A comparative study of perfusion CT and (99m)Tc-HMPAO SPECT measurement to assess cerebrovascular reserve capacity in patients with internal carotid artery occlusion

BACKGROUND AND PURPOSE: Patients with internal carotid artery (ICA) occlusion can demonstrate impaired cerebral vascular reserve (CVR). The detection of CVR using single photon emission CT (SPECT) is nowadays widely accepted as a predictor in the diagnostic pathway in patients considered for cerebral revascularization. Recently perfusion CT (PCT) gained widely acceptance in stroke imaging The present study was aimed at comparing the results of perfusion CT (PCT) and (99m)Tc-HMPAO SPECT with acetazolamide challenge in patients with ICA occlusion. METHODS: 13 patients were included in the prospective evaluation. Both PCT and (99m)Tc-HMPAO SPECT were performed before and after the administration of acetazolamide. In detail, regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), adapted time to peak (Tmax) and mean transit times (MTT) were compared with SPECT data. RESULTS: (99m)Tc-HMPAO SPECT demonstrated an impairment of CVR in six patients. A preserved CVR was present in seven patients. All patients with impaired CVR proven by SPECT had a delayed MTT (mean +2.98 s) and a delayed Tmax (mean + 5.9 s), (both p < 0.005 compared with the non occluded side). 66% of patients with impaired CVR in SPECT showed a complete correlation of Tmax measurements in PCT with a high positive predictive value (PPV: 88.8%). CONCLUSION: The prospective study demonstrated a highly significant correlation of perfusion parameters as' detected by (99m)Tc-HMPAO SPECT and the Tmax as detected by PCT in patients with ICA occlusion. Therefore this easy-to-perform technique seems to be an adequate method for the evaluation of cerebral perfusion in patients with ICA occlusion.