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We demonstrate a new technique to quantify longitudinal changes in magnetization transfer ratio (MTR) magnetic resonance imaging (MRI). These changes are indicative of demyelination and remyelination. This technique comprises a definition of ΔMTR lesions, which are identified directly from the MTR images, and an automatic procedure for segmenting these(More)
Examining the frequency content of signals is critical in many applications, from neuroscience to astronomy. Many techniques have been proposed to accomplish this. One of these, the S-transform, provides simultaneous time and frequency information similar to the wavelet transform, but uses sinusoidal basis functions to produce frequency and globally(More)
The American Academy of Actuaries is the public policy organization for actuaries practicing in all specialties within the United States. A major purpose of the Academy is to act as the public information organization for the profession. The Academy is nonpartisan and assists the public policy process through the presentation of clear and objective(More)
We report a method that uses " completeness " to estimate the number of exrasolar planets discovered by an observing program with a direct-imaging instrument. We develop a completeness function for Earth-like planets on " habitable " orbits for an instrument with a central field obscuration, uniform sensitivity in an annular detection zone, and limiting(More)
It is thought that gray and white matter (GM and WM) have different perfusion and diffusion thresholds for cerebral infarction in humans. We sought to determine these thresholds with voxel-by-voxel, tissue-specific analysis of co-registered acute and follow-up magnetic resonance (MR) perfusion- and diffusion-weighted imaging. Quantitative cerebral blood(More)
We investigated fluctuations in brain volume throughout the day using statistical modeling of magnetic resonance imaging (MRI) from large populations. We applied fully automated image analysis software to measure the brain parenchymal fraction (BPF), defined as the ratio of the brain parenchymal volume and intracranial volume, thus accounting for variations(More)
This document is a work of the U.S. Government and is in the public domain. It may be distributed and copied subject to the following stipulation: Copyrights to graphics included in this document are reserved by original copyright holders or their assignees, and are used here with permission. on matters involving science and technology policy," and "shall(More)
In this study of 263 heart, kidney, liver, and pancreas transplant patients, BK virus (BKV) and JC virus (JCV) DNAemia were observed most commonly in kidney and/or pancreas transplant patients (26%), although they were also observed, to a lesser extent, in heart (7%) and liver (4%) transplant patients. The majority of episodes of polyomavirus DNAemia were(More)
A novel and automated technique is described for removing fMRI image artifacts resulting from motion outside of the imaging field of view. The technique is based on the Stockwell transform (ST), a mathematical operation that provides the frequency content at each time point within a time-varying signal. Using this technique, 1D Fourier transforms (FTs) are(More)
Multiple sclerosis (MS) is characterized by the formation of demyelinating lesions in the white matter (WM). However, the timecourse of the evolution of healthy white matter into fully demyelinated lesions in MS is not well understood. We use a recently proposed technique to examine magnetization transfer ratio (MTR) timecourses in lesions segmented from(More)