A new method to estimate rCBF using IMP and SPECT without any blood sampling

We developed and evaluated a method to measure rCBF without any blood sampl ing by using iodine-123 IMP and SPECT. An integral of arterial input functi on, integral Ca-T(D)(t)dt, can be expressed as TC(T)/CO, where TC(T) is rad ioactivity delivered to the body in T minutes and CO is cardiac output. If T is acceptably small, rCBF can be determined by means of a microsphere mod el analysis with IMP as Cb(T)/(TC(T)/CO), where Cb(T) is cerebral radioacti vity at T minutes. We derived TC(T) and CO from a chest dynamic scan. The m ethod was applied to 45 patients who underwent rCBF studies (58 studies) wi th arterial blood sampling (ABS). Data from the chest scan were analyzed in comparison with ABS data in the first 28 studies, and equations for correc tion yielding an accurate TC(T)/CO were derived. The validity of the propos ed method was evaluated in the subsequent 30 studies. The method yielded rC BF (rCBF-test) which agreed well with rCBF obtained by a two-compartment mo del analysis of dynamic SPECT and ABS data (rCBF-ref) with the mean and SD of differences between rCBF-test and rCBF-ref being 1.0 and 2.7 ml/100g/min , respectively. In eleven subjects who underwent more than two studies, a p ercentage change in rCBF-test between the studies also closely approximated that of rCBF-ref (y = 1.11x + 2.63, r = 0.92). The method can be used with acceptable reliability to measure rCBF without any blood sampling.