Tissue preparation technique for microsphere assays of blood flow

A simple method for preparing standardized tissue samples for microsphere assay of tissue blood flow is described. By reduction of tissue samples into a liquid state and centrifugation of the microspheres to the bottom of conical-shaped counting vials, the microspheres within all tissue and blood reference samples attain the same counting geometry. The validity and reproducibility of this technique has been established for planar-configured gamma-ray detectors in an in-situ porcine kidney model. A positive correlation coefficient of r = 0.99 was observed between the total kidney blood flow, as measured by a calibrated Transonic flow probe, and the microsphere reference sample technique.