Experimental measurement of the correlation between CT number and heavy ion range

Abstract

For precision delivery of the Bragg peak of a heavy-ion beam to a target volume in ion beam therapy, it is necessary to know the tissue stopping power. A general approach to solve this problem in ion beam therapy is to convert X-ray CT (computed tomography) numbers into water-equivalent path length (WEPL) coefficients using a CT-WEPL calibration curve for all voxels traversed by the beam. This work aims at establishing a CT-WEPL coefficient calibration curve for the heavy ion therapy project at IMP, so as to compute the range of carbon ion beams in tissues easily according to the patient CT data. Several tissue-equivalent materials were applied to measure their WEPL coefficients using a high-energy carbon ion beam in this work. A CT-WEPL calibration curve was obtained through fitting the measured data, which can be used directly for dose optimization and facilitates the design of patient treatment plans significantly at IMP.