Abstract
BACKGROUND/AIM: Because current image-guided radiotherapy systems can only correct six axes, it is impossible to correct the twisting of cervical vertebrae. The purpose of this study was to clarify the relationship between cervical vertebrae twisting and cranial angle. MATERIALS AND METHODS: Nineteen patients who underwent intensity-modulated radiation therapy were retrospectively reviewed. Twisting of cervical vertebrae was analysed using planning computed tomography (CT) and megavoltage CT images for image-guided radiotherapy. RESULTS: Although the cranial angle during planning CT was not strongly correlated with twisting (correlation coefficient <0.7), when the patients were divided into two groups by cranial angle, the twisting of the small-angle group was significantly reduced. Specifically, cranial angles of <25° significantly and efficiently reduced the twisting of the upper cervical vertebra compared with those of the other groups. CONCLUSION: Twisting of the upper cervical vertebrae is reduced by using a cranial angle of <25° during planning CT.