A method for determining 212Bi by TDCR Cherenkov counting.

212Bi is one of the potential medical alpha emitters for targeted alpha therapy, and development of a precise activity measurement method for 212Bi is necessary. In this work, a triple-to-double coincidence ratio (TDCR) Cherenkov method for the measurement of 212Bi activity was established. 224Ra source, calibrated by alpha spectrometry, was utilized for the method development. Cherenkov radiation emitted from the progenies of 224Ra was studied in details, demonstrating that 212Bi and its daughter 208Tl would dominate the production of Cherenkov photons while the contributions from 224Ra, 220Rn, 216Po, 212Pb and 212Po can be negligible. Potential counting loss of 212Pb and 212Bi owing to the emanation of 220Rn from the sample solution was also studied, and no obvious influence was obsevered. Thus, the TDCR Cherenkov quench curve was prepared using 224Ra as a 212Bi source. The performance of the method was examined using spiked samples with the 212Bi activities varied from 1.69 to 91.31 Bq, and the measured results agreed well with the expected values. The minimum detectable activity was determined to be 0.21 Bq. [ABSTRACT FROM AUTHOR]