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[Assessment of parotid gland dose variations by helical tomotherapy adaptive system in head and neck cancer].

The paper introduces a helical tomotherapy (HT) adaptive system in assessment of parotid gland dose variation in head and neck cancer. The system, which helical therapy unit is equipped with, is based on megavoltage computed tomography (MVCT) images to calculate the actual volume and dose of region of interest (ROI). Whether to change plan is judged on the fact for the realization of adaptive radiotherapy. One case of nasopharyngeal carcinoma was as a sample to evaluate parotid gland dose variation during the treatment. On every week and last time, patient was scanned by MVCT before treatment, a total of eight MVCT images. As the treatment progressed, the parotid gland volume was shrinking and the dose was increasing. The parotids volume variation was negatively related with D50 and V1 (both P < 0.05).