Ultrasound-guided percutaneous microwave ablation of benign thyroid nodules: experimental and clinical studies

Purpose: To obtain the treatment parameters of internally cooled microwave antenna and to evaluate the feasibility of ultrasound-guided percutaneous microwave ablation (MWA) for benign thyroid nodules. Materials and methods: MWAs were performed by microwave antenna (16G) in ex vivo porcine liver. The lesion diameters achieved in different groups (20, 25, and 30 W for 3, 5, 7, 10, and 12 min) were compared. The clinical study was approved by the ethics committee. Written informed consent was obtained from all patients. MWA was performed in 11 patients (male to female ratio=1:10; mean age, 50 +/- 7 years) with 11 benign thyroid nodules. Ultrasound scan, laboratory data, and clinical symptoms were evaluated before and 1 day and 1, 3, 6, 9, and 12 months after the procedure. Results: In ex vivo study, the ablation lesion at 30 W 12 min tended to have appropriate scope and spherical shape. In clinical study, the follow-up periods ranged from 1 to 9 months. At the last follow-up, the largest diameter decreased from 2.9 +/- 1.0 (range, 1.6-4.1) to 1.9 +/- 0.7 (range, 0.4-3.0) cm (P<0.01), and the volume decreased from 5.30 +/- 4.88 (range, 0.89-14.81) to 2.40 +/- 2.06 (range, 0.02-6.35) ml (P<0.01). The volume reduction ratio was 45.99 +/- 29.90 (range, 10.56-98.15) %. The cosmetic grading score was reduced from 3.20 +/- 0.79 to 2.30 +/- 0.95 (P<0.05). One patient experienced temporary nerve palsy and was recovered within 2 months after treatment. Conclusion: The internally cooled microwave antenna can yield ideal ablation lesions, and ultrasound-guided percutaneous MWA is a feasible technique for benign thyroid nodules.