Objective:Radiotherapy is the primary treatment for nasopharyngeal carcinoma,but it frequently leads to radiotherapy-induced temporal lobe injury(RTLI).Magnetic resonance imaging(MRI)is the main diagnostic method for RTLI after radiotherapy for nasopharyngeal carcinoma,but it is prone to missed diagnoses.This study aims to investigate the causes of missed diagnoses of RTLI in nasopharyngeal carcinoma patients undergoing MRI after radiotherapy. Methods:Clinical and MRI data from nasopharyngeal carcinoma patients diagnosed and treated with radiotherapy at Xiangya Hospital of Central South University,from January 2010 to April 2021,were collected.Two radiologists reviewed all head and neck MRIs(including nasopharyngeal and brain MRIs)before and after radiotherapy of identify cases of late delayed response-type RTLI for the first time.If the original diagnosis of the initial RTLI in nasopharyngeal carcinoma patients did not report temporal lobe lesions,it was defined as a missed diagnosis.The first diagnosis of RTLI cases was divided into a missed diagnosis group and a non-missed diagnosis group.Clinical and imaging data were compared between the 2 groups,and multivariate logistic regression analysis was used to identify independent risk factors for MRI missed diagnoses of initial RTLI. Results:A total of 187 nasopharyngeal carcinoma with post-radiotherapy RTLI were included.The original diagnostic reports missed 120 cases and accurately diagnosed 67 cases,with an initial RTLI diagnosis accuracy rate of 35.8%and a missed diagnosis rate of 64.2%.There were statistically significant differences between the missed diagnosis group and the non-missed diagnosis group in terms of lesion size,location,presence of contralateral temporal lobe lesions,white matter high signal,cystic degeneration,hemorrhage,fluid attenuated inversion recovery(FLAIR),and examination site(all P<0.05).Multivariate logistic regression analysis showed that lesions≤25 mm,non-enhancing lesions,lesions without cystic degeneration or hemorrhage,lesions located only in the medial temporal lobe,and MRI examination only of the nasopharynx were independent risk factors for missed MRI diagnosis of initial RTLI(all P<0.05). Conclusion:The missed diagnosis of initial RTLI on MRI is mainly related to lesion size and location,imaging characteristics,and MRI examination site.