Improving a scissor‐action couch for conformal arc radiotherapy and radiosurgery

We have developed a method to improve the setup accuracy of a Varian Clinac 6/100 couch for delivering conformal arc therapy using a tertiary micro multileaf collimator (MLC) system. Several immobilization devices have been developed to improve the mechanical stability and isocenter alignment of the couch: turn‐knob harnesses, double‐track alignment plates, and a drop‐in rod that attaches the couch to the concrete floor. These add‐on components minimize the intercomponent motion of the couch's scissor elevator, which allows consistent treatment setup. The accuracy of our isocenter couch alignment is an improvement over the above devices, within 1 mm of their accuracy. The couch has been used with over 15 patients and with over 50 modulated conformal arc treatment deliveries at our institution. PACS numbers: 87.53.Kn, 87.53.Ly, 87.56.Da