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Age-related microstructural changes in brain white matter can be studied by utilizing indices derived from diffusion tensor imaging (DTI): apparent diffusion coefficient (ADC) and fractional anisotropy (FA). The objective of this study is to examine alterations in FA and ADC by employing exploratory voxel-based analysis (VBA) and region(s) of interest(More)
We present a new method for automatic segmentation of heterogeneous image data that takes a step toward bridging the gap between bottom-up affinity-based segmentation methods and top-down generative model based approaches. The main contribution of the paper is a Bayesian formulation for incorporating soft model assignments into the calculation of(More)
We generalize the total variation restoration model, introduced by Rudin, Osher, and Fatemi in 1992, to matrix-valued data, in particular, to diffusion tensor images (DTIs). Our model is a natural extension of the color total variation model proposed by Blomgren and Chan in 1998. We treat the diffusion matrix D implicitly as the product D = LL(T), and work(More)
Diffusion-weighted images based on echo planar sequences suffer from distortions due to field inhomogeneities from susceptibility differences as well as from eddy currents arising from diffusion gradients. In this paper, a novel approach using nonlinear warping based on optic flow to correct distortions of baseline and diffusion weighted echo planar images(More)
PURPOSE To investigate a tetrahedral diffusion gradient encoding scheme to measure the diffusion tensor in vivo for human calf muscle. MATERIALS AND METHODS The theoretical TE which maximizes the signal-to-noise ratio (SNR) of the diffusion images was derived for both the orthogonal and tetrahedral sampling strategies and the SNR advantage verified(More)
Proton phase shift imaging methods with keyholing were developed to rapidly monitor temperature during MR-guided radiofrequency (RF) interventional procedures on a .2-T open configuration scanner. Temperature calibration was performed on thermally controlled gel phantom and ex vivo bovine liver samples. Keyholing methods were implemented for rapid imaging(More)
PURPOSE To create an average atlas of knee femoral cartilage morphology, to apply the atlas for quantitative assessment of osteoarthritis (OA), and to study localized sex differences. MATERIALS AND METHODS High-resolution 3D magnetic resonance imaging (MRI) data of the knee cartilage collected at 3 T as part of the Osteoarthritis Initiative (OAI) were(More)
In magnetic resonance imaging susceptibility artifacts occur at the interface of substances with large magnetic susceptibility differences, resulting in geometric distortions of the image at those boundaries. The susceptibility artifacts are often subtle on clinical images and if not carefully examined they may lead to misdiagnosis. Magnetic susceptibility(More)
The development of comprehensive picture archive and communication systems (PACS) has mainly been limited to proprietary developments by vendors, though a number of freely available software projects have addressed specific image management tasks. The openSourcePACS project aims to provide an open source, common foundation upon which not only can a basic(More)
The response of signal intensity to transient (on-off) motor and sensory stimulation has been well studied; however, the dependence of signal response on the duration of stimulus requires further characterization. The objective of this study was to determine the time course of signal response in the human visual cortex to prolonged, sustained stimulation(More)