Fig. 3
From: Estimating vastus lateralis muscle volume from a single ultrasound image
An estimation for the assessment of vastus lateralis muscle volume. (A) Muscle cross-sectional area (ACSA) at 50% of muscle length correlated with muscle volume (R2 = 0.347), with large 95% confidence intervals for slope (14.7 [9.6–19.8] cm) and intercept (248 [112–384] cm3). (B) Anatomical cross-sectional areas (ACSAs) measured at 10% intervals along the length of the vastus lateralis (VL) were expressed relative to the maximum ACSA per individual and plotted against the corresponding relative muscle length in 34 participants. A fourth-order polynomial was derived from the dataset, and integration over the relative muscle length and ACSA resulted in a constant “muscle shape factor” (\(\:\lambda\:\)), which can be used to estimate vastus lateralis muscle volume taking into account a single ACSA measurement at 50% muscle length and the entire muscle length\(\:.\) (C) Individual muscle shape factors correlated moderately to muscle size. (D) Comparing measured and estimated VL muscle volume based on the equation in (A) showed a very strong correlation, albeit with a correction factor of 9.6%. (E) Slope-corrected muscle volume estimations closely resembled absolute muscle volumes. (F) Accuracy of vastus lateralis muscle volume estimation holds true in an independent validation cohort (n = 35). (G) Bland-Altman analysis of both cohorts showed a bias of -3 ± 44 cm3with 95% limits of agreement ranging from − 82 to 83 cm3.
