The clinical feasibility and effect of online ExacTrac 6 degree-of-freedom system for head-and-neck cancer

Purpose: Online adaptive correction in image-guided intensity-modulated radiotherapy appears to be a promising approach for precision radiation treatment in head-and-neck tumors. This research is designed to evaluate the setup uncertainties in the left-right (L-R), superior-inferior (S-I), and anterior-posterior (A-P) directions and rotational variations: pitch, roll, and yaw for head-and-neck cancer (HNC) patients with the ExacTrac 6 degree-of-freedom (6D) image-guided radiotherapy (IGRT) system. Materials and Methods: The setup errors measured by ExacTrac 6D IGRT system at the treatment unit with respect to the planning computed tomography were recorded for 40 patients with head-and-neck tumors. The residual setup errors were computed and quantitatively analyzed. Results: The results indicated that the setup errors measured in the S-I direction were larger than the other two directions. For the three rotational angles, the results were very close. The verifications showed that after the first correction, the overall setup errors were generally