From planar to SPECT-CT brain perfusion study in brain death determination: our experience from 2010 to 2023.

Purpose: Radionuclide brain perfusion studies using a lipophilic radiopharmaceutical are recognized as reliable ancillary tests for brain death determination in various clinical guidelines. We aim to share our experience with the SPECT-CT protocol.

Materials and methods: All studies performed between 2010 and 2023 were included. Planar, SPECT, and SPECT-CT images were analyzed and categorized as showing normal intracranial perfusion, residual cerebellar activity, definitive absence of intracranial perfusion, or residual intracranial activity. These findings were compared with the final diagnosis for each study, which was based on available clinical information, radiologic, and nuclear medicine images.

Results: A total of 117 brain perfusion studies for brain death determination were performed. Of these, 106 (91%) were reported as definitive for the absence of intracranial perfusion and were concordant with the clinical diagnosis of brain death. In the remaining 11 cases, 5 (4%) showed normal brain perfusion, and 6 (5%) demonstrated residual intracranial activity. Among the 5 studies with normal perfusion, all (100%) were correctly identified on planar-only images. Of the 106 patients with a definitive diagnosis of absent brain perfusion, 56.6% (60/106) showed a definitive planar result, 36.8% (39/106) had a probable result, 3.8% (4/106) showed possible intracranial activity, and in 2.8% (3/106), planar images were not performed. A total of 105 studies with tomographic images were analyzed. Of the 4 studies showing residual cerebellar activity, all (100%) were correctly identified on SPECT images. Of the 98 studies with definitive absence of intracranial perfusion, 91.8% (90/98) showed no cerebral activity on tomographic images. The remaining 8.2% (8/98) showed mild cerebral activity. Notably, 5 of these patients underwent SPECT-CT imaging, and were correctly reclassified as having intracranial bleeding, which led to a final diagnosis of absent brain perfusion. For the 53 SPECT-CT studies analyzed, all patients were correctly categorized as either having absent brain perfusion or residual cerebellar perfusion, with no cases of normal perfusion or residual cerebral perfusion observed. Challenging cases are also discussed, including 3 patients who underwent repeat brain perfusion studies after an initial normal or inconclusive report.

Conclusions: In this article, we share our experience with brain perfusion studies in brain death determination and the evolution of our protocol over the past decade. SPECT-CT has become our standard protocol, allowing us to confidently categorize patients as having either normal brain perfusion, absent brain perfusion, or residual partial brain perfusion. This approach reflects the clinical need for an unbiased and accurate test of intracranial perfusion.