TY - JOUR ID - 12319 TI - Dosimetric Effect Resulting From the Collimator Angle, the Isocenter Move, and the Gantry Angle Errors JO - Iranian Journal of Medical Physics JA - IJMP LA - en SN - AU - Oulhouq, Yassine AU - Rrhioua, Abdeslem AU - Zerfaoui, Mustapha AU - Bakari, Dikra AD - HASSAN II Oncology Center, University Hospital Mohammed VI & LPMR, Faculty of sciences, University Mohamed 1st, Oujda, Morocco AD - LPMR, Faculty of sciences, University Mohamed 1st, Oujda, Morocco AD - LPMR, Faculty of sciences, University Mohamed 1st, Oujda, Morocco AD - National School of Applied Sciences, University Mohamed 1st, Oujda, Morocco Y1 - 2019 PY - 2019 VL - 16 IS - 5 SP - 355 EP - 361 KW - collimator angle KW - Dosimetry KW - granty angle KW - Head and neck KW - Linac KW - Radiotherapy DO - 10.22038/ijmp.2019.30616.1350 N2 - Introduction: Dose distribution can be affected by diverse parameters, such as beam orientations, and collimator angles. These parameters should respect and maintain the international recommended levels during the realization of the quality assurance protocols of linear accelerators. This study aimed at evaluating the dosimetric effects on treatment quality considering the mechanical error fluctuations in the recommended range. Material and Methods: This study included ten patients with head and neck cancer. All of them were treated using three-dimensional conformal radiotherapy with the simple 3-field classic technique. Initially, an optimized treatment plan was computed for each patient. Afterward, similar calculations were executed by varying isocenter position, gantry and collimator angles. Eventually, dosimetric evaluations based on dose-volume histograms were studied and analyzed by Wilcoxon signed rank test for each plan. Results: The analysis of the dose-volume histograms of tumor volumes and organs at risk, as well as the dosimetry calculation, revealed that the small errors of 0.5° in gantry and collimator angles have minimal effects on dose distribution. However, the variation in isocenter coordinating up to 1 mm may influence the patients’ treatment quality, particularly in the spinal cord and the brainstem, in which Wilcoxon's test showed significant effects in all plans. Conclusion: According to the results, the quality of the treatment plans is almost insensitive to the errors of the gantry and the collimator angles of the order 0.5° though it is relatively sensitive to isocenter errors (1 mm). These should be reduced in order to avoid overdose when applying the conventional 3-field technique. UR - https://ijmp.mums.ac.ir/article_12319.html L1 - https://ijmp.mums.ac.ir/article_12319_149efe2c54c643bd18a3dcd339fc3fc0.pdf ER -