MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Medical Image Analysis' source. Fri, 12 Mar 2010 15:30:10 +0100 http://www.medworm.com/index.php?rid=3249719&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841510000034%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249719 Mon, 08 Feb 2010 15:34:46 +0100 3249719 http://www.medworm.com/index.php?rid=3249720&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001492%2Fabstract%3Frss%3Dyes Abstract: The aim of this paper is to review existing approaches to the automatic detection and segmentation of masses in mammographic images, highlighting the key-points and main differences between the used strategies. The key objective is to point out the advantages and disadvantages of the various approaches. In contrast with other reviews which only describe and compare different approaches qualitatively, this review also provides a quantitative comparison. The performance of seven mass detection methods is compared using two different mammographic databases: a public digitised database and a local full-field digital database. The results are given in terms of Receiver Operating Characteristic (ROC) and Free-response Receiver Operating Characteristic (FROC) analysis. (Source: Medical ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249720 Mon, 28 Dec 2009 00:00:00 +0100 3249720 http://www.medworm.com/index.php?rid=3249730&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001480%2Fabstract%3Frss%3Dyes Abstract: In this paper, different methods to improve atlas based segmentation are presented. The first technique is a new mapping of the labels of an atlas consistent with a given intensity classification segmentation. This new mapping combines the two segmentations using the nearest neighbor transform and is especially effective for complex and folded regions like the cortex where the registration is difficult. Then, in a multi atlas context, an original weighting is introduced to combine the segmentation of several atlases using a voting procedure. This weighting is derived from statistical classification theory and is computed offline using the atlases as a training dataset. Concretely, the accuracy map of each atlas is computed and the vote is weighted by the accuracy of the atlases. ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249730 Thu, 17 Dec 2009 00:00:00 +0100 3249730 http://www.medworm.com/index.php?rid=3249727&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001467%2Fabstract%3Frss%3Dyes Abstract: In this paper, we propose a new technique for the estimation of contrast enhancement curves of Dynamic Contrast-Enhanced sequences, which takes the most from the interdependence between this estimation problem and the registration problem raised by possible movements occurring in sequences. The technique solves the estimation and registration problems simultaneously in an iterative way. However, unlike previous techniques, a pixel classification scheme is included within the estimation so as to compute enhancement curves on pixel classes instead of single pixels. The classification scheme is designed using a descendant hierarchical approach. Due to this tree approach, the number of classes is set automatically and the whole technique is entirely unsupervised. Moreover, some speci... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249727 Mon, 14 Dec 2009 00:00:00 +0100 3249727 http://www.medworm.com/index.php?rid=3249725&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001479%2Fabstract%3Frss%3Dyes Abstract: A multiple hypothesis tracking approach to the segmentation of small 3D vessel structures is presented. By simultaneously tracking multiple hypothetical vessel trajectories, low contrast passages can be traversed, leading to an improved tracking performance in areas of low contrast. This work also contributes a novel mathematical vessel template model, with which an accurate vessel centerline extraction is obtained. The tracking is fast enough for interactive segmentation and can be combined with other segmentation techniques to form robust hybrid methods. This is demonstrated by segmenting both the liver arteries in CT angiography data, which is known to pose great challenges, and the coronary arteries in 32 CT cardiac angiography data sets in the Rotterdam Coronary Artery Algor... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249725 Mon, 14 Dec 2009 00:00:00 +0100 3249725 http://www.medworm.com/index.php?rid=3249721&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001443%2Fabstract%3Frss%3Dyes Abstract: Radiotherapy for brain glioma treatment relies on magnetic resonance (MR) and computed tomography (CT) images. These images provide information on the spatial extent of the tumor, but can only visualize parts of the tumor where cancerous cells are dense enough, masking the low density infiltration. In radiotherapy, a 2cm constant margin around the tumor is taken to account for this uncertainty. This approach however, does not consider the growth dynamics of gliomas, particularly the differential motility of tumor cells in the white and in the gray matter. In this article, we propose a novel method for estimating the full extent of the tumor infiltration starting from its visible mass in the patients’ MR images. This estimation problem is a time independent problem where we do n... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249721 Mon, 30 Nov 2009 00:00:00 +0100 3249721 http://www.medworm.com/index.php?rid=3249726&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001406%2Fabstract%3Frss%3Dyes We present a novel approach that allows to simultaneously separate and segment multiple interwoven tubular tree structures. The algorithm consists of two main processing steps. First, the tree structures are identified and corresponding shape priors are generated by using a bottom–up identification of tubular objects combined with a top–down grouping of these objects into complete tree structures. The grouping step allows us to separate interwoven trees and to handle local disturbances. Second, the generated shape priors are utilized for the intrinsic segmentation of the different tubular systems to avoid leakage or undersegmentation in locally disturbed regions. We have evaluated our method on phantom and different clinical CT datasets and demonstrated its ability to correctly obtain/... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249726 Mon, 23 Nov 2009 00:00:00 +0100 3249726 http://www.medworm.com/index.php?rid=3249728&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001236%2Fabstract%3Frss%3Dyes Abstract: In ultrasound images, acoustic shadows appear as regions of low signal intensity linked to boundaries with very high acoustic impedance differences. Acoustic shadows can be viewed either as informative features to detect lesions or calcifications, or as damageable artifacts for image processing tasks such as segmentation, registration or 3D reconstruction. In both cases, the detection of these acoustic shadows is useful. This paper proposes a new method to detect these shadows that combines a geometrical approach to estimate the B-scans shape, followed by a statistical test based on a dedicated modeling of ultrasound image statistics. Results demonstrate that the combined geometrical-statistical technique is more robust and yields better results than the previous statistical tech... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249728 Thu, 19 Nov 2009 00:00:00 +0100 3249728 http://www.medworm.com/index.php?rid=3249731&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001418%2Fabstract%3Frss%3Dyes Abstract: We propose in this article a content-based image retrieval (CBIR) method for diagnosis aid in medical fields. In the proposed system, images are indexed in a generic fashion, without extracting domain-specific features: a signature is built for each image from its wavelet transform. These image signatures characterize the distribution of wavelet coefficients in each subband of the decomposition. A distance measure is then defined to compare two image signatures and thus retrieve the most similar images in a database when a query image is submitted by a physician. To retrieve relevant images from a medical database, the signatures and the distance measure must be related to the medical interpretation of images. As a consequence, we introduce several degrees of freedom in the syste... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249731 Wed, 18 Nov 2009 00:00:00 +0100 3249731 http://www.medworm.com/index.php?rid=3249729&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001388%2Fabstract%3Frss%3Dyes Abstract: The filtering of the Diffusion Weighted Images (DWI) prior to the estimation of the diffusion tensor or other fiber Orientation Distribution Functions (ODF) has been proved to be of paramount importance in the recent literature. More precisely, it has been evidenced that the estimation of the diffusion tensor without a previous filtering stage induces errors which cannot be recovered by further regularization of the tensor field. A number of approaches have been intended to overcome this problem, most of them based on the restoration of each DWI gradient image separately. In this paper we propose a methodology to take advantage of the joint information in the DWI volumes, i.e., the sum of the information given by all DWI channels plus the correlations between them. This way, all ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249729 Mon, 16 Nov 2009 00:00:00 +0100 3249729 http://www.medworm.com/index.php?rid=3249722&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150900139X%2Fabstract%3Frss%3Dyes Abstract: This paper presents several experimental techniques and concepts in the process of measuring mechanical properties of very soft tissue in an ex vivo tensile test. Gravitational body force on very soft tissue causes pre-compression and results in a non-uniform initial deformation. The global digital image correlation technique is used to measure the full-field deformation behavior of liver tissue in uniaxial tension testing. A maximum stretching band is observed in the incremental strain field when a region of tissue passes from compression and enters a state of tension. A new method for estimating the zero-strain state is proposed: the zero strain position is close to, but ahead of the position of the maximum stretching band, or in other words, the tangent of a nominal stress–s... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249722 Mon, 16 Nov 2009 00:00:00 +0100 3249722 http://www.medworm.com/index.php?rid=3249724&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001212%2Fabstract%3Frss%3Dyes Abstract: The detection of brain aneurysms plays a key role in reducing the incidence of intracranial subarachnoid hemorrhage (SAH) which carries a high rate of morbidity and mortality. The majority of non-traumatic SAH cases is caused by ruptured intracranial aneurysms and accurate detection can decrease a significant proportion of misdiagnosed cases. A scheme for automated detection of intracranial aneurysms is proposed in this study. Applied to the segmented cerebral vasculature, the method detects aneurysms as suspect regions on the vascular tree, and is designed to assist diagnosticians with their interpretations and thus reduce missed detections. In the current approach, the vessels are segmented and their medial axis is computed. Small regions along the vessels are inspected and the... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249724 Thu, 12 Nov 2009 00:00:00 +0100 3249724 http://www.medworm.com/index.php?rid=3249723&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001224%2Fabstract%3Frss%3Dyes In this study, soft tissue experiments on porcine livers were performed to measure the surface deformation and force response of soft tissues resulting from indentation loading depending on various indentation depths and two different tip shapes. Measurements were carried out with a three-dimensional (3D) optical system and a force transducer. Using the surface deformation and force response results, we estimated the maximum radius of influence, which can be utilized to determine the minimal required soft tissue model size for the FEM simulation. Considering the influence of the boundary conditions, the model was designed and integrated into an inverse FEM optimization algorithm to estimate the model parameters. The mechanical behavior of large deformations was characterized with FE modeli... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3249723 Fri, 06 Nov 2009 00:00:00 +0100 3249723 http://www.medworm.com/index.php?rid=2941869&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001078%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941869 Fri, 30 Oct 2009 15:11:17 +0100 2941869 http://www.medworm.com/index.php?rid=3038412&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001182%2Fabstract%3Frss%3Dyes Abstract: We propose a technique to simultaneously estimate the local fiber orientations and perform multi-fiber tractography. Existing techniques estimate the local fiber orientation at each voxel independently so there is no running knowledge of confidence in the measured signal or estimated fiber orientation. Further, to overcome noise, many algorithms use a filter as a post-processing step to obtain a smooth trajectory. We formulate fiber tracking as causal estimation: at each step of tracing the fiber, the current estimate of the signal is guided by the previous. To do this, we model the signal as a discrete mixture of Watson directional functions and perform tractography within a filtering framework. Starting from a seed point, each fiber is traced to its termination using an unscent... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038412 Mon, 26 Oct 2009 00:00:00 +0100 3038412 http://www.medworm.com/index.php?rid=3038413&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001194%2Fabstract%3Frss%3Dyes Abstract: Segmentation of medical images can be achieved with the help of model-based algorithms. Reliable boundary detection is a crucial component to obtain robust and accurate segmentation results and to enable full automation. This is especially important if the anatomy being segmented is too variable to initialize a mean shape model such that all surface regions are close to the desired contours. Several boundary detection algorithms are widely used in the literature. Most use some trained image appearance model to characterize and detect the desired boundaries. Although parameters of the boundary detection can vary over the model surface and are trained on images, their performance (i.e., accuracy and reliability of boundary detection) can only be assessed as an integral part of the ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038413 Fri, 23 Oct 2009 00:00:00 +0100 3038413 http://www.medworm.com/index.php?rid=3038414&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000851%2Fabstract%3Frss%3Dyes The authors would like to include an acknowledgment for their published article. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038414 Thu, 22 Oct 2009 00:00:00 +0100 3038414 http://www.medworm.com/index.php?rid=3038411&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509001170%2Fabstract%3Frss%3Dyes Abstract: A novel similarity measure for registering magnetic resonance (MR) and computed tomography (CT) images has been designed and built. MR–CT registration methods often rely on the statistical intensity relationship between the images. The proposed similarity measure instead depends on the statistical relationship between the complex phase order between the images. By utilizing the complex phase order likelihood (CPOL) as a similarity measure, structural relationships instead of intensity relationships are explicitly used. This approach can be advantageous for MR–CT registration, where the intensities of the CT imagery have highly complex and nonlinear relationships with the intensities of corresponding MR imagery but simpler linear structural relationships. This new similarity m... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038411 Wed, 21 Oct 2009 00:00:00 +0100 3038411 http://www.medworm.com/index.php?rid=3038410&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000887%2Fabstract%3Frss%3Dyes Abstract: Atlas-based segmentation is a powerful generic technique for automatic delineation of structures in volumetric images. Several studies have shown that multi-atlas segmentation methods outperform schemes that use only a single atlas, but running multiple registrations on volumetric data is time-consuming. Moreover, for many scans or regions within scans, a large number of atlases may not be required to achieve good segmentation performance and may even deteriorate the results. It would therefore be worthwhile to include the decision which and how many atlases to use for a particular target scan in the segmentation process. To this end, we propose two generally applicable multi-atlas segmentation methods, adaptive multi-atlas segmentation (AMAS) and adaptive local multi-atlas segme... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038410 Thu, 15 Oct 2009 00:00:00 +0100 3038410 http://www.medworm.com/index.php?rid=3038408&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000863%2Fabstract%3Frss%3Dyes Abstract: In this paper, we investigate the use of 3-D echocardiography (echo) data for respiratory motion correction of roadmaps in image-guided cardiac interventions. This is made possible by tracking and calibrating the echo probe and registering it to the roadmap coordinate system. We compare two techniques. The first uses only echo–echo registration to predict a motion-correction transformation in roadmap coordinates. The second combines echo–echo registration with a model of the respiratory motion of the heart. Using experiments with cardiac MRI and 3-D echo data acquired from eight volunteers, we demonstrate that the second technique is more robust than the first, resulting in motion-correction transformations that were accurate to within 5mm in 60% of cases, compared to 42% for... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038408 Mon, 12 Oct 2009 00:00:00 +0100 3038408 http://www.medworm.com/index.php?rid=3038409&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000875%2Fabstract%3Frss%3Dyes Abstract: In this paper we propose a novel approach for characterizing effective connectivity in functional magnetic resonance imaging (fMRI) data. Unlike most other methods, our approach is nonlinear and does not rely on a priori specification of a model that contains structural information of neuronal populations. Instead, it relies on a nonlinear autoregressive exogenous model and nonlinear system identification theory; the model’s nonlinear connectivities are determined using a least squares method. A statistical test was developed to quantify the significance of the influence that regions exert on one another. We compared this approach with a linear method and applied it to the human visual cortex network. Results show that this method can be used to model nonlinear interaction betw... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038409 Fri, 25 Sep 2009 00:00:00 +0100 3038409 http://www.medworm.com/index.php?rid=3038407&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150900084X%2Fabstract%3Frss%3Dyes Abstract: In this paper, a specific method is presented to facilitate the semi-automatic segmentation of liver tumors and liver metastases in CT images. Accurate and reliable segmentation of tumors is essential for the follow-up of cancer treatment. The core of the algorithm is a level set method. The initialization is generated by a spiral-scanning technique based on dynamic programming. The level set evolves according to a speed image that is the result of a statistical pixel classification algorithm with supervised learning. This method is tested on CT images of the abdomen and compared with manual delineations of liver tumors. The described method outperformed the semi-automatic methods of the other participants of the “3D Liver Tumor Segmentation Challenge 2008”. Evaluating the al... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038407 Tue, 22 Sep 2009 00:00:00 +0100 3038407 http://www.medworm.com/index.php?rid=3038406&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000838%2Fabstract%3Frss%3Dyes Abstract: Gland segmentation is an important step to automate the analysis of biopsies that contain glandular structures. However, this remains a challenging problem as the variation in staining, fixation, and sectioning procedures lead to a considerable amount of artifacts and variances in tissue sections, which may result in huge variances in gland appearances. In this work, we report a new approach for gland segmentation. This approach decomposes the tissue image into a set of primitive objects and segments glands making use of the organizational properties of these objects, which are quantified with the definition of object-graphs. As opposed to the previous literature, the proposed approach employs the object-based information for the gland segmentation problem, instead of using the p... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=3038406 Tue, 22 Sep 2009 00:00:00 +0100 3038406 http://www.medworm.com/index.php?rid=2941876&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000796%2Fabstract%3Frss%3Dyes By means of this addendum we would like to give credit to an important work by closely related to one of the results of our paper recently published in this journal (). A key point in the implementation of the filtering approach proposed in is the inversion of the function given by Eq. (B.11). While the expression for was derived previously by the authors , an efficient solution for computing from B was presented independently by . Handling this function is an important component of the method we describe in , therefore, the above-mentioned paper should have been referred. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941876 Tue, 22 Sep 2009 00:00:00 +0100 2941876 http://www.medworm.com/index.php?rid=2941872&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000814%2Fabstract%3Frss%3Dyes Abstract: A fully automated, fast method to detect the fovea and the optic disc in digital color photographs of the retina is presented. The method makes few assumptions about the location of both structures in the image. We define the problem of localizing structures in a retinal image as a regression problem. A kNN regressor is utilized to predict the distance in pixels in the image to the object of interest at any given location in the image based on a set of features measured at that location. The method combines cues measured directly in the image with cues derived from a segmentation of the retinal vasculature. A distance prediction is made for a limited number of image locations and the point with the lowest predicted distance to the optic disc is selected as the optic disc center. ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941872 Mon, 07 Sep 2009 00:00:00 +0100 2941872 http://www.medworm.com/index.php?rid=2941875&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000826%2Fabstract%3Frss%3Dyes Abstract: This paper presents a novel data-driven method for image intensity normalisation, which is a prerequisite step for any kind of image comparison. The method involves a novel application of the Siddon algorithm that was developed initially for fast reconstruction of tomographic images and is based on a linear normalisation model with either one or two parameters. The latter are estimated by maximising the line integral, computed using the Siddon algorithm, in the 2D joint intensity distribution space of image pairs. The proposed normalisation method, referred to as Siddon Line Integral Maximisation (SLIM), was compared with three other methodologies, namely background ratio (BAR) scaling, linear fitting and proportional scaling, using a large number of synthesised datasets. SLIM wa... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941875 Thu, 03 Sep 2009 00:00:00 +0100 2941875 http://www.medworm.com/index.php?rid=2736412&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000656%2Fabstract%3Frss%3Dyes The 11th International Conference on Medical Imaging and Computer Assisted Intervention, MICCAI 2008, was held at the Helen and Martin Kimmel Center of New York University, New York City, USA from 6th September to 10th September 2008. A record number of over 1000 people attended the conference and the workshops. MICCAI is the premier international conference in this domain, with in depth papers on the multidisciplinary fields of biomedical image computing and analysis, computer assisted intervention and medical robotics. The conference brings together biological scientists, clinicians, computer scientists, engineers, mathematicians, physicists and other interested researchers and offers them a forum to exchange ideas in these exciting and rapidly growing fields. The conference is both very... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736412 Thu, 27 Aug 2009 12:46:47 +0100 2736412 http://www.medworm.com/index.php?rid=2736405&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000802%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736405 Thu, 27 Aug 2009 12:46:46 +0100 2736405 http://www.medworm.com/index.php?rid=2941870&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150900067X%2Fabstract%3Frss%3Dyes Abstract: Vascular diseases are among the most important public health problems in developed countries. Given the size and complexity of modern angiographic acquisitions, segmentation is a key step toward the accurate visualization, diagnosis and quantification of vascular pathologies.Despite the tremendous amount of past and on-going dedicated research, vascular segmentation remains a challenging task. In this paper, we review state-of-the-art literature on vascular segmentation, with a particular focus on 3D contrast-enhanced imaging modalities (MRA and CTA). We structure our analysis along three axes: models, features and extraction schemes. We first detail model-based assumptions on the vessel appearance and geometry which can embedded in a segmentation approach. We then review the ima... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941870 Thu, 13 Aug 2009 00:00:00 +0100 2941870 http://www.medworm.com/index.php?rid=2941871&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000668%2Fabstract%3Frss%3Dyes Abstract: A fully automated 3D centerline modeling algorithm for coronary arteries is presented. It utilizes a subset of standard rotational X-ray angiography projections that correspond to one single cardiac phase. The algorithm is based on a fast marching approach, which selects voxels in 3D space that belong to the vascular structure and introduces a hierarchical order. The local 3D propagation speed is determined by a combination of corresponding 2D projections filtered with a vessel enhancing kernel.The best achievable accuracy of the algorithm is evaluated on simulated projections of a virtual heart phantom, showing that it is capable of extracting coronary centerlines with an accuracy that is mainly limited by projection and volume quantization (⩽0.25mm). The algorithm is reasonab... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941871 Mon, 03 Aug 2009 00:00:00 +0100 2941871 http://www.medworm.com/index.php?rid=2941873&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000644%2Fabstract%3Frss%3Dyes Abstract: Segmentation of contrast-enhanced abdominal CT images is required by many clinical applications of computer aided diagnosis and therapy planning. The research on automated methods involves different organs among which the liver is the most emphasized. In the current clinical practice more images (at different phases) are acquired from the region of interest in case of a contrast-enhanced abdominal CT examination. The majority of the existing methods, however, use only the portal-venous image to segment the liver. This paper presents a method that automatically segments the liver by combining more phases of the contrast-enhanced CT examination. The method uses region-growing facilitated by pre- and post-processing functions, which incorporate anatomical and multi-phase information... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941873 Fri, 24 Jul 2009 00:00:00 +0100 2941873 http://www.medworm.com/index.php?rid=2736415&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000620%2Fabstract%3Frss%3Dyes Abstract: Computing, visualizing and interpreting statistics on shapes like curves or surfaces is a real challenge with many applications ranging from medical image analysis to computer graphics. Modeling such geometrical primitives with currents avoids to base the comparison between primitives either on a selection of geometrical measures (like length, area or curvature) or on the assumption of point-correspondence. This framework has been used relevantly to register brain surfaces or to measure geometrical invariants. However, while the state-of-the-art methods efficiently perform pairwise registrations, new numerical schemes are required to process groupwise statistics due to an increasing complexity when the size of the database is growing.In this paper, we propose a Matching Pursuit A... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736415 Mon, 20 Jul 2009 23:00:00 +0100 2736415 http://www.medworm.com/index.php?rid=2736414&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000607%2Fabstract%3Frss%3Dyes Abstract: Cardiologists use two-dimensional projection images in conventional X-ray coronary angiography for the assessment of three-dimensional structures. During minimally invasive interventions there is a need to clearly visualize and analyze contrast filled coronary arteries, surrounding tissue, and implanted devices. Three-dimensional reconstruction of these structures is challenging due to the cardiac and respiratory motion. In this paper we describe a method to automatically generate motion compensated reconstructions of various structures using rotational X-ray angiography.The method uses markers on a device or guide wire to identify and estimate the motion of an object or region of interest in order to register and motion compensate the projection images to generate a motion compe... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736414 Mon, 20 Jul 2009 23:00:00 +0100 2736414 http://www.medworm.com/index.php?rid=2736416&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000632%2Fabstract%3Frss%3Dyes Abstract: A constrained non-rigid registration (CNRR) algorithm for use in prostate image-guided adaptive radiotherapy is presented in a coherent mathematical framework. The registration algorithm is based on a global rigid transformation combined with a series of local injective non-rigid multi-resolution cubic B-spline Free Form Deformation (FFD) transformations. The control points of the FFD are used to non-rigidly constrain the transformation to the prostate, rectum, and bladder. As well, the control points are used to rigidly constrain the transformation to the estimated position of the pelvis, left femur, and right femur. The algorithm was tested with both 3D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) dose plan data sets. The 3DCRT dose plan set consis... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736416 Thu, 16 Jul 2009 23:00:00 +0100 2736416 http://www.medworm.com/index.php?rid=2736413&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000619%2Fabstract%3Frss%3Dyes Abstract: The majority of patients with clinically diagnosed heart failure have normal systolic pump function and are commonly categorized as suffering from diastolic heart failure. The left ventricle (LV) remodels its structure and function to adapt to pathophysiological changes in geometry and loading conditions, which in turn can alter the passive ventricular mechanics. In order to better understand passive ventricular mechanics, a LV finite element (FE) model was customized to geometric data segmented from in vivo tagged magnetic resonance images (MRI) data and myofibre orientation derived from ex vivo diffusion tensor MRI (DTMRI) of a canine heart using nonlinear finite element fitting techniques. MRI tissue tagging enables quantitative evaluation of cardiac mechanical function with h... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736413 Thu, 16 Jul 2009 23:00:00 +0100 2736413 http://www.medworm.com/index.php?rid=2604557&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150900053X%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604557 Thu, 16 Jul 2009 11:33:50 +0100 2604557 http://www.medworm.com/index.php?rid=2736408&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000486%2Fabstract%3Frss%3Dyes We present a method for the estimation of various features of the tissue micro-architecture using the diffusion magnetic resonance imaging. The considered features are designed from the displacement probability density function (PDF). The estimation is based on two steps: first the approximation of the signal by a series expansion made of Gaussian–Laguerre and Spherical Harmonics functions; followed by a projection on a finite dimensional space. Besides, we propose to tackle the problem of the robustness to Rician noise corrupting in-vivo acquisitions. Our feature estimation is expressed as a variational minimization process leading to a variational framework which is robust to noise. This approach is very flexible regarding the number of samples and enables the computation of a large se... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736408 Mon, 13 Jul 2009 23:00:00 +0100 2736408 http://www.medworm.com/index.php?rid=2736411&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000516%2Fabstract%3Frss%3Dyes Abstract: A scheme for the automatic detection of nodules in thoracic computed tomography scans is presented and extensively evaluated. The algorithm uses the local image features of shape index and curvedness in order to detect candidate structures in the lung volume and applies two successive k-nearest-neighbour classifiers in the reduction of false-positives.The nodule detection system is trained and tested on three databases extracted from a large-scale experimental screening study. The databases are constructed in order to evaluate the algorithm on both randomly chosen screening data as well as data containing higher proportions of nodules requiring follow-up. The system results are extensively evaluated including performance measurements on specific nodule types and sizes within the ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736411 Sun, 12 Jul 2009 23:00:00 +0100 2736411 http://www.medworm.com/index.php?rid=2736409&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000498%2Fabstract%3Frss%3Dyes Abstract: Accurate cortical thickness estimation is important for the study of many neurodegenerative diseases. Many approaches have been previously proposed, which can be broadly categorised as mesh-based and voxel-based. While the mesh-based approaches can potentially achieve subvoxel resolution, they usually lack the computational efficiency needed for clinical applications and large database studies. In contrast, voxel-based approaches, are computationally efficient, but lack accuracy. The aim of this paper is to propose a novel voxel-based method based upon the Laplacian definition of thickness that is both accurate and computationally efficient. A framework was developed to estimate and integrate the partial volume information within the thickness estimation process. Firstly, in a La... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736409 Sun, 12 Jul 2009 23:00:00 +0100 2736409 http://www.medworm.com/index.php?rid=2736410&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000504%2Fabstract%3Frss%3Dyes Abstract: Biomechanical models that simulate brain deformation are gaining attention as alternatives for brain shift compensation. One approach, known as the “forced-displacement method”, constrains the model to exactly match the measured data through boundary condition (BC) assignment. Although it improves model estimates and is computationally attractive, the method generates fictitious forces and may be ill-advised due to measurement uncertainty. Previously, we have shown that by assimilating intraoperatively acquired brain displacements in an inversion scheme, the Representer algorithm (REP) is able to maintain stress-free BCs and improve model estimates by 33% over those without data guidance in a controlled environment. However, REP is computationally efficient only when a few da... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736410 Thu, 09 Jul 2009 23:00:00 +0100 2736410 http://www.medworm.com/index.php?rid=2736407&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000474%2Fabstract%3Frss%3Dyes Abstract: Efficiently obtaining a reliable coronary artery centerline from computed tomography angiography data is relevant in clinical practice. Whereas numerous methods have been presented for this purpose, up to now no standardized evaluation methodology has been published to reliably evaluate and compare the performance of the existing or newly developed coronary artery centerline extraction algorithms. This paper describes a standardized evaluation methodology and reference database for the quantitative evaluation of coronary artery centerline extraction algorithms. The contribution of this work is fourfold: (1) a method is described to create a consensus centerline with multiple observers, (2) well-defined measures are presented for the evaluation of coronary artery centerline extrac... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736407 Tue, 30 Jun 2009 23:00:00 +0100 2736407 http://www.medworm.com/index.php?rid=2736406&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000462%2Fabstract%3Frss%3Dyes Abstract: Measures of brain changes can be computed from sequential MRI scans, providing valuable information on disease progression for neuroscientific studies and clinical trials. Tensor-based morphometry (TBM) creates maps of these brain changes, visualizing the 3D profile and rates of tissue growth or atrophy. In this paper, we examine the power of different nonrigid registration models to detect changes in TBM, and their stability when no real changes are present. Specifically, we investigate an asymmetric version of a recently proposed Unbiased registration method, using mutual information as the matching criterion. We compare matching functionals (sum of squared differences and mutual information), as well as large-deformation registration schemes (viscous fluid and inverse-consiste... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2736406 Wed, 24 Jun 2009 23:00:00 +0100 2736406 http://www.medworm.com/index.php?rid=2604559&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000449%2Fabstract%3Frss%3Dyes Abstract: Diffusion MRI has become an established research tool for the investigation of tissue structure and orientation. Since its inception, Diffusion MRI has expanded considerably to include a number of variations such as diffusion tensor imaging (DTI), diffusion spectrum imaging (DSI) and Q-ball imaging (QBI). The acquisition and analysis of such data is very challenging due to its complexity. Recently, an exciting new Kalman filtering framework has been proposed for DTI and QBI reconstructions in real-time during the repetition time (TR) of the acquisition sequence. In this article, we first revisit and thoroughly analyze this approach and show it is actually sub-optimal and not recursively minimizing the intended criterion due to the Laplace–Beltrami regularization term. Then, we ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604559 Sun, 14 Jun 2009 23:00:00 +0100 2604559 http://www.medworm.com/index.php?rid=2604563&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000450%2Fabstract%3Frss%3Dyes Abstract: We propose a selective method of measurement for computing image similarities based on characteristic structure extraction and demonstrate its application to flexible endoscope navigation, in particular to a bronchoscope navigation system. Camera motion tracking is a fundamental function required for image-guided treatment or therapy systems. In recent years, an ultra-tiny electromagnetic sensor commercially became available, and many image-guided treatment or therapy systems use this sensor for tracking the camera position and orientation. However, due to space limitations, it is difficult to equip the tip of a bronchoscope with such a position sensor, especially in the case of ultra-thin bronchoscopes. Therefore, continuous image registration between real and virtual bronchosco... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604563 Tue, 09 Jun 2009 23:00:00 +0100 2604563 http://www.medworm.com/index.php?rid=2604566&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000401%2Fabstract%3Frss%3Dyes In this study, we extend the application of a brain–skull contact BC by incorporating it into an inversion estimation scheme for the deformation field using the steepest gradient descent (SGD) framework. The technique allows parenchymal surface motion normal to the skull while maintaining stress-free BCs at the craniotomy and minimizing the effect of measurement noise. Application of the algorithm in five clinical cases using sparse data generated at the tumor boundary confirms the significance of brain–skull BCs in the model response. Specifically, the results demonstrate that the contact BC enhances model flexibility and achieves improved or comparable performance at the tumor boundary (recovering about 85% of the deformation) relative to that obtained when normal motion of the paren... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604566 Wed, 03 Jun 2009 23:00:00 +0100 2604566 http://www.medworm.com/index.php?rid=2604561&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000437%2Fabstract%3Frss%3Dyes Abstract: Real-time cardiac MRI appears as a promising technique to evaluate the mechanical function of the heart. However, ultra-fast MRI acquisitions come with an important signal-to-noise ratio (SNR) penalty, which drastically reduces the image quality. Hence, a real-time denoising approach would be desirable for SNR amelioration. In the clinical context of cardiac dysfunction assessment, long acquisitions are required and for most patients the acquisition takes place with free breathing. Hence, it is necessary to compensate respiratory motion in real-time.In this article, a real-time and interactive method for sequential registration and denoising of real-time MR cardiac images is presented. The method has been experimented on 60 fast MRI acquisitions in five healthy volunteers and fiv... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604561 Sun, 31 May 2009 23:00:00 +0100 2604561 http://www.medworm.com/index.php?rid=2604565&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000413%2Fabstract%3Frss%3Dyes In this study, an automatic method to detect hard exudates is proposed. The algorithm is based on mixture models to dynamically threshold the images in order to separate exudates from background. A postprocessing technique, based on edge detection, is applied to distinguish hard exudates from cotton wool spots and other artefacts. We prospectively assessed the algorithm performance using a database of 80 retinal images with variable colour, brightness, and quality. The algorithm obtained a sensitivity of 90.2% and a positive predictive value of 96.8% using a lesion-based criterion. The image-based classification accuracy is also evaluated obtaining a sensitivity of 100% and a specificity of 90%. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604565 Thu, 28 May 2009 23:00:00 +0100 2604565 http://www.medworm.com/index.php?rid=2604558&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000425%2Fabstract%3Frss%3Dyes Abstract: Statistical shape models (SSMs) have by now been firmly established as a robust tool for segmentation of medical images. While 2D models have been in use since the early 1990s, wide-spread utilization of three-dimensional models appeared only in recent years, primarily made possible by breakthroughs in automatic detection of shape correspondences. In this article, we review the techniques required to create and employ these 3D SSMs. While we concentrate on landmark-based shape representations and thoroughly examine the most popular variants of Active Shape and Active Appearance models, we also describe several alternative approaches to statistical shape modeling. Structured into the topics of shape representation, model construction, shape correspondence, local appearance models ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604558 Wed, 27 May 2009 23:00:00 +0100 2604558 http://www.medworm.com/index.php?rid=2604564&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000395%2Fabstract%3Frss%3Dyes This article presents an overview of these algorithms, the way they work, their benefits and their limits. The aim of this review is to explain and to categorize the various algorithms into groups and their application in the field of medical signal analysis. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604564 Tue, 26 May 2009 23:00:00 +0100 2604564 http://www.medworm.com/index.php?rid=2604562&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000383%2Fabstract%3Frss%3Dyes Abstract: Prostate biopsy is the current gold-standard procedure for prostate cancer diagnosis. Existing prostate biopsy procedures have been mostly focusing on detecting cancer presence. However, they often ignore the potential use of biopsy to estimate cancer volume (CV) and Gleason Score (GS, a cancer grade descriptor), the two surrogate markers for cancer aggressiveness and the two crucial factors for treatment planning. To fill up this vacancy, this paper assumes and demonstrates that, by optimally sampling the spatial patterns of cancer, biopsy procedures can be specifically designed for estimating CV and GS. Our approach combines image analysis and machine learning tools in an atlas-based population study that consists of three steps. First, the spatial distributions of cancer in a ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604562 Sun, 24 May 2009 23:00:00 +0100 2604562 http://www.medworm.com/index.php?rid=2604560&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000371%2Fabstract%3Frss%3Dyes Abstract: We propose the use of Perturbation theory to reduce noise in Diffusion Tensor (DT) fields. Diffusion Tensor Imaging (DTI) encodes the diffusion of water molecules along different spatial directions in a positive definite, symmetric tensor. Eigenvectors and eigenvalues of DTs allow the in vivo visualization and quantitative analysis of white matter fiber bundles across the brain. The validity and reliability of these analyses are limited, however, by the low spatial resolution and low Signal-to-Noise Ratio (SNR) in DTI datasets. Our procedures can be applied to improve the validity and reliability of these quantitative analyses by reducing noise in the tensor fields. We model a tensor field as a three-dimensional Markov Random Field and then compute the likelihood and the prior te... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604560 Sun, 17 May 2009 23:00:00 +0100 2604560 http://www.medworm.com/index.php?rid=2394763&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000309%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2394763 Thu, 07 May 2009 19:59:00 +0100 2394763 http://www.medworm.com/index.php?rid=2604567&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000280%2Fabstract%3Frss%3Dyes Abstract: The brain deformation that occurs during neurosurgery is a serious issue impacting the patient “safety” as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians’ experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an exte... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2604567 Sun, 12 Apr 2009 23:00:00 +0100 2604567 http://www.medworm.com/index.php?rid=2362030&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000868%2Fabstract%3Frss%3Dyes Abstract: The aim of this work was to demonstrate the correspondence between a macroscopic 3D computer model of electrophysiology (i.e., the Aliev–Panfilov model) parametrized with MR data and experimental characterization of action potential propagation in large porcine hearts, ex vivo, using optical methods (based on voltage-sensitive fluorescence). A secondary goal was to use one of these studies to demonstrate an optimized method for regional adjustment of critical model parameters (i.e., adjustment of the local conductivity from the isochronal maps obtained via optical images). There was good agreement between model behaviour and experiment using fusion of optical and MR data, and model parameters from previous work in the literature. Specifically, qualitative comparison between com... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362030 Wed, 01 Apr 2009 04:00:00 +0100 2362030 http://www.medworm.com/index.php?rid=2362029&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000698%2Fabstract%3Frss%3Dyes Conclusions: The model results suggest that uniformity of mechanical contraction in non-scarred regions in the failing heart during biventricular pacing is independent of scar size for a fixed pacing site. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362029 Wed, 01 Apr 2009 04:00:00 +0100 2362029 http://www.medworm.com/index.php?rid=2362028&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000972%2Fabstract%3Frss%3Dyes In conclusion, Hyperelastic Warping provides a unique alternative for quantifying regional LV deformation during systole without the need for tags. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362028 Wed, 01 Apr 2009 04:00:00 +0100 2362028 http://www.medworm.com/index.php?rid=2362027&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000686%2Fabstract%3Frss%3Dyes Abstract: Deformation and structure of the cardiac wall can be assessed non-invasively by imaging techniques such as magnetic resonance imaging. Understanding the (patho-)physiology that underlies the observed deformation and structure is critical for clinical diagnosis. However, much about the genesis of deformation and structure is unknown. In the present computational model study, we hypothesize that myofibers locally adapt their orientation to achieve minimal fiber-cross fiber shear strain during the cardiac cycle. This hypothesis was tested in a 3D finite element model of left ventricular (LV) mechanics by computation of tissue deformations and subsequent adaptation of initial myofiber orientations towards those in the deformed tissue. As a consequence of adaptation, local tissue peak... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362027 Wed, 01 Apr 2009 04:00:00 +0100 2362027 http://www.medworm.com/index.php?rid=2362026&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000960%2Fabstract%3Frss%3Dyes This special issue of Medical Image Analysis presents modelling studies of cardiac anatomy and physiology. The studies represent a selection from scientific research introduced at the Fourth International Conference on Functional Imaging and Modelling of the Heart (FIMH). The conference was held on the 7th to 9th of June 2007 at the University of Utah, Salt Lake City, Utah, USA. The FIMH proceedings consist of 48 peer reviewed full articles (). The 29 oral and 28 poster presentations made the FIMH conference a major event for those interested in cardiac modelling, imaging, and image processing. More than 120 participants from 17 countries attended the FIMH conference. A novel feature was the industry session. Invited speakers from companies, which offer products for cardiac diagnosis and t... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362026 Wed, 01 Apr 2009 04:00:00 +0100 2362026 http://www.medworm.com/index.php?rid=2362025&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001412%2Fabstract%3Frss%3Dyes We describe approaches based on a mixture of particle filters and based on independent particle filters. For the latter, we have developed a penalization strategy that prevents the problem of filter coalescence (merging) in cases where objects lie in close proximity. A quantitative comparison based on synthetic image sequences is carried out to evaluate the performance of our approaches. In total, eight different tracking approaches have been evaluated. We have also applied these approaches to real microscopy images of HIV-1 particles and have compared the tracking results with ground truth obtained from manual tracking. It turns out that the probabilistic approaches based on independent particle filters are superior to the deterministic schemes as well as to the approaches based on a mixt... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362025 Wed, 01 Apr 2009 04:00:00 +0100 2362025 http://www.medworm.com/index.php?rid=2362024&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001400%2Fabstract%3Frss%3Dyes Abstract: Wireless Capsule Endoscopy (WCE) provides a means to obtain a detailed video of the small intestine. A single session with WCE may produce nearly 8h of video. Its interpretation is tedious task, which requires considerable expertise and is very stressful. The Model of Deformable Rings (MDR) was developed to preprocess WCE video and aid clinicians with its interpretation. The MDR uses a simplified model of a capsule’s motion to flexibly match (register) consecutive video frames. Essentially, it computes motion-descriptive characteristics and produces a two-dimensional representation of the gastrointestinal (GI) tract’s internal surface – a map. The motion-descriptive characteristics are used to indicate video fragments which exhibit segmentary contractions, peristalsis, refr... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362024 Wed, 01 Apr 2009 04:00:00 +0100 2362024 http://www.medworm.com/index.php?rid=2362023&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001357%2Fabstract%3Frss%3Dyes Abstract: Obtaining validation data and comparison metrics for segmentation of magnetic resonance images (MRI) are difficult tasks due to the lack of reliable ground truth. This problem is even more evident for images presenting pathology, which can both alter tissue appearance through infiltration and cause geometric distortions. Systems for generating synthetic images with user-defined degradation by noise and intensity inhomogeneity offer the possibility for testing and comparison of segmentation methods. Such systems do not yet offer simulation of sufficiently realistic looking pathology. This paper presents a system that combines physical and statistical modeling to generate synthetic multi-modal 3D brain MRI with tumor and edema, along with the underlying anatomical ground truth, Mai... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362023 Wed, 01 Apr 2009 04:00:00 +0100 2362023 http://www.medworm.com/index.php?rid=2362022&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001187%2Fabstract%3Frss%3Dyes Abstract: Displacement estimation is a key step in the evaluation of tissue elasticity by quasistatic strain imaging. An efficient approach may incorporate a tracking strategy whereby each estimate is initially obtained from its neighbours’ displacements and then refined through a localized search. This increases the accuracy and reduces the computational expense compared with exhaustive search. However, simple tracking strategies fail when the target displacement map exhibits complex structure. For example, there may be discontinuities and regions of indeterminate displacement caused by decorrelation between the pre- and post-deformation radio frequency (RF) echo signals. This paper introduces a novel displacement tracking algorithm, with a search strategy guided by a data quality indic... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362022 Wed, 01 Apr 2009 04:00:00 +0100 2362022 http://www.medworm.com/index.php?rid=2362021&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001175%2Fabstract%3Frss%3Dyes Abstract: Several algorithms for measuring the cortical thickness in the human brain from MR image volumes have been described in the literature, the majority of which rely on fitting deformable models to the inner and outer cortical surfaces. However, the constraints applied during the model fitting process in order to enforce spherical topology and to fit the outer cortical surface in narrow sulci, where the cerebrospinal fluid (CSF) channel may be obscured by partial voluming, may introduce bias in some circumstances, and greatly increase the processor time required.In this paper we describe an alternative, voxel based technique that measures the cortical thickness using inversion recovery anatomical MR images. Grey matter, white matter and CSF are identified through segmentation, and e... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362021 Wed, 01 Apr 2009 04:00:00 +0100 2362021 http://www.medworm.com/index.php?rid=2362020&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150800114X%2Fabstract%3Frss%3Dyes We present a fully automated phase unwrapping algorithm (ΦUN) which is optimized for high-resolution magnetic resonance imaging data. The algorithm is a region growing method and uses separate quality maps for seed finding and unwrapping which are retrieved from the full complex information of the data. We compared our algorithm with an established method in various phantom and in vivo data and found a very good agreement between the results of both techniques. ΦUN, however, was significantly faster at low signal to noise ratio (SNR) and data with a more complex phase topography, making it particularly suitable for applications with low SNR and high spatial resolution. ΦUN is freely available to the scientific community. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362020 Wed, 01 Apr 2009 04:00:00 +0100 2362020 http://www.medworm.com/index.php?rid=2362019&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001138%2Fabstract%3Frss%3Dyes Abstract: VS is a simple system consisting of several techniques for various volumetric problems. Based on the marching cubes algorithm, it operates with one space sweep through the voxels and extracts all topological information: detection of all isosurfaces, partitioning the data into connected components on the basis of surface connectivity, and association of surfaces with any internal surfaces to arbitrary levels of nesting. VS extends Baker’s “Weaving Wall” method by associating topological cavities with their outer surface, and by using efficient data structures for the voxel traversal and for the connected component detection. Its runtime, on average, is only about 2% more than the speeded-up marching cubes algorithm. VS operates on the original voxels without using the conto... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362019 Wed, 01 Apr 2009 04:00:00 +0100 2362019 http://www.medworm.com/index.php?rid=2362018&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001035%2Fabstract%3Frss%3Dyes Abstract: Efficient and accurate techniques for simulation of soft tissue deformation are an increasingly valuable tool in many areas of medical image computing, such as biomechanically-driven image registration and interactive surgical simulation. For reasons of efficiency most analyses are based on simplified linear formulations, and previously almost all have ignored well established features of tissue mechanical response such as anisotropy and time-dependence. We address these latter issues by firstly presenting a generalised anisotropic viscoelastic constitutive framework for soft tissues, particular cases of which have previously been used to model a wide range of tissues. We then develop an efficient solution procedure for the accompanying viscoelastic hereditary integrals which all... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362018 Wed, 01 Apr 2009 04:00:00 +0100 2362018 http://www.medworm.com/index.php?rid=2362017&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001023%2Fabstract%3Frss%3Dyes Abstract: Images from different individuals typically cannot be registered precisely because anatomical features within the images differ across the people imaged and because the current methods for image registration have inherent technological limitations that interfere with perfect registration. Quantifying the inevitable error in image registration is therefore of crucial importance in assessing the effects that image misregistration may have on subsequent analyses in an imaging study. We have developed a mathematical framework for quantifying errors in registration by computing the confidence intervals of the estimated parameters (3 translations, 3 rotations, and 1 global scale) for the similarity transformation.The presence of noise in images and the variability in anatomy across ind... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362017 Wed, 01 Apr 2009 04:00:00 +0100 2362017 http://www.medworm.com/index.php?rid=2362016&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000984%2Fabstract%3Frss%3Dyes Abstract: Some surfaces present folding patterns formed by juxtapositions of ridges and valleys as, for example, the cortical surface of the human brain. The fundamental problem with ridges is to find a correspondence among and analyze the variability among them. Many techniques to achieve these goals exist but use scalar functions. Depth maps are used to efficiently project the geometry of folds into a scalar function in the case where a natural projection plane exists. However, in most cases of curved surfaces, there is no natural projection plane to represent folding patterns.This paper studies the problem of shape matching and analysis of folding patterns by extending the notion of depth maps when no natural projection plane exists. The novel depth measure is called a depth potential f... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362016 Wed, 01 Apr 2009 04:00:00 +0100 2362016 http://www.medworm.com/index.php?rid=2362015&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000716%2Fabstract%3Frss%3Dyes The objective function of the conventional fuzzy C-means (FCM) method is modified to allow multiscale classification processing where the result from a coarse scale supervises the classification in the next fine scale. The method is robust for noise and low-contrast MR images because of its multiscale diffusion filtering scheme. The new method was compared with the conventional FCM method and a modified FCM (MFCM) method. Validation studies were performed on synthesized images with various contrasts and on the McGill brain MR image database. Our MsFCM method consistently performed better than the conventional FCM and MFCM methods. The MsFCM method achieved an overlap ratio of greater than 90% as validated by the ground truth. Experiments results on real MR images were given to demonstrate ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362015 Wed, 01 Apr 2009 04:00:00 +0100 2362015 http://www.medworm.com/index.php?rid=2362014&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000164%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362014 Wed, 01 Apr 2009 04:00:00 +0100 2362014 http://www.medworm.com/index.php?rid=2362013&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000188%2Fabstract%3Frss%3Dyes (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2362013 Wed, 01 Apr 2009 04:00:00 +0100 2362013 http://www.medworm.com/index.php?rid=2495261&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000073%2Fabstract%3Frss%3Dyes Abstract: We propose a novel approach for the simultaneous segmentation of multiple structures with competitive level sets driven by fuzzy control. To this end, several contours evolve simultaneously toward previously defined anatomical targets. A fuzzy decision system combines the a priori knowledge provided by an anatomical atlas with the intensity distribution of the image and the relative position of the contours. This combination automatically determines the directional term of the evolution equation of each level set. This leads to a local expansion or contraction of the contours, in order to match the boundaries of their respective targets. Two applications are presented: the segmentation of the brain hemispheres and the cerebellum, and the segmentation of deep internal structures. ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495261 Thu, 12 Mar 2009 00:00:00 +0100 2495261 http://www.medworm.com/index.php?rid=2495267&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000139%2Fabstract%3Frss%3Dyes Abstract: A novel Sampling Sphere Orientation Distribution (SSOD) method based on mobile sampling spheres is developed for describing microstructural anisotropy of trabecular bone using grayscale images. Efficient implementation of SSOD on segmented and unsegmented 3D CT images of human trabecular bone samples from different anatomical locations is demonstrated. The second order fabric tensor of SSOD corresponds well with the one derived from the mean intercept length (MIL) method applied on segmented images. The results of SSOD are extended to higher order fabric approximations and the effect of sampling sphere radius is examined. Finally, performance of the method on artificial microstructures is presented. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495267 Mon, 09 Mar 2009 00:00:00 +0100 2495267 http://www.medworm.com/index.php?rid=2495266&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000127%2Fabstract%3Frss%3Dyes Abstract: Creation of a transjugular intrahepatic portosystemic shunt (TIPS) requires passage of a needle toward a moving target that is only seen transiently by X-ray prior to needle passage. Intraoperative, 3D target localization would facilitate target access and improve the safety of the procedure. The clinical assumption is that patients undergoing the TIPS procedure possess rigid, cirrhotic livers that undergo only intraoperative translation without significant deformation or rotation. Based upon this assumption, we hypothesize that the position of any unseen, 3D target point within the liver can be determined intraoperatively by precalculation of the relative positions of the target point to a different 3D point that can be tracked intraoperatively. This paper examines this hypothes... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495266 Fri, 06 Mar 2009 00:00:00 +0100 2495266 http://www.medworm.com/index.php?rid=2495263&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000097%2Fabstract%3Frss%3Dyes Abstract: Automated and accurate segmentation of the aorta in 4D (3D+time) cardiovascular magnetic resonance (MR) image data is important for early detection of congenital aortic disease leading to aortic aneurysms and dissections. A computer-aided diagnosis (CAD) method is reported that allows one to objectively identify subjects with connective tissue disorders from 16-phase 4D aortic MR images. Starting with a step of multi-view image registration, our automated segmentation method combines level-set and optimal surface segmentation algorithms in a single optimization process so that the final aortic surfaces in all 16 cardiac phases are determined. The resulting aortic lumen surface is registered with an aortic model followed by calculation of modal indices of aortic shape and motion. ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495263 Tue, 24 Feb 2009 00:00:00 +0100 2495263 http://www.medworm.com/index.php?rid=2495265&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000115%2Fabstract%3Frss%3Dyes Abstract: Unsupervised decomposition of static linear mixture model (SLMM) with ill-conditioned basis matrix and statistically dependent sources is considered. Such situation arises when low-dimensional low-intensity multi-spectral image of the tumour in the early stage of development is represented by the SLMM, wherein tumour is spectrally similar to the surrounding tissue. The original contribution of this paper is in proposing an algorithm for unsupervised decomposition of low-dimensional multi-spectral image for high-contrast tumour visualisation. It combines nonlinear band generation (NBG) and dependent component analysis (DCA) that itself combines linear pre-processing transform and independent component analysis (ICA). NBG is necessary to improve conditioning of the extended mixing ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495265 Mon, 23 Feb 2009 00:00:00 +0100 2495265 http://www.medworm.com/index.php?rid=2495264&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000103%2Fabstract%3Frss%3Dyes We present in this paper an augmented reality guidance system for liver thermal ablation in interventional radiology. To show the relevance of our methodology, the system is incrementally evaluated on an abdominal phantom and then on patients in the operating room. The system registers in a common coordinate system a preoperative image of the patient and the position of the needle that the practitioner manipulates. The breathing motion uncertainty is taken into account with a respiratory gating technique: the preoperative image and the guidance step are synchronized on expiratory phases. In order to fulfil the real-time constraints, we have developed and validated algorithms that automatically process and extract feature points. Since the guidance interface is also a major component of the... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495264 Mon, 23 Feb 2009 00:00:00 +0100 2495264 http://www.medworm.com/index.php?rid=2495262&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000085%2Fabstract%3Frss%3Dyes Abstract: For many orthopaedic, neurological, and oncological applications, an exact segmentation of the vertebral column including an identification of each vertebra is essential. However, although bony structures show high contrast in CT images, the segmentation and labelling of individual vertebrae is challenging.In this paper, we present a comprehensive solution for automatically detecting, identifying, and segmenting vertebrae in CT images. A framework has been designed that takes an arbitrary CT image, e.g., head-neck, thorax, lumbar, or whole spine, as input and provides a segmentation in form of labelled triangulated vertebra surface models. In order to obtain a robust processing chain, profound prior knowledge is applied through the use of various kinds of models covering shape, g... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495262 Mon, 23 Feb 2009 00:00:00 +0100 2495262 http://www.medworm.com/index.php?rid=2495260&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000061%2Fabstract%3Frss%3Dyes Conclusion: The teleoperated 1-DOF needle driver system presented in this paper demonstrates the feasibility of implementing a MRI-compatible robot for RFA of breast tumors with haptic feedback capability. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495260 Thu, 19 Feb 2009 00:00:00 +0100 2495260 http://www.medworm.com/index.php?rid=2495259&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150900005X%2Fabstract%3Frss%3Dyes Abstract: Computing the orientation distribution function (ODF) from high angular resolution diffusion imaging (HARDI) signals makes it possible to determine the orientation of fiber bundles of the brain. The HARDI signals are samples measured from a spherical shell and thus require processing on the sphere. Past work on ODF estimation involved using the spherical harmonics or spherical radial basis functions. In this work, we propose three novel directional functions able to represent the measured signals in a very compact manner, i.e., they require very few parameters to completely describe the measured signal. Analytical expressions are derived for computing the corresponding ODF. The directional functions can represent diffusion in a particular direction and mixture models can be used ... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495259 Fri, 06 Feb 2009 00:00:00 +0100 2495259 http://www.medworm.com/index.php?rid=2495258&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000048%2Fabstract%3Frss%3Dyes We describe a system for respiratory motion correction of MRI-derived roadmaps for use in X-ray guided cardiac catheterisation procedures. The technique uses a subject-specific affine motion model that is quickly constructed from a short pre-procedure MRI scan. We test a dynamic MRI sequence that acquires a small number of high resolution slices, rather than a single low resolution volume. Additionally, we use prior knowledge of the nature of cardiac respiratory motion by constraining the model to use only the dominant modes of motion. During the procedure the motion of the diaphragm is tracked in X-ray fluoroscopy images, allowing the roadmap to be updated using the motion model. X-ray image acquisition is cardiac gated. Validation is performed on four volunteer datasets and three patient... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495258 Fri, 23 Jan 2009 00:00:00 +0100 2495258 http://www.medworm.com/index.php?rid=2495257&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000036%2Fabstract%3Frss%3Dyes Abstract: Diffusion tensor MRI (DT-MRI) is an imaging technique that is gaining importance in clinical applications. However, there is very little work concerning the human heart. When applying DT-MRI to in vivo human hearts, the data have to be acquired rapidly to minimize artefacts due to cardiac and respiratory motion and to improve patient comfort, often at the expense of image quality. This results in diffusion weighted (DW) images corrupted by noise, which can have a significant impact on the shape and orientation of tensors and leads to diffusion tensor (DT) datasets that are not suitable for fibre tracking. This paper compares regularization approaches that operate either on diffusion weighted images or on diffusion tensors. Experiments on synthetic data show that, for high signal-... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495257 Wed, 21 Jan 2009 00:00:00 +0100 2495257 http://www.medworm.com/index.php?rid=2495256&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841509000024%2Fabstract%3Frss%3Dyes Abstract: Automated interpretation and classification of functional MRI (fMRI) data is an emerging research field that enables the characterization of underlying cognitive processes with minimal human intervention. In this work, we present a method for the automated classification of human thoughts reflected on a trial-based paradigm using fMRI with a significantly shortened data acquisition time (less than one minute). Based on our preliminary experience with various cognitive imagery tasks, six characteristic thoughts were chosen as target tasks for the present work: right-hand motor imagery, left-hand motor imagery, right foot motor imagery, mental calculation, internal speech/word generation, and visual imagery. These six tasks were performed by five healthy volunteers and functional i... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495256 Mon, 19 Jan 2009 00:00:00 +0100 2495256 http://www.medworm.com/index.php?rid=2495255&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS136184150800145X%2Fabstract%3Frss%3Dyes Abstract: In MRI scans that are acquired in a slice-by-slice manner, patient motion during scanning can cause adjacent slices to overlap, resulting in duplicate coverage in some areas and missing coverage in others. Scans in which multiple slices are acquired simultaneously and interleaved with other sets of slices are particularly vulnerable because a single movement can result in the misalignment and overlap of many slices. Despite the fact that considerable data losses can occur even with few visible artifacts, this problem has received very little attention from MRI researchers. The primary goals of this paper are: (1) to raise awareness of the problem in the MRI community and (2) to present an efficient multiscale algorithm that accurately quantifies the amount of data loss. Validatio... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495255 Fri, 09 Jan 2009 00:00:00 +0100 2495255 http://www.medworm.com/index.php?rid=2941879&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001436%2Fabstract%3Frss%3Dyes We present two biomechanical models of cortical folding which integrate 3D geometry and information taken from MRI scans of fetal sheep brains at a number of key developmental stages. The first model utilises diffusion tensor imaging (DTI) measurements of white matter fibre orientation in the fetal sheep brains as a cue to the tension forces that may regulate folding. In the second model, tangential cortical growth is modelled by osmotic expansion of the tissue and regulated by inhomogeneous white matter rigidity as a biomechanism of cortical folding. This is based on quantitative analysis of cortical growth and inhomogeneous white matter anisotropy measured from the MRI data. We demonstrate that structural and diffusion tensor MRI can be combined with finite element modelling and an expli... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941879 Mon, 05 Jan 2009 00:00:00 +0100 2941879 http://www.medworm.com/index.php?rid=2941874&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001448%2Fabstract%3Frss%3Dyes Abstract: Constructing a 3D bone surface model from a limited number of calibrated 2D X-ray images (e.g. 2) and a 3D point distribution model is a challenging task, especially, when we would like to construct a patient-specific surface model of a bone with pathology. One of the key steps for such a 2D/3D reconstruction is to establish correspondences between the 2D images and the 3D model. This paper presents a 2D/3D correspondence building method based on a non-rigid 2D point matching process, which iteratively uses a symmetric injective nearest-neighbor mapping operator and 2D thin-plate splines based deformations to find a fraction of best matched 2D point pairs between features extracted from the X-ray images and those extracted from the 3D model. The estimated point pairs are then use... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941874 Mon, 22 Dec 2008 00:00:00 +0100 2941874 http://www.medworm.com/index.php?rid=2941878&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001424%2Fabstract%3Frss%3Dyes Abstract: Real time computation of soft tissue deformation is important for the use of augmented reality devices and for providing haptic feedback during operation or surgeon training. This requires algorithms that are fast, accurate and can handle material nonlinearities and large deformations. A set of such algorithms is presented in this paper, starting with the finite element formulation and the integration scheme used and addressing common problems such as hourglass control and locking. The computation examples presented prove that by using these algorithms, real time computations become possible without sacrificing the accuracy of the results. For a brain model having more than 7000 degrees of freedom, we computed the reaction forces due to indentation with frequency of around 1000Hz... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941878 Wed, 17 Dec 2008 00:00:00 +0100 2941878 http://www.medworm.com/index.php?rid=2941880&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001205%2Fabstract%3Frss%3Dyes Abstract: In this paper, we present a new computationally efficient numerical scheme for the minimizing flow approach for optimal mass transport (OMT) with applications to non-rigid 3D image registration. The approach utilizes all of the gray-scale data in both images, and the optimal mapping from image to image is the inverse of the optimal mapping from to . Further, no landmarks need to be specified, and the minimizer of the distance functional involved is unique. Our implementation also employs multigrid, and parallel methodologies on a consumer graphics processing unit (GPU) for fast computation. Although computing the optimal map has been shown to be computationally expensive in the past, we show that our approach is orders of magnitude faster then previous work and is capable of find... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941880 Tue, 09 Dec 2008 00:00:00 +0100 2941880 http://www.medworm.com/index.php?rid=2941877&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508001114%2Fabstract%3Frss%3Dyes A novel partnership between surgeons and machines, made possible by advances in computing and engineering technology, could overcome many of the limitations of traditional surgery. By extending surgeons’ ability to plan and carry out surgical interventions more accurately and with less trauma, Computer-Integrated Surgery (CIS) systems could help to improve clinical outcomes and the efficiency of health care delivery. CIS systems could have a similar impact on surgery to that long since realized in Computer-Integrated Manufacturing (CIM). Mathematical modeling and computer simulation have proved tremendously successful in engineering. Computational mechanics has enabled technological developments in virtually every area of our lives. One of the greatest challenges for mechanists is to ext... Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2941877 Fri, 24 Oct 2008 00:00:00 +0100 2941877 http://www.medworm.com/index.php?rid=2495268&cid=s_38553_37_f&fid=38553&url=http%3A%2F%2Fwww.radiologysource.org%2Fperiodicals%2Fmedima%2Farticle%2FPIIS1361841508000959%2Fabstract%3Frss%3Dyes The correct author line with affiliations are given above. (Source: Medical Image Analysis) Medical Image Analysis journals http://www.medworm.com/rss/comments.php?id=2495268 Mon, 18 Aug 2008 23:00:00 +0100 2495268