[High resolution autoradiographic detection of beta-gamma emitters in biological tissues: case of Indium 111]

The present paper proposes an efficient autoradiographic procedure for the microscopic localisation in biological tissues of both low energy electrons and electrons released at relatively high energy. These are emitted by radioactive tracers, decaying by electron capture and/or internal conversion, that are increasingly used in biology and medicine. A detailed inventory of the corpuscular and electromagnetic radiations has been established in the specific case of Indium-111, with emphasis placed on those presenting an autoradiographic interest. As far as the electromagnetic component is concerned, the probability for producing secondary electrons as a function of distance from the source has been calculated. The range of the electrons in the emulsion and in a tissue-like medium has also been taken into account. The comparison with experiments using isolated lymphocytes labelled with 111In-oxine confirms the feasibility to localize and quantify with a high resolution beta-gamma emitters within biological systems by autoradiographic imaging.