Clinical Value Of ^99mTc-MIBI Scintigraphy In Patients With Differentiated Thyroid Carcinoma After First Radioactive Inodine-131 Treatment

Objective:The aim of this study was to evaluate the clinical value of 99mTc-MIBI scintigraphy in the follow-up of patients with DTC after their first radioiodine therapy, by comparing the results with post-therapy 131I whole body scan (Rx-WBS).Materials and Methods:Retrospectively analysis of 192 hospitalized patients with DTC in Nuclear Medicine Department of the First Affiliated Hospital of Chongqing Medical University, all patients had received total or subtotal thyroidectomy and pathologically diagnosed as DTC,171 papillary and 21 follicular carcinomas. Underwent 99mTc-MIBI scan (average dosage: 740-925 MBq) after their first radioiodine therapy 6 months later, then followed by 131I therapy. Rx-WBS was performed 4 days after oral administration of the therapeutic dose 131I (average dosage:5550-8140 MBq). Then, comparing the results of those two imagings. Before the second course of I therapy, all patients had received thyroxine withdrawal for 4 weeks and tested the serum level of thyroglobulin (Tg), thyroglobulin antibody (TgAb) and thyroid stimulating hormone(TSH). Data were analyzed by chi-square test and t-test.Results:1. A total of 191 patients’imaging results were included in the final analysis, we found 65 positive cases,99mTc-MIBI scan found 37(56.9%) and Rx-WBS found 60(92.3%), Rx-WBS has a significantly higher sensitivity than 99mTc-MIBI scan (χ2=14.7, p<0.01).2. There are 43 thyroid remnants,99mTc-MIBI scan detected 17 (39.5%) and Rx-WBS detected 43(100%),99mTc-MIBI scan’s sensitivity in detecting thyroid remnants was significantly lower than Rx-WBS (χ2=24.0, p<0.01).3. There are 22 metastatic lesions,99mTc-MIBI scan found 20 (90.9%) and Rx-WBS found 17(77.3%),99mTc-MIBI scan’s sensitivity in detecting metastases is higher than 131I scans, but without significant difference (χ2=0.57, p>0.05).4. The serum Tg level of 99mTc-MIBI+ and/or 131I+ groups was significantly higher than the 99mTc-MIBI1131I- group (p<0.01), and that of 99mTc-MIBI+/131I- group is significantly higher than the 99mTc-MIBI-/131I+ group (t=-2.7, p<0.05).Conclusions:1. Our data indicate that 99mTc-MIBI scintigraphy has a relatively higher sensitivity in finding metastases for DTC patients after first radioiodine therapy, but its value in detecting thyroid remnants is limited. Combination of 99mTc-MIBI scan and Rx-WBS can improve the diagnostic value of DTC recurrence and metastases.2. Both 99mTc-MBI scans’ and Rx-WBS’ results has a good correlation with the serum Tg level.