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 technique that consists in delivering a uniform X-ray dose to the entire 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 heterogeneities, is made up of a translating bed, a linear accelerator, a vision system for body thickness assessment, a dynamically controlled 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 controlled 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.