Storage-phosphor autoradiography: A rapid and highly sensitive method for spatial imaging and quantitation of radioisotopes

Abstract

This study evaluates a storage-phosphor imaging system for rapid autoradiography and quantitation of β- and γ-ray emitters in mice. Known quantities of authentic 3H, 14C, and 195mPt (0.06 to 31,714 DPM/mm 2) were exposed to imaging plates of the storage-phosphor system for 0.5 min to 15 hr at room temperature. Immediately after exposure, the imaging plates were scanned and the autoradiograms were quantified. Radioactivity as low as 1.8 DPM/mm 2 ( 3H), 0.06 DPM/mm 2 ( 14C) and 3.1 DPM/mm 2 ( 195mPt) was visualized and quantified in 8 hr ( 3H and 14C) and 6 min ( 195mPt), respectively. The system displayed a linear range of four to five orders of magnitude ( 14C: 0.5 to 6,914 DPM/mm 2 for 2-hr exposure; 3H: 1.8 to 15,372 DPM/mm 2 for 15-hr exposure; and 195mPt: 66 to 198,000 DPM 6 min-exposure). Variation from scan-to-scan was small (< 1% to 5%) and was more pronounced at the lower detection limits and exposure periods. Similar sensitivity, linearity, and variability were obtained in cryosections of murine tumors treated with 14C-fluorouracil or 3H-epinephrine and whole-body autoradiograms of mice treated with 195mPt-cisplatin via liver. The high sensitivity allowed noninvasive imaging of live unanesthetized mice treated with 195mPt with a short exposure time (105 sec). These results validate, for the first time, the high sensitivity, linearity, and wide dynamic range of storage-phosphor technology for quantitative autoradiography of 14C, 3H, and 195mPt isotopes. Storage-phosphor imaging will be useful in rapid quantitative autoradiographic disposition studies of radiolabeled drugs and excipients in vitro and in vivo.