Cerebral perfusion reserve SPECT imaging before and during acetazolamide test using consecutive 99mTc-HMPAO SPECT

The present study was to determine the feasibility of using simple consecutive Tc-99m hexamethylpropyleneamine oxime (Tc-99m HMPAO) SPECT in evaluating cerebral perfusion reserve in cerebrovascular disorder. Thirty three patients underwent the first SPECT scanning 2 min after iv injection of 555 MBq (15 mCi) of Tc-99m HMPAO, and simultaneously received one gram of acetazolamide. The time required in the first scanning was 13 min during which the efficacy of acetazolamide appeared. The second scanning was performed in the same manner as the first scanning. Cerebral blood flow before acetazolamide load was seen on the first SPECT (pre-load images). Acetazolamide-loaded images were obtained by subtracting the first from the second SPECT images (post-load images). Cerebral blood flow reactivity was examined by visual comparison of tracer activity in lesions to that in the surrounding tissue. None of the patients had acetazolamide-related symptoms. In 28 (85%) of the 33 patients, there was a significant difference in Tc-99m HMPAO uptake between pre-load and post-load images. Since both pre-load and post-load images are obtained in a short time (30 min), and the post-load images provide the additional information as well, the present Tc-99m HMPAO SPECT technique with iv injection of acetazolamide is considered clinically feasible at a time in evaluating cerebral perfusion reserve. (N.K.)