Can, S.Karaçetin, D.Meriç, N.2019-11-292019-11-292018http://hdl.handle.net/20.500.12575/68384The purpose of this study is to evaluate the volume change of critical structures and its effect on cumulative dose by employing tighter CTV-to-PTV margins for target level II/III through a GPU-based (Geometric Processing Unit) deformable image registration. Ten H&N cases treated with simultaneous integrated boost (SIB) on a tomotherapy were retrospectively analysed (Accuracy Inc., CA). Each patient had one planning CT and daily kVCT images during the radiation treatment course. The standard – margin plan was generated by giving 3-mm margin to CTV1-3 and compared with the 0-mm margin plan for CTV2-3. However, 3 mm margin of PTV1 was saved to provide tumor coverage. The volume of right parotid gland was decreased significantly for patients who lost more weight during the treatment course. The mean volume reduction was 11.7 % with the range of 29.3- 1.3 % and 13.5 % with the range of 25.9- 5.7 % in right and left parotid glands respectively. The difference in the delivered dose regarding standard margin plan and 0- mm margin plan was ≈ 10 % for the cord, ≈ 8 % and ≈ 19 % for the left and right parotid gland respectively. IGRT is one of the most effective tools to correct set-up error and allow the planner to reduce margin. In addition, GPUbased 3D image framework was crucial for dose accumulation and evaluation of critical structures and targets. In this study, it was proved that acceptable cumulative dose for region of interest is consummated when connected with weekly kCVT guidance by using tighter CTV-to-PTV margins for level II and III targets for head and neck cases. On the other hand, change in volume did not affect the cumulative dose of critical structures when tighter CTV-to-PTV margin was employed.trDeformable Image RegistrationHead and NeckArticle510116