Comparison of perfusion CT and brain SPECT in STA/MCA anastomosis patients

Objectives To evaluate the hemodynamic parameters of perfusion CT with respect to brain perfusion SPECT in the patients who received superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis.

Methods Sixteen patients (M:F = 12:4, age 42±13 y) received successful STA-MCA anastomosis surgery due to Moyamoya disease (n = 11) or atherosclerosis (n = 5). Basal/acetazolamide-challenged brain SPECT and perfusion CT were performed before and after surgery, with the interval between CT and SPECT less than a week. Basal perfusion and cerebrovascular reserve index (CVRI) of MCA territory were measured on SPECT by the uptake counts normalized to the cerebellum. On perfusion CT, cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) were obtained in the MCA territory. For MTT and TTP, delay of each parameter was defined as the delta between lesion and contralateral side.

Results On SPECT, basal perfusion and CVRI of MCA territory improved significantly after surgery (40.0±3.1 to 41.2±3.5; P = 0.045, and -8.4±6.4 to -3.4±4.8; P=0.003, respectively). CBF, CBV, MTT, and TTP on perfusion CT did not show significant improvement. However, MTT delay and TTP delay showed significant improvement (3.3±3.4 to 0.5±1.4 s; P = 0.01, and 2.6±2.4 to 0.1±1.1 s; P = 0.002, respectively). There was no significant correlation between SPECT and CT, for any parameters of each modality.

Conclusions MTT delay and TTP delay on perfusion CT may represent the hemodynamic improvement after STA-MCA anastomosis. However, they represent different aspects of hemodynamics from perfusion SPECT, probably due to vascular reserve and coverage of territory.