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Biomedical Imaging, 2002. Proceedings. 2002 IEEE International Symposium on

Date 7-10 July 2002

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Displaying Results 1 - 25 of 270
  • 2002 IEEE International Symposium On Biomedical Imaging [front matter]

    Publication Year: 2002 , Page(s): i - xxxi
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  • 2002 IEEE International Symposium on Biomedical Imaging (Cat. No.02EX608)

    Publication Year: 2002
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  • Author index

    Publication Year: 2002 , Page(s): 1063 - 1071
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  • Three dimensional nonlinear inversion for diffuse optical tomography

    Publication Year: 2002 , Page(s): 54 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    We show results for full three-dimensional nonlinear inversion of the parameters of a diffusive partial differential equation, specifically for an optical tomography application. We compute functional derivatives of the parameters with respect to the mean-squared error using the adjoint field method, and implement two forms of regularization. In the first, a penalty term is introduced into the error functional, and in the second, the solution to the inverse problem is assumed to belong to a parametrized class of functions. In the case where this assumption is correct, our results demonstrate that the parameters can recovered with high accuracy, yielding a better inversion result than the traditional Tikhonov-type approach. View full abstract»

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  • Retinal image registration using control points

    Publication Year: 2002 , Page(s): 349 - 352
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    A method for registering pairs of digital ophthalmic images of the retina is presented using anatomical features as control points present in both images. In general, the matching between control points is unknown, however. An automated algorithm is used to determine the matching pairs of control points in the two images as follows. Using two control points from each image, rigid global transform (RGT) coefficients were calculated for all possible combinations of control point pairs. The set of RGT coefficients was then exhaustively searched and the cluster of coefficients associated with the matched control point pairs identified. This cluster was identified by calculating the Euclidean distance between each set of RGT coefficients and its Rth nearest neighbor and then using the EM algorithm to identify matched pairs of control points. Once control point pairs were established, registration of the two images was achieved by using linear regression to optimize the bilinear or 2nd order polynomial. Two examples of registration are shown. The first is an example of cross-modal image registration using an optical image and a fluorescein angiogram of an eye. The second examples shows an example of the registration of two images of an infant eye captured thirteen days apart. View full abstract»

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  • Capturing contextual dependencies in medical imagery using hierarchical multi-scale models

    Publication Year: 2002 , Page(s): 165 - 168
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB) |  | HTML iconHTML  

    In this paper we summarize our results for two classes of hierarchical multi-scale models that exploit contextual information for detection of structure in mammographic imagery. The first model, the hierarchical pyramid neural network (HPNN), is a discriminative model which is capable of integrating information either coarse-to-fine or fine-to-coarse for microcalcification and mass detection. The second model, the hierarchical image probability (HIP) model, captures short-range and contextual dependencies through a combination of coarse-to-fine factoring and a set of hidden variables. The HIP model, being a generative model, has broad utility, and we present results for classification, synthesis and compression of mammographic mass images. The two models demonstrate the utility of the hierarchical multi-scale framework for computer assisted detection and diagnosis. View full abstract»

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  • Spectrum analysis of microwave breast examination data and reconstructed images

    Publication Year: 2002 , Page(s): 62 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (530 KB) |  | HTML iconHTML  

    A broadband microwave tomographic imaging system is being developed for breast cancer detection which exploits the significant electrical property contrast between normal and malignant tissue. The improved image reconstruction algorithm directly processes the log-magnitude and phase values of the measured fields with the frequency rich data set being utilized to acquire the absolute scattered phase terms, especially when multiple wrapping has occurred. In addition, a lower contrast coupling medium has been selected which alleviates certain problems associated with the phase unwrapping task but also appears to reduce artifacts associated with higher permittivity contrasts between the surrounding coupling medium and the breast. Sequences of multi-plane image sets from a low contrast medium examination of a 53 year old woman over a broad frequency range are presented to illustrate the general consistency of the images over the range and to demonstrate the improved resolution at the higher frequencies. View full abstract»

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  • Performance of an MEG adaptive-beamformer technique in the presence of correlated neural activities: correlation-coefficient estimation and time-course retrieval

    Publication Year: 2002 , Page(s): 1019 - 1022
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    The influence of temporarily correlated source activities on neuromagnetic reconstruction by adaptive beamformer techniques is investigated. It is known that the spatial filter weight of an adaptive beamformer cannot perfectly block correlated signals. This causes two major influences on the reconstruction results: time course distortions and reductions in reconstructed signal intensifies. The reduction in signal intensity for sources with a medium degree of correlation is found to be insignificant. The time course distortion for such sources, however, may not be negligible. Our analysis shows that the magnitude correlation coefficient between two correlated sources can be accurately estimated by using the beamformer outputs. A method of retrieving the original time courses using estimated correlation coefficients is developed. Our numerical experiments demonstrate that reasonably accurate time courses can be retrieved from considerably distorted time courses even when the signal-to-noise ratio is low. View full abstract»

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  • Advances in measurements of ultrasound fields in the frequency range 20-60 MHz

    Publication Year: 2002 , Page(s): 978 - 980
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (337 KB) |  | HTML iconHTML  

    A powerful measurement technique suitable for virtually continuous calibration of ultrasonic hydrophone probes in the frequency range 250 kHz-60 MHz is described and frequency responses of PVDF polymer hydrophones are presented. The validity of the calibration results was examined using independent calibration techniques. The values of sensitivity in V/Pa obtained using a linear swept frequency technique were compared with those which were determined from the measurements employing nonlinear wave propagation. Also, the sensitivity against frequency data obtained here were compared with the data provided by an independent national laboratory. The overall agreement between the calibration results obtained using different techniques mentioned above was within ±1 dB at frequencies up to 25 MHz. The uncertainty increased gradually with increasing frequency and was determined to be ±2.5 dB at 60 MHz. A spatial averaging correction model is being developed to minimize this uncertainty. The near continuous frequency plots in the 40-60 MHz bandwidth were not reported so far and reveal that the ultrasonic hydrophone probes response is largely controlled by their design architecture. View full abstract»

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  • Processing GeneChip® array images

    Publication Year: 2002 , Page(s): 42 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (423 KB) |  | HTML iconHTML  

    Processing Affymetrix® GeneChip® array images requires accurate and robust methods. Algorithms are designed to handle a wide variety of input image data. Execution time and interface to database products are considered during design and development. Evaluating the image processing algorithms include analysis of application results, such as, gene expression and genotyping. View full abstract»

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  • Imaging and characterization of coronary lesions with optical coherence tomography

    Publication Year: 2002 , Page(s): 106 - 109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB) |  | HTML iconHTML  

    An intravascular OCT system is described for simultaneous acquisition of backscatter, polarization, and spectroscopic images from coronary arteries. Preliminary experiments were carried out to test the performance of the system in tissue phantoms and in excised arteries. Images displaying measurements of fibrous tissue content and water content in diseased lesions are presented. The results encourage further development of multi-modality OCT imaging for clinical application. View full abstract»

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  • Near infrared optical tomographic imaging of fluid containing tissues

    Publication Year: 2002 , Page(s): 70 - 73
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (462 KB) |  | HTML iconHTML  

    In recent years near-infrared optical tomographic imaging (OTI) has made big strides towards becoming a clinically relevant medical imaging modality. Imaging of dynamic changes in blood parameters, functional brain imaging, and breast imaging are the most advanced areas of application of this novel technique. In this study we focus on difficulties that are encountered when OTI is employed for imaging tissues that contain fluid-filled regions. Examples of such tissues are the brain, which contains low scattering cerebrospinal fluids, joints, which enclose translucent synovial fluids, and the maternal abdomen, which is filled with amniotic fluid. In these cases widely accepted image reconstruction schemes that rely on the diffusion approximation have limited applicability, and more advanced model-based iterative image reconstructions methods that make use of the equation of radiative transfer promise more accurate results. View full abstract»

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  • Cone-beam reconstruction for Micro-CT

    Publication Year: 2002 , Page(s): 384 - 387
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    X-ray micro-CT has been a focus in the CT/Micro-CT Lab, the University of Iowa. In this paper, some recent progress we made on cone-beam micro-CT is described. First, we address approximation reconstruction using Feldkamp-type algorithms with multiple X-ray sources and displaced detector configurations. Then, we explain three types of artifacts associated with exact reconstruction in the Grangeat framework. Finally, we report the convergence of a generalized block-iterative Landweber scheme. Representative images from simulation and experiments are also given. View full abstract»

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  • Shape of phased array Doppler ultrasound sample volumes

    Publication Year: 2002 , Page(s): 974 - 977
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    Some of the methods used to reduce estimation errors make use of simplified models of the Doppler sample volume (SV). However, these models do not accurately take into account the SV's shape and pressure distribution. The SV can be accurately simulated through the inclusion of a Doppler time gate to a B-mode simulation based on the underlying physics of ultrasound propagation and reception from a linear phased array transducer, including the effects of focusing and attenuation. A commercial diagnostic B-mode/Doppler ultrasound system was simulated to produce four SVs at different axial depths and lengths. It was found that every SV's axial length was larger than the theoretical length used in its design. The further the SV was away from a focal depth, the greater its size in that dimension. The pressure distribution was not symmetrical about the center of the SV, but rather skewed towards the transducer. View full abstract»

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  • Simultaneous validation of image segmentation and assessment of expert quality [tumor MRI application]

    Publication Year: 2002 , Page(s): 94 - 97
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    Characterizing the performance of image segmentation approaches has been a persistent challenge. Interactive drawing of the desired segmentation by domain experts has often been the only acceptable approach, and yet suffers from intra-expert and inter-expert variability. Algorithms have been sought in order to remove the variability introduced by experts. The accuracy of segmentations of medical images has been difficult to quantify in the absence of a "ground truth" segmentation for clinical data. Although physical or digital phantoms can help, they have so far been unable to reproduce the full range of imaging and anatomical characteristics observed in clinical data. An attractive alternative is comparison to a collection of segmentations by experts, but the most appropriate way to compare segmentations has been unclear. We present here a method for computing a maximum likelihood estimate of the "ground truth" segmentation from a group of expert segmentations, and a simultaneous measure of the quality of each expert. This approach readily enables the assessment of an automated image segmentation algorithm, and direct comparison of expert and algorithm performance. View full abstract»

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  • Design of minimally invasive optical imaging probes to track vascular gene expression: a Monte Carlo simulation analysis

    Publication Year: 2002 , Page(s): 285 - 288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (374 KB) |  | HTML iconHTML  

    A Monte Carlo simulation analysis of optical probe design for minimally invasive tracking of gene expression in the vasculature was performed. The simulations based on efficient light delivery for excitation of green fluorescent protein (GFP) marker revealed the possibility of using percutaneous probes and intravascular probes to detect gene expression in the vessel walls. A percutaneous probe of 5 mm diameter and an intravascular probe of 2 mm diameter produced identical fluence distribution in the media-intima interface of a diseased aorta for optimal excitation of GFP. But there was a seven-fold increase in the fluence rate in the normal aorta by the intravascular probe. View full abstract»

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  • Joint estimation of cardiac kinematics and material parameters from noisy imaging data and uncertain mechanical model

    Publication Year: 2002 , Page(s): 113 - 116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (366 KB) |  | HTML iconHTML  

    There have been many efforts using image analysis algorithms to study cardiac kinematics, or using biomechanics strategies to study myocardial material properties. In this paper, we propose a novel stochastic mechanics strategy and an extended Kalman filter (EKF) computational framework to estimate the cardiac kinematics functions and material model parameters simultaneously, given a particular a priori myocardial material model with uncertain parameters and a posteriori noisy imaging/imaging-derived data. We address the issues concerning the data-dependent uncertainty of the constraining mechanical models (and their parameters), which are needed in the ill-posed problems. Because of the periodic nature of the cardiac dynamics, we conclude experimentally that it is possible to adopt this physical-model based optimal estimation approach to achieve converged estimates. Results from canine MR phase contrast images and linear elastic model are presented. View full abstract»

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  • Support vector machines for oral lesion classification

    Publication Year: 2002 , Page(s): 173 - 176
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    We investigate support vector machines (SVM) in the context of oral lesion classification using digital color images as input. Two common lesions of similar visual appearance to the human observer were evaluated: oral leukoplakia, which is a potentially pre-cancerous lesion, and oral lichenoid reactions (with subclasses of atrophic, plaqueformed and reticular reactions), which are usually harmless lesions. In total, 89% (212 out of 238, 5-fold CV) were correctly classified in a two-class problem (precancerous vs. non-pre-cancerous) and 78% (61 out of 78, hold-out) into four classes (complete classification). The proposed method can be used as a decision support tool in CADx systems for oral lesion classification and detection of potentially pre-cancerous lesions. View full abstract»

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  • Automated interictal spike detection and source localization in MEG using ICA and spatial-temporal clustering

    Publication Year: 2002 , Page(s): 785 - 788
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (374 KB) |  | HTML iconHTML  

    MEG dipole localization of epileptic spikes is useful in epilepsy surgery for mapping the extent of abnormal cortex and to focus intracranial electrodes. Visually analyzing large amounts of data produces fatigue and error. Most existing methods are based on matching of interictal spike templates or predictive filtering of the data and do not explicitly include source localization as part of the analysis. We describe a fully automated method that combines time-series analysis with source localization to detect clusters of focal generators within the brain that produce interictal spike activity. We first use an ICA (Independent Component Analysis) method to decompose the multichannel MEG data and identify those components that exhibit spikelike characteristics. From these detected spikes we then find those whose spatial topographies across the array are consistent with focal neural sources and determine the foci of equivalent current dipoles and their associated time courses. Finally we perform a clustering of the sources based on distance metrics that takes into consideration both their locations and time courses. Tight clusters of equivalent current dipoles with a fit of greater than 95% are considered to be the reliably determined sources and are the final output of our detection scheme. View full abstract»

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  • A novel approach to quantitative analysis of electrophoretic gel images of DNA fragments

    Publication Year: 2002 , Page(s): 899 - 902
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (449 KB) |  | HTML iconHTML  

    A novel methodology of DNA gel image analysis has been proposed that is based on 2D image processing methods instead of previously used 1D Gaussian deconvolution. The algorithms specifically tailored to band boundary detection and image intensity homogeneity characterization have been developed. The proposed methodology involves a modified type of user interaction. View full abstract»

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  • Three dimensional functional cartography of the human basal ganglia by registration of optical and histological serial sections

    Publication Year: 2002 , Page(s): 329 - 332
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (577 KB) |  | HTML iconHTML  

    In functional neurosurgery, there is a need for accurate localisation of the functional targets. One example is given by Parkinson's disease. The surgical intervention is based on the introduction of electrodes in the subthalamic nucleus. This nucleus is targeted on pre-operative stereotactic MR acquisitions. But MR imaging of the basal ganglia is intrinsically limited, first by image resolution, and second by the relationship between the measured MR signal and the real anatomy, not clearly understood. On the other hand, detailed and accurate cartography of the basal ganglia can be performed on post mortem histological serial sections. Indeed, histology overcomes the limitations of MR imaging. Moreover, staining of histological sections allows to recover functional information. But histology is by nature two-dimensional. An histological data set consists in a series of disorganized serial sections, as three dimensional shape information was lost during sectioning. Therefore, the first step toward the integration of histological and MR information is to perform a reliable three dimensional reconstruction of the histological volume. Acquisition of photographs during sectioning, showing the histological sections before sectioning, as well as fiducial landmarks, allows to reconstruct a volume with three dimensional integrity, and is further used to register each histological section with its corresponding optical section. View full abstract»

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  • Volumetric quantification of coronary arteries reconstructed by fusion between intravascular ultrasound and biplane angiography

    Publication Year: 2002 , Page(s): 891 - 894
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    Fusion of intravascular ultrasound (IVUS) and biplane X-ray angiography leads to a geometrically correct representation of coronary vessels. A comparison of three volume quantification methods - polytope, Watanabe, and Simpson-based - is reported. The three methods allow local estimation of plaque accumulation. To determine volumetric indices, space between the lumen and adventitia surfaces is subdivided and each of the volume elements considered separately to achieve volume quantification. Polyhedral volume elements are employed and their volumes estimated by each of the proposed approaches. The volume quantification methods were validated in 92 computer-generated shapes and tested on routine patient data. All three methods were found highly accurate. By comparing the volume quantification errors, the polytope and Watanabe methods were found statistically significantly more accurate than the Simpson-based approach. View full abstract»

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  • Mapping cortical connectivity with diffusion MRI

    Publication Year: 2002 , Page(s): 392 - 394
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (275 KB) |  | HTML iconHTML  

    Functional brain imaging methods have contributed enormously to our knowledge of the anatomic location of particular brain functions. However, there remains a significant gap in our understanding of how these regions communicate as part of a distributed network. This shortcoming is due in large part to the scarcity of information on the connectivity of the human brain compared to, for example, our knowledge of such anatomy in lower primates. Recently, investigators have undertaken to infer neuroanatomic connectivity from magnetic resonance diffusion imaging, an MRI method which measures the molecular mobility of the endogenous water in tissue. The method is based on the observation that in fibrous tissues such as skeletal muscle and white matter, the diffusion is greater along the direction of the fibers relative to, for example, the perpendicular direction. The direction of greatest diffusion provides an indication of the local white matter fiber direction within each voxel. The connectivity inference problem is then, simply stated, how to infer large-scale neuroanatomic connectivity from such fiber direction maps. Here, we present a physically-motivated, statistical framework for the connectivity inference problem. The particular benefits of the formulation include encapsulation of the unresolved aspects of the problem, and a statistical construction suitable for hypothesis testing of anatomical connectivity differences between groups of subjects. View full abstract»

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  • Non rigid registration in neuroimaging: from a retrospective evaluation of global approaches to new advances in local and hybrid methods

    Publication Year: 2002 , Page(s): 469 - 472
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (465 KB) |  | HTML iconHTML  

    Within the scope of three-dimensional brain imaging and brain functional mapping, we present a retrospective evaluation framework of inter-individual fusion scheme to register brain cortical anatomy and functional activations. The evaluation methodology relies on global and local criteria such as gray/white matter segmentation map overlap, correlation ratio of the mean Lvv intensities (i.e. 3D measure of the curvature of the cortex from the MRI volumes), distance and shape variation of cortical sulcal landmarks (segmented using the "active ribbon" approach). Visual and global measures seem to promote the non-linear global registration methods while local measures, based on sulci, did not show any significant differences between all global methods. As a perspective, new approaches are introduced to account for these local cortical deformations by means of either introducing sparse constraints in global registration methods or by introducing a local non-linear registration framework based on active shape models of local cortical features. View full abstract»

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  • Rapid semi-automated segmentation and analysis of neuronal morphology and function from confocal image data

    Publication Year: 2002 , Page(s): 233 - 236
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (363 KB) |  | HTML iconHTML  

    Confocal microscopy combined with cellular labeling techniques can be an effective method for imaging the morphology of a cell as well as various functional characteristics in vivo. Current analysis methods are manual, and therefore, time-consuming and prone to error. Through the development of custom algorithms and application design, the analysis process can be improved to decrease analysis time and increase reproducibility. Utilizing off-the-self PC hardware and software, a custom application was designed that would provide useful three-dimensional (3D) segmentation and analysis tools to analyze confocal image data of neurons. Techniques such as dynamic thresholding, adaptive filtering, and morphological processing were implemented to provide a robust and efficient analysis package. The automated method was compared with the standard manual method using two metrics - reproducibility and overall time necessary for analysis. The semi-automated method was more time efficient with very high reproducibility. Additional studies are necessary to further assess and improve upon the automated technique. View full abstract»

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