Cerebral blood flow determinations using fluorescent microspheres: variations on the sedimentation method validated

We validate a modification of the sedimentation method for measuring fluore scent microspheres (FM) that improves the determination of regional cerebra l blood flow (rCBF). Our FM method for rCBF determination is compared to th e radioactive microspheres (RM) method for rCBF measurement by simultaneous injection of one radioactive and two fluorescent labeled doses, at two sep arate time points, into the left ventricle of a pig. The pig was killed, th e brain and spinal cord removed, and divided into 92 pieces averaging 0.83 g. Our modifications to FM analysis by sedimentation includes. 2 instead of 1 week of autolysis, pellet washing with 1% Triton X-100 instead of 0.25% Tween 80, phosphate buffer addition during rinse, fluorescent dye extractio n using 2-ethoxyethylacetate instead of 2-(2-ethoxyethoxy)ethyl acetate and polypropylene instead of glass tubes. Comparing rCBF using Sc46 RM, to yel low-green and orange FM, yielded mean differences of 0.026 and 0.021 ml/min per piece, respectively. Sn-113 RM compared to blue-green and scarlet FM g ave mean differences of - 0.010 and 0.137 ml/min per piece, respectively. A ll RM-FM differences, except those for scarlet FM, are within acceptable li mits. This assay provides a reliable method for determining rCBF. (C) 1999 Elsevier Science B.V. All rights reserved.