Quantitative comparison of the bolus and steady-state methods for measurement of cerebral perfusion and oxygen metabolism: Positron emission tomography study using O-15-gas and water

To evaluate a new simplified bolus method for measurement of cerebral perfu sion and metabolism, the parametric images with that method were compared w ith those obtained from the conventional steady-state method with O-15-gas. The new method also provided images of arterial blood volume (V,), which i s a different parameter from cerebral blood volume (CBV) obtained using a ( CO)-O-15 technique. Seven healthy volunteers and 10 patients with occlusive cerebrovascular diseases underwent positron emission tomography (PET) scan s with both methods. Three-weighted integration was applied to calculate re gional cerebral blood flow (rCBF) and regional cerebral metabolic rate of o xygen (rCMRO(2)) in the bolus method. Global and regional CBF and CMRO2 in volunteers were compared between the two methods and used as control data. Regional values in patients also were evaluated to observe differences betw een the bilateral hemispheres. Both rCBF and rCMRO(2) were linearly well co rrelated between the two methods, although global difference in CMRO2 was s ignificant. The difference in each parametric image except for V, was signi ficant between the bilateral hemispheres in patients. The bolus method can simplify oxygen metabolism studies and yield parametric images comparable w ith those with the steady state method, and can allow for evaluation of V, simultaneously. Increase in CBV without a change in V, suggested the increa se might mainly be caused by venous dilatation in the ischemic regions.