The role of Tc-99(m)-tetrofosmin in the evaluation of thyroid nodules

Various radionuclides, including Ga-67, Tl-201 and Tc-99(m)-sestamibi, have been used to differentiate benign from malignant thyroid nodules. Tc-99(m) -tetrofosmin, a lipophilic cationic radiotracer, and 99Tcm-sestamibi have a lso been reported to accumulate in thyroid rumours. Ln this study, we evalu ated the role of Tc-99(m)-tetrofosmin in the differentiation of malignant f rom benign thyroid nodules. Seventy-nine patients with solitary non-functio ning thyroid nodules were included in the study. Fine-needle aspiration bio psy was performed in all patients. Sixty patients were subsequently operate d on and 19 patients refused surgery. After the injection of 370 MBq Tc-99( m)-tetrofosmin, static images at 5, 30, 60, 120 and 180 min were acquired. Both visual and semi-quantitative analysis was performed. On visual interpr etation, the nodules with late retention were classified as positive for ma lignancy and nodules without late retention were classified as negative for malignancy. In the semi-quantitative analysis, regions of interests were d rawn over the nodule and contralateral normal thyroid tissue. The average n umber of counts was recorded and tumour-to-normal thyroid tissue ratios cal culated. Post-operative histology revealed 19 malignant and 41 benign nodul es. Of the benign nodules, adenomas behaved similarly to the malignant nodu les with late retention of tracer, while adenomatous nodules revealed no la te retention on delayed images and could be differentiated from malignant t umours. In the semi-quantitative analysis, there was a significant differen ce in tumour-to-normal tissue ratios for adenomatous nodules and malignant rumours as well as adenomas. We conclude that it is not possible to differe ntiate between malignant and benign thyroid nodules with Tc-99(m)-tetrofosm in. However, Tc-99(m)-tetrofosmin scintigraphy is helpful in selecting nodu les that can be cured by surgical intervention. ((C) 2000 Lippincott Willia ms & Wilkins).