New equivalent sphere approximation for BFO dose estimation: Solar particle events

The use of a 5 cm tissue equivalent sphere model to obtain dose estimates for the blood-forming organs from energetic space radiations has been widespread for some time. Recent studies have noted that calculated doses obtained using the 5 cm equivalent sphere model were very conservatively overestimated when compared to those obtained with a detailed body geometry. Such conservatism may introduce significant shield weight penalties if used in spacecraft design studies. The use of detailed human geometry models will yield more accurate estimates of blood-forming organ doses and dose equivalents, but with a concomitant reduction in computational ease. In this work we propose a preliminary, yet new blood-forming organ equivalent sphere approximation for use in estimating SPE exposure and in shield design studies that is more realistic than the existing 5-cm approximation.