A lyoluminescent tissue-equivalent dosemeter for pion therapy beams.

The light emitted when pion irradiated glucose is dissolved in luminol solution has been found to be proportional to the pion beam depth dose distribution in water as determined by a TE ionisation chamber. The lyoluminescence of glucose overlaps very closely with the response profile of the ionisation chamber to the 170 MeV/c pi--mesons giving a Bragg peak to plateau ratio of 3:1. In comparison, the thermoluminescence response of LiF (TLD-700) to pions has been found to deviate significantly from this ratio. The close tissue equivalence of glucose, non-toxicity and its excellent lyoluminescent retention properties are important advantages over currently used dosemeters in clinical pion therapy, especially when direct in vivo measurements are considered. Pion doses ranging between 0.5 Gy (50 rad) and 30 Gy (3000 rad) were measured with an accuracy +/- 5% and reproducibility 3-5%.