Clinical immobilization techniques for proton therapy

Proton therapy through the use of the Bragg peak affords clinicians a tool with which highly conformal dose can be delivered to the target while minimizing integral dose to surrounding healthy tissue. To gain maximum benefit from proton therapy adequate patient immobilization must be maintained to ensure accurate dose delivery. While immobilization in external beam radiation therapy is designed to minimize inter- and intra-fraction target motion, in proton therapy there are other additional aspects which must be considered, chief of which is accurately determining and maintaining the targets water-equivalent depth along the beam axis. Over the past 23 years of treating with protons, the team at the James M. Slater Proton Treatment and Research Center at Loma Linda University Medical Center have developed and implemented extensive immobilization systems to address the specific needs of protons. In this publication we review the immobilization systems that are used at Loma Linda in the treatment of head and neck, prostate, upper GI, lung and breast disease, along with a description of the intracranial radiosurgery immobilization system used in the treatment of brain metastasis and arteriovenous malformations (AVM's).