Multinuclear MRI Can Depict Metabolic and Energetic Changes in Mild Traumatic Brain Injury.

Abstract

Mild traumatic brain injuries (TBIs) are frequent in the European population. The pathophysiological changes after TBI include metabolic changes, but these are not observable using current clinical tools. We aimed to evaluate multinuclear MRI as a mean of assessing these changes. In our model, pigs were exposed to a controlled cortical impact (CCI) directly on the dura and scanned at 2 h and 2 days after injury. A multinuclear MRI protocol was used. It included hyperpolarized [1-¹³C]pyruvate MRI, which allows depiction of hyperpolarized carbon-13, through its metabolism from pyruvate to lactate or bicarbonate. At Day 2, cerebral microdialysis were performed, and tissue was obtained for analyses. At Day 0, the cerebral blood flow was reduced in the affected hemisphere (TBI: 31.7 mL/100 mL/min, contralateral: 35.6 mL/100 mL/min, p = 0.1227), and the impacted area showed reduced oxygenation (R₂*, TBI: 33.11 s^-1, contralateral: 22.20 s^-1, p = 0.035). At both days, the lactate-to-pyruvate ratios (hyperpolarized [1-¹³C]pyruvate) were increased (Day 0: p = 0.023, Day 2: p = 0.022). However, this study can only evaluate the total injury and, thus, cannot differentiate effects from craniotomy and CCI. This metabolic difference was not found using cerebral microdialysis nor a lactate dehydrogenase (LDH) activity assay. The metabolic changes depicted in this study contributes to our understanding of mild TBI; however, the clinical potential of multinuclear MRI is yet to be determined.