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Proton MR spectroscopic imaging (MRSI) at higher magnetic fields (B(0)) suffers metabolite localization errors from different chemical-shift displacements (CSDs) if spatially-selective excitation is used. This phenomenon is exacerbated by the decreasing radiofrequency (RF) field strength, B(1), at higher B(0)s, precluding its suppression with stronger(More)
A survey of Galactic gamma-ray sources at a median energy of ∼20 TeV has been performed using the Milagro Gamma Ray Observatory. Eight candidate sources of TeV emission are detected with pre-trials significance > 4.5σ in the region of Galactic longitude l ∈ [30 • , 220 • ] and latitude b ∈ [−10 • , 10 • ]. Four of these sources, including the Crab nebula(More)
Although recent studies indicate that use of a single global transverse relaxation time, T(2), per metabolite is sufficient for better than +/-10% quantification precision at intermediate and short echo-time spectroscopy in young adults, the age-dependence of this finding is unknown. Consequently, the age effect on regional brain choline (Cho), creatine(More)
The transverse relaxation times, T(2), of N-acetylaspartate (NAA), total choline (Cho), and creatine (Cr) obtained at 3T in several human brain regions of eight healthy volunteers are reported. They were obtained simultaneously in 320 voxels with three-dimensional (3D) proton MR spectroscopy ((1)H-MRS) at 1 cm(3) spatial resolution. A two-point protocol,(More)
Fast, high-resolution, longitudinal relaxation time (T1) mapping is invaluable in clinical and research applications. It has been shown that two spoiled gradient recalled echo (SPGR) images acquired in steady state with variable flip angles is an attractive alternative to the multi-image sets previously acquired with inversion or saturation recovery. The(More)
Although Fourier gradient phase-encoding and Hadamard radio-frequency encoding are two established spatial MR localization techniques, the absence of voxel-shift and interpolation postprocessing algorithms for the latter has always placed it at a discouraging disadvantage. This article presents a method for voxel-shift and interpolation of Hadamard-encoded(More)
Quantitative MR metrics (e.g., T1, T2, diffusion coefficients, and magnetization transfer ratios (MTRs etc)) are often derived from two images collected with one acquisition parameter changed between them (the "two-point" method). Since a low signal-to-noise-ratio (SNR) adversely affects the precision of these metrics, averaging is frequently used, although(More)
The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes(More)
Fast, 3D radio-frequency transmit field (B1) mapping is important for parallel transmission, spatially selective pulse design and quantitative MRI applications. It has been shown that actual flip angle imaging--two interleaved spoiled gradient recalled echo images acquired in steady state with two very short time delays (TR1, TR2)--is an attractive method(More)
The 7 year data set of the Milagro TeV observatory contains 2.2 x 10(11) events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of approximately 10 degrees has been found in two localized regions of unknown origin with greater than 12sigma significance.(More)