¹⁸F-FDG PET/CT In The Evaluation Of Salivary Gland Inflammation After ¹³¹I Residual Ablation For Patients With Differentiated Thyroid Carcinoma And Correlation Between Salivary Dynamic Scintigraphy

Objective:To investigate the value of 18F-FDG PET/CT in the evaluation of salivary gland inflammation after 131I residual ablation for patients with differentiated thyroid carcinoma?DTC?,and the correlation with salivary dynamic scintigraphy.Methods:Retrospective analysis of 18F-FDG PET/CT images before and after ¹³¹I treatments was performed in patients with DTC.We measured the maximum standard uptake values?SUVmax?of FDG in bilateral parotid and submandibular glands using regional areas of interest?ROI?.Analysis the uptake ratio?UR?and excretion fraction?EF?values of salivary gland imaging before and after ¹³¹I treatmen;SUVmax of bilateral parotid and submandibular gland before and after treatment was also measured and compared in patients receiving 1.85GBq and 3.7GBq ¹³¹I.The correlation between 18F-FDG PET/CT and salivary gland imaging was also analyzed.Results:Out of 230 patients treated in our hospital,151 met the inclusion criteria and were included.The baseline characteristics of the patients included 106 female cases,aged 48.3±11?19-80 years?.All the included patients had FDG PET/CT scan before and after ¹³¹I treatment.Statistically significant differences of SUVmax were observed in parotid?1.44±0.43 and 1.93±0.62,t=8.62,P=0.00?and submandibular?2.62±0.77and 2.88±0.77,t=2.79,P=0.006?)gland before and after the treatment of¹³¹I.The SUVmax in parotid and submandibular gland before and after 1.85GBq,3.7GBq 131I treatments was 1.45±0.48 and 1.98±0.657?t=5.63,P=0.00?,1.48±0.44and1.93±0.63?t=6.77,P=0.00?;2.54±0.77and 2.96±0.82?t=3.61,P=0.001?,2.65±0.75and 2.84±0.75?t=2.14,P=0.04?,respectively with statistical significance.Compared with 1.85GBq,3.7GBq ¹³¹I treatment showed no significant difference in SUVmax of the parotid and submandibular gland?P>0.05?.The UR in parotid gland before and after ¹³¹I treatments had statistical significance.Left:1.66±0.74 and1.35±0.56?t=2.38,P=0.023?,Right:1.74±0.63 and1.62±0.50?t=1.28,P=0.042?.There was no significant difference in EF%of parotid glands before and after the treatment of ¹³¹I?P>0.05?.The changes of parotid SUVmax correlated with UR by salivary dynamic scintigraphy before and after treatment.Conclusion:18F-FDG PET/CT sensitively evaluates the radiation induced inflammatory status of salivary gland caused by 131I treatment in patients with DTC.1.85GBq and 3.7GBq 131I equally cause the radioactive inflammation in salivary gland which has little correlation with the radioactivity and needs to be confirmed by further studies.3.7 GBq treatment may have a long effect on salivary glands of patients.