Ultrasound Changes in Salivary Glands after Radioactive Iodine Treatment in Benign Diseases and Differentiated Cancer of Thyroid Glands in Consideration of Dose and Time Dependency.

Purpose: To assess ultrasound (US) features observed in salivary glands after radioactive iodine treatment (RAIT) in relation to the dose and time interval after RAIT.

Materials and methods: A retrospective analysis of US findings regarding the salivary glands of patients presenting after RAIT due to thyroid cancer (Group 1, n=99) or benign thyroid diseases (Group 2, n=25). The control group consisted of randomly selected patients (no RAIT, Group 3, n=100). Groups were compared regarding RAIT dose, symptoms, and US findings (duct dilation, hypoechoic/heterogeneous parenchyma, parenchymal loss). The association of the presence of US parameters after RAIT with various dose levels (2000-15000MBq) and time intervals (24, 60, 120 months) and the differences between the groups was evaluated.

Results: Significant differences between US parameters were noted when comparing Group 1 with Group 2 or 3. Nothing of relevant significance was noted when Groups 2 and 3 were compared. US features indicating a slight or moderate sialadenitis showed the most significant associations with doses <4000MBq and time intervals <24 months after RAIT. US changes indicating a serious sialadenitis or even gland atrophy showed the most significant association at doses between >7000-9000MBq and when US was performed >60 months after RAIT.

Conclusion: Our results point to a dose and time dependency of pathologic US findings in RAIT-induced effects on the major salivary glands. Based on the US findings, a better estimation of the current impact of RAIT on the salivary glands and the further prognosis appears possible.