Localized Thyroid Tissue Ablation by High Intensity Focused Ultrasound: Volume Reduction, Effects on Thyroid Function and Immune Response

Purpose: The aim of this study was to assess the effectiveness of high intensity focused ultrasound (HIFU) in reducing thyroid nodule volume while preserving thyroid function as measured by immunological response. Materials and Methods: 12 patients (9 females) whose average age was 56.9 years (37 - 81) were treated with HIFU in an ambulatory setting. All patients had a single benign thyroid nodule treated in one HIFU session. The median nodular outline volume (NOV) was 3.4 ml (range 0.6 - 5.0 ml). The therapeutic ultrasound probe (Echopulse (R) THC900 888-H) used works with a frequency of 3MHz, reaching temperatures of 80-90 degrees C and a mean output between 87.6 and 192.8 W. To assess possible effects of HIFU on thyroid function, serum levels of triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), thyroglobulin (hTg) and antibodies against thyroglobulin (TAbs), thyrotropin receptors (TRAbs) and thyroid peroxidase (TPOAbs) were measured at enrollment, 24-hours post-HIFU treatment and at 3-month follow-up. Pre-post thyroglobulin reduction was measured to evaluate the success of ablation and the nodular outline volume (NOV) was evaluated at baseline and the 3-month follow-up to assess effectiveness. Results: All measured hormone levels were within normal ranges and remained stable (p > 0.05). No clinically meaningful immune reaction was induced (p > 0.05). Thyroglobulin serum levels increased significantly at 24 hours after ablation (p < 0.05) and decreased significantly at the 3-month follow-up (p < 0.05), returning to pre-ablative levels. The median reduction in nodular outline volume (NOV) was 55 % (p < 0.05). Conclusion: HIFU is a safe and effective alternative for treating benign thyroid nodules, while preserving thyroid function. Further investigations with multiple treatments should be conducted to evaluate whether additional treatments can achieve greater volume reduction.