Abstract 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® THC900 888-H) used works with a frequency of 3 MHz, reaching temperatures of 80 – 90° 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. Key points: • HIFU is a safe and effective method to treat thyroid nodules. • HIFU does not interfere with thyroid gland function. • HIFU does not induce any immune response like Graves’ disease. Citation Format: • Korkusuz H, Sennert M, Fehre N et al. Localized Thyroid Tissue Ablation by High Intensity Focused Ultrasound: Volume Reduction, Effects on Thyroid Function and Immune Response. Fortschr Röntgenstr 2015; 187: 1011 – 1015

High-intensity focused ultrasound (HIFU) is a promising, non-invasive technique in treating benign thyroid nodules (TNs). The aim of this study was to evaluate the efficacy of HIFU to induce clinically meaningful shrinkage in benign predominantly solid TNs and to identify variables that influence or predict the magnitude of TN volume reduction.

Ziel: Das Ziel dieser Studie war, die Effektivitat von hochintensivem fokussiertem Ultraschall (HIFU) zu beurteilen. Es wurden die Volumenreduktion der Knoten, die Funktion der Schilddruse und eventuell auftretende Immunreaktionen evaluiert. Material und Methoden: Zwolf Patienten (neun weiblich, Durchschnittsalter 56,9 Jahre) wurden ambulant mit HIFU an der Schilddruse behandelt. Alle Patienten hatten einen einzelnen benignen Schilddrusenknoten, der in jeweils einer Therapiesitzung behandelt wurde. Das mittlere Knotenvolumen (nodular outline volume) betrug 3,4ml (Bereich 0,6–5,0ml). Die therapeutische Ultraschallsonde (Echopulse® THC900888-H), die in dieser Studie verwendet wurde, arbeitet mit einer Frequenz von 3MHz, erreicht eine mittlere Temperatur von 80–90 °C und sendet eine mittlere akustische Leistung von 87,6 bis 192,8 Watt aus. Die Serumspiegel von Trijodthyronin (T3), Thyroxin (T4), Thyreotropin (TSH), Thyreoglobulin (hTg) und zusatzlich Antikorper gegen Thyreoglobulin (TAK), Thyreotropin-Rezeptoren (TRAK) und Thyreoperoxidase (TPO) wurden bei der Aufnahme, 24 Stunden nach der Therapie und drei Monate nach der Therapie gemessen. Die pra-post Thyreoglobulin-Reduktion wurde gemessen, um den Erfolg der Ablation einzuschatzen. Auserdem wurde das Knotenvolumen mit der Variable Nodular Outline Volume (NOV) untersucht, um die Effektivitat zu bestimmen. Ergebnisse: Die Hormonspiegel sind stabil geblieben (p 0,05). Die Serumthyreoglobulinspiegel sind 24 Stunden nach der Ablation signifikant angestiegen (p >0,05). 3 Monate nach der Ablation wiederum sind sie signifikant abgefallen (p <0,05) und erreichten das pra-ablative Niveau. Abstract !

Objective: The aim of this study was to assess whether high-intensity focused ultrasound (HIFU), a new and promising method for the treatment of benign hot and cold thyroid nodules using thermal ablation, has an impact on thyroid function, and to evaluate its feasibility in outpatient settings. Additionally, a possible difference in the treatment of solid and complex thyroid nodules was evaluated. Method: Ten patients with one thyroid nodule each (six cold and four hot nodules) underwent HIFU in January 2014. Four nodules were solid and six nodules were complex. Serum levels of triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), thyroglobulin (hTg) and additionally antibodies against hTg (TAK), TSH receptors (TRAK) and thyroid peroxidase (TPO) were measured at enrolment and 24 h after the HIFU treatment. The pre- and post-thyroglobulin reduction was measured to evaluate the scale of ablation. In addition, patients' pain was recorded on a numeric rating scale from 0 to 10. Results: The HIFU treatment did not affect thyroid function, since hormone levels stayed stable (p<0.05). No serious immune reaction was induced. Thyroglobulin serum levels increased significantly (p<0.05) and were correlated to the total energy emitted by HIFU (p<0.1). The results of complex thyroid nodules did not differ from solid thyroid nodules. Similarly, the results of hot thyroid nodules did not differ from cold thyroid nodules. All patients tolerated the whole treatment and no severe complications were observed. Conclusion: HIFU is a safe and effective method to treat benign, solid, complex, hot and cold thyroid nodules preserving thyroid function. Further developments of the system are needed to gain suitability for daily use.

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 99mTc.