Implementation of a water compensator for total body irradiation

This paper presents the design, implementation, and testing of an integrated system for improving dose homogeneity in total body irradiation (TBI). TBI is a radiation therapy tech- nique that consists in delivering a uniform X-ray dose to the en- tire body of the patient. Because of variations in patient’s tissues thickness and density, achieving a uniform dose over the entire body is one of the major challenges in TBI. The system proposed in this paper, whose main goal is to compensate for tissues hetero- geneities, is made up of a translating bed, a linear accelerator, a vision system for body thickness assessment, a dynamically con- trolled water filter, and a main control unit. The water filter, placed between the X-ray source and the patient, is made up of an array of 70 small water containers (cells). The water level in each cell is con- trolled in real time, so as to modify the dose distribution both in the transverse direction and in the longitudinal direction. A prototype of the water filter system was implemented and tested, achieving good results in terms of dose uniformity.