CALIBRATION OF [I-123] IODINE-LABELED TISSUE STANDARDS FOR AUTORADIOGRAPHIC STUDIES

Autoradiographic images can be analyzed with computer-assisted microdensitometry relative to radioactive reference standards to provide quantitative measurements of regional radioactivity concentrations. [I-123]Iodine containing sections of brain paste have been calibrated relative to plastic-embedded tritium(H-3) and 125Iodine standards. For exposure times of 8, 12 and 24 h, plastic-embedded standards covered a range concentrations of [I-123]iodine from 1000 to 100,000 dpm/mg wet weight. Iodine-123 radioactivity was linear with section thickness from 5 to 30-mu-m. These studies confirmed the feasibility of using commercially available longer-lived reference standards to provide [I-123]iodine equivalent values in absolute units of dpm (or mu-Ci) per mg tissue.