Aixplorer system

Several ultrasound machines in our radiology department were used to perform muscle ultrasound examinations including: an Aixplorer system (Supersonic Imagine SA, Aix-en Provence, France), S2000 system (Siemens-Acuson, Mountain View, CA, USA), S3000 system (Siemens-Acuson, Mountain View, CA, USA), and LOGIQ E9 system (GE, Wauwatosa, WI, USA). These machines were equipped with linear broadband transducers operating at 5–14, 5–14, 4–9, and 4–15 MHz, respectively. The spatial resolution of these ultrasound systems ranged from 0.5 to 1 mm. Each subject was examined by the same examiner using one of these ultrasound machines. The system settings were not fixed but adjusted individually. For each subject, transverse ultrasound B-mode images of bilateral rectus femoris and sartorius muscles were obtained. For each muscle, one B-mode image was selected that included as much of the muscle as possible. Therefore, four muscle ultrasound images were measured for each subject. A doctor experienced in the analysis of muscle ultrasound images used Adobe Photoshop software (Adobe Systems, Mountain View, CA, USA) to manually outline the muscle contour, avoiding the surrounding fascia. The maximum transverse diameter of the rectus femoris and sartorius muscles in the participants ranged from 2 to 4 cm.

The ultrasound examinations were conducted in the Department of Oncological Endocrinology and Nuclear Medicine of MSCI in Warsaw, the Department of Endocrinology and Metabolic Diseases of the Medical University of Lodz, the Department of Endocrinology, Metabolism, and Internal Medicine of PUMS, and the Department of Imaging Diagnostics at the Medical University of Warsaw. The neck ultrasound examinations were performed with the use of linear transducers (7–18 MHz by Aplio XG, Toshiba Medical Systems, Japan; 5–12-MHz by iU22, Philips Medical Systems, Bothell, Wash), and 5–15 MHz by the AIXPLORER system, (Supersonic Imagine, Aix-en-Provence, France).
Ultrasound (US) examinations were performed by one of five sonographers (two radiologists, three endocrinologists) with 9 to 22 years of experience in thyroid imaging. Physicians were blinded to the FNAB results and the final postsurgical verification when reassessing the US examinations and determining the EU-TIRADS score. During the US, the transverse and longitudinal planes for both the gland and the nodules were obtained while the patient was in the supine position. The anteroposterior, transverse, and longitudinal diameters of the gland and nodules were measured on frozen images during examination and were archived. The US features of the thyroid nodules were also prospectively recorded.

Conventional thyroid ultrasonography examinations were performed by experienced sonographers and endocrinologists in our institution’s outpatient clinic with the use of the AIXPLORER system by Supersonic Imagine and the ALOKA alpha-7 with 2–10 MHz linear transducers. Selection of lesions for further FNAB was determined by the PET/CT scan results. Fine needle aspiration biopsy was performed with G×1,5″ (0.5×40 mm) needles under ultrasound guidance. Specimens were then smeared, fixed in alcohol and further assessed by pathologists as a routine medical procedure. Final results were reported using the conventional Bethesda system [16] .

Conventional US and Shear-Wave Elastography (SWE) were performed with AIXPLORER system by Supersonic Imagine. The following parameters of particular lesions were assessed: echogenicity (hypo-, hyper-, and isoechogenic), the presence of calcifications (micro or macro), presence of halo (hypoechogenic rim), shape (oval, round, or “taller than wide”), margins (well defined or diffused), composition (solid, predominantly solid, predominantly cystic, or cystic), and elasticity of the nodules (assessed quantitatively; the mean stiffness of each nodule, so called Q-box mean, expressed in kPa was used in further calculations). The final diagnosis of the character of thyroid nodules (benign or malignant) was based on a histological examination performed as a routine medical procedure after surgery. The detailed characteristics of the group are available in the previously published paper [10 (link)].