MRSI of the medial temporal lobe at 7 T in explosive blast mild traumatic brain injury

PURPOSE: Up to 19% of veterans returning from the wars in Iraq and Afghanistan have a history of mild traumatic brain injury with 70% associated with blast exposure. Tragically, 20-50% of this group reports persistent symptoms, including memory loss. Unfortunately, routine clinical imaging is typically normal, making diagnosis and clinical management difficult. The goal of this work was to develop methods to acquire hippocampal MRSI at 7 T and evaluate their sensitivity to detect injury in veterans with mild traumatic brain injury. METHODS: At 7 T, hippocampal MRSI measurements are limited by: (1) poor B0 homogeneity; (2) insufficient B1+ strength and homogeneity; and (3) chemical shift dispersion artifacts. To overcofme these limitations we: (1) used third degree B0 shimming; (2) an inductively decoupled transceiver array with radiofrequency shimming; and (3) a volume localized single slice sequence using radiofrequency shimming-based outer volume suppression. RESULTS: In 20 controls and 25 veterans with mild traumatic brain injury due to blast exposure with memory impairment, hippocampal N-acetyl aspartate to choline (P Language: en