The Planar Scan And SPECT/CT Image Analysis Of Remnant Thyroid Tissue For Differentiated Thyroid Carcinoma

Objective:To evaluate the diagnostic value of Tc-99m pertcehnetate scanning to detect remnant thyroid tissue in patients with differentiated thyroid ccarcinoma?DTC?,and to evaluate the number and sites of thyroid remnant after total thyroidectomy,then analyse the possible reason for the remnant to enhance physician,s understanding,providing guidence for therapy.Methods:Retrospectively entrolled 187 patients?61 men,126 women?with DTC who underwent total thyroidectomy.The 99 m Tc scans and post-ablative ¹³¹I SPECT/CT were performed on all patients,and all of them were followed up to 6-12 months after radioiodine ablation to evaluate the outcome of the ablation.All scans were interpreted and localize the remnant thyroid tissue by two experienced nuclear physcians who wre blinded to the study.¹³¹I SPECT/CT was considered to be the gold-standard method for the diagnosis of remnant thyroid tissue,and we compared the efficacy of Tc-99m pertcehnetate scanning to detect remnant tissue with this method.And the result Tc-99m pertcehnetate scanning were compared with the outcome of remnant radioiodine ablation to evaluate the relationship between them.And statistic the number and sites of thyroid remnant.Results:For patients with unequivocally positive Tc-99m uptake,the sensitivity was 78%,and if equivocal Tc-99m uptake was counted as positive the sensivity was89%?patient-based?.And for site-based analyses the sensitivity was 73% and 86%.The specificity and positive predictive value?PPV?was 100% for both patient-based and site-based measurements;The successful ablation rate of patients with unequivocally positive Tc-99m uptake was 59%,and 62%for patients with equivocal Tc-99m uptake,62%for patients with negative uptake,there are no statistical differences between them;186 patients of 187 have thyroid remnan after total thyroidectomy,thyroid remnant were identified on the SPECT/CT imaging at thyroglossal duct 69/186?37.1%?,at pyramidal lobe 35/186?18.8%?,at superior thyroid poles 54/186?29%?,in isthmus region9/186?4.8%?,in Berry's ligament 53/186?28.5%?,in lobar regions 87/186?46.8%?;No significant difference regarding age,gender,histopathology,radioactive iodine dose,TSH level,stimulated thyroglubulin?s Tg?levels and outcome of remnant ablation between the two groups with or without thyroglossal duct remnant.Conclusion:Tc-99m pertcehnetate scanning can be a good tool for estimation of remnant mass before radioiodine treatment,the result of Tc-99m pertcehnetate scintigraphy cannot predict the outcome of ¹³¹I ablation;In spite of total thyroidectomy,nearly all of the patients have thyroid remnant,the remnant is related to the protection of important structures such as the recurrent laryngeal nerve,the superior laryngeal nerve,the parathyroid,and so on,thyroglossal duct remnant can be frequently observed on ¹³¹I-SPECT/CT images,there is no difference of s Tg level and the outcome of radioactive ablation in patients with or without thyroglossal duct remnant.