A vital device for administering radiotherapy, especially intensity-modulated radiation treatment (IMRT) is the Central Opening Carbon-Fiber Couch. There doesn't seem to be any evidence in the literature about the impact of the thickest section (edge couch) on the dose distribution, even though multiple tests were conducted with the radiation field incident on the center of the couch. In this study, we evaluated and improved the computed beam profile doses for the under-couch fields for various field sizes for energy 6MV to reduce the skin surface dosage.
The beam profile dose was determined using OCTAVIUS detector 1500 with OCTAVIUS 4D modular phantom and Elekta's Monaco 5.11.03 Treatment Planning System (TPS) using three calculating algorithms: Collapsed Cone (CC), Monte Carlo (MC), and pencil beam (PB).
As the radiation treatment beam traverses through the treatment CONNEXION central opening couch, the radiation treatment beam passes through the central aperture couch to deliver the treatment. There are differences between the measured and calculated (using CC and MC) isodose profiles of about 8% at angle 130o and these errors decrease with increasing gantry angle until the couch effect disappears at angle 150o on the left side and similarly on the right side. There are no doses calculated in the couch effect zone using PB algorithm.