Accounting for the effects of carbon fibre treatment couches in the XiO treatment planning system

An investigation was conducted to determine the impact of two carbon fibre couch tops on treatment planning and to establish a method by which these couch tops may be accounted for in the XiO treatment planning system. In this study, the effects of the Civco Universal and the Medical Intelligence iBeam evo carbon fibre couch tops were investigated. Customised templates were developed in Focal to mimic the effects of these patient support devices and each template was then included in calculations performed by the XiO treatment planning system. The accuracy of modelling the couch tops in this manner was investigated and it was shown that, while using the customised couch templates, XiO modelled the increase in the surface dose due to treating through the couch tops at 180° to 1.0% ± 1.7%. The attenuation due to the presence of the couches was modelled to within 0.5% ± 0.4% for angles that pass through the flat central region of the couch tops and to within 1.4% ± 1.2% for angles that passed through their rapidly varying edges. When the couch templates were not included in XiO, the calculated dose at depth was recorded to be, in some cases, up to 5.3% ± 1.0% more than corresponding measured values. It was concluded that using the method described in this study it is possible to accurately model the effect of carbon fibre couch tops in the XiO treatment planning system.