Department of Radiation Oncology and Research Institute, Pusan National University Yangsan Hospital and Pusan National University School of Medicine, Yangsan, South Korea , apex7171@hanmail.net
Abstract: (210 Views)
Background: Due to the complicated dose calculations, in volumetric modulated arc therapy (VMAT), treatment errors may occur with changes around the lesion due to changes in the patient volume. The head and neck contain many major organs at risks (OAR)s increasing the likelihood of volume changes in OARs due to the effects of radiotherapy. Materials and Methods: The dose distribution and effects according to the changes in patient volume were analyzed while maintaining the same beam and irradiation conditions as in the initial treatment plan. The volume was extracted to quantify the volume change by setting the region of interest (ROI) of a fan-shaped area formed tangentially to the planning target volume (PTV), with the spinal cord as the center in the transverse plane. Results: As the radiation treatment progressed, the head and neck volume changes accelerated. As the volume change increased, the target's low-dose distribution area, the incident dose to the spinal cord and parotid gland, and the incident dose to the target periphery increased. In particular, an increase in the target's cold spot and the incident dose to the parotid gland can cause late effects as well as insufficient treatment. Conclusion: The alteration in dose distribution can be anticipated by monitoring the shift in patient volume using the ROI extraction method outlined in this study.
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