| Popis: |
Accuracy and reproducibility of the patient’s position are fundamental to the successful delivery of radiation therapy. The purpose of this study was to analyze the magnitude of setup errors and the impact of those corrections on the delivered dose to the tumor and organs at risk (OARs). A series of 30 patients with H&N cancer were enrolled in a trial to examine daily radiation set-up accuracy. These patient where treated with field design using an advanced 3D planning techniques (ConPas). Immobilisation and alignment were performed using thermoplastic masking, base plate fixation, three point laser alignment and portal imaging evaluation per protocol. Positional errors were applied in initial plans and trough DVH, dose to the tumor and normal nearby healthy structures were analyzed. For all patient mean set-up errors were 0.23 cm, 0.28 cm, 0.19 cm in three directions (lat., long., vert.). The standard deviations for systematic setup corrections in lat., long, and vert. directions were 0.24 cm, 0.10 cm, 0.27 cm respectively. The quality of dose coverage for the PTV degraded slightly and dose to OARs change significantly (maximal change: medulla 8.29 %, Parotid L 8, 4 %, Parotid D 14, 7 %). The accuracy of patient positioning will improve the success of radiation treatment. The use of specific clinical protocols for patients' setup can effectively detect setup errors and this will reduce radiation dose to critical organs. |
