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This page shows you the most recent publications within this specialty of the MedWorm directory. This is page number 28.

Sparsity-Exploiting Robust Multidimensional Scaling
Multidimensional scaling (MDS) seeks an embedding of $N$ objects in a $p< N$ dimensional space such that inter-vector distances approximate pairwise object dissimilarities. Despite their popularity, MDS algorithms are sensitive to outliers, yielding grossly erroneous embeddings even if few outliers contaminate the available dissimilarities. This work introduces robust MDS approaches exploiting the degree of sparsity in the outliers present. Links with compressive sampling lead to robust MDS solvers capable of coping with unstructured and structured outliers. The novel algorithms rely on a majorization-minimization appro...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Optimal Pivot Selection in Fast Weighted Median Search
Weighted median filters are increasingly being used in signal processing applications and thus fast implementations are of importance. This paper introduces a fast algorithm to compute the weighted median (WM) of $N$ samples which has linear time and space complexity as opposed to $O(N log N)$ which is the time complexity of traditional sorting algorithms. A popular selection algorithm often used to find the WM in large data sets is Quickselect whose performance is highly dependent on how the pivots are chosen. We introduce an optimization based pivot selection strategy which results in significantly improved performance a...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Block-Sparse Recovery via Convex Optimization
Given a dictionary that consists of multiple blocks and a signal that lives in the range space of only a few blocks, we study the problem of finding a block-sparse representation of the signal, i.e., a representation that uses the minimum number of blocks. Motivated by signal/image processing and computer vision applications, such as face recognition, we consider the block-sparse recovery problem in the case where the number of atoms in each block is arbitrary, possibly much larger than the dimension of the underlying subspace. To find a block-sparse representation of a signal, we propose two classes of nonconvex optimizat...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Proof of Convergence and Performance Analysis for Sparse Recovery via Zero-Point Attracting Projection
A recursive algorithm named zero-point attracting projection (ZAP) is proposed recently for sparse signal reconstruction. Compared with the reference algorithms, ZAP demonstrates rather good performance in recovery precision and robustness. However, any theoretical analysis about the mentioned algorithm, even a proof on its convergence, is not available. In this work, a strict proof on the convergence of ZAP is provided and the condition of convergence is put forward. Based on the theoretical analysis, it is further proved that ZAP is nonbiased and can approach the sparse solution to any extent, with the proper choice of s...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

STFT With Adaptive Window Width Based on the Chirp Rate
An adaptive time-frequency representation (TFR) with higher energy concentration usually requires higher complexity. Recently, a low-complexity adaptive short-time Fourier transform (ASTFT) based on the chirp rate has been proposed. To enhance the performance, this method is substantially modified in this paper: i) because the wavelet transform used for instantaneous frequency (IF) estimation is not signal-dependent, a low-complexity ASTFT based on a novel concentration measure is addressed; ii) in order to increase robustness to IF estimation error, the principal component analysis (PCA) replaces the difference operator f...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Discrete-Time LTI Systems Beyond Convolution
Examples for LTI systems are found in the literature that cannot be represented as a convolution. Their outputs can be approximated by outputs of FIR filters and considered as generalized convolution systems. These examples illustrate that impulse and frequency response provide no complete description of the system. In this paper, a general theory for discrete-time LTI systems is represented. LTI systems are defined on a signal space, which is a vector space, closed with respect to a shift operation. Signals are not necessarily bounded and need not belong to a normed vector space. Vector space concepts like dependent and i...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

On the Design of Highly Accurate and Efficient IIR and FIR Filters
We describe a systematic method for designing highly accurate and efficient infinite impulse response (IIR) and finite impulse response (FIR) filters given their specifications. In our approach, we first meet the specifications by constructing an IIR filter with, possibly, a large number of poles. We then construct, for any given accuracy, an optimal IIR version of such filter (with a minimal number of poles). Finally, also for any given accuracy, we convert the IIR filter to an efficient FIR filter cascade (either serial or parallel). Since in this FIR approximation the non-causal part of the IIR filter only introduces an...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Peak-Error-Constrained Sparse FIR Filter Design Using Iterative SOCP
In this paper, a novel algorithm is proposed to design sparse FIR filters. It is known that this design problem is highly nonconvex due to the existence of $l_{0}$ -norm of a filter coefficient vector in its objective function. To tackle this difficulty, an iterative procedure is developed to search a potential sparsity pattern, which is then used to compute the final solution by solving a convex optimization problem. In each iterative step, the original sparse filter design problem is successively transformed to a simpler subproblem. It can be proved that under a weak condition, globally optimal solutions of these subprob...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Spatio-Temporal Diffusion Strategies for Estimation and Detection Over Networks
We present diffusion algorithms for distributed estimation and detection over networks that endow all nodes with both spatial cooperation abilities and temporal processing abilities. Each node in the network is allowed to share information locally with its neighbors; this step amounts to sharing and processing of spatial data. At the same time, each node is allowed to filter and process past estimates to improve estimation accuracy through an overall collaborative process. In this manner, the resulting distributed algorithms consist of three stages: adaptation, spatial processing, and temporal processing. Moreover, the ord...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Adaptive Widely Linear Reduced-Rank Interference Suppression Based on the Multistage Wiener Filter
We propose a widely linear multistage Wiener filter (WL-MSWF) receiver to suppress inter-/intra-symbol interference, multiuser interference, and narrowband interference in a high data rate direct-sequence ultra wideband (DS-UWB) system. The proposed WL receiver fully exploits the second-order statistics of the received signal, yielding a smaller Minimum Mean Square Error (MMSE) than the linear receiver. The WL-MSWF receiver mainly consists of a low-rank transformation and an adaptive reduced-rank filter. The rank-reduction is achieved via a transformation matrix. Based on the linear MSWF concept, two constructions of this ...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Low-Complexity Variable Forgetting Factor Mechanism for Blind Adaptive Constrained Constant Modulus Algorithms
In this paper, we propose a novel low-complexity variable forgetting factor (VFF) mechanism for blind adaptive constrained constant modulus (CCM) recursive least squares (RLS) algorithms applied to linear interference suppression in direct-sequence code-division multiple access (DS-CDMA) systems. The proposed variable forgetting factor mechanism employs an updated component related to the time average of the constant modulus (CM) cost function to automatically adjust the forgetting factor in order to ensure good tracking of the interference and the channel. Convergence and tracking analyses are carried out. Analytical expr...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Recursive Group Lasso
We introduce a recursive adaptive group lasso algorithm for real-time penalized least squares prediction that produces a time sequence of optimal sparse predictor coefficient vectors. At each time index the proposed algorithm computes an exact update of the optimal $ell_{1,infty}$-penalized recursive least squares (RLS) predictor. Each update minimizes a convex but nondifferentiable function optimization problem. We develop an on-line homotopy method to reduce the computational complexity. Numerical simulations demonstrate that the proposed algorithm outperforms the $ell_{1}$ regularized RLS algorithm for a group sparse sy...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Sparse Bayesian Methods for Low-Rank Matrix Estimation
Recovery of low-rank matrices has recently seen significant activity in many areas of science and engineering, motivated by recent theoretical results for exact reconstruction guarantees and interesting practical applications. In this paper, we present novel recovery algorithms for estimating low-rank matrices in matrix completion and robust principal component analysis based on sparse Bayesian learning (SBL) principles. Starting from a matrix factorization formulation and enforcing the low-rank constraint in the estimates as a sparsity constraint, we develop an approach that is very effective in determining the correct ra...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

An Efficient Parametric Technique for Doppler-Delay Estimation
Receiving an output signal that is a weighted sum of Doppler and delay shifted versions of an input signal arises in various engineering systems including radar, sonar, and communications. It is often desired to estimate the Doppler and delay parameters from noisy measurements of the output signal. An estimation algorithm is developed herein for the Doppler frequencies, delays, and amplitudes, for a specific choice of the input. The algorithm is based on a computationally efficient search-free frequency estimation technique for the sum of complex exponentials. Asymptotic performance bounds are developed for the estimated p...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

A Semidefinite Relaxation-Based Algorithm for Robust Attitude Estimation
This paper presents a tractable method for solving a robust attitude estimation problem, based on a weighted least squares approach with nonlinear constraints. Attitude estimation requires information of a few vector quantities, each obtained from both a sensor and a mathematical model. By considering the modeling errors, measurement noise, sensor biases and offsets as infinity-norm bounded uncertainties, we formulate a robust optimization problem, which is nonconvex with nonlinear cost and constraints. The robust min-max problem is approximated with a nonconvex minimization problem using an upper bound. A new regularizati...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

SNR and Noise Variance Estimation for MIMO Systems
Accurate signal-to-noise ratio (SNR) and noise variance estimation are extremely important aspects of receiver design in multiple-input multiple-output (MIMO) systems. Typically, these parameters are estimated using known pilot/training symbols. However, significant improvements may be made by using both the known pilot symbols as well as the unknown data symbols. In this paper, we address SNR and noise variance estimation of MIMO systems for both a data aided (DA) model, a non-data aided (NDA) model, as well as a mixed model that uses known and unknown data symbols. The Cramér–Rao lower bound (CRLB) and modi...
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

IEEE Transactions on Signal Processing publication information
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

Table of contents
Presents the table of contents for this issue of the periodical.
Source: IEEE Transactions on Signal Processing - July 28, 2012 Category: Biomedical Engineering Source Type: research

IEEE Transactions on Biomedical Engineering Associate Editors
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

IEEE Transactions on Biomedical Engineering information for authors
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Heterogeneity of Intrinsic Repolarization Properties Within the Human Heart: New Insights From Simulated Three-Dimensional Current Surfaces
Heterogeneity of repolarization properties is pivotal for both physiology and pathology of the heart and mathematical models of different cardiac cell types that are tuned to experimental data in order to reproduce it in silico. Repolarization heterogeneity is described most of the times with reference to one or the other of the many repolarization parameters, like action potential (AP) form and duration, or the maximum conductance of a given ion current, which are nonlinearly connected and frequently overdetermined. A compact representation of models dynamics would help their standardization, their use, and the understand...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Mapping Infected Cell Phenotype
Quantitative modeling of the phenotypic changes in the host cell during the bacterial infection makes it possible to explore an empirical relation between the infection stages and the quantifiable host-cell phenotype. A statistically reliable model of this relation can facilitate therapeutic defense against threats due to natural and genetically engineered bacterium. In the preliminary experiment, we have collected several thousand cell images over a period of 72 h of infection with a 2-h sampling frequency that covers various stages of infection by Francisella tularenesis (Ft). Segmentation of macrophages in images...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Variation of Respiratory Resistance Suggests Optimization of Airway Caliber
Physiologically optimized processes, such as respiration, walking, and cardiac function, usually show a range of variability about the optimized value. Airway resistance has, in the past, been noted as variable, and this variability has been connected to pulmonary disease (e.g., asthma). A hypothesis was presented many years ago that postulated airway resistance as an optimized parameter in healthy individuals, and we have noticed that respiratory measurements made with the airflow perturbation device (APD) tend to be variable in nature. It was posited that this variability indicates that respiratory resistance is optimize...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Ex Vivo Measurement of Postmortem Tissue Changes in the Crystalline Lens by Brillouin Spectroscopy and Confocal Reflectance Microscopy
Use of Brillouin spectroscopy in ophthalmology enables noninvasive, spatially resolved determination of the rheological properties of crystalline lens tissue. Furthermore, the Brillouin shift correlates with the protein concentration inside the lens. In vitro measurements on extracted porcine lenses demonstrate that results obtained with Brillouin spectroscopy depend strongly on time after death. The intensity of the Brillouin signal decreases significantly as early as 5 h postmortem. Moreover, the fluctuation of the Brillouin frequency shift inside the lens increases with postmortem time. Images of lens tiss...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

An Optimization-Based Study of Equivalent Circuit Models for Representing Recordings at the Neuron–Electrode Interface
Extracellular neuroelectronic interfacing is an emerging field with important applications in the fields of neural prosthetics, biological computation, and biosensors. Traditionally, neuron–electrode interfaces have been modeled as linear point or area contact equivalent circuits but it is now being increasingly realized that such models cannot explain the shapes and magnitudes of the observed extracellular signals. Here, results were compared and contrasted from an unprecedented optimization-based study of the point contact models for an extracellular “on-cell” neuron–patch electrode and a plan...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Biopsy Needle Localization Using Magnetic Induction Imaging Principles: A Feasibility Study
The accurate navigation and location of a biopsy needle is of main clinical interest in cases of image-guided biopsies for patients with suspected cancerous lesions. Magnetic induction (MI) imaging is a relatively new simple and low-cost noninvasive imaging modality that can be used for measuring the changes of electrical conductivity distribution inside a biological tissue. The feasibility of using MI principles for measuring and imaging the location of a biopsy needle in a tissue with suspected lesion was studied in simulations and with an experimental system. A contactless excitation/sensing unit was designed, and raste...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Bioimpedance Analysis for the Characterization of Breast Cancer Cells in Suspension
The bioimpedance spectroscopy (BIS) technique is potentially a useful tool to differentiate malignancy based on the variation of electrical properties presented by different tissues and cells. The different tissues and cells present variant electrical resistance and reactance when excited at different frequencies. The main purpose of this area of research is to use impedance measurements over a low-frequency bandwidth ranging from 1 kHz to 3 MHz to 1) differentiate the pathological stages of cancer cells under laboratory conditions and 2) permit the extraction of electrical parameters related to cellular info...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

An Automatic Patient-Adapted ECG Heartbeat Classifier Allowing Expert Assistance
In this paper, we present a patient-adaptable algorithm for ECG heartbeat classification, based on a previously developed automatic classifier and a clustering algorithm. Both classifier and clustering algorithms include features from the RR interval series and morphology descriptors calculated from the wavelet transform. Integrating the decisions of both classifiers, the presented algorithm can work either automatically or with several degrees of assistance. The algorithm was comprehensively evaluated in several ECG databases for comparison purposes. Even in the fully automatic mode, the algorithm slightly improved the pe...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Novel Passive Element Circuits for Microdosimetry of Nanosecond Pulsed Electric Fields
Microdosimetric models for biological cells have assumed increasing significance in the development of nanosecond pulsed electric field technology for medical applications. In this paper, novel passive element circuits, able to take into account the dielectric dispersion of the cell, are provided. The circuital analyses are performed on a set of input pulses classified in accordance with the current literature. Accurate data in terms of transmembrane potential are obtained in both time and frequency domains for different cell models. In addition, a sensitivity study of the transfer function for the cell geometrical and die...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Vision-Based Proximity Detection in Retinal Surgery
In retinal surgery, surgeons face difficulties such as indirect visualization of surgical targets, physiological tremor, and lack of tactile feedback, which increase the risk of retinal damage caused by incorrect surgical gestures. In this context, intraocular proximity sensing has the potential to overcome current technical limitations and increase surgical safety. In this paper, we present a system for detecting unintentional collisions between surgical tools and the retina using the visual feedback provided by the opthalmic stereo microscope. Using stereo images, proximity between surgical tools and the retinal surface ...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Accelerating Cardiac Bidomain Simulations Using Graphics Processing Units
In this study, the feasibility of multi-GPU bidomain simulations is demonstrated by running strong scalability benchmarks using a state-of-the-art model of rabbit ventricles. The model is spatially discretized using the finite element methods (FEM) on fully unstructured grids. The GPU code is directly derived from a large pre-existing code, the Cardiac Arrhythmia Research Package (CARP), with very minor perturbation of the code base. Overall, bidomain simulations were sped up by a factor of 11.8 to 16.3 in benchmarks running on 6–20 GPUs compared to the same number of CPU cores. To match the fastest GPU simul...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Multilead Measurement System for the Time-Domain Analysis of Bioimpedance Magnitude
In this study, a novel multilead bioimpedance measurement system was designed. This was particularly aimed at the time-domain analysis of bioimpedance magnitude. Frequency division multiplexing was used to avoid overlapping between excitation signals; undersampling, to reduce the hardware requirements; and power isolated active current sources, to reduce the electrical interactions between leads. These theoretical concepts were implemented on a prototype device. The prototype was tested on equivalent circuits and a saline tank in order to assess excitation signal interferences and electrical interactions between leads. The...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Fractional-Order Time Series Models for Extracting the Haemodynamic Response From Functional Magnetic Resonance Imaging Data
The postprocessing of functional magnetic resonance imaging (fMRI) data to study the brain functions deals mainly with two objectives: signal detection and extraction of the haemodynamic response. Signal detection consists of exploring and detecting those areas of the brain that are triggered due to an external stimulus. Extraction of the haemodynamic response deals with describing and measuring the physiological process of activated regions in the brain due to stimulus. The haemodynamic response represents the change in oxygen levels since the brain functions require more glucose and oxygen upon stimulus that implies a ch...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Phase Synchronization Analysis of EEG Signals: An Evaluation Based on Surrogate Tests
Phase synchronization (PS) analysis has been demonstrated to be a useful method to infer functional connectivity with multichannel neural signals, e.g., electroencephalography (EEG). Methodological problems on quantifying functional connectivity with PS analysis have been investigated extensively, but some of them have not been fully solved yet. For example, how long a segment of EEG signal should be used in estimating PS index? Which methods are more suitable to infer the significant level of estimated PS index? To address these questions, this paper performs an intensive computation study on PS analysis based on surrogat...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Points of Interest and Visual Dictionaries for Automatic Retinal Lesion Detection
In this paper, we present an algorithm to detect the presence of diabetic retinopathy (DR)-related lesions from fundus images based on a common analytical approach that is capable of identifying both red and bright lesions without requiring specific pre- or postprocessing. Our solution constructs a visual word dictionary representing points of interest (PoIs) located within regions marked by specialists that contain lesions associated with DR and classifies the fundus images based on the presence or absence of these PoIs as normal or DR-related pathology. The novelty of our approach is in locating DR lesions in the optic f...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Gaze Estimation Interpolation Methods Based on Binocular Data
Video oculography (VOG) is one of the most commonly used techniques for gaze tracking because it enables nonintrusive eye detection and tracking. Improving the eye tracking’s accuracy and tolerance to user head movements is a common task in the field of gaze tracking; thus, a thorough study of how binocular information can improve a gaze tracking system’s accuracy and tolerance to user head movements has been carried out. The analysis is focused on interpolation-based methods and systems with one and two infrared lights. New mapping features are proposed based on the commonly used pupil-glint vector using dif...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Robust Closed-Loop Minimal Sampling Method for HIV Therapy Switching Strategies
The emergence of drug-resistant strains of human immunodeficiency virus during antiretroviral therapy is a major cause of treatment failure and disease progression. Development of a resistant strain necessitates switching to a new antiretroviral regimen composed of novel drugs. Recent work has shown that current methods of switching antiviral therapies carry significant unnecessary risk of subsequent failures, and optimal switching schedules to minimize this risk have been proposed. These switching schedules require frequent sampling of viral load during an induced phase of transient viral load reduction, with the goal of ...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Vibro- and Electrotactile User Feedback on Hand Opening for Myoelectric Forearm Prostheses
In this study, performance of a grasping task is investigated for different hand opening feedback conditions on 15 healthy subjects and validated on three patients. The opening of a virtual hand was controlled by a scroll wheel. Feedback about hand opening was given via an array of eight vibrotactile or electrotactile stimulators placed on the forearm, relating to eight hand opening positions. A longitudinal and transversal orientation of the array and four feedback conditions were investigated: no feedback, visual feedback, feedback through vibrotactile or electrotactile stimulation, and addition of an extra stimulator fo...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

A Stable and Real-Time Nonlinear Elastic Approach to Simulating Guidewire and Catheter Insertions Based on Cosserat Rod
Interventional Radiology procedures (e.g., angioplasty, embolization, stent graft placement) provide minimally invasive therapy to treat a wide range of conditions. These procedures involve the use of flexible tipped guidewires to advance diagnostic or therapeutic catheters into a patient’s vascular or visceral anatomy. This paper presents a real-time physically based hybrid modeling approach to simulating guidewire insertions. The long, slender body of the guidewire shaft is simulated using nonlinear elastic Cosserat rods, and the shorter flexible tip composed of a straight, curved, or angled design is modeled usin...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Slip Speed Feedback for Grip Force Control
In this study, we propose an enhanced slip feedback modality, with potential for myoelectric-based prosthetic applications, that relays information regarding slip events, particularly slip occurrence and slip speed. The proposed feedback modality, implemented using electrotactile stimulation, was evaluated in psychophysical studies of slip control in a simplified setup. The obtained results were compared with vision and a binary slip feedback that transmits on–off information about slip detection. The slip control efficiency of the slip speed display is comparable to that obtained with vision feedback, and it clearl...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Automated Fiducial Localization in CT Images Based on Surface Processing and Geometrical Prior Knowledge for Radiotherapy Applications
We propose a novel method for radio-opaque external marker localization in CT scans for infrared (IR) patient set-up in radiotherapy. Efforts were focused on the quantification of uncertainties in marker localization in the CT dataset as a function of algorithm performance. We implemented a 3-D approach to fiducial localization based on surface extraction and marker recognition according to geometrical prior knowledge. The algorithm parameters were optimized on a clinical CT dataset coming from 35 cranial and extra-cranial patients; the localization accuracy was benchmarked at variable image resolution versus laser tracker...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Intention-Based EMG Control for Powered Exoskeletons
Electromyographical (EMG) signals have been frequently used to estimate human muscular torques. In the field of human-assistive robotics, these methods provide valuable information to provide effectively support to the user. However, their usability is strongly limited by the necessity of complex user-dependent and session-dependent calibration procedures, which confine their use to the laboratory environment. Nonetheless, an accurate estimate of muscle torque could be unnecessary to provide effective movement assistance to users. The natural ability of human central nervous system of adapting to external disturbances coul...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Uncertainty Analysis of Ventricular Mechanics Using the Probabilistic Collocation Method
Uncertainty and variability in material parameters are fundamental challenges in computational biomechanics. Analyzing and quantifying the resulting uncertainty in computed results with parameter sweeps or Monte Carlo methods has become very computationally demanding. In this paper, we consider a stochastic method named the probabilistic collocation method, and investigate its applicability for uncertainty analysis in computing the passive mechanical behavior of the left ventricle. Specifically, we study the effect of uncertainties in material input parameters upon response properties such as the increase in cavity volume,...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

A Minimal Model of Tumor Growth Inhibition in Combination Regimens Under the Hypothesis of No Interaction Between Drugs
One important issue in the preclinical development of an anticancer drug is the assessment of the compound under investigation when administered in combination with other drugs. Several experiments are routinely conducted in xenograft mice to evaluate if drugs interact or not. Experimental data are generally qualitatively analyzed on empirical basis. The ability of deriving from single drug experiments a reference response to the joint administrations, assuming no interaction, and comparing it to real responses would be key to recognize synergic and antagonist compounds. Therefore, in this paper, the minimal model of tumor...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

A 64-Channel Transmitter for Investigating Parallel Transmit MRI
Multiple channel radiofrequency (RF) transmitters are being used in magnetic resonance imaging to investigate a number of active research topics, including transmit SENSE and B$_1$ shimming. Presently, the cost and availability of multiple channel transmitters restricts their use to relatively few sites. This paper describes the development and testing of a relatively inexpensive transmit system that can be easily duplicated by users with a reasonable level of RF hardware design experience. The system described here consists of 64 channels, each with 100 W peak output level. The hardware is modular at the level of four cha...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Automatic Segmentation of Polyps in Colonoscopic Narrow-Band Imaging Data
Colorectal cancer is the third most common type of cancer worldwide. However, this disease can be prevented by detection and removal of precursor adenomatous polyps during optical colonoscopy (OC). During OC, the endoscopist looks for colon polyps. While hyperplastic polyps are benign lesions, adenomatous polyps are likely to become cancerous. Hence, it is a common practice to remove all identified polyps and send them to subsequent histological analysis. But removal of hyperplastic polyps poses unnecessary risk to patients and incurs unnecessary costs for histological analysis. In this paper, we develop the first part of ...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

Noninvasive Measurement of Physiological Signals on a Modified Home Bathroom Scale
A commercial bathroom scale with both handlebar and footpad electrodes was modified to enable measurement of four physiological signals: the ballistocardiogram (BCG), electrocardiogram (ECG), lower body impedance plethysmogram (IPG), and lower body electromyogram (EMG). The BCG, which describes the reaction of the body to cardiac ejection of blood, was measured using the strain gauges in the scale. The ECG was detected using handlebar electrodes with a two-electrode amplifier. For the lower body IPG, the two electrodes under the subject's toes were driven with an ac current stimulus, and the resulting differential v...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

A Robust and Sensitive Metric for Quantifying Movement Smoothness
The need for movement smoothness quantification to assess motor learning and recovery has resulted in various measures that look at different aspects of a movement’s profile. This paper first shows that most of the previously published smoothness measures lack validity, consistency, sensitivity, or robustness. It then introduces and evaluates the spectral arc-length metric that uses a movement speed profile’s Fourier magnitude spectrum to quantify movement smoothness. This new metric is systematically tested and compared to other smoothness metrics, using experimental data from stroke and healthy subjects as ...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

An Implantable RF Solenoid for Magnetic Resonance Microscopy and Microspectroscopy
We present an implantable microcoil for diverse clinical applications, with a microliter coil volume. The design is loosely based on implantable depth electrodes, in which a flexible tube serves as the substrate, and a metal stylet is inserted into the tube during implantation. The goal is to provide enhanced signal-to-noise ratio (SNR) of structures that are not easily accessed by surface coils. The first-generation prototype was designed for implantation up to 2 cm, and provided initial proof-of-concept for microscopy. Subsequently, we optimized the design to minimize the influence of lead inductances, and to thereby dou...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research

A Novel Methodology for Assessing the Bounded-Input Bounded-Output Instability in QT Interval Dynamics: Application to Clinical ECG With Ventricular Tachycardia
The goal of this paper is to present a new methodology for assessing the bounded-input bounded-output (BIBO) stability in QT interval (QTI) dynamics from clinical ECG. The ECG recordings were collected from 15 patients who experienced ventricular tachycardia (VT). Ten-minute-long ECG recordings extracted immediately before the onset of a chosen VT, one per patient, were assembled into a VT group, while the control group comprised 10-min-long ECGs extracted 1 h before VT onset and at least 1 h after any prior arrhythmic event. Each 10-min recording was subdivided into 1-min ECG recordings (minECGs). The QTI dynamics of each...
Source: IEEE Transactions on Biomedical Engineering - July 28, 2012 Category: Biomedical Engineering Source Type: research