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 degrees 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.. analysis was carried out with criteria of 2% / 2 mm. The passing rate shall over than 90%. If the passing rate of. analysis was lower than 90%, two-isocenter plan was created and carried out. analysis as well. Results: According to the. analysis, when the distance from lesions to the single-isocenter was more than 6cm, both in the horizontal or 45 degrees direction, the passing rate was lower than 90%. Based on. 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.