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Tc-99m-tetrofosmin scintigraphy: an alternative scintigraphic method for following up differentiated thyroid
H J Gallowitsch1, E Kresnik, P Mikosch
1Department of Nuclear Medicine and Special Endocrinology, LKH Klagenfurt, Austria.
Aim:
The usefulness of the myocardial perfusion agent, Tc-99m-tetrofosmin (Myoview) in the follow-up of differentiated thyroid carcinoma was evaluated in a clinical study of 15 patients, primary treated with thyroidectomy and high-dose I-131-therapy (2960-3700 MBq). 12 with suspected recurrence and metastases and three patients without any suspicion and compared with other non-specific tracers like TI-201 and Tc-99m-sestamibi.
Method:
Twelve patients with elevated thyroglobulin (Tg) levels of more than 10 ng/ml (group A), four of these had negative I-131 scans, and three patients with Tg levels less than 10 ng/ml (group B) were examined under TSH suppressive L-Thyroxine treatment. Whole body scans were taken with Tl-201 (74 MBq: 20 mn post injection), Tc-99m-sestamibi (370 MBq: 20-60 min post injection) and Tc-99m-tetrofosmin (370 MBq: 20-60 min post injection). Tumor/background ratios and optional time/activity analyses (up to 150 min post injection) were evaluated using the region of interest approach.
Results:
Compared with Tl-201 (T/BG: 1.59, +/- 0.396). Tc-99m-tetrofosmin showed slightly but not significant better T/BG ratios and detection rates (T/BG: 1.76, +/- 0.345). Tc-99m-sestamibi (1.51, +/- 0.31 p = 0.05) showed significantly lower values than Tc-99m-tetrofosmin
Conclusion:
In the light of these results, scintigraphy with Tc-99m-tetrofosmin seems to be a possibly sensitive imaging modality in the follow-up of DTC with possible advantages concerning T/Bg ratio, background clearance, detection rate and dosimetry compared with Tl-201 and Tc-99m-sestamibi, especially in patients with elevated Tg level and no iodine uptake, but further investigations are needed to confirm our preliminary results.