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 t echnetium-99m dimercaptosuccinic acid [Tc-99m(V)-DMSA], thallium-201 a nd technetium-99m sestamibi (MIBI) has been reported to be useful in t he detection of medullary thyroid carcinoma (MTC), We undertook a stud y 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 meta static MTC, All patients underwent total thyroidectomy and had persist ently elevated serum calcitonin levels after the surgery, Scintigraphi c 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 contem poraneous 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 re maining three patients no lesions were detected during diagnostic eval uation. Tc-99m(V)-DMSA showed all of the soft tissue metastases but co uld not show two bone lesions, On the other hand, MIBI imaging was fal se-negative in 22 (52%) sites and Tl-201 was false-negative in 34 (80% ) sites, Overall, lesion detection sensitivities for Tc-99m(V)-DMSA, M IBI 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 o f MTC patients.