Autoradiography: its methodology at the present time.

The autoradiographic methods used in biological and medical research are reviewed from an historical viewpoint. It is pointed out that early methodological research was directed at the selection of suitable detector substances for radiation (nuclear emulsions) and at the preparation and application of suitable layers of these detectors to biological samples. On the other hand, later research was more concentrated on aspects of the preparation of the biological components of the specimens. In particular, the retention of biochemicals in the tissue sample was studied in detail. Research in the quantification of the emulsion response to alpha and beta radiation paved the way for certain quantitative applications of autoradiography. This has been followed by the derivation of models for the measurement of image spread and the evolution of image analysis methods which allow refined determinations of the specific radioactivity of fine structures taking into account losses and gains of silver grains by image spread. The sum of all these advances is a methodology capable of localizing and quantifying radioactivity and hence making chemical processes from an organism and organ level down almost to the present limits of anatomical delineation.