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Background Microwave ablation (MWA) and radiofrequency ablation (RFA) have recently attracted interest as minimally invasive treatment modalities for papillary thyroid carcinoma (PTC). However, the ablation outcomes of T1N0M0 PTC are not well characterized. Purpose To evaluate the efficacy and safety of thermal ablation (MWA or RFA) of solitary T1N0M0 PTC in patients who were ineligible for (due to presence of comorbid cardiovascular disease, renal failure, other malignancy, etc) or who refused surgery. Materials and Methods This was a retrospective multicenter study of 847 patients (660 women) who underwent thermal ablation for PTC (673 T1a, 174 T1b) between March 2015 and March 2020; of these patients, 645 underwent MWA and 202 underwent RFA. The mean age of patients was 46 years ± 11 (standard deviation) (age range, 18-81 years); the mean follow-up time was 22 months ± 13 (range, 6-60 months). Changes in tumor size and volume and the rates of technical success, tumor disappearance, disease progression, and complications were assessed. Results The technical success rate was 100%. Relative to preablation measurements, the maximum diameter and volume of the ablation zone increased during the 1st month after ablation (P < .001), whereas there was no difference by the 3rd month; subsequently, the tumors showed reduction in size at 6, 9, and 12 months (all P < .001). Complete disappearance of tumors occurred in 68% of patients (577 of 847; 69% [466 of 673] in the T1a group vs 64% [111 of 174] in the T1b group; P < .001). The postablation disease progression rate was 1.1% (nine of 847 patients; 0.9% [six of 673 patients] in the T1a group vs 1.7% [three of 174 patients] in the T1b group; P = .54). The overall complication rate was 3.4% (29 of 847 patients; 2.7% [18 of 673 patients] in the T1a group vs 6.3% [11 of 174 patients] in the T1b group; P = .02). Conclusion This multicenter study provided evidence that thermal ablation is an effective and safe treatment option in selected -patients with solitary T1N0M0 papillary thyroid carcinoma. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Baek and Cho in this issue.

Background Ultrasound-guided thermal ablation plays an important role in the management of thyroid disease. The objective of this study was to evaluate the feasibility, efficacy, and safety of thermal ablation for patients with solitary T1bN0M0 papillary thyroid carcinoma (PTC) who are ineligible for or unwilling to undergo surgery. Materials and Methods Data pertaining to 172 patients (38 males and 134 females) who received thermal ablation therapy at 12 hospitals between April 2015 and March 2020 were retrospectively analyzed. The mean duration of follow-up was 24.9 ± 14.1 months (range, 12–60). The technical feasibility, technical success, efficacy, and safety of treatment were analyzed. Postablation tumor size at various time points was compared with preablation measurement. Results All patients selected for thermal ablation received enlarged ablation, according to contrast-enhanced ultrasound postablation. The maximum diameter and volume of ablation zone at 6, 12, 18, 24, 36, and 48 months postablation were significantly smaller than those recorded preablation (P Conclusion Thermal ablation may be a feasible, effective, and safe treatment option for patients with solitary T1bN0M0 PTC who are ineligible for or unwilling to undergo surgery. It may provide a novel treatment option for selected patients.

Background: To evaluate the feasibility and safety of microwave ablation (MWA) for PTC with metastatic cervical lymph nodes who are ineligible for or refuse surgery. Materials and Methods: Twenty patients of unifocal PTC with metastatic cervical lymph nodes from three hospitals were enrolled in this study, and MWAs were performed. Contrast-enhanced ultrasound was used to evaluate the extent of ablation. The volume of the ablated area and thyroid hormones were measured. Results: PTC nodules in 9 patients completely disappeared at the end of follow-up. Compared with the volume before ablation, the mean volume reduction ratio of ablated lesions was 0.414 ± 0.700 (range: -1.92-0.95) at postoperative 6 months. The patients' thyroid function tests were normal at the end of follow-up. New lymph node metastasis was found in one patient during follow-up visits and she underwent a second MWA procedure. For the other patients, no new PTC nodule, local recurrence or cervical lymph node metastasis were suspected on ultrasound by the end of follow-up. No distant metastasis was encountered during the follow up. None of the patients developed hypocalcemia, permanent hoarseness or skin burns. Conclusions: MWA is a minimal invasive and safe method in treating PTC with cervical lymph node metastasis.

In order to improve the efficiency of debugging and assembling optical fiber collimator and to facilitate mass production, Automatic assembly technology of optical fiber collimator was studied. A new method was proposed to assemble optical fiber collimator by detecting minimal receiving beam spot. First, the relation was analyzed between the detected spot radius and the distance from the emitting end to reception end according to Gaussian beam transmission theory. Then, an automation system was designed to detect the minimal receiving beam spot when the distance was suitable. The optical fiber collimator was successfully assembled after being fixed. Experimental results show that the coupling loss between two collimators is less than 0.53dB when the wavelength of the transmitting light is 1550nm and the distance between two collimators is less than 1 mm.