Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947123
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Small (down to 1 mV/mm) electric fields will polarize neurons by only a small amount; for this reason small electric fields have previously been considered to have no physiologically relevant effects. However, here we pr...Small (down to 1 mV/mm) electric fields will polarize neurons by only a small amount; for this reason small electric fields have previously been considered to have no physiologically relevant effects. However, here we propose a novel mechanism by which the non-linear properties of single neurons 'amplify' very small electric fields. Specifically, an amplified change in timing of action potential firing (DeltaT) is inversely proportional to the slope of depolarizing ramp stimulation and proportional to the amount of polarization (DeltaV) caused by the electric fields: DeltaT=DeltaV/(ramp slope). Thus, when responding to slow depolarizing synaptic input, small electric fields can have significant effects on spike timing. Hippocampal CA1 pyramidal neurons were depolarized with injections of depolarizing current ramps approximating synaptic input. Simultaneously, neurons were polarized by either DC holding currents or extracellular uniform DC electrical fields and the resulting changes in spike timing quantified. Consistent with our hypothesis, the polarization induced by each method was found to affect firing time linearly with the amount of polarization, scaled (amplified) with the inverse of the injected ramp slope consistent with our hypothesis.
Huang H, Chen Y, Xu W
… +5 more, Sundaram H, Olson L, Ingalls T, Rikakis T, He J
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947122
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A previous design of a biofeedback system for Neurorehabilitation in an interactive multimodal environment has demonstrated the potential of engaging stroke patients in task-oriented neuromotor rehabilitation. This repor...A previous design of a biofeedback system for Neurorehabilitation in an interactive multimodal environment has demonstrated the potential of engaging stroke patients in task-oriented neuromotor rehabilitation. This report explores the new concept and alternative designs of multimedia based biofeedback systems. In this system, the new interactive multimodal environment was constructed with abstract presentation of movement parameters. Scenery images or pictures and their clarity and orientation are used to reflect the arm movement and relative position to the target instead of the animated arm. The multiple biofeedback parameters were classified into different hierarchical levels w.r.t. importance of each movement parameter to performance. A new quantified measurement for these parameters were developed to assess the patient's performance both real-time and offline. These parameters were represented by combined visual and auditory presentations with various distinct music instruments. Overall, the objective of newly designed system is to explore what information and how to feedback information in interactive virtual environment could enhance the sensorimotor integration that may facilitate the efficient design and application of virtual environment based therapeutic intervention.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947121
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We present a forward-modeling-based sampling of diffusion-tensor imaging (DTI) integral curves. This work has the potential to generate accurate brain neural fiber models that fit the data well with an economic number of...We present a forward-modeling-based sampling of diffusion-tensor imaging (DTI) integral curves. This work has the potential to generate accurate brain neural fiber models that fit the data well with an economic number of curves. DTI integral curves are integrated from the first eigenvector field of the DTI field. Usually the seed points are generated randomly or from a regular grid in the data volume. The resulting set of integral curves is dense around the long and skinny neural fiber structures and sparse around the short and fat structures. There is currently a lack of quantitative indication of how well various models fit the data. We build a forward model that simulates diffusion-weighted images (DWIs) from the DTI integral curves based on a multi-tensor model. We employ the sum of the difference between the simulated DWIs and the acquired DWIs as the goal function and optimize the placement of the DTI integral curves with a greedy algorithm and a simulated annealing algorithm. The results show that with the same number of curves, the optimized set of DTI integral curves fit better to the data than randomly seeded integral curves.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947120
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An entirely automated approach for the recognition of the face of a people starting from her/his images is presented. The approach uses a computational attention module to find automatically the most relevant facial feat...An entirely automated approach for the recognition of the face of a people starting from her/his images is presented. The approach uses a computational attention module to find automatically the most relevant facial features using the Focus Of Attentions (FOA) These features are used to build the model of a face during the learning phase and for recognition during the testing phase. The landmarking of the features is performed by applying the active contour model (ACM) technique, whereas the active shape model (ASM) is adopted for constructing a flexible model of the selected facial features. The advantages of this approach and opportunities for further improvements are discussed.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947119
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Neuroblastoma is a childhood cancer of the nervous system. Current prognostic classification of this disease partly relies on morphological characteristics of the cells from H&E-stained images. In this work, an automated...Neuroblastoma is a childhood cancer of the nervous system. Current prognostic classification of this disease partly relies on morphological characteristics of the cells from H&E-stained images. In this work, an automated cell nuclei segmentation method is developed. This method employs morphological top-hat by reconstruction algorithm coupled with hysteresis thresholding to both detect and segment the cell nuclei. Accuracy of the automated cell nuclei segmentation algorithm is measured by comparing its outputs to manual segmentation. The average segmentation accuracy is 90.24+/-5.14%
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947118
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Diffusion Tensor Imaging (DTI) tractography is a computationally intensive procedure. The most time consuming operation is the tracking of fibers from every voxel in the scanned volume. Fiber tracking can be accelerated...Diffusion Tensor Imaging (DTI) tractography is a computationally intensive procedure. The most time consuming operation is the tracking of fibers from every voxel in the scanned volume. Fiber tracking can be accelerated significantly by use of reconfigurable hardware, such as Field Programmable Gate Arrays (FPGAs), which can track fibers at very high speed by exploiting the flexibility, parallelism and high on-chip bandwidth. Such acceleration has the potential to lead to realtime tractography. In this paper we isolate key kernels within the tracking step and through a simulation study, analyze a specific FPGA architecture comprising deeply pipelined kernel chains running in parallel. Our results suggest that the FPGA based computer architecture could achieve a two orders of magnitude speed-up in the fiber-tracking algorithm over an optimized C-code.
Lu Y, Zheng J, Jiang Y
… +3 more, Yang M, Fu B, Hou W
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947117
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The Progressive Image Transmission (PIT) technique has been used to alleviate the communication problem related to transmit large volume of medical image data. In this study, we propose a novel PIT algorithm based on wav...The Progressive Image Transmission (PIT) technique has been used to alleviate the communication problem related to transmit large volume of medical image data. In this study, we propose a novel PIT algorithm based on wavelet transform, DPCM coding and non-uniform scalar quantization. Experimental results have confirmed the efficiency of the proposed scheme. The achieved bit rate for the first recognizable picture can be as low as 0.05 bit/pixel transmitted in less than 1.0 second for a 512x512 256-gray scale medical image. The reconstructed image shows higher quality than that obtained by the Set Partitioning In Hierarchical Trees (SPIHT) algorithm, which makes it a winning choice for medical image transmission through low speed communication channels.
Doyle S, Rodriguez C, Madabhushi A
… +2 more, Tomaszeweski J, Feldman M
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947116
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In this paper we present a computer-aided diagnosis (CAD) system to automatically detect prostatic adenocarcinoma from high resolution digital histopathological slides. This is especially desirable considering the large...In this paper we present a computer-aided diagnosis (CAD) system to automatically detect prostatic adenocarcinoma from high resolution digital histopathological slides. This is especially desirable considering the large number of tissue slides that are currently analyzed manually - a laborious and time-consuming task. Our methodology is novel in that texture-based classification is performed using a hierarchical classifier within a multi-scale framework. Pyramidal decomposition is used to reduce an image into its constituent scales. The cascaded image analysis across multiple scales is similar to the manner in which pathologists analyze histopathology. Nearly 600 different image texture features at multiple orientations are extracted at every pixel at each image scale. At each image scale the classifier only analyzes those image pixels that have been determined to be tumor at the preceding lower scale. Results of quantitative evaluation on 20 patient studies indicate (1) an overall accuracy of over 90% and (2) an approximate 8-fold savings in terms of computational time. Both the AdaBoost and Decision Tree classifiers were considered and in both cases tumor detection sensitivity was found to be relatively constant across different scales. Detection specificity was however found to increase at higher scales reflecting the availability of additional discriminatory information.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947115
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In this paper, we describe a new approach for reconstructing 3D strains in the myocardium using tagged MR images. We first segment the myocardium using a 3D deformable model driven by image gradients and Gabor filter res...In this paper, we describe a new approach for reconstructing 3D strains in the myocardium using tagged MR images. We first segment the myocardium using a 3D deformable model driven by image gradients and Gabor filter responses. Tags are automatically detected and tracked as deformable thin plates during systole and early diastole. To keep the tracking results more stable and consistent, we use a combination of gradient information, an intensity probabilistic model, the phase information, and a temporal-spatial smoothness constraint. Based on the tag deformation, we compute a dense displacement in the myocardium around both ventricles. The displacements in x-, y-, and z- directions are calculated separately and are combined to form the final displacement maps. We do not use the information outside the segmented surface of the myocardium to avoid displacement errors caused by noises, artifacts, and correlations between different regions in the myocardium. The strain in the myocardium during the heart cycle is derived from the displacement. This method accepts images of either a tag grid or separate horizontal and vertical tag lines as its input. Experimental results on phantom and real data demonstrate good performance of this method in calculating the myocardial strain.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947114
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A novel image capture and retrieval system has been developed for use in a range of telehealth applications in the home and in residential care facilities. The system is based around the JPEG 2000 standard and uses the P...A novel image capture and retrieval system has been developed for use in a range of telehealth applications in the home and in residential care facilities. The system is based around the JPEG 2000 standard and uses the PTP protocol for image capture from any high resolution digital camera and the Kakadu suite of JPEG2000 utilities to serve the collected images via a proxy server over any available communication channel from telephone lines to broadband services. When coupled with an image processing system such as the AMWIS system for pressure wound management, the system provides a high level of clinical functionality suitable for a wide range of telemedicine applications in rural and remote sites.
Narasimha-Iyer H, Can A, Roysam B
… +1 more, Stern J
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947113
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Detection and analysis of changes from retinal images is important in clinical practice, quantitative scoring of clinical trials, computer-assisted reading centers, and in medical research. This paper presents a fully-au...Detection and analysis of changes from retinal images is important in clinical practice, quantitative scoring of clinical trials, computer-assisted reading centers, and in medical research. This paper presents a fully-automated approach for robust detection and classification of changes in longitudinal time-series of fluorescein angiograms (FA). The changes of interest here are related to the development of choroidal neo-vascularization (CNV) in wet macular degeneration. Specifically, the changes in CNV regions as well as the retinal pigment epithelium (RPE) hypertrophic regions are detected and analyzed to study the progression of disease and effect of treatment. Retinal features including the vasculature, vessel branching/crossover locations, optic disk and location of the fovea are first segmented automatically. The images are then registered to sub-pixel accuracy using a 12-dimensional mapping that accounts for the unknown retinal curvature and camera parameters. Spatial variations in illumination are removed using a surface fitting algorithm that exploits the segmentations of the various features. The changes are identified in the regions of interest and a Bayesian classifier is used to classify the changes into clinically significant classes. The automated change analysis algorithms were found to have a success rate of 83%
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947112
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A method for obtaining the optimal and specific sensor parameters for a tool-tip mountable ultrasonic transducer micro-array is presented. The ultrasonic transducer array sensor parameters, such as frequency of operation...A method for obtaining the optimal and specific sensor parameters for a tool-tip mountable ultrasonic transducer micro-array is presented. The ultrasonic transducer array sensor parameters, such as frequency of operation, element size, inter-element spacing, number of elements and transducer geometry are obtained using a quadratic programming method to obtain a maximum directivity while being constrained to a total array size of 4 mm2 and the required resolution for retinal imaging. The technique is used to design a uniformly spaced NxN transducer array that is capable of resolving structures in the retina that are as small as 2 microm from a distance of 100 microm. The resultant 37x37 array of 16 microm transducers with 26 microm spacing will be realized as a Capacitive Micromachined Ultrasonic Transducer (CMUT) array and used for imaging and robotic guidance during retinal microsurgery.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947111
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In this article, we focus on the complementary role of watermarking with respect to medical information security (integrity, authenticity ...) and management. We review sample cases where watermarking has been deployed,...In this article, we focus on the complementary role of watermarking with respect to medical information security (integrity, authenticity ...) and management. We review sample cases where watermarking has been deployed, we conclude that watermarking has found a niche role in healthcare systems, as an instrument for protection of medical information, for secure sharing and handling of medical images. The concern of medical experts on the preservation of documents diagnostic integrity remains paramount.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947109
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Electronic Health Records (EHR)/Electronic Patient Records (EPR)/Electronic Medical Records (EMR) provide the basis for e-Health services. Since information in these records (containing patient healthcare information) ne...Electronic Health Records (EHR)/Electronic Patient Records (EPR)/Electronic Medical Records (EMR) provide the basis for e-Health services. Since information in these records (containing patient healthcare information) need to be shared amongst multiple healthcare providers and healthcare professionals, privacy issues of EHR have been a major inhibitor in the implementation of EHR/EMR/EPR systems. This paper presents EHR privacy requirements in the context of two major e-Health frameworks, namely HealthLink in Australia and HIPAA in USA. The paper concludes with a discussion of some evolving Web-based solutions.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947107
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Magnetic stimulation is a technique to excite biological tissues by means of a time-varying magnetic field. This induced electric field can depolarize the cell membrane so as to evoke an action potential that propagates...Magnetic stimulation is a technique to excite biological tissues by means of a time-varying magnetic field. This induced electric field can depolarize the cell membrane so as to evoke an action potential that propagates along neurons, eventually being transmitted to other neurons or to a muscular cell. Design of a magnetic stimulator requires modeling of the impulse propagation along the nerve cell, as well as numerical simulations for coil design optimization to determine adequate excitation levels as well as the degree of focalization on a given target cell. In this paper we report on a new methodology to calculate the stimulation field for the case of the traditional slinky coil geometry, that greatly reduces computation time, thus facilitating simulation studies of the dynamics of electric impulse propagation along a nerve cell.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947106
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This paper describes microassembly techniques for an out-of-plane three-dimensional microelectrode array for neural stimulating and recording in the central nervous system. An interlocking mechanism has been introduced i...This paper describes microassembly techniques for an out-of-plane three-dimensional microelectrode array for neural stimulating and recording in the central nervous system. An interlocking mechanism has been introduced into the microassembly components to facilitate the process, increase the robustness of the assembled device and improve the yield of the overall system. In-vivo testing has demonstrated full functionality of the microassembled 3D array.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947105
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In this paper, a mathematic model is applied to characterize spectral activity associated with fast oscillatory rhythms inherent in inspiratory discharges. Based on the estimated parameters, features are extracted to all...In this paper, a mathematic model is applied to characterize spectral activity associated with fast oscillatory rhythms inherent in inspiratory discharges. Based on the estimated parameters, features are extracted to allow the model to discriminate between changes in the location, magnitude, and shape of spectral activities under basal conditions and during pharmacological blockade of gap junctions.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947104
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The present study was designed to characterize respiratory fluctuations in awake, healthy humans under resting conditions. Specifically, we used Allan factor and dispersional analysis to test whether the fluctuations in...The present study was designed to characterize respiratory fluctuations in awake, healthy humans under resting conditions. Specifically, we used Allan factor and dispersional analysis to test whether the fluctuations in breath number, respiratory period, and breath amplitude were fractal or random in nature. The results can be summarized as follows. Fluctuations in all three parameters were fractal in nine subjects. There were four subjects in whom only the fluctuations in breath number and amplitude were fractal, three subjects in whom only fluctuations in breath number were fractal, and two subjects in whom only fluctuations in breath number and respiratory period were fractal. Fluctuations in the three parameters occurred randomly in the remaining two subjects. The data suggest that fractal fluctuations in breath number, respiratory period, and breath amplitude are controlled by separate processes.
Tweedie M, Subramanian R, Lemoine P
… +5 more, Craig I, McAdams ET, McLaughlin JA, Maccraith B, Kent N
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947103
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Miniaturised point-of-care cardiac marker sensors are being developed, based on impedimetric sensing of cardiac enzyme capture by an antibody layer immobilised on a planar gold electrode sensor. Gold/Ti-on-glass substrat...Miniaturised point-of-care cardiac marker sensors are being developed, based on impedimetric sensing of cardiac enzyme capture by an antibody layer immobilised on a planar gold electrode sensor. Gold/Ti-on-glass substrates have been used, in a 2 electrode configuration, with antibodies immobilised on the working electrode. Microfluidic structures have been fabricated by a CO2 laser, in 25 mum thick pressure sensitive adhesive (PSA), on a PMMA lid, and the structure bonded on top of the planar sensor. Microfluidic blood/serum delivery has been investigated using a visualisation dye. Some flow problems are observed if the sensor is exposed to air for several days, suggesting that flow channel nanopillars and hermetic encapsulation may be required to guarantee flow properties in commercially produced modules. Work is ongoing to characterise the impedimetric signal changes for myoglobin capture by antimyoglobin, using these sensors. Fifty micron thick PSA, incorporating a robust spacer layer, will be used to give better definition of channel walls.
Conf Proc IEEE Eng Med Biol Soc
· 2006 · PMID 17947102
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Intracortical microelectrodes currently have great potential as a neural prosthesis in patients with neurodegenerative disease or spinal cord injury. In an effort to improve the consistency of neural probe performance, m...Intracortical microelectrodes currently have great potential as a neural prosthesis in patients with neurodegenerative disease or spinal cord injury. In an effort to improve the consistency of neural probe performance, many modifications to probe design are focused on reducing the tissue encapsulation. Since researchers have shown that small polymer fibers (less than 7-microm diameter) induce a small to non-existent encapsulation layer in the rat subcutis, we have proposed a neural probe design with similarly small diameter structures. This paper discusses the fabrication and design parameters of a microscale neural probe with a sub-cellular lattice structure. We developed a microfabrication process using SU-8 and parylene-C to create the relatively thick probe shank and thin lateral arms. The stiff penetrating shank (70-microm by 42-microm) had an SU-8 core that allowed control over stiffness and simplified the process. Parylene-only structures lateral to the shank could be defined with a 4-microm feature-size to meet our sub-cellular criterion. We fabricated four varying geometries for implantation into the neocortex of seven Sprague-Dawley rats. Our in vivo testing verifies that despite the flexible substrate and small dimensions (4-microm x 5-microm), these devices are mechanically robust and practical as neural probes. These devices provide an important tool for neural engineers to investigate the tissue response around sub-cellular structures and potentially improve device efficacy.