Comparison of sonographic appearance of normal and postradiotherapy parotid glands: a preliminary study

This study was undertaken to evaluate and compare the grey-scale and Doppler sonographic features of postradiotherapy (RT) and normal parotid glands. A total of 10 patients with previous head and neck RT and with different degrees of xerostomia were included. Another 10 healthy subjects, who are age and gender-matched with the 10 patients, were also recruited. Grey-scale and Doppler ultrasound examinations of parotid glands were performed on both the patients and healthy subjects. The parotid glands were assessed for their size, echogenicity, echotexture, conspicuity of intraparotid ducts, blood flow velocity and vascular resistance. Results showed that post-RT parotid glands tended to be smaller than normal parotid glands with a significant difference in the transverse dimension (p < 0.05). Normal parotid glands appeared homogeneous, hyperechoic relative to the adjacent muscles and had marginally seen intraparotid ducts. Post-RT parotid glands were heterogeneous, isoechoic (50%) or hypoechoic (50%) relative to the adjacent muscles, and the intraparotid ducts were either marginally (50%) or obviously (50%) seen on ultrasound. The PSV, RI and PI of normal parotid glands were significantly higher than that of post-RT parotid glands (p < 0.05). However, the difference in EDV between normal and post-RT parotid glands was not significant (p > 0.05). In conclusion, ultrasound is useful in assessing parotid glands. To avoid image misinterpretation, post-RT changes in the sonographic appearance of parotid glands should be considered in examining patients with previous head and neck RT.