PT  - JOURNAL ARTICLE
AU  - Klaus A. Hamacher
AU  - Robert B. Den
AU  - Elana I. Den
AU  - George Sgouros
TI  - Cellular Dose Conversion Factors for α-Particle–Emitting Radionuclides of Interest in Radionuclide Therapy
DP  - 2001 Aug 01
TA  - Journal of Nuclear Medicine
PG  - 1216--1221
VI  - 42
IP  - 8
4099  - http://jnm.snmjournals.org/content/42/8/1216.short
4100  - http://jnm.snmjournals.org/content/42/8/1216.full
SO  - J Nucl Med2001 Aug 01; 42
AB  - α-Particle–emitting radionuclides are of increasing interest in radionuclide therapy. The decay scheme of α-emitting radionuclides typically includes a chain of unstable progeny. It is generally assumed that α-particle emission by the parent radionuclide will break the chemical bond with its carrier molecule and that the resulting daughter atom will no longer be associated with the carrier molecule. If the daughter is very short lived, it will not have enough time to be carried any significant distance from the site of parent decay and a cellular, absorbed dose estimate must consider the energy deposited by the daughter as well as the parent. Depending on the site of parent decay and the expected removal rate of daughter atoms from this site, the contribution of emissions from longer-lived daughters may also be warranted. In this study, dose conversion factors (DCFs) for cellular dimensions that incorporate the fate of daughter radionuclides were derived for 225Ac, 213Bi, 211At, and 223Ra, the α-particle–emitting radionuclides of interest in radionuclide therapy. Methods: The dose contribution of daughter radionuclides at the site of parent decay was made dependent on a cutoff time parameter, which was used to estimate the fraction of daughter decays expected at the site of parent decay. Previously tabulated S values (cell-surface to nucleus and cell-surface to cell) for each daughter in the decay scheme were scaled by this fraction and a sum over all daughters was performed to yield a cutoff time–dependent set of corresponding DCF values for each radionuclide. Results: DCF values for the absorbed dose to the nuclear or cellular volume from cell-surface decays are presented as a function of the cutoff time for 4 different cellular and nuclear dimensions. Conclusion: In contrast to the cellular S values that account only for parent decay, the DCF values provided in this study make it possible to easily include the contribution of daughter decays in cellular α-particle emitter dose calculations.