AUTHOR=Högelin Emil Rydell , Thulin Kajsa , von Walden Ferdinand , Fornander Lotta , Michno Piotr , Alkner Björn 

TITLE=Reliability and Validity of an Ultrasound-Based Protocol for Measurement of Quadriceps Muscle Thickness in Children

JOURNAL=Frontiers in Physiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.830216

DOI=10.3389/fphys.2022.830216

ISSN=1664-042X

ABSTRACT=Introduction and aims: Accurate determination of skeletal muscle size is of great importance in multiple settings including resistance exercise, aging, disease and disuse. Ultrasound (US) measurement of muscle thickness (MT) is a method of relatively high availability and low cost. The present study aims to evaluate a multisite ultrasonographic protocol for measurement of MT with respect to reproducibility and correlation to gold-standard measurements of muscle volume (MV) with magnetic resonance imaging (MRI) in children. 
Material and methods: 15 children completed the study (11±1 yrs, 41±8 kg, 137±35 cm). Following 20 min supine rest, two investigators performed US MT measurements of all four heads of the m. quadriceps femoris, at pre-determined sites. Subsequently, MRI scanning was performed and MV was estimated by manual contouring of individual muscle heads. 
Results: Ultrasound measurement of MT had an intra-rater reliability of ICC=0.985-0.998 (CI 95%=0.972–0.998) and inter-rater reliability of ICC=0.868-0.964 (CI 95%=0.637-0.983). The US examinations took less than 15 minutes, per investigator. Muscle thickness of all individual quadriceps muscles correlated significantly with their corresponding MV as measured by MRI (overall r=.789, p<.001). 
Conclusion: The results of this study indicate that US measurement of MT using a multisite protocol is a competitive alternative to MRI scanning, especially with respect to availability and time consumption. Therefore, US MT could allow for wider clinical and scientific implementation.