シンポジウム3

[S3-4] Brain Metabolite Mapping at 7T using MRSI

^〇Hetherigton Hoby P. (Professor, Director, MR Research Center Department of Radiology, University of Pittsburgh)

With the advent of high field 3T and ultrahigh field 7T MR systems, significant improvements in both SNR and spectral resolution were expected for spectroscopic imaging studies of brain. Unfortunately, limitations in B ₁ strength and homogeneity and limited B₀ homogeneity present significant hurdles to achieving these advantages. To overcome these hurdles we have developed a combined approach utilizing transceiver arrays and B₀ shimming with a high degree (4^th+) B₀ shim insert. The transceiver array and B₁ shimming based localization minimizes extra-cerebral lipids allowing the entire brain within the slice to be visualized by MRSI at 7T. This has been highly accurate in predicting surgical outcome in patients with both neocortical and temporal lobe epilepsy. Use of the high degree B₀ shim insert reduces the static inhomogeneity up to a factor of ~2 for both slices and 3D slabs. The improved homogeneity has enabled us to routinely perform MRSI studies in challenging brain regions such as the anterior hippocampus and identify neuronal injury in MRI negative veterans with mild traumatic brain injury and persistent memory impairment. We have built upon these methods by developing a homonuclear polarization transfer pulse sequence which significantly improves the accuracy of spectroscopic images of glutamate (Glu), glutamine (Gln) and gamma amino butyric acid (GABA). Use of these methods has enabled us to measure glutamine elevations in epilepsy patients receiving Depakote and GABA increases in the thalami of epilepsy patients responding to treatment with valproate.