Quantitative evaluation of salivary gland dysfunction after radioiodine therapy using salivary gland scintigraphy

The most frequent non-thyroidal complication of high-dose (131)I therapy for thyroid carcinoma is salivary gland dysfunction, which may be transient or permanent. In this study, we assessed radioiodine-induced permanent salivary gland dysfunction using quantitative salivary gland scintigraphy.

Salivary scintigraphy was performed with (99m)Tc-pertechnetate on 50 thyroid carcinoma patients who had been given radioiodine for thyroid ablation; 20 normal subjects were imaged as the control population. Dynamic scintigraphy was performed and time-activity curves for four major salivary glands were generated. The glandular functional parameters maximum secretion, time at maximum count and uptake ratio of the parotid and submandibular glands were calculated. Correlation of the administered dose and subjective symptoms with findings of salivary gland scintigraphy was evaluated.

The maximum secretion and uptake ratio were decreased in 46% and 42% of patients who received radioiodine therapy, respectively. Salivary gland dysfunction correlated well with the administered dose. The parotid glands were more affected than the submandibular glands. Fifty-two per cent of patients were symptomatic, 69.23% of whom showed salivary gland dysfunction.

Parenchymal damage to the salivary glands induced by radioactive iodine treatment can be evaluated by salivary gland scintigraphy. The impairment was worse in parotid glands and increased with the total dose. The maximum secretion and uptake ratio were found to be sufficiently sensitive to distinguish the severity of the damage.