Design of an Innovative Water Filter for Total Body Irradiation

Total Body Irradiation (TBI) is a radiological therapy mainly used for patient conditioning before bone marrow transplantation. Basically, the therapy consists in delivering a suited X-ray dose to the entire body of the patient. Achieving a uniform dose over the whole body is one of the major problems because of variations in thickness and density of patient’s tissues. This paper presents the design of an innovative integrated system for improving dose homogeneity in TBI. The system is made up of a translating bed, an X-ray linear accelerator, a vision system for body thickness assessment, a dynamically controlled water filter and a main control unit for modules integration and synchronization. The core of the system is the water filter, which consists in an array of 70 small water containers (referred to as cells). The filter is located between the Xray source and the patient. The water level in each cell can be on-line modified introducing a small amount of water through an electric on-off valve. This way, water levels can be regulated so as to modify dose distribution in the transversal direction. Moreover, by translating the bed, dose delivery can be modulated even in the longitudinal direction.