Comparison of microsphere and Xenon-133 clearance method in measuring skeletal muscle and cerebral blood flow.

Abstract

The 133Xe clearance method was compared with the microsphere method in measurement of skeletal muscle and cerebral blood flow (CBF). Over a wide range of flows (1-47 ml/min .times. 100 g), these 2 methods were compared with direct measurements of venous outflow in the gracilis muscle. Regression equations related the 133Xe (stochastic method) and microsphere measurements of flow to venous outflow. 133Xe clearance and microspheres accurately measure flow in an isolated organ with a simple bloody supply. When CBF was measured with 133Xe, extracerebral contamination and scattered radiation were minimized by ligation of the external carotid artery, removal of the soft tissue of the head, injection of the 133Xe into the internal carotid artery and use of Pb shielding and a collimated detector. In 10 dog CBF (range, 12-200 ml/min .times. 100 g) measured with 133Xe was substantially less than that measured with microspheres. In 18 baboons when mean CBF < 120 ml/min .times. 100 g, there was a good relationship between values obtained with 133Xe (stochastic method) and microspheres. Regression equations related those 2 measurements. At flow rates > 120 ml/min .times. 100 g, values obtained for mean CBF with 133Xe (stochastic method) and microspheres differed widely. Fast and slow clearance curves obtained with 133Xe (compartmental analysis) were compared with grey and white matter flows measured with microspheres; the 2 techniques yielded results which differed widely. Although the 133Xe clearance method (stochastic analysis) and microspheres provide similar values for mean CBF in baboons under some experimental conditions, values obtained with the 2 techniques differ importantly under several conditions.