This study aimed to investigate whether variations in the gain settings of ultrasound devices influence the correlation between muscle echo intensity and intramuscular fat percentage derived from MRI.
A total of 20 healthy adults (12 males and 8 females) aged 19–64 years without any neurological or orthopedic diseases were included in this study. The quadriceps muscle of the dominant leg was imaged using ultrasound and MRI. Ultrasound images were taken in the supine position at 25%, 50%, and 75% of the distance between the greater trochanter and the femoral lateral epicondyle. Ultrasound imaging was performed with five different gain settings (52%, 61%, 70%, 82%, and 91%). Muscle echo intensity and intramuscular fat percentage of the rectus femoris and vastus intermedius muscles were measured from ultrasound and MRI images using image analysis software (ImageJ). The muscle echo intensity was measured using grayscale analysis. The intramuscular fat percentage was measured from MRI images obtained using the GRE-Dixon sequence. The corrected echo intensity was calculated from the muscle echo intensity in ultrasound images using Young’s correction formula. Statistical analyses were performed using Excel. The intraclass correlation coefficient of the muscle echo intensity obtained from the ultrasound images was calculated. Pearson’s correlation coefficients between muscle echo intensity and intramuscular fat percentage were calculated for all participants and separately by gender at each gain setting of the ultrasound device.
For all participants, the correlation coefficients between the corrected echo intensity of the rectus femoris at 25% position and the intramuscular fat percentage were moderate (0.52–0.55) across all gain settings. In males, a significant correlation was observed between echo intensity and intramuscular fat percentage (0.72–0.79) for both the rectus femoris and vastus intermedius muscles across all gain settings. In females, no significant correlation was observed for both muscles, regardless of the gain setting or measurement position.
This study investigated the correlation between muscle echo intensity and intramuscular fat percentage based on variations in the gain setting of the ultrasound device. The findings indicate that muscle echo intensity can be measured at the central 25% of the thigh length using any gain setting in males. However, the correction formula used for males cannot be applied to females. Therefore, a different formula should be considered.
In males, evaluation of muscle quality using ultrasound can predict muscle strength and functional abilities.
muscle echo intensity
gain
