Quantitative distribution studies in animals: Cross-validation of radioluminography versus liquid-scintillation measurement

The results of a cross-validation of the radioluminography (RLG) and liquid scintillation counting (LSC) methods are presented. The methods for the de termination of radioactivity concentrations were compared in 16 organs, aft er administration of C-14-labeled substances to rats. LSC measurements of t wo kinds were used as reference methods for RLG: (1) quantitative determina tion of radioactivity after conventional dissection (interindividual compar ison) and (2) quantitative determination of radioactivity in tissue punches taken from the whole-body sections after they had undergone RLG; measureme nt (intraindividual comparison), Blood standards containing known concentra tions were used for calibration. For statistical evaluation log-linear regr ession analysis of paired concentration values and organ-specific 95% confi dence intervals of the log-transformed RLG/LSC concentration quotients were compared. For most organs, the slopes of the regression lines and the mean s of the concentration quotients were within the defined equivalence range of 0.80-1.25. Deviations were distinctly smaller in the intraindividual com parison. For some organs, however, it became clear that found concentration s were affected by self-absorption (RLG) and by differences in sample prepa ration (LSC). In conclusion, quantification with RLG; is a reliable and rep roducible method with comparable measurement precision and greater accuracy in respect of tissue localization, compared to LSC (dissection). (C) 2000 Academic Press.