Isotope Study of Brain Blood Turnover in Vascular Disease

Presented here are data concerning brain circulation (pool turnover) time obtained through the application of an intravenous radioisotope technique. We have attempted to establish normal values and to compare these with results obtained from a group of patients with clinically evident cerebrovascular disease.

The technique has been described in detail in an earlier report.¹ Briefly, a rapidly excreted γ-emitting indicator, I¹³¹ iodohippurate, is injected intravenously, and its subsequent passage through the cranial blood pool is monitored by an external detection system. The parameter of this passage most readily derived, as will be shown, is the transit (circulation) time of the cranial blood pool. This transit time is in the range of 6 to 11 seconds in healthy adults with values near the lower extreme of this range in the young and approaching the upper extreme in healthy old age. Our results indicate most patients with a history of