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In evaluating the efficacy of α-particle emitters, a cell survival curve is often determined for a particular source-target configuration. Investigators often wish to use this information about survival for a different source-target configuration which might be more appropriate for a therapeutic application. Since the population cell survival parameter, D 0 , is a function of the source-target configuration, it is important to determine the individual cell survival parameter, Z 0 , which is more fundamental. Unlike D 0 , Z 0 does not depend upon the microdosimetric variations in the specific energy distribution resulting from changes in the source-target configuration. Instead it is determined by the cell sensitivity and the radiation quality. However, the calculation of Z 0 from the data on survival involves computing the microdosimetric specific energy distributions of the radiation. This paper describes an approximate but sufficiently accurate method for determining Z 0 from D 0 if the first and second moments of the single-hit specific energy distributions are known or can be estimated. Examples of applications are given. This may alleviate the need for multihit microdosimetric calculations.

This study examined the effect of internal exposure to α-particle radiation on subsequent fertility among women employed in the radium dial industry prior to 1930, when appreciable amounts of radium were often ingested through the practice of pointing the paint brush with the lips. The analysis was limited to women for whom a radium body burden measurement had been obtained and who were married prior to age 45 (n = 603). Internal radiation dose to the ovary was calculated based on initial intakes of radium-226 and radium-228, average ovarian mass, number and energy of α particles emitted, fraction of energy absorbed within the ovary, effective retention integrals and estimated photon irradiation. Time between marriage and pregnancy, number of pregnancies and number of live births served as surrogates for fertility. Radiation appeared to have no effect on fertility at estimated cumulative ovarian dose equivalents below 5 Sv; above this dose, however, statistically significant declines in both number of pre...

A previous analysis of non-stochastic dose (Jostes et al., Radiat. Res. 127, 211-219, 1991; Schwartz et al., Health Phys. 62, 458-461, 1992) based on data obtained during irradiations of C-18 cells in suspension by alpha particles emitted from two forms (chelated and ionic) of 212Bi was made using survival curves. No appreciable difference in slope (1/D0) was found between the two forms. Such non-stochastic analyses do not account for the large differences in specific energies deposited in the individual cell nuclei. This microdosimetric (stochastic) analysis aims to determine the survival sensitivity (1/z0) of the individual C-18 cells using the distribution of specific energies deposited in the individual cell nuclei. The resulting sensitivity is greater for the alpha particles emitted from the chelated 212Bi than from the ionic 212Bi. An attempt to account for this greater sensitivity in terms of greater LET of alpha particles passing through the cell nuclei from the chelated 212Bi is unsuccessful. Instead the greater sensitivity disappears if the microdosimetric analysis uses average values for the radii of the cell and of its nucleus rather than the values (from the peak in the cell size distribution) used by the non-stochastic dose analysis.