A method for the determination of microvascular volume in tissue samples.

An estimate of the volume of the microvascular bed in injected tissue specimens of human bowel has been made by measuring the concentration of injected contrast material using X-ray fluorescent analysis. The contrast medium used was barium sulphate and this completely fills the microvasculature in excised specimens. The concentration of barium in excised tissue samples has been determined by measuring the ratio of gamma-ray induced X-ray fluorescence in the barium to the 90 degree Compton scattered 140 keV gamma rays from a collimated 99Tcm source. Barium concentration was estimated in tissue samples from 45 specimens of normal bowel and 11 specimens of radiation damaged bowel. The radiation group showed a highly significant reduction (p less than 0.001) in barium concentration and therefore vascular volume. The mean percentage error for barium concentration measured on two separate occasions in 45 randomly selected tissue samples was 5%.