Identification Of Factors That Affect The Attenuation Of Muscle Echo Intensity: A Human Cadaver Study

B-mode ultrasonography has been widely used to assess the size, i.e. thickness, and composition, i.e. echo intensity, of human skeletal muscles in the previous studies. One of the most serious problems among related studies is that ultrasound echo beam attenuation can induce underestimate of echo intensity, particularly for muscles located in deep regions. PURPOSE: The purpose of this study was to examine the effect of surface tissues, e.g., subcutaneous adipose tissue (SCAT) and rectus femoris (RF) muscle thickness, on RF and vastus intermedius (VI) echo intensity using human cadavers. METHODS: A real time B-mode ultrasonography system was used to measure the SCAT, muscle thickness, and echo intensity. Ultrasound images were obtained using the following acquisition parameters: frequency, 10 MHz; gain, 70 dB; depth, 2 or 3 cm; number of focal points, 1 (at top of image). The echo intensity of the RF and VI at the mid-thigh was measured in 24 legs of 14 cadavers. Firstly, measurements were made without any treatment, then SCAT was removed to measure “raw” echo intensity of the RF. Finally, RF was removed to measure raw echo intensity of the VI. Stepwise regression analysis was performed with raw RF echo intensity or raw VI echo intensity as dependent variables and SCAT thickness, RF muscle thickness, and VI muscle thickness as dependent variables. RESULTS: RF muscle thickness was identified as a significant variable to explain the variation in raw RF echo intensity (adjusted R2 = 0.508). Also, VI muscle thickness was identified as a significant variable to explain the variation in raw VI echo intensity (adjusted R2 = 0.485). CONCLUSIONS: These results suggest that the most important factor influencing raw echo intensity is the echo attenuation caused by the muscle being measured itself, rather than the SCAT or the muscle located in the upper layer.