Verification of Patient Setup Error in Tomotherapy through Image Guided Radiation Therapy (IGRT) Procedure

Abstract

Purpose: To evaluate the interfraction setup errors in different treatment sites with Tomotherapy by mega-voltage computerized tomography (MVCT). Materials and Methods: This study included 13 patients underwent radiotherapy with Tomotherapy. There were 7, 3 and 3 patients belonged to head and neck cancer, thoracic and pelvis cancer, respectively. These three subgroups were analyzed separately. The interfraction setup errors were evaluated by comparing daily series MVCT with initial simulation KVCT three dimensionally. Both automatic and manual methods were used for determination of these errors. Results: For 208 daily MVCT check-up for head and neck tumor, average shift was 0.3±2.3 mm for lateral direction (x), 0.0±2.6 mm for longitudinal direction (y), 2.3±1.8 mm for vertical direction (z), and 0.6±0.9 degree for longitudinal axis (roll) rotation. For 80 daily MVCT check-up for thoracic tumor, average shift was -0.4±2.4 mm for x direction, -2.6±2.9 mm for y-direction, 2.5±3.9 mm for z-direction, and 0.4±0.5 degree for roll axis rotation. For 76 daily MVCT check-up for pelvic tumor, average shift was 0.3±3.9 mm for x direction, -2.4±4.8 mm for y-direction, 8.3±4.3 mm for z-direction, and 0.4±0.3 degree for roll axis rotation. The pattern of shifts showed a random distribution except z direction. Conclusion: Except from z-direction of pelvic tumor, there was no significant difference between automatic and manual methods among different treatment sites and different direction errors.