[Dosimetric correction for a six degrees carbon fiber couch]

We investigated experimentally and clinically the influence of a six degree (6D) carbon fiber couch on conventional radiation therapy. We used 4, 6 and 10 MV X-rays and compared dose distributions based on correction methods, i.e. monitor unit (MU) addition, including computed tomography (CT) couch, and the couch modeling. Additionally, we evaluated the clinical value of dosimetric correction for the 6D couch in 30 patients treated with multi-field irradiation. In the phantom study, the maximum difference of isocenter doses attributable to the 6D couch was 5.1%; the difference was reduced with increasing X-ray energy. Although the isocenter dose based on each correction method was precise within ±1%, MU addition underestimated the surface dose. In the clinical study, the maximum difference of isocenter doses attributable to the 6D couch was 2.7%. The correction methods for the 6D couch provide for highly precise treatment planning. However, the clinical indication of complicated correction methods should be considered for each institution or each patient, because the influence of the 6D couch was reduced with multi-field irradiation.