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Medical Imaging, IEEE Transactions on

Issue 1 • Date Mar 1995

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Displaying Results 1 - 18 of 18
  • Simultaneous usage of homologous points, lines, and planes for optimal, 3-D, linear registration of multimodality imaging data

    Page(s): 1 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    The authors have extended point-based registration to include simultaneous registration of points, lines, and planes, to permit accurate and easily implemented three-dimensional (3-D) registration of multimodal data sets for fusion of clinical anatomic and functional imaging modalities. Constructive geometry is used to define user-identified features where each feature's role in the reconstruction is weighted based on its relative statistical quality, i.e., variance. The algorithm employs singular value decomposition (SVD) and optimization techniques to find the minimum weighted least mean square error (LMSE) affine solution. The new method is generally more accurate due to the availability of more features to register. Notably the error surface contains only one minimum. Different subclasses of affine solutions can be obtained based on appropriateness and sufficiency of the number and type of input features. Preliminary results indicate that this method is useful in multimodal diagnostic image fusion View full abstract»

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  • A discrete dynamic contour model

    Page(s): 12 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1536 KB)  

    A discrete dynamic model for defining contours in 2-D images is developed. The structure of this model is a set of connected vertices. With a minimum of interaction, an initial contour model can be defined, which is then automatically modified by an energy minimizing process. The internal energy of the model depends on local contour curvature, while the external energy is derived from image features. Solutions are presented to avoid undesirable deformation effects, like shrinking and vertex clustering, which are common in existing active contour models. The deformation process stops when a local minimum of the energy function is reached. The final shape of the model is a reproducible approximation of the desired contour. Results of applying the method to computer-generated images, as well as clinical images, are presented View full abstract»

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  • A nonsmoothing approach to the estimation of vessel contours in angiograms

    Page(s): 162 - 172
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    Accurate and fully automatic assessment of vessel (stenoses) dimensions in angiographic images has been sought as a diagnostic tool, in particular for coronary heart disease. Here, the authors propose a new technique to estimate vessel borders in angiographic images, a necessary first step of any automatic analysis system. Unlike in previous approaches, the obtained edge estimates are not artificially smoothed; this is extremely important since quantitative analysis is the goal. Another important feature of the proposed technique is that no constant background is assumed, this making it well suited for nonsubtracted angiograms. The key aspect of the authors' approach is that continuity/smoothness constraints are not used to modify the estimates directly derived from the image (which would introduce distortion) but rather to elect (without modifying) candidate estimates. Robustness against unknown background is provided by the use a morphological edge operator, instead of some linear operator (such as a matched filter) which has to assume known background and known vessel shape View full abstract»

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  • Statistics of deformations in histology and application to improved alignment with MRI

    Page(s): 25 - 35
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    An exact registration of magnetic resonance images (MRI) with histological sections is impeded by local deformations resulting from histological preparation procedures. Therefore, it is desirable to know the probability density function of spatial deformations in order to estimate optimal global least-square transformation parameters from suitable landmarks. For this reason, the statistics of deformations is investigated. It is shown analytically that the frequency of occurrence of the absolute geometrical differences (deformations) are Rayleigh-Bessel distributed for anisotropic histological preparation procedures and Rayleigh distributed in the case of isotropic procedures. The probabilistic analysis is given in conjunction with an iterative optimization technique in order to ensure that the probability density function is within a threshold required for the application to experimental data. The application of the analytical model is investigated with real data. It is shown with this data that the extent of deformations varies with the size of the histological section. An individual threshold can be selected on the basis of a Rayleigh-function restricting local corrections to small parts of the image. Thus, global misalignment in each section can be avoided, resulting in an improved 3-D reconstruction of the volume, i.e., the transitions from one section to the next are more continuous View full abstract»

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  • A modified expectation maximization algorithm for penalized likelihood estimation in emission tomography

    Page(s): 132 - 137
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    The maximum likelihood (ML) expectation maximization (EM) approach in emission tomography has been very popular in medical imaging for several years. In spite of this, no satisfactory convergent modifications have been proposed for the regularized approach. Here, a modification of the EM algorithm is presented. The new method is a natural extension of the EM for maximizing likelihood with concave priors. Convergence proofs are given View full abstract»

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  • Segmentation of cardiac cine MR images for extraction of right and left ventricular chambers

    Page(s): 56 - 64
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    A two-stage algorithm for extraction of the ventricular chambers (endocardial surfaces) in flow-enhanced magnetic resonance images is described. In the first stage, the approximate locations and sizes of the endocardial surfaces are determined by intensity thresholding. In the second stage, points on each approximated surface are repositioned to nearest locally maximum gradient magnitude points and a generalized cylinder is fitted to them. Examples of ventricular chambers in cine MR images determined by this algorithm are presented View full abstract»

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  • Ultrasonic transmission tomography in refracting media: reduction of refraction artifacts by curved-ray techniques

    Page(s): 173 - 188
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    The present work concerns the problem of refraction artifacts in ultrasonic transmission tomography. The reconstruction is improved by curved-ray methods, combined with algebraic reconstruction techniques. The problem of acoustic ray tracing and image interpolation has been carefully studied, and different reconstruction algorithms have been developed and compared. The effect of the geometrical characteristics of the set-up and the studied medium characteristics (geometry and acoustical properties) on the reconstruction accuracy are considered. Some simulation results are presented which show an encouraging reduction of the refraction artifacts. The results have been confirmed by experiments carried out with agar-gel phantoms. The experimental device and procedure are described and straight- and curved-ray reconstructions are shown. Reconstruction quality can be improved significantly for refractive index variations of up to 10%, which seems sufficient for soft tissue imaging; yet there are some limiting factors, such as multipath propagation, if any, or the difficulty of choosing an initial value for the reconstruction View full abstract»

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  • Retrospective correction of intensity inhomogeneities in MRI

    Page(s): 36 - 41
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    Medical imaging data sets are often corrupted by multiplicative inhomogeneities, often referred to as nonuniformities or intensity variations, that hamper the use of quantitative analyses. The authors describe an automatic technique that not only improves the worst situations, such as those encountered with magnetic resonance imaging (MRI) surface coils, but also corrects typical inhomogeneities encountered in routine volume data sets, such as MRI head scans, without generating additional artifact. Because the technique uses only the patient data set, the technique can be applied retrospectively to all data sets, and corrects both patient independent effects, such as rf coil design, and patient dependent effects, such as attenuation of overlying tissue experienced both in high field MRI and X-ray computed tomography (CT). The authors show results for several MRI imaging situations including thorax, head, and breast. Following such corrections, region of interest analyses, volume histograms, and thresholding techniques are more meaningful. The value of such correction algorithms may increase dramatically with increased use of high field strength magnets and associated patient-dependent rf attenuation in overlying tissues View full abstract»

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  • Energy dependence of scatter components in multispectral PET imaging

    Page(s): 138 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    High resolution images in PET based on small individual detectors are obtained at the cost of low sensitivity and increased detector scatter. These limitations can be partially overcome by enlarging discrimination windows to include more low-energy events and by developing more efficient energy-dependent methods to correct for scatter radiation from all sources. The feasibility of multispectral scatter correction was assessed by decomposing response functions acquired in multiple energy windows into four basic components: object, collimator and detector scatter, and trues. The shape and intensity of these components are different and energy-dependent. They are shown to contribute to image formation in three ways: useful (true), potentially useful (detector scatter), and undesirable (object and collimator scatter) information to the image over the entire energy range. With the Sherbrooke animal PET system, restoration of detector scatter in every energy window would allow nearly 90% of all detected events to participate in image formation. These observations suggest that multispectral acquisition is a promising solution for increasing sensitivity in high resolution PET. This can be achieved without loss of image quality if energy-dependent methods are made available to preserve useful events as potentially useful events are restored and undesirable events removed View full abstract»

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  • An active contour model for mapping the cortex

    Page(s): 65 - 80
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    A new active contour model for finding and mapping the outer cortex in brain images is developed. A cross-section of the brain cortex is modeled as a ribbon, and a constant speed mapping of its spine is sought. A variational formulation, an associated force balance condition, and a numerical approach are proposed to achieve this goal. The primary difference between this formulation and that of snakes is in the specification of the external force acting on the active contour. A study of the uniqueness and fidelity of solutions is made through convexity and frequency domain analyses, and a criterion for selection of the regularization coefficient is developed. Examples demonstrating the performance of this method on simulated and real data are provided View full abstract»

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  • Robust simultaneous detection of coronary borders in complex images

    Page(s): 151 - 161
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB)  

    Visual estimation of coronary obstruction severity from angiograms suffers from poor inter- and intraobserver reproducibility and is often inaccurate. In spite of the widely recognized limitations of visual analysis, automated methods have not found widespread clinical use, in part because they too frequently fail to accurately identify vessel borders. The authors have developed a robust method for simultaneous detection of left and right coronary borders that is suitable for analysis of complex images with poor contrast, nearby or overlapping structures, or branching vessels. The reliability of the simultaneous border detection method and that of the authors' previously reported conventional border detection method were tested in 130 complex images, selected because conventional automated border detection might be expected to fail. Conventional analysis failed to yield acceptable borders in 65/130 or 50% of images. Simultaneous border detection was much more robust (p<.001) and failed in only 15/130 or 12% of complex images. Simultaneous border detection identified stenosis diameters that correlated significantly better with observer-derived stenosis diameters than did diameters obtained with conventional border detection (p<0.001), Simultaneous detection of left and right coronary borders is highly robust and has substantial promise for enhancing the utility of quantitative coronary angiography in the clinical setting View full abstract»

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  • A fully automated optimization algorithm for determining the 3-D patient contour from photo-peak projection data in SPECT

    Page(s): 122 - 131
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    The class of noninverse problems versus inverse problems is discussed. A general optimization approach to solving certain constrained noninverse problems is presented. This approach is applied in the area of single photon emission computed tomography to estimate the patient outer contour directly from the photo-peak projection data. The resulting algorithm is fully automated, fast, and the determined 3-D patient contour satisfies smoothness constraints. The accuracy and reliability of the algorithm is evaluated through Monte Carlo simulations, patient studies, and an experimental validation study View full abstract»

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  • A method for correcting the depth-of-interaction blurring in PET cameras

    Page(s): 146 - 150
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    A method is presented for correcting PET images for the blurring caused by variations in the depth-of-interaction in position-sensitive gamma ray detectors. The method uses an empirically determined, tabulated relationship between depth-of-interaction and most probable pulse-height to estimate the unknown depth from the measured pulse-height for each detected gamma ray. In the case of one fine-cut 50×50×30 mm BGO block detector, the method is shown to improve the detector resolution by 25%, averaged over the 50×50 mm face, measured in the geometry corresponding to detection at the edge of the field-of-view. Strengths and weaknesses of the method are discussed and its potential usefulness for improving the images of future PET cameras is assessed View full abstract»

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  • Effect of real-time weighted integration system for rapid calculation of functional images in clinical positron emission tomography

    Page(s): 116 - 121
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    A system has been developed to rapidly calculate images of parametric rate constants, without acquiring dynamic frame data for clinical positron emission tomography (PET). This method is based on the weighted-integration algorithms for the two- and three-compartment models, and hardware developments (real-time operation and a large cache memory system) in a PET scanner, Headtome-IV, which enables the acquisition of multiple sinograms with independent weight integration functions. Following the administration of the radiotracer, the scan is initiated to collect multiple time-weighted, integrated sinograms with three different weight functions. These sinograms are reconstructed and the images, with the arterial blood data, are inserted into the operational equations to provide parametric rate constant images. The implementation of this method has been checked in H215 O and 18F-fluorophenylalanine (18FPhe) studies based on a two-compartment model, and in a 18F-fluorodeoxyglucose (18FDG) study based on the three-compartment model. A volunteer study, completed for each compound, yielded results consistent with those produced by existing nonlinear fitting methods. Thus, this system has been developed capable of generating rapidly quantitative, physiological images, without dynamic data acquisition, which will be of great advantage to PET in the clinical environment. This system would also be of great advantage in the new generation high-resolution PET tomography, which acquire data in a 3-D, septaless mode View full abstract»

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  • Fourier correction for spatially variant collimator blurring in SPECT

    Page(s): 100 - 115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1576 KB)  

    In single-photon emission computed tomography (SPECT), projection data are acquired by rotating the photon detector around a patient, either in a circular orbit or in a noncircular orbit. The projection data of the desired spatial distribution of emission activity is blurred by the point-response function of the collimator that is used to define the range of directions of gamma-ray photons reaching the detector. The point-response function of the collimator is not spatially stationary, but depends on the distance from the collimator to the point. Conventional methods for deblurring collimator projection data are based on approximating the actual distance-dependent point-response function by a spatially invariant blurring function, so that deconvolution methods can be applied independently to the data at each angle of view. A method is described here for distance-dependent preprocessing of SPECT projection data prior to image reconstruction. Based on the special distance-dependent characteristics of the Fourier coefficients of the sinogram, a spatially variant inverse filter can be developed to process the projection data in all views simultaneously. The algorithm is first derived from Fourier analysis of the projection data from the circular orbit geometry. For circular orbit projection data, experimental results from both simulated data and real phantom data indicate the potential of this method. It is shown that the spatial filtering method can be extended to the projection data from the noncircular orbit geometry. Experiments on simulated projection data from an elliptical orbit demonstrate correction of the spatially variant blurring and distortion in the reconstructed image caused by the noncircular orbit geometry View full abstract»

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  • Methods of graph searching for border detection in image sequences with applications to cardiac magnetic resonance imaging

    Page(s): 42 - 55
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    Automated border detection using graph searching principles has been shown useful for many biomedical imaging applications. Unfortunately, in an often unpredictable subset of images, automated border detection methods may fail. Most current edge detection methods fail to take into account the added information available in a temporal or spatial sequence of images that are commonly available in biomedical image applications. To utilize this information the authors extended their previously reported single frame graph searching method to include data from a sequence. The authors' method transforms the three-dimensional surface definition problem in a sequence of images into a two-dimensional problem so that traditional graph searching algorithms may be used. Additionally, the authors developed a more efficient method of searching the three-dimensional data set using heuristic search techniques which vastly improve execution time by relaxing the optimality criteria. The authors have applied both methods to detect myocardial borders in computer simulated images as well as in short-axis magnetic resonance images of the human heart. Preliminary results show that the new multiple image methods may be more robust in certain circumstances when compared to a single frame method and that the heuristic search techniques may reduce analysis times without compromising robustness View full abstract»

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  • Estimating linear functionals of a PET image

    Page(s): 81 - 87
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    The authors discuss the effect of having a finite number of detectors on the estimation of a bounded linear functional of a PET image. They argue that the functional should be estimated directly from the detector counts and give an estimate of the effect of the binning of the counts to order D-2, where D is the number of detectors. The authors then suggest an estimator that includes a data determined bias correction reducing the bias to o(D-2) View full abstract»

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  • Automatic determination of LV orientation from SPECT data

    Page(s): 88 - 99
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    Presents a new method to determine the orientation or pose of the left ventricle (LV) of the heart from cardiac SPECT (single photon emission computed tomography) data. This proposed approach offers an accurate, fast, and robust delineation of the LV long-axis. The location and shape of the generated long-axis can then be utilized to define automatically the tomographic slices for enhanced visualization and quantification of the clinical data. The methodology is broadly composed of two main steps: (1) volume segmentation of cardiac SPECT data; and (2) topological goniometry, a novel approach incorporating volume visualization and computer graphics ideas to determine the overall shape of 3-D objects. The outcome of the algorithm is a 3-D curve representing the overall pose of the LV long-axis. Experimental results on both phantom and clinical data (50 technetium-99m and 74 thallium-201) are presented. An interactive graphical interface to visualize the volume (3-D) data, the left ventricle, and its pose is an integral part of the overall methodology. This technique is completely data driven and expeditious, making it viable for routine clinical use View full abstract»

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Aims & Scope

IEEE Transactions on Medical Imaging (T-MI) encourages the submission of manuscripts on imaging of body structures, morphology and function, and imaging of microscopic biological entities. The journal publishes original contributions on medical imaging achieved by various modalities, such as ultrasound, X-rays (including CT) magnetic resonance, radionuclides, microwaves, and light, as well as medical image processing and analysis, visualization, pattern recognition, and related methods. Studies involving highly technical perspectives are most welcome. The journal focuses on a unified common ground where instrumentation, systems, components, hardware and software, mathematics and physics contribute to the studies.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Milan Sonka
Iowa Institute for Biomedical Imaging
3016B SC, Department of Electrical and Computer Engineering
The University of Iowa
Iowa City, IA  52242  52242  USA
milan-sonka@uiowa.edu