Target dose accuracy of single-isocenter stereotactic body radiation therapy for multiple lung lesions

Background: to investigate the maximum distance from lesions to the single-isocenter that can ensure the accuracy of dose delivery for single-isocenter/two-lesions intensity modulated radiotherapy (imrt) lung stereotactic body radiation therapy (sbrt). materials and methods: we employed a lung phantom made of acrylic material. sixteen gross tumor volumes (gtvs) of the same shape and size were delineated on the ct images. the single-isocenter was placed on the center of the first gtv (gtv1). six gtv centers were located at left and were 2-7 cm away from the single-isocenter. nine gtv centers were in the 45° direction and were 2-10 cm away from the single-isocenter. plans were created for the first planning target volume (ptv1) and other fifteen ptvs separately with the same isocenter. compass was used to verify the treatment plans. γ analysis was carried out with criteria of 2% / 2 mm. the passing rate shall over than 90%. if the passing rate of γ analysis was lower than 90%, two-isocenter plan was created and carried out γ analysis as well. results: according to the γ analysis, when the distance from lesions to the single-isocenter was more than 6cm, both in the horizontal or 45° direction, the passing rate was lower than 90%. based on γ analysis, two-isocenter plans were created. after verification, the passing rate was higher than 90%. conclusions: the maximum distance of using singleisocenter to treat multiple lung lesions is 5 cm. the result provides a reference for our center and other centers when using this technique to treat multiple lung lesions.