Dosimetry in single lung cells by means of microautoradiographic activity measurements

After inhalation of compounds containing promethium-147 in the lungs of mice most of the activity is deposited in the form of local concentrations (hotspots). By means of a special quantitative microautoradiographic method using stripping film ORWO K 105, measurements of the activity of single hotspots of about 10(-14) Ci are possible. A microphotometer with a variable measuring diaphragm is used for the determination of the density profile of the autoradiographic image in order to get hotspot depth within the biological specimen. To determine hotspot activity it is necessary to calibrate the film with a Pm-147 plane source. The systematic and random errors of the method are discussed in detail, giving a total error of +/- 21% (SD) for one hotspot activity measurement. A few examples of biological results obtained by the method are given. Simple models are used to calculate doses absorbed in macrophage and alveolar cell nuclei from the measured activities.