Quantitation of rat cerebral blood flow using 99mTc-HMPAO

IntroductionTechnetium-99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) is potentially useful for the assessment of cerebral blood flow (CBF) in small animals. In this paper, a procedure for quantitation of rat CBF using 99mTc-HMPAO was determined.MethodsBiodistribution of 99mTc-radioactivity in normal rats was determined after intravenous administration of 99mTc-HMPAO. Acetazolamide treated rats were intravenously administered with the mixture of 99mTc-HMPAO and N-isopropyl-[125I]iodoamphetamine ([125I]IMP), and arterial blood was then collected for 5 min. After blood sampling, the brain radioactivity concentration was measured with the auto-well γ counter.ResultsThe brain radioactivity concentration after intravenous administration of 99mTc-HMPAO was steady from 14 s to 60 min post-injection. A double tracer experiment using 99mTc-HMPAO and [125I]IMP showed that 19 s was the average of the optimal integration interval of arterial blood 99mTc-radioactivity concentration to obtain CBF values measured by 99mTc-HMPAO identical to those determined by [125I]IMP. The CBF value determined by 99mTc-HMPAO, calculated by dividing the brain radioactivity concentration at 5 min post-injection by the integrated arterial blood radioactivity concentration until 19 s post-injection, was well correlated with CBF as determined by [125I]IMP.ConclusionThese results suggest that the CBF quantitation procedure described in this paper could be useful for rat CBF assessment.