PET investigation of post-traumatic cerebral blood volume and blood flow

Hemodynamic changes following traumatic brain injury (TBI) may reflect cellular damage leading to secondary injury. The purpose of this study was to investigate the regional hemodynamic parameters acutely after TBI among regions in and around contusions. Sixteen patients (11 male, 5 female) showing evidence of contusion on CT and 18 normal volunteers (12 male, 6 female) underwent positron emission tomography (PET) with O-15 CO and O-15 H2O to estimate cerebral blood volume (CBV) and cerebral blood flow (CBF), respectively. A flow to volume ratio (FVR = CBF/CBV) was also calculated as an index of vasodilatation. The hemodynamic parameters were compared among contusion, pericontusion, and remote areas. Globally, hemodynamic parameters did not differ between patients and normal volunteers, and did not correlate with intracranial pressure (ICP). Regionally, contusional and pericontusional areas showed significantly lower CBF and FVR compared with normal volunteers, while CBV did not differ significantly. The correlation between CBF and CBV was significant (r = 0.37, p < 0.01). Remote areas did not show a significant difference in any of the PET parameters. In conclusion, regional brain edema is likely to occur in contusion and pericontusion areas, while some of the contusional tissue may show vascular engorgement.