Evaluation of Systems for Quantitation of Autoradiograms ¹ , ²

Automated systems for the evaluation of autoradiograms were compared with the traditional method of manual counting. The automated systems included televison image analysis systems, reflectance/densitometric systems, and semiautomatic digitizing pad systems. Highly automated analysis systems were considered applicable for quantitation of autoradiograms when the subcellular location of the radioactivity is not an important consideration, when background is low, and when operator interaction with the system can be kept at a minimum. In many cases the relationship between silver grains and cell compartments is important for interpretation of the results. Under these conditions, the most rapid, reproducible and reliable method would combine measurement of cellular dimensions with a digitizing pad and manual counting of silver grains by the observer. Such a system should be connected to a computer for formatting and statistical evaluation of the data. Initial testing of a quantitative autoradiographic technique indicated that the autoradiographic slide is a reliable estimator of the radioactivity present in the tissue of experimental animals injected with tritium labeled compounds. Accuracy in counting was lost when silver grains became coincident. Thus, a system for the quantitation of silver grains in relation to cellular morphology requires careful selection of exposure time, computer assisted measurement of cellular dimensions, operator evaluation of silver grains and computerized statistical analysis of the data.