Estimation of range and dose distribution for bi-material targets in heavy-ion irradiation

In order to evaluate the field irradiated with incident ions and the deposited dose distribution in a patient body, we have proposed to use the positron emitters produced through projectile fragmentation reactions of stable heavy ions. In the previous, years, we established the method to estimate the range of incident ions and the dose distribution in uniform targets by using the MLE method. In this year, we performed irradiation experiments for bi-material targets consisting of PMMA, lung equivalent material, water, etc. with 12C of 290 MeV/u and 16O of 350 MeV/u. The annihilation events from the positron emitters produced by 12C and 16O ions were detected with a positron camera for 500 s just after the irradiation. Then the range was determined in each target by applying the MLE method. Consequently, for all the targets, the evaluated ranges agreed with those calculated from the depth-dose distributions measured with an ionization chamber within an accuracy of 3.0 mm. (author)