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

• Published in: Magnetic resonance in medicine Vol. 71; no. 4; pp. 1358 - 1367
• Main Authors: Hetherington, Hoby P., Hamid, Hamada, Kulas, Joseph, Ling, Geoffrey, Bandak, Faris, de Lanerolle, Nihal C., Pan, Jullie W.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.04.2014; Wiley Subscription Services, Inc
• Subjects: 7 T; Adult; Aspartic Acid - analogs & derivatives; Aspartic Acid - metabolism; Biomarkers - blood; Blast Injuries - diagnosis; Blast Injuries - metabolism; Brain Injuries - diagnosis; Brain Injuries - metabolism; Choline - metabolism; Creatine - metabolism; Explosions; Female; hippocampus; Hippocampus - injuries; Hippocampus - metabolism; Hippocampus - pathology; Humans; Magnetic Resonance Imaging - methods; Magnetic Resonance Spectroscopy - methods; Male; mild traumatic brain injury; Military Personnel; Molecular Imaging - methods; MRSI; Reproducibility of Results; Sensitivity and Specificity; Temporal Lobe - injuries; Temporal Lobe - metabolism; Temporal Lobe - pathology; Tissue Distribution; United States; United States; 7 T; hippocampus; mild traumatic brain injury; MRSI
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.24814

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 < 0.001) and N‐acetyl aspartate to creatine (P < 0.001) were decreased in comparison to control subjects. Conclusion With the appropriate methods robust spectroscopic imaging of the hippocampus can be carried out at 7 T. MRSI at 7 T can detect hippocampal injury in veterans with mild traumatic brain injury. Magn Reson Med 71:1358–1367, 2014. © 2013 Wiley Periodicals, Inc.