Objective To evaluate salivary gland function damage and analyze related factors by diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with nasopharyngeal carcinoma after intensity modulated radiation therapy.

Methods Twenty-eight patients with newly-diagnosed nasopharyngeal carcinoma were enrolled. All patients underwent IMRT, and DW-MRI scan and dry mouth rating were performed before radiotherapy, the 4th weeks of radiotherapy, the end of radiotherapy, and 3, 6 and 12 months after radiotherapy. DW-MRI scans included resting state and acid stimulation.

Results There were significant differences in the grade of dry mouth of nasopharyngeal carcinoma patients between 6, 12 months after radiotherapy and 3 months after radiotherapy, the end of radiotherapy (all P < 0.05). Before the radiotherapy, the parotid ADC values were statistically significant at rest, acid stimulation at the 3rd and 6th minutes(all P < 0.05). At the 4th week of radiotherapy, the end of radiotherapy and 3 months after radiotherapy, the ADC value increased overall, but there was no significant difference in acid stimulation time (all P > 0.05). At 6 and 12 months after radiotherapy, the ADC value gradually decreased, and again showed a rise and then decreased, and then slowly increased for a long time. The difference between the 3rd and 6th minutes of acid stimulation was statistically significant (P < 0.05). The submandibular glands and parotid glands were similar in acid-stimulated state before radiotherapy. The change rate of ADC value was positively correlated with the change rate of salivary gland volume. The change rates of ADC value and salivary gland volume were positively correlated with the average dose.

Conclusion DW-MRI has certain evaluation value on the salivary gland function damage of nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.