The following examples were obtained using the volumetric EPSI sequence at 3 Tesla, using an 8-channel phased array head coil.
Whole-brain MRSI is combined with other imaging modalities to provide a comprehensive picture of altered structure, function, and metabolism with brain cancer:
This figure shows multiparametric MR images for a brain tumor study, as: a) NAA; b) Cho; c) Cho/Cre; d) Lactate; e) ADC; f) FA; g) CBF; h) CBV; i) quantitative T1; j) T2 MRI, k) T1 post-contrast; and l) T1 MRI. MRSI data obtained for TE=70ms
The whole-brain MRSI acquisition enables comprehensive mapping of multiple metabolites. This following example is for a grade III astrocytoma, and the result illustrates mapping of choline, glycine and lactate, which are markers of actively growing tumor tissue.
This data was obtained in collaboration with Dr. RK Gupta.
Z-score maps indicating reduced NAA in subjects with Amyotrophic lateral sclerosis relative to age-matched controls. Images are scaled relative to the variance of the normal subject group. Light-blue voxels indicate a significant reduction of NAA.
Data courtesy of Drs. Govind and Sharma. Also see V. Govind et al. Comprehensive evaluation of 1H MR-observed brain metabolites of the corticospinal tract in amyotrophic lateral sclerosis. PLoS ONE,7:e35607 (2012)
This image shows the distributions of altered metabolite levels in a group of subjects with minimal (Group) and moderate (Group B) traumatic brain injury.
See also A.A. Maudsley et al. Associations of age, gender, and body mass with MR-observed brain metabolites and tissue distributions. NMR in Biomed. 25(4):580-93 (2012).
By using a simple spin-echo excitation and lipid nulling metabolite mapping of the brain can be done at short TEs. The following example shows results obtained for TE=15 ms in a normal subject, using a reduced k-space acquisition (15 min. acquisition time):
All metabolite values are signal normalized, i.e. are directly comparable between subjects and across data obtained at different times. Note the absence of artifacts from subcutaneous lipids that are a concern for standard MRSI implementations. The speckled region in frontal brain represents areas where spectral quality is inadequate due to local magnetic susceptibility effects.