Patients with nasopharyngeal malignancies (NPM) are generally treated by nasopharyngeal irradiation. In order to evaluate curative effect, gadolinium-based contrast agents (GBCAs)-based MRI examinations are always performed repeatedly. Whether the nasopharyngeal irradiation affects the T1 signal intensity (SI) in DN remains unclear. 68 NPM patients and 68 suitable control patients were enrolled. We found that the uptake rate of gadolinium from the NPM was significantly higher than that from control patients. We speculated that the nasopharyngeal irradiation increases the T1 SI by the damage to the blood–brain barrier (BBB).