation and experiment measurements showed that the concentration of LDL was about 35% higher at the blood/arterial wall interface than in the lumen on the distal side of the stenosis. Atherosclerotic lesions with abundant lipid deposits were observed and stromal derived factor-1 (SDF-1) was detected at the distal end of the stenosis, while the straight segment was plaque-free. In vitro studies demonstrated that LDL-induced SDF-1 expression in endothelial cells and increased monocyte adhesion to endothelial cells in a dose-dependent manner. The adhesion was suppressed when endothelial cells were pretreated with SDF-1 antibody...

Functionalized Nanowire-Based Antigen Detection Using Frequency-Based Signals

IEEE Transactions on Biomedical Engineering — Wed, 21 Dec 2011 00:24:57 +0100

As part of clinical diagnosis, a clinician is required to detect disease causing antigens, bacteria, or viruses in serum, saliva, or other biological samples. Usually, this requires the sample to be sent to a pathology laboratory for analysis. Silicon nanowires can be made into sensitive molecular sensors. When being functionalized with antibodies, they are capable of detecting femto molar concentrations of antigens in real time. Biological molecules at a pH different from their isoelectric point exhibit a net charge. When an antigen attaches to the antibody on the nanowire, the net charged on the antigen displaces free carriers in the nanowire changing its conductance. To date, detection methods have been based upon directly measuring the change in dc conductance. This is difficult and re...