SPLIT-DOSE IODINE-123-IMP SPECT - SEQUENTIAL QUANTITATIVE REGIONAL CEREBRAL BLOOD-FLOW CHANGE WITH PHARMACOLOGICAL INTERVENTION

At least two quantitative rCBF measurements are needed to evaluate rCB F changes with pharmacological intervention. We have developed the spl it dose I-123-IMP SPECT method, which enables measurement of rCBF to b e repeated in a short time. Methods: Thirty-one cerebrovascular diseas e patients were investigated to assess reproducibility and vasoreactiv ity to acetazolamide. During 44-min dynamic SPECT imaging, I-123-IMP i njection and respective arterial sampling were performed twice at an i nterval of about 25 min. The rCBF values were calculated using a micro sphere model in which the washout of I-123-IMP from the brain can be n egligible in the first several minutes after injection. For the second rCBF measurement, the remaining activity due to the first I-123-IMP i njection was estimated and subtracted from the total brain activity. R esults: In ten patients, two consecutive resting mean rCBF values in t he MCA territory (CBF1 and CBF2) had good correlation (CBF1 = 47.4 +/- 4.0 (ml/min/100 mi: mean +/- s.d.), CBF2 = 45.2 +/- 8.2, CBF2 = 0.900 CBF1 + 2.9, r = 0.915). In 11 patients with occlusive lesions in the unilateral ICA system, mean rCBF in the MCA territory was increased by only 27.7% +/- 14.0% in the affected side by al-g intravenous acetazo lamide injection, while 44.5% +/- 12.3% increase was found in the nona ffected side. In 10 patients without a major arterial lesion, a 49.7% +/- 17.0% increase of rCBF was demonstrated. Conclusions: This split d ose method I-123-IMp SPECT can be useful to estimate vascular reserve.