Localized spin lattice relaxation time (Tl) measurements of the individual chemically shifted nuclear magnetic resonance (NMR) peaks may afford better tissue characterization. These measurements require methods to accurately and efficiently localize the region of interest. A number of such methods have been reported in literature, out of which four show a great deal of promise. These are 1) depth resolved surface coil spectroscopy, 2) localization based on imaging principles, 3) volume selective excitation (VSE) and 4) image selected in vivo spectroscopy (ISIS). The proposed project will 1) implement these four methods on the imager/spectrometer built in our laboratory, 2) compare these methods for their relative accuracies and efficiencies using phantoms, 3) develop and implement pulse sequences to measure local Tl based on inversion recovery, and 4) determine the optimum methods for local Tl measurements under a given set of experimental conditions using phantoms. Good localization was achieved on our system, using the VSE method on phantoms. These studies have also pointed out the need to shorten the gradient settling times. This will initially be achieved by shaping the current through the gradient coils. It is expected that these studies will enable us to accurately measure local relaxation times in-vivo for a better tissue characterization.
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