Vastus lateralis muscle cross-sectional area ultrasonography validity for image fitting in humans.

The present study aimed to determine the concurrent validity of ultrasound (US) measurement of the vastus lateralis muscle (VL) cross-sectional area (CSA) having magnetic resonance imaging (MRI) as the gold standard measurement, in a heterogeneous sample of participants. Thirty-one individuals (52.44 ± 16.37 years; 1.67 ± 0.11 m; 75.25 ± 13.82 kg) volunteered to participate in the study. All the images were performed in the right leg. Image-fitting technique (US) and computerized planimetry technique (US and MRI) were used to determine the VL CSA. The typical error (TE) of measurement was used to determine the concurrent validity of the US measurements. Our results demonstrated good validity of the US compared with the MRI measurements (TE = 0.37 cm; coefficient of variation = 1.75%). The Bland-Altman plot demonstrated bias of 0.07 ± 0.53 cm and limits of agreement of 0.96-1.11 cm. Based on our TE, bias and limits of agreement, we concluded that the US image-fitting technique is valid to assess the VL CSA in a heterogeneous sample of participants. Thereby, US can be used instead of MRI to assess changes in skeletal muscle morphology.