Technetium-99m tetrofosmin imaging in thyroid diseases: comparison with Tc-99m-pertechnetate, thallium-201 and Tc-99m-methoxyisobutylisonitrile scans

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Abstract
Technetium-99m tetrofosmin is a lipophilic phosphine used for myocardial perfusion imaging. Biodistribution studies have shown significant thyroid uptake of tetrofosmin and preliminary reports have suggested that tetrofosmin imaging may be of value in patients with thyroid cancer. In this study, tetrofosmin whole-body scintigraphy was performed in 35 patients with evidence of thyroid diseases. All patients underwent laboratory evaluation of thyroid function as well as99mTc pertechnetate scan, thallium-201 (n=16)99mTc-methoxyisobutylisonitrile (MIBI) (n=19) whole-body studies. Thyroid images were semi-quantitatively analysed by a 4-point score: O=no significant uptake; 1=uptake increased as compared to background activity, but inferior to normal thyroid tissue; 2=uptake equal to normal thyroid tissue; 3=uptake superior to normal thyroid tissue. Pathology examinations were obtained. A total of 41 thyroid nodules were detected, of which 15 were goitre nodules, 13 adenomas and 13 malignant lesions. In goitre nodules, concordant results of tetrofosmin and pertechnetate uptake (score 1 or 0) were observed in the majority of lesions (87%). In function adenomas (n=10), both tetrofosmin uptake and pertechnetate uptake were score 3. In non-function adenomas (n=3), tetrofosmin uptake was score 3, while pertechnetate uptake was score 0. In six malignant lesions, tetrofosmin uptake was score 3, while pertechnetate uptake was score 0; in the other seven lesions, where a prevalence of goitre abnormalities was observed, results of tetrofosmin and pertechnetate uptake were similar (score 0 or 1). In seven (70%) of the ten patients with malignant nodules, whole-body tetrofosmin images showed increased abnormal uptake in a total of 28 extra-thyroid tumour sites, as subsequently confirmed by other techniques. When tetrofosmin images were compared to 201T1 and99mTc-MIBI scans, concordant results were observed in all cases. In conclusion, tetrofosmin imaging may be particularly useful to characterize and stage patients with malignant thyroid nodules; it shows similar results to thallium but provides better image quality. Comparable findings were observed between tetrofosmin and MIBI studies. Thus, tetrofosmin may be an alternative to thallium and MIBI in the aforementioned patients.