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W T Sobol

Publications and source records attributed to W T Sobol.

22 records · Page 2Linked to original sources
PubMedDate not supplied

A new method of computing spin-lattice relaxation maps in magnetic resonance imaging using fast scanning protocols.

A new algorithm to compute spin-lattice relaxation (T1) maps in magnetic resonance imaging (MRI) by using fast imaging protocols and monitoring the magnetization evolution towards a steady state is proposed. This algorithm uses a general least-squares fit to multiple point experimental data and is thus much more precise than the standard two-point fit. Since this imaging protocol is designed to consume time comparable to that of standard clinical protocols, it has an advantage in comparison to traditional multiple point protocols, which require considerably longer scanning times. In addition to T1 maps the protocol can generate final images suitable for clinical diagnosis. Thus it is possible to generate relaxation data without considerably lengthening the total required MRI study time. The results of phantom testing of this protocol are reported.

Algorithms↗
PubMedDate not supplied

NMR spin-lattice relaxation in tissues with high concentration of paramagnetic contrast media: evaluation of water exchange rates in intact rat muscle.

High concentrations of GdDTPA in extracellular water of tissue cause the intrinsic relaxation rate of water to become greater than the coupling rate between intracellular and extracellular water compartments. The fast exchange limit is no longer valid and distinctly nonexponential spin-lattice recovery is observed. T1 relaxation recovery was characterized by a double exponential curve when striated rat muscle was immersed in a highly concentrated (110 Mm) isotonic solution of GdDTPA. When the water exchange rate through cell membranes in intact muscle tissue was calculated (using a two-compartment exchange model) and compared to similar data determined from T2 Carr-Purcell-Meiboom-Gill experiments, a significant discrepancy was found.

Animals↗
PubMedDate not supplied

Broad line quantitative chemical shift spectroscopy.

Proton NMR spectroscopy was applied to quantitate the measurement of total body water/fat distributions in vivo. A special MR protocol was developed to excite a thick slab of tissue and display the magnitude NMR spectrum of the collected response signal. Very short echo time TE (8 ms) and long repetition time TR (4000 ms) were used to minimize relaxation damping of the signal intensities. The spectrum was then decomposed into individual lines and proton densities of different species were calculated. Proton density information was converted into weight percentage data using stoichiometrical and physiological information. The technique was validated using phantoms that contained different mixtures of water/maize oil. A high-resolution NMR spectrum of maize oil samples was used to determine the stoichiometric information. The test results showed good agreement with the known composition of the phantom within the whole range of water content (0-100%). This method is very fast since no phase encoding of data is required. Preliminary results for monkeys show promising potential in clinical applications.

Adipose Tissue↗