Abstract: An improved process for the measurement of blood circulation by means of colored microspheres is presented, which process replaces the previous counting procedure when using colored microspheres by a rapidly reproducible measurement method. This avoids the complicated and expensive use of radioactively labelled microspheres. At the same time, a coloring process for the preparation of the microspheres is presented which is distinguished by homogeneous and intensive coloration of the microspheres.

Abstract: Microspheres labeled with a dye for which the absorption spectra is known permit the measurement of blood flows, particularly regional myocardial blood flow (RMBF), without radiation safety concerns and radioactive waste disposal problems. Polystyrene spheres, nominally of diameter 15.+-.0.1 [SD] um and density 1.09 g/ml, are dyed with a fixed quantity, nominally 30 picograms per microsphere, with one of several, nominally 5, colored dyes. The colored microspheres (CM) are injected into the left atrium or into a coronary perfusion. The CM are extracted from myocardium and blood by digestion with KOH and subsequent microfiltration. The dyes are then recovered from the CM within a defined volume of a solvent, and their concentrations are determined by spectrophotometry. The composite absorbance or emission spectra of several dyes are mathematically resolved using matrix inversion. Leaching of dye from the CM was less than 0.