Radiotherapy positioning and target area delineation
palate
CT scanning was performed with a slice thickness of 3 mm, a slice spacing of 3 mm, and a reconstruction matrix of 512 × 512 and reached up to the top of the skull and down to 5 cm below the clavicle head. A cross was created with a 3D laser light on the left, middle, and right of the mask. The lead wire was pasted to the mask as a CT imaging mark, followed by CT scanning. After the scanning, the oral stent or simple glass bottle was removed, and the mask was worn. Next, CT scanning was performed again with the same parameters according to the same three crosses. All of the obtained image data were transported to the MIM image for fusion and uploaded to the planning system Monaco for target area delineation and planning design. As per ICRU 50 and ICRU 62 reports, the radiotherapist outlined the radiotherapy target area and normal tissues including the spinal cord, larynx, bilateral parotid gland, upper cheek, and soft palate. Thereafter, the approved plan was imported into the Elekta linear accelerator system. All patients underwent IMRT, during which all irradiation fields were used with standardized operations. The prescribed dose was 60 Gy/30 fractions. The same organ-at-risk (OAR) dose constraint parameters were utilized for all plans, and all IMRT plans were completed by an experienced physician.