A simple chemical method of labeling hematoporphyrin derivative with technetium‐99m

Hematoporphyrin derivative(HPD), a fluorescent compound known to be selectively accumulated in neoplasms, is labeled with 99mTc by a chemical method. Radiochemical analyses indicated that the labeled product contains an average of 91% 99mTc‐HPD, 6% unbound 99mTc‐(Sn)complex species and less than 3% free 99mTc. Data from acid precipitation analysis demonstrate the presence of two radiolabeled HPD fractions; an insoluble black precipitate and an acid soluble fraction with an average of 66% and 25% respectively. The labeling mechanism is not known. Presumably, labeling of HPD involves the formation of a coordinated complex with reduced 99mTc forming a radioactive metalloporphyrin compound. 99mTC‐HPD, like the parent compound, exhibits strong fluorescence when exposed to an appropriate ultra violet light source.