MedWorm: Biomedical Engineering Top 20

Airway Wall Stiffening Increases Peak Wall Shear Stress: A Fluid-Structure Interaction Study in Rigid and Compliant Airways.

Annals of Biomedical Engineering — Wed, 17 Feb 2010 00:00:00 +0100

Authors: Xia G, Tawhai MH, Hoffman EA, Lin CL The airflow characteristics in a computed tomography (CT) based human airway bifurcation model with rigid and compliant walls are investigated numerically. An in-house three-dimensional (3D) fluid-structure interaction (FSI) method is applied to simulate the flow at different Reynolds numbers and airway wall stiffness. As the Reynolds number increases, the airway wall deformation increases and the secondary flow becomes more prominent. It is found that the peak wall shear stress on the rigid airway wall can be five times stronger than that on the compliant airway wall. When adding tethering forces to the model, we find that these forces, which produce larger airway deformation than without tethering, lead to more skewed velocity profiles in...

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Fast and continuous plasma extraction from whole human blood based on expanding cell-free layer devices.

Biomedical Microdevices — Sat, 06 Mar 2010 00:00:00 +0100

Authors: Sollier E, Cubizolles M, Fouillet Y, Achard JL This paper presents promising microfluidic devices designed for continuous and passive extraction of plasma from whole human blood. These designs are based on red cells lateral migration and the resulting cell-free layer locally expanded by geometric singularities such as an enlargement of the channel or a cavity adjacent to the channel. After an explanation of flow patterns, different tests are described that confirm the advantages of both proposed singularities, providing a 1.5 and 2X increase in extraction yield compared to a reference device, for 1:20 diluted blood at 100 microL/min. Devices have also been successively optimized, with extraction yields up to 17.8%, and biologically validated for plasma extraction, with no prot...

Nuclear science symposium and medical imaging conference

IEE Transactions on Medical Imaging — Mon, 01 Mar 2010 00:00:00 +0100

(Source: IEE Transactions on Medical Imaging)

Performance of bench-scale membrane bioreactor under real work conditions using pure oxygen: viscosity and oxygen transfer analysis.

Bioprocess and Biosystems Engineering — Thu, 11 Feb 2010 00:00:00 +0100

Authors: Rodríguez FA, Martínez-Toledo MV, González-López J, Hontoria E, Poyatos JM Pure oxygen to supply the aerobic condition was used in the performance of a bench-scale submerged membrane bioreactor (MBR). The pilot plant was located in the wastewater treatment plant of the city of Granada (Spain) and the experimental work was divided into two stages (Unsteady state and steady state conditions). Operation parameters (MLSS, MLVSS and dissolved oxygen concentration) and physical characteristics (temperature, conductivity, pH, COD and BOD(5)) were daily monitored. The results showed the capacity of the MBR systems to remove organic material under a hydraulic retention time of 18.46 h and sludge retention time of 18.6 days. Therefore, Viscosity of the sludge and alp...

Effects of Scleral Stiffness Properties on Optic Nerve Head Biomechanics.

Annals of Biomedical Engineering — Tue, 29 Dec 2009 00:00:00 +0100

Authors: Eilaghi A, Flanagan JG, Simmons CA, Ethier CR The biomechanical environment within the optic nerve head, important in glaucoma, depends strongly on scleral biomechanical properties. Here we use a range of measured nonlinear scleral stress-strain relationships in a finite element (FE) model of the eye to compute the biomechanical environment in the optic nerve head at three levels of intraocular pressure (IOP). Three stress-strain relationships consistent with the 5th, 50th and 95th percentiles of measured human scleral stiffness were selected from a pool of 30 scleral samples taken from 10 eyes and implemented in a generic FE model of the eye using a hyperelastic five-parameter Mooney-Rivlin material model. Computed strains within optic nerve head tissues depended strongly on ...

Digital Heart-Rate Variability Parameter Monitoring and Assessment ASIC

IEEE Transactions on Biomedical Circuits and Systems — Tue, 26 Jan 2010 16:54:09 +0100

This paper describes experimental results for an application-specific integrated circuit (ASIC), designed for digital heart rate variability (HRV) parameter monitoring and assessment. This ASIC chip measures beat-to-beat (RR) intervals and stores HRV parameters into its internal memory in real time. A wide range of short-term and long-term ECG signals obtained from Physionet was used for testing. The system detects R peaks with millisecond accuracy, and stores up to 2 min of continuous RR interval data and up to 4 min of RR interval histogram. The prototype chip was fabricated in a 0.5- $mu$m complementary metal–oxide semiconductor technology on a 3$,times,$ 3 ${rm mm}^{2}$ die area, with a measured dynamic power consumption of 10 $mu $W and measured leakage current of 2.62 nA. The ...

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Multirate Filterbank Design: A Relaxed Commutant Lifting Approach

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:00 +0100

In this paper, we reformulate the design of the IIR synthesis filters in classical multirate systems as an interpolation problem involving a norm called the ${cal P}_{m}$ norm where $m$ is any positive integer. This interpolation problem can be solved using relaxed commutant lifting techniques in operator theory. The ${cal P}_{m}$ norm is actually a tradeoff in handling energy distortion and error peak distortion. Our development allows the designer to select from a family of filters the one which is best suited for a specific application. The well-known $H^{2}$ and $H^{infty}$ design methods can be viewed as special cases when $m=1$ and $mrightarrowinfty$ respectively. The computation relies mainly on FFT techniques and a finite section of certain Toeplitz matrices. The resulting filters ...

Color Graphs for Automated Cancer Diagnosis and Grading

IEEE Transactions on Biomedical Engineering — Mon, 01 Mar 2010 00:00:00 +0100

This paper reports a new structural method to mathematically represent and quantify a tissue for the purpose of automated and objective cancer diagnosis and grading. Unlike the previous structural methods, which quantify a tissue considering the spatial distributions of its cell nuclei, the proposed method relies on the use of distributions of multiple tissue components for the representation. To this end, it constructs a graph on multiple tissue components and colors its edges depending on the component types of their endpoints. Subsequently, it extracts a new set of structural features from these color graphs and uses these features in the classification of tissues. Working with the images of colon tissues, our experiments demonstrate that the color-graph approach leads to 82.65% test ac...

MRI image-based FE modelling of the pelvis system and bladder filling.

Computer Methods in Biomechanics and Biomedical Engineering — Fri, 12 Feb 2010 00:00:00 +0100

In this study, high-resolution magnetic resonance imaging was performed in the transaxial, coronal and sagittal planes to provide comprehensive structural details of the bladder and surrounding systems. Detailed finite-element (FE) models that were specific to each participant were developed by rendering the images, and the process of bladder filling was simulated. The overall model of bladder deformation was compared with repeated images of the filled bladder that were obtained using computed tomography to validate the FE models. The relationship between the changes in the key dimensions of the bladder and the increase in bladder volume during the filling process was also investigated. The numerical results showed that the bladder dimensions increased linearly with its volume during the f...

Retinopathy Online Challenge: Automatic Detection of Microaneurysms in Digital Color Fundus Photographs

IEE Transactions on Medical Imaging — Fri, 01 Jan 2010 00:00:00 +0100

The detection of microaneurysms in digital color fundus photographs is a critical first step in automated screening for diabetic retinopathy (DR), a common complication of diabetes. To accomplish this detection numerous methods have been published in the past but none of these was compared with each other on the same data. In this work we present the results of the first international microaneurysm detection competition, organized in the context of the Retinopathy Online Challenge (ROC), a multiyear online competition for various aspects of DR detection. For this competition, we compare the results of five different methods, produced by five different teams of researchers on the same set of data. The evaluation was performed in a uniform manner using an algorithm presented in this work. Th...

Triangular neuronal networks on microelectrode arrays: an approach to improve the properties of low-density networks for extracellular recording.

Biomedical Microdevices — Mon, 14 Sep 2009 23:00:00 +0100

In this study, we followed an alternative strategy to increase the portion of neurons located at the electrodes by designing a network in confined geometries. Guided settlement and outgrowth of neurons is accomplished by taking control over the adhesive properties of the MEA surface. Using microcontact printing a triangular two-dimensional pattern of the adhesion promoter poly-D-lysine was applied to the MEA offering a meshwork that at the same time provides adhesion points for cell bodies matching the electrode positions and gives frequent branching points for dendrites and axons. Low density neocortical networks cultivated under this condition displayed similar properties to random networks with respect to the cellular morphology but had a threefold higher electrode coverage. Electrical ...

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2010 IEEE Workshop on Signal Processing Systems

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

Quality without compromise

IEEE Transactions on Signal Processing — Thu, 18 Mar 2010 16:53:03 +0100

(Source: IEEE Transactions on Signal Processing)

Comparison of AdaBoost and Support Vector Machines for Detecting Alzheimer's Disease Through Automated Hippocampal Segmentation

IEE Transactions on Medical Imaging — Fri, 01 Jan 2010 00:00:00 +0100

We compared four automated methods for hippocampal segmentation using different machine learning algorithms: 1) hierarchical AdaBoost, 2) support vector machines (SVM) with manual feature selection, 3) hierarchical SVM with automated feature selection (Ada-SVM), and 4) a publicly available brain segmentation package (FreeSurfer). We trained our approaches using T1-weighted brain MRIs from 30 subjects [10 normal elderly, 10 mild cognitive impairment (MCI), and 10 Alzheimer's disease (AD)], and tested on an independent set of 40 subjects (20 normal, 20 AD). Manually segmented gold standard hippocampal tracings were available for all subjects (training and testing). We assessed each approach's accuracy relative to manual segmentations, and its power to map AD effects. We then converted the se...

Carotid Atheroma Rupture Observed In Vivo and FSI-Predicted Stress Distribution Based on Pre-rupture Imaging.

Annals of Biomedical Engineering — Tue, 16 Mar 2010 00:00:00 +0100

Authors: Leach JR, Rayz VL, Soares B, Wintermark M, Mofrad MR, Saloner D Atherosclerosis at the carotid bifurcation is a major risk factor for stroke. As mechanical forces may impact lesion stability, finite element studies have been conducted on models of diseased vessels to elucidate the effects of lesion characteristics on the stresses within plaque materials. It is hoped that patient-specific biomechanical analyses may serve clinically to assess the rupture potential for any particular lesion, allowing better stratification of patients into the most appropriate treatments. Due to a sparsity of in vivo plaque rupture data, the relationship between various mechanical descriptors such as stresses or strains and rupture vulnerability is incompletely known, and the patient-specific util...

A novel online method to monitor autonomic nervous activity based on arterial wall impedance and heart rate variability

Medical and Biological Engineering and Computing — Tue, 02 Feb 2010 07:00:13 +0100

Abstract This paper proposes a new method of evaluating autonomic nervous activity using the mechanical impedance of arterial walls and heart rate variability. The cardiovascular system is indispensable to life maintenance functions, and homeostasis is maintained by the autonomic nervous system. Accordingly, it is very important to be able to make diagnosis based on autonomic nervous activity within the body’s circulation. The proposed method was evaluated in surgical operations; the mechanical impedance of the arterial wall was estimated from arterial blood pressure and a photoplethysmogram, and heart rate variability was estimated using electrocardiogram R–R interval spectral analysis. In this paper, we monitored autonomic nervous system activity using the proposed s...

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Analysis and Modeling of Snore Source Flow With Its Preliminary Application to Synthetic Snore Generation

IEEE Transactions on Biomedical Engineering — Mon, 01 Mar 2010 00:00:00 +0100

With the emerging use of snore properties for clinical purposes, there is a need to understand the characteristics of snore source flow (SF)—the acoustic source in snore production. This paper attempts to analyze and model both SF and its derivative (SFD), along with its preliminary application to the generation of synthetic snores. SFs and SFDs were extracted from natural snores via an iterative adaptive inverse filtering approach, and subsequently parameterized into various time- and amplitude-based parameters to quantify the oscillatory maneuvers of snore excitation source (ES). The SF and SFD waveforms were also, respectively, modeled using the first and second derivatives of the Gaussian probability density function. Subjective and objective measures, including paired compariso...

Strategies for utilisation of food-processing wastes to produce lipases in solid-state cultures of Rhizopus oryzae.

Bioprocess and Biosystems Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: López E, Deive FJ, Longo MA, Sanromán MA The aim of the present study was to investigate the feasibility of several food-processing wastes as support substrate for lipolytic enzymes production by the fungus Rhizopus oryzae under solid-state conditions. Different experiments were conducted to select the variables that allow obtaining high levels of lipolytic enzyme activity. In particular, the use of inert and non-inert solid materials and lipidic and surfactant compounds was evaluated. It was observed that the addition of Triton X-100 together with barley bran involved lipolytic production values tenfold higher than the cultures exclusively grown on an inert support. In addition, from preliminary thermoinactivation kinetics studies, it was concluded that the strategy...

A simple new device to examine human stance: the totter-slab

Biomedizinische Technik/Biomedical Engineering — Thu, 04 Feb 2010 17:02:30 +0100

This article describes a new measuring device to investigate balancing strategies of human stance: the totter-slab, i.e., a standing plate suspended with steel cables to hooks on a steel frame. First, we analysed the physical properties of the device by recording free oscillations under different conditions [varying amplitude, mass and centre of mass (COM) height]. This allowed us to determine the eigenfrequency and the damping coefficient D (Source: Biomedizinische Technik/Biomedical Engineering)

Development and characterization of a FIA system for selective assay of L: -ascorbic acid in food samples.

Bioprocess and Biosystems Engineering — Fri, 12 Mar 2010 00:00:00 +0100

Authors: Vig A, Igloi A, Adanyi N, Gyemant G, Csutoras C, Kiss A An amperometric detector and an enzymatic reaction were combined for the measurement of L: -ascorbic acid. The enzyme cell (containing immobilized ascorbate oxidase) was connected to a flow injection analyzer (FIA) system with a glassy carbon electrode as an amperometric detector. During optimization and measurements two sample injectors were used, one before and one after the enzyme cell, thus eliminating the background interferences. Subtraction of the signal area given in the presence of enzyme from the one given in the absence of enzyme was applied for measuring analyte concentrations and calibration at 400 mV. Analysis capacity of system is 25 samples/hour. The relative standard deviation (RSD) was below 5% (5 times ...