Intra- And Inter-rater Reliability Of Panoramic Ultrasound Muscle Image Quantification Of The Quadriceps Femoris

Abstract

Ultrasound (US) devices have become commonplace in sport and research facilities. These devices allow practitioners to assess skeletal muscle morphology characteristics, such as muscle thickness, muscle cross-sectional area (mCSA), and muscle quality. It is vital to standardize and assess the reliability of US image analysis to compare results across raters and investigations. PURPOSE: The purpose of this project was to assess the intra- and inter-rater reliability of panoramic quadriceps femoris US images using standardized methodologies. METHODS: Quadriceps images were obtained from previous projects conducted in our laboratory. Fifteen vastus lateralis and 10 rectus femoris images were assessed for muscle thickness, mCSA, and muscle quality, quantified by echo intensity, in ImageJ by three investigators. Data were analyzed through standard error of the measurement (SEM), intraclass correlation coefficients (ICC) with 95% confidence intervals (CI), and coefficients of variations (CV). RESULTS: Muscle thickness had an SEM of 0.19, mCSA had an SEM of 2.32, and echo intensity was 3.09. The inter-rater reliability of muscle thickness, mCSA, and echo intensity of were high with ICCs of 0.994 (95% CI: 0.989-0.997; p < 0.001), 0.999 (0.997-0.999; p < 0.001), and 0.999 (0.999-1.000; p < 0.001), respectively. CVs for the muscle thickness was 2.9 + 2.2%, mCSA was 3.5 + 3.2%, and echo intensity was 1.6 + 1.4%. Intra-rater reliability was also high for each rater and each outcome, as each rater had an ICC greater than 0.989 for all outcomes. CONCLUSION: Panoramic US images of the vastus lateralis and rectus femoris can be reliably assessed across and among independent raters using a set of standardized analysis methods. Future projects should be conducted with the goal of assessing the reliability of panoramic ultrasound of various other skeletal muscles of the upper- and lower-body.