Kyoto University Hospital has recently introduced a stereotactic body frame(SBF)for radiotherapy for lung tumors. Twenty-one patients were treated between July 1998 and March 2000 at Kyoto University Hospital for solitary pulmonary nodules. The study was performed to evaluate the feasibility of three-dimensional(3D)conformal radiotherapy for a solitary lung tumor using the SBF. The clinically applicable range of the beam direction was mapped to avoid collisions between the gantry, couch, and the SBF prior to its clinical application. After mapping the beam direction range, 3D conformal radiotherapy using the SBF was carried out. The SBF has a fixed thickness. The irradiation dose has been absorbed by the SBF, and the target reference dose has been somewhat attenuated. Therefore, we measured dose attenuation in the direction of the beam relative to the SBF. The average percentage of dose attenuation was 9.3%. The precision of setting a target reference dose in stereotactic radiotherapy is important clinically. As a result, a correction factor of 9.3% was used, and a comparison between the absence of a recent planning dose and the presence of a recent planning dose was performed. Furthermore, treatment planning using a chest phantom was carried out, and the target reference dose was compared using a dosimeter. It is thought that the correction method evaluated in this study is needed for precise control of the target reference dose.
