ABSTRACT
Objective To semiquantify salivary gland damage after 131I treatment in patients post thyroidectomy using salivary gland scintigraphy. Methods Fifty-six patients underwent salivary gland scintigraphy 6 months after 131I ablation therapy following thyroidectomy, including 21 with both baseline (before 131I treatment) and follow-up (6 months after the 1st 131I treatment) imaging. Salivary gland function was quantified by uptake ratios at 4 minutes (UR4) and 15 minutes (UR15), and excretory index at maximum secretion (MS), time duration from stimulation to minimum count (Tmin ). Paired t test was used for the 21 patients with both baseline and follow-up imaging. All the studies were divided into four groups: before 131I therapy, after 1st therapy, after 2nd therapy, and after 3rd or more times of therapy. Group differences were evaluated by the one-way analysis of variance (ANOVA)/Kruskal-Wallis test. Spearman test was used to analyze the correlation between the parameters and times of therapy. Results After the 1st 131I therapy, UR15 for the left and right parotid glands were 16% and 14% lower than the baseline, respectively (t=2.188, 3.322, both P0.05). Among the four groups, significantly different parameters for both parotid glands were found: UR4, UR15, MS for the left parotid of the four groups were 1.76±0.29, 2.60±0.38, (72.8±24.2)%; 1.55±0.34, 2.15±0.51, (64.4±21.6)%; 1.55±0.40, 2.02±0.68, (57.2±34.2)%; 1.45±0.33, 1.69±0.46, (30.6±36.9)%; respectively (F values for UR4 and UR15 were 7.018, 3.112 and H value for MS was 12.240, all P0.05). According to pair-pair comparison, only the degree of reduction of UR15 for parotid glands was significantly different between the 1st and 2nd therapy (P<0.05). UR4, UR15, MS for bilateral parotid glands reduced significantly after 3 or more times of therapy (all P<0.05).The parametres UR4, UR15, MS were correlated with times of 131I therapy (r:-0.296 to -0.566, all P<0.05). Conclusions Salivary uptake function is impaired slightly after the 1st radioiodine therapy. After several times of therapy, both parotid uptake and excretion functions are impaired. Submandibular functions are not affected even after repeated 131I therapy.