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Gamma-aminobutyric acid (GABA) and glutamate are implicated in numerous neuropsychiatric and substance abuse conditions, but their spectral overlap with other resonances makes them a challenge to quantify in humans. Gabapentin, marketed for the treatment of seizures and neuropathic pain, has been shown to increase in vivo GABA concentration in the brain of(More)
In hyperoxic contrast studies modulated by the blood oxygenation level-dependent effect, it is often assumed that hyperoxia is a purely intravascular, positive contrast agent in T 2*-weighted images, and the effects that are not due to blood oxygenation level-dependent contrast are small enough to be ignored. In this study, this assumption is re-evaluated(More)
Spin-lattice relaxation in the rotating frame (T1rho) dispersion spectroscopy and imaging were used to study normal and enzymatically degraded bovine articular cartilage. Normal specimens demonstrate significant T1rho "dispersion" (approximately 60 to approximately 130 ms) in the 100 Hz to 9 kHz frequency range. Proteoglycan-degraded specimens have 33%(More)
RATIONALE AND OBJECTIVES To determine the in vivo feasibility of quantifying early degenerative changes in patellofemoral joint of symptomatic human knee using spin-lattice relaxation time in the rotating frame (T(1rho)) magnetic resonance imaging (MRI). MATERIALS AND METHODS All the MRI experiments were performed on a 1.5 T whole-body GE Signa clinical(More)
Proteoglycan (PG) depletion-induced changes in T1rho (spin-lattice relaxation in rotating frame) relaxation and dispersion in articular cartilage were studied at 4T. Using a spin-lock cluster pre-encoded fast spin echo sequence, T1rho maps of healthy bovine specimens and specimens that were subjected to PG depletion were computed at varying spin-lock(More)
RATIONALE AND OBJECTIVES The authors performed this study to (a) measure changes in T2 relaxation rates, signal-to-noise ratio (SNR), and contrast with sequential depletion of proteoglycan in cartilage; (b) determine whether there is a relationship between the T2 relaxation rate and proteoglycan in cartilage; and (c) compare the T2 mapping method with the(More)
In this article, both sodium magnetic resonance (MR) and T1rho relaxation mapping aimed at measuring molecular changes in cartilage for the diagnostic imaging of osteoarthritis are reviewed. First, an introduction to structure of cartilage, its degeneration in osteoarthritis (OA) and an outline of diagnostic imaging methods in quantifying molecular changes(More)
Using sodium multiple quantum filtered methods, we have, for the first time, demonstrated the presence of residual quadrupolar interaction in human skeletal muscle and brain in vivo. Surface coils were used in both skeletal muscle and brain studies on healthy human volunteers. Theoretical analysis shows that even with arbitrary flip angles the double(More)
Glutamate, a major neurotransmitter in the brain, shows a pH- and concentration-dependent chemical exchange saturation transfer effect (GluCEST) between its amine group and bulk water, with potential for in vivo imaging by nuclear magnetic resonance. GluCEST asymmetry is observed ∼3 p.p.m. downfield from bulk water. Middle cerebral artery occlusion in the(More)
One of the first effects of degenerative osteoarthritis is the loss of proteoglycans from the matrix of articular cartilage. Using a model of osteoarthritic change where the cartilage has been enzymatically degraded with trypsin, the sodium NMR characteristics of the cartilage were determined as a function of changes in the proteoglycan content. The results(More)