A NEW QUANTITATIVE METHOD TO EVALUATE THE BIODISTRIBUTION OF A RADIOLABELED TRACER FOR MELANOMA USING WHOLE-BODY CRYOSECTIONING AND A GASEOUS DETECTOR - COMPARISON WITH CONVENTIONAL TISSUE COMBUSTION TECHNOLOGY

Whole-body autoradiography (WBA) and multi-wire proportional counting allow for spatial imaging of the radioactive material present in the t issues and organs of dehydrated animal sections. AMBIS 4000 counting o f whole-body cryosections offers a sensitive, accurate and reproducibl e novel method for the quantitative measurement of the tissue distribu tion of a [C-14] radiopharmaceutical. Intensity of AMBIS 4000 counting (net cpm/mm(2)) and concentration of radioactivity (nCi/g) were linea rly related, yielding a standard curve. Evaluating biodistribution (a) provides pharmacokinetic data for predicting the potential tissue dep osition of an absorbed dose of radioactivity in man, and (b) allows vi sual and quantitative evaluation of radioactivity in small anatomical structures that otherwise could not be detected by conventional tissue combustion technology. This new method of WBA, coupled with AMBIS 400 0 counting, should prove a valuable method for pharmacodynamic studies , and afford a predictive tool for nuclear medicine by assessing speci fic targeting of selected tissues.