Effect of adipose and muscle tissue thickness on skeletal muscle echo intensity and passive shear modulus: An ultrasound elastography approach.

Abstract

Although the growing studies investigating muscle echo intensity (EI) and shear modulus, little is known about the effects of adipose tissue thickness (ATT) on these measures. We investigated whether ATT influences the EI and shear modulus measurements of the human tibialis anterior superficial (TA_superficial) and deep (TA_deep) compartments. Ultrasound measurements were taken from the TA at rest, near the highest cross-sectional area, in ten physically active adults in the following conditions: without fat layers and with one and two fat layers. The EI and shear modulus of both TA_superficial and TA_deep were determined, and the best-fit regression model was calculated to assess the influence of ATT on EI and shear modulus. A repeated measures ANOVA were adopted to investigate the differences in EI and shear modulus in the different fat layers. The ATT was seen to affect the EI of both TA_superficial (R² = 0.58; p < 0.001) and TA_deep (R² = 0.44; p < 0.001). When the thickness of TA_superficial was summed with ATT, the EI of TA_deep was also affected but to a less extent (R² = 0.25; p = 0.004). No significant influence of ATT on shear modulus was seen for both TA compartments (p ≥ 0.061). While EI decreased in both TA compartments (p < 0.05), the repeated measures ANOVA revealed that only TA_deep shear modulus decreased with the addition of two fat layers (p = 0.005). Corrective formula for EI measurements was determined. Thus, while skeletal muscle EI measurements should be corrected for the thickness of subcutaneous adipose tissue as well as the depth of region of interest, shear modulus does not.