Introduction: When clinical examination is not reliable for the diagnosis of brain death (BD), the preferred confirmatory ancillary test at our institution is nuclear medicine perfusion test (NMPT). Computed tomographic angiography (CTA) has been recognized in detecting intracranial circulatory arrest in BD, but there has been no standard set for establishing the absence of cerebral flow. The current study is designed to quantitatively analyze CTA, assess its accuracy compared to NMPT, and define set parameters for BD confirmation.
Methods: This is a retrospective clinical study, conducted from 2007-2014. Eighty patients evaluated. If clinical examination was consistent with BD, NMPT was performed followed immediately by CTA (n=60). A control group with normal CTA study was randomly selected (n=20). Assessment of NMPT and quantitative CTA analysis measuring the Hounsfield units (HU) of the horizontal segment of middle cerebral artery (M1), precommunicating segment of anterior cerebral artery (A1), and basilar artery (BA) was performed.
Results: Patients with clinical examination consistent with BD: 50% demonstrated intracranial circulatory arrest on NMPT and CTA (-/-), 38% demonstrated intracranial circulatory arrest on NMPT but intracranial perfusion on CTA (-/+), 12% demonstrated perfusion on both NMPT and CTA (+/+). Analysis of variance for M1, A1, and BA showed that +/+ group varied significantly from the -/- and -/+ groups (p = <0.002 for M1 and p = <0.025 for A1). The BA -/- group did not vary significantly from the -/+ patients (p = .778).
Conclusions: Data ranges within each group and the statistically significant difference between the groups, suggest that an average M1 HU less than
125 (98% sensitive, 100% specific), A1 HU less than 80 (96% sensitive, 100% specific), and BA HU less than of 95 (100% sensitive, 100%
specific) on CTA could be used as a definitive cutoff value for confirming the absence of flow. Using one value for all three arteries, a maximum cutoff HU of 80 correlated with no flow, and therefore confirmation of brain death (96% sensitivity and 100% specificity).
Patient Care: It is hoped that the results will aid in the confirmation of brain death in those patients too unstable to undergo clinical verification of brain death.
Learning Objectives: Be able to understand how to use quantitative analysis of CTA to confirm the diagnosis of brain death. Be able to differentiate between stasis filling and cerebral perfusion using CTA.