Abstract: Objective The aim of this study was to explore the effectiveness of self-made oral humidity detection device to assist in evaluating the degree of parotid gland damage in radiotherapy for nasopharyngeal carcinoma,so as to guide doctors to change the radiotherapy plan in time,reduce the radiation dose to parotid gland,and reduce the incidence of xerostomia after radiotherapy. Methods A retrospective analysis was conducted on the relationship between oral humidity and parotid gland dose of radiotherapy in 60 patients with nasopharyngeal carcinoma using oral detection devices in the Department of Oncology of Southwest Medical University Affiliated Hospital from January 1,2022 to December 31,2022.According to the method of changing the radiotherapy plan,patients were divided into experimental group(n=30)and control group(n=30).The patients in the experimental group used a self-made oral humidity detection device to detect oral humidity,when 30 patients with oral relative humidity below 65% underwent CT simulation positioning and changed the radiotherapy plan to reduce the dose of parotid gland;The control group patients collected oral humidity but did not interfere in the radiotherapy plan,and only underwent CT positioning during the mid-term radiotherapy.The average oral humidity,parotid gland,and target area dose parameters of patients were analyzed after radiotherapy.The follow-up questionnaire was conducted to evaluate the life quality of patients in terms of dry mouth,decreased taste,difficulty opening mouth,and dental caries in two groups. Results The average oral humidity(t=2.938,P＜0.05),the D_mean of average dose of bilateral parotid glands(t_left=-2.076,t_right=-2.094,P＜0.05),the D₅₀ for dose of 50% volume of bilateral parotid glands(t_left=-2.123,t_right=-2.230,P＜0.05),and the volume percentage V₃₀ of bilateral parotid gland dose(t_left=-2.505,t_right=-2.491,P＜0.05)in patients were significantly reduced in the experimental group compared to the control group,while there was no statistically significant differences in target area dosimetric parameters(P＞0.05).The dry mouth and taste loss in the experimental group were lower than those of the control group(P＜0.05),and the difficulty in opening the mouth and caries scores were lower than those of the control group,but the difference was not statistically significant(P＞0.05). Conclusion The oral humidity detection device can detect the oral humidity of radiotherapy patients in time,objectively evaluate the impact of radiation on patient's parotid gland,guide doctors to change the radiotherapy treatment plan in a timely manner,minimize the degree of parotid gland damage,and improve their quality of life in nasopharyngeal carcinoma radiotherapy patients.At the same time,the device is easy to operate,time-consuming,and non-invasive,which improves the effectiveness and safety of radiotherapy technology and is worth promoting this device.

Key words: Oral humidity, Radiation therapy, Nasopharyngeal carcinoma, Dosimetry, Parotid gland