Image Based Quality Assurance of Range Compensator for Proton Beam Therapy

Kim, Jin Sung; Yoon, Myonggeun; Kim, Dongwook; Lim, Young Kyung; Kwak, Jungwon; Park, Soah; Shin, Dong Ho; Shin, Jungwook; Lee, Se Byeong; Park, Sung Yong; Cho, Kwan Ho

Abstract

The main benefit of proton therapy over photon beam radiotherapy is the absence of exit dose, which offers the opportunity for highly conformal dose distributions to target volume while simultaneously irradiating less normal tissue. For proton beam therapy two patient specific beam modifying devices are used. The aperture is used to shape the transverse extension of the proton beam to the shape of the tumor target and a patient-specific compensator attached to the block aperture when required and used to modify the beam range as required by the treatment plan for the patient. A block of range shifting material, shaped on one face in such a way that the distal end of the proton field in the patient takes the shape of the distal end of the target volume. The mechanical quality assurance of range compensator is an essential procedure to confirm the 3 dimensional patient-specific dose distributions. We proposed a new quality assurance method for range compensator based on image processing using X-ray tube of proton therapy treatment room. The depth information, boundaries of each depth of plan compensatorfile and x-ray image of compensator were analyzed and presented over 80% matching results with proposed QA program.