Proton MR Spectroscopic Imaging (MRSI) enables non- invasive measurement of tissue metabolite distributions and offers considerable potential as a diagnostic imaging technique for localization of epilepsy, a devastating condition that affects thousands of children and adults. The proposed technique development is aimed at improving the effectiveness of these techniques for presurgical evaluation of epilepsy. The measurement of metabolite distributions in human brain is possible with only modest spatial resolution, for which conventional Fourier reconstruction methods result in errors associated with the truncated sampling. To improve the quality of the metabolite images, new reconstruction methods will be developed that do not suffer from these limitations and which enable improved spatial resolution for reconstruction of stronger metabolite signals. This will be achieved by using a Bayesian framework to incorporate known spatial and spectral information into an optimization reconstruction procedure. Although computationally intensive, these new methods can now be practically applied with the availability of low-cost multiprocessor computers.
A second aim of this proposal is to develop methods for measurement of brain pH distributions using proton MR observation, which will provide additional diagnostic information as well as improving understanding of metabolic changes associated with epilepsy. This will be achieved by using a signal enhancement technique based on the administration of histidine and development of specialized parametric spectral analysis procedures. This measurement will offer increased sensitivity over previously used phosphorus measurements, as well as providing the capability for pH measurement on standard clinical MRI instrumentation. The developed MRSI techniques will be evaluated for detection of focal metabolic abnormalities associated with epilepsy. The improved metabolite image reconstruction and regional pH measurement techniques also have potential clinical applications in other areas, such as cancer, stroke, and brain trauma.
