Ascendus

The following data were recorded before treatment: three diameters of the nodules (largest diameter, d1 and two perpendicular diameters, d2 and d3); the composition of the nodules (assessed by US examiner subjectively); the cosmetic grading score (CGS; 1: no palpable mass, 2: invisible but palpable mass, 3: visible mass visible only to experienced clinician's eyes, and 4: easily visible mass) [32] ; and the symptomatic score (SS; visual analog scale, 0-10) indicating the distress of patients. The volume (V) of the nodules was calculated using the following equation:
US examination of thyroid nodules was performed before treatment and at each follow-up (1, 3, 6 and 12 months postoperatively and every 6 months thereafter) with a Hitachi Ascendus instrument (L75-type high-frequency linear array, frequency range: 5-18 MHz). The MWA therapy instrument used was a KY-2000 (Kangyou Medical, Nanjing, China) that consists of a microwave generator, a flexible low-loss coaxial cable and a cooled 16-G shaft antenna (a 10-cm shaft coated with polytetrafluoroethylene and a 3-mm narrow radiating segment 3 mm from the tip). The generator can produce 1-100 W of power at 2450 MHz; the energy we used for thyroid ablation was between 30 and 50 W. Cooled MWA was applied to reduce the occurrence of complications [19, 33, 34] .

Ultrasound systems with 4.0-8.0 MHz linear transducers and 2.0-5.0 MHz convex array probes were used (Philips IU22, Koninklijke Philips NV, and Hitachi Ascendus). All of the examinations were performed by experienced sonographers (with > 5 years of experience). Training courses on how to collect the standard images and save them to the picture archiving and communication system (PACS) were organized for the sonographers.

Using the GE Logiq E9 at a transducer frequency of 6-15 MHz or the Hitachi Ascendus at a transducer frequency of 5-18 MHz, a designated experienced sonographer performed ultrasonography Doppler to measure the intima-media thickness (IMT) of the common carotid artery (CCA). The distance between the first and second echogenic line edges was used to determine the IMT. The mean value of the IMT was computed after three sets of measurements were made. The ankle pressures of both legs were measured and the ABI was calculated.

Worst pain and pain during walking was collected with a numerical rating scale going from 0 (indicating no pain) to 10 (worst imaginable pain). For ultrasonographical assessment of the Achilles tendon, we used a Hitachi Ascendus with an 18 Hz linear transducer.
Ultrasonographical measures were collected due to their potential association with patient symptoms (15, 16) . Doppler settings were the same for all patients, with a gain setting just below the noise level and pulse repetition frequency set to 1.0. Tendon thickness was measured at the thickest point in a longitudinal scan perpendicular to the greatest width of the tendon (the true thickness) in accordance with earlier recommendations (17) . All included patients had ultrasonographically determined spindle-shaped thickening, inhomogeneity and hypoechogenicity of the symptomatic tendon with increased Doppler activity. Doppler settings were the same for all patients, with a gain setting just below the noise level and the V scale set to 350. We ranked the colour Doppler activity from grades 0 to 4, where grade 0 = no activity, 1 = single vessel, 2 = Doppler activity in >25%, 3 = Doppler activity in 25% to 50%, and 4 = Doppler activity in > 50% (18) . The same experienced specialist in rheumatology performed both the measurements before and after the surgery and was blinded to the treatment.