Diffusion-weighted MRI at the Late Stage after Radiotherapy for Evaluating Salivary Gland Injury

Abstract

Objective: Salivary gland injury is the main complication of radiotherapy for nasopharyngeal carcinoma (NPC) patients. The purpose of this study was to evaluate the value of diffusion-weighted magnetic resonance imaging (DW-MRI) as a reliable tool to assess salivary gland function in NPC patients after radiotherapy. Materials and Methods: This study analysed the MR images of 31 NPC patients at different time points within 2-3 years after radiotherapy. The changes in the apparent diffusion coefficient (ADC) and its relationship with radiation dose were analysed. Results: Both the parotid and submandibular gland ADC values increased significantly 3-6 months after radiotherapy and then decreased gradually. The ADC value of the parotid gland was positively correlated with radiation dose at the late stage (P = 0.012, r = 0.359). The submandibular gland ADC change value (P = 0.035) and change ratio (P = 0.027) of the high radiation dose group were significantly lower than those of the low dose group at the late stage. Conclusion: The correlation between ADC values of parotid and submandibular glands and the radiation dose indicated that DW-MRI could be helpful in evaluating salivary gland injury after radiotherapy.