Comparison of Tc-99m(V)-DMSA, Tl-201 and Tc-99m-MIBI imaging in the follow-up of patients with medullary carcinoma of the thyroid

Radionuclide scanning with tumour-seeking agents such as pentavalent technetium-99m dimercaptosuccinic acid [Tc-99m(V)-DMSA], thallium-201 and technetium-99m sestamibi (MIBI) has been reported to be useful in the detection of medullary thyroid carcinoma (MTC), We undertook a study in 14 MTC patients to determine the comparative imaging potential of Tl-201, MIBI and Tc-99m(V)-DMSA in the detection of recurrent or metastatic MTC, All patients underwent total thyroidectomy and had persistently elevated serum calcitonin levels after the surgery, Scintigraphic studies were carried out 20 min after the injection of 111 MBq of Tl-201 or 555 MBq of MIBI and 2 h following the injection of 370 MBq of Tc-99m(V)-DMSA. All scintigraphic findings were correlated with contemporaneous CT or MRI studies, CT, MRI and bone scans showed 42 (26 bone, 16 soft tissue) metastatic sites in II of the 14 patients. In the remaining three patients no lesions were detected during diagnostic evaluation. Tc-99m(V)-DMSA showed all of the soft tissue metastases but could not show two bone lesions, On the other hand, MIBI imaging was false-negative in 22 (52%) sites and Tl-201 was false-negative in 34 (80%) sites, Overall, lesion detection sensitivities for Tc-99m(V)-DMSA, MIBI and Tl-201 were 95%, 47% and 19% respectively. We conclude that Tc-99m(V)-DMSA is clearly superior to MIBI and Tl-201 in the follow-up of MTC patients.