Estimation of cerebral oxygen utilization rate by single-bolus 15O2 inhalation and dynamic positron emission...

This study shows that regional CMRO2 can be estimated by means of nonlinear regression using dynamic positron emission tomographic data acquired during 1 min following single-bolus inhalation of 15O2. The feasibility of simultaneous estimation of CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), and CMRO2 was assessed by simulations using the model of Mintun et al. Four oxygen metabolic measurements, each consisting of a CBF, CBV, and 15O2 bolus study, were carried out on three volunteers. Regional values for CBF, CBV, OER, and CMRO2 were derived in two ways: from the fits of the time-activity curves of the dynamic 15O2 bolus study alone [CMRO2(fit)] and from the three separate studies [CMRO2 (control)]. For the 56 regions of interest analyzed, using a fit interval of 60 s, CMRO2(fit) was 93.4 +/- 7.8% of CMRO2(control) (mean +/- SD) with a correlation coefficient of r = 0.95. CMRO2(control) ranged from 87 to 290 mumol/min/100 g. Individual simultaneous estimates of CBF, CBV, and OER were not reliable. Finally, we found that the validity of the model was limited in practice to the first minute after tracer inhalation.