Quantitative analysis of autoradiograms

Quantitative autoradiography of macroscopic specimens using computer-assisted image analysis is now widely used for studying the distribution of peptide receptors in the brain and peripheral tissues and more recently has been used to measure mRNA in tissue sections by in situ hybridisation. The spatial distribution of radiolabelled substances in tissue can be detected by the blackening of the emulsion in sheets of radiation-sensitive film and the resulting pattern of optical densities within the autoradiogram can be quantified by comparison with a calibrated radioactive scale. In this review, the technique of computer-assisted densitometry is described together with guidelines for the selection and preparation of radioactive standards. Strategies are discussed for ensuring that radioactivity can be measured and quantified using film-based emulsions with a precision approaching that of conventional counting techniques.