Early assessment of high-intensity focused ultrasound treatment of benign thyroid nodules by scintigraphic means

BACKGROUND: High-intensity focused ultrasound (HIFU) allows to inflict intracorporal thermal lesions without penetrating the skin or damaging the surrounding tissue. This analysis intends to assess the magnitude of HIFU-induced ablations within benign thyroid nodules using scintigraphic imaging with (99m)Tc. METHODS: Ten cold, hot, or indifferent nodules were treated using multiple pulses of HIFU to induce temperatures of around 85°C within the ablation zone. Pre- and posttreatment, uptake values of (99m)Tc-pertechnetate or (99m)Tc-MIBI were recorded. The pre-post reduction of nodular uptake was evaluated to assess ablation magnitude. RESULTS: Relative nodular uptake in relation to total thyroidal uptake decreased after one session of HIFU in all cases. Median (99m)Tc-MIBI uptake reduction was 35.5% (ranging from 11% to 57%; p < 0.1), while (99m)Tc-pertechnetate scintigraphy showed a median uptake reduction of 27% (range 10% to 44%; p < 0.1). No major complications were observed. CONCLUSIONS: HIFU appears to be safe and is an easy to perform means of thermal ablation. This study shows that HIFU treatment in thyroidal nodules can be evaluated by scintigraphic means shortly after the intervention. Due to small sample size, the exact magnitude of HIFU ablation efficiency in thyroidal nodules remains a value to be assessed in a larger study.