An US device probe (Vscan with Dual Probe, GE Healthcare, Tokyo, Japan) was used to obtain ultrasound images of the thigh muscles, including the rectus femoris and vastus intermedius (Fig. 1 ). The device was equipped with both a phased-array cardiac probe with a bandwidth of 1.7–3.8 MHz and a field of view of 70° and a linear vascular probe with a bandwidth 3.3–8.0 MHz, an aperture of 2.9 cm, and a maximum scanning depth of 8 cm.
Each participant was scanned in a relaxed supine position. The examiner placed the probe on the anterior aspect of the thigh, perpendicular to its long axis at a point midway between the anterior superior iliac spine and the proximal end of the patella according to a previous study.9 (link)) The examiner identified the subcutaneous adipose tissue, rectus femoris, vastus intermedius, and the femur. Excess gel was applied to the skin to minimize distortion. Three examiners performed image acquisition to investigate inter- and intra-rater reliabilities on the dominant limb. Among the three examiners, two were physicians and one was a physiotherapist. The examiners were specialists who had conducted evaluations using US in a clinical setting for at least 3 years. Furthermore, each examiner had received training from an experienced musculoskeletal sonographer (R.H.). All trials by the three examiners in the present study were conducted independently within 2 h of the first examination to avoid fluctuations in the measurement and analysis of muscle parameters. On the US device screen, the cursor was used to mark the top border of the rectus femoris and the bottom border of the vastus intermedius. This allowed the instrument to calculate the muscle thickness as the sum of the muscle thickness of the rectus femoris and vastus intermedius. Each examiner performed three measurements to allow assessment of intra-rater reliability. After each investigation, the participant was returned to the initial position and the skin was cleaned to remove any gel or markings. This ensured that each image and dataset were acquired independently with reduced risk of measurement bias, such as anchoring.
Each participant was scanned in a relaxed supine position. The examiner placed the probe on the anterior aspect of the thigh, perpendicular to its long axis at a point midway between the anterior superior iliac spine and the proximal end of the patella according to a previous study.9 (link)) The examiner identified the subcutaneous adipose tissue, rectus femoris, vastus intermedius, and the femur. Excess gel was applied to the skin to minimize distortion. Three examiners performed image acquisition to investigate inter- and intra-rater reliabilities on the dominant limb. Among the three examiners, two were physicians and one was a physiotherapist. The examiners were specialists who had conducted evaluations using US in a clinical setting for at least 3 years. Furthermore, each examiner had received training from an experienced musculoskeletal sonographer (R.H.). All trials by the three examiners in the present study were conducted independently within 2 h of the first examination to avoid fluctuations in the measurement and analysis of muscle parameters. On the US device screen, the cursor was used to mark the top border of the rectus femoris and the bottom border of the vastus intermedius. This allowed the instrument to calculate the muscle thickness as the sum of the muscle thickness of the rectus femoris and vastus intermedius. Each examiner performed three measurements to allow assessment of intra-rater reliability. After each investigation, the participant was returned to the initial position and the skin was cleaned to remove any gel or markings. This ensured that each image and dataset were acquired independently with reduced risk of measurement bias, such as anchoring.
