The usefulness of a new carbon fiber couch as a countermeasure for the attenuation by metal supports of a couch attached to a linear accelerator in rotation therapy

A treatment couch attached to a linear accelerator (attached couch or A. couch) has metal supports. In full rotation therapy, attenuation of absorbed dose by these supports can not be ignored. Therefore, our institution has devised a new couch of carbon fiber (C.F. couch) for brain tumors or head and neck lesions. We evaluated the influence of both couches in rotation therapy with 4 MV or 10 MV photon beam. For the A. couch, the maximum dose attenuation at full rotation was 4-5% at 4 MV and 4% at 10 MV. On the other hand, the influence of the C.F. couch was negligible. Consequently, the influence of the A. couch in full rotation should not be ignored. Our results suggested the need to correct the metal support-induced attenuation. Our C.F. couch was useful as a countermeasure for the attenuation by metal supports of the attached couch in rotation therapy. (author)