Validity of Quantitative and Qualitative Assessments of Skeletal Muscles in the Lower Extremities Using Ultrasound Imaging : A Literature Review

Purpose: To explore the use of ultrasound (US) for quantitative and qualitative assessment of muscles (especially the tongue) in dentistry, we performed investigations using muscles of the lower extremities. These muscles are often used to assess skeletal muscles in general. We aimed to determine whether there was a correlation between quantitative and qualitative assessments of lower extremity muscles using diagnostic US and computed tomography (CT) scans in adults.
Procedure: We conducted a search for English articles published in PubMed and Scopus from its inception up to October 18, 2022. We used a combination of the keywords “muscle,” “ultrasonography,” and “computed tomography” for the search. Additionally, we manually searched through relevant journals and search engines.
Main findings: After applying the inclusion criteria, we ultimately selected seven studies for inclusion in this review. These seven studies focused on muscle mass and involved ultrasonographic evaluations of muscle thickness and cross-sectional area as well as CT evaluations of muscle volume and cross-sectional area. Two studies also evaluated muscle quality using echo intensity (EI) for US assessment and CT values for CT assessment. In three of the seven studies, there was a significant correlation between the US and CT results. Three studies also determined an intraclass correlation coefficient (≥0.8 in all three) to determine the correlation between CT and US. In both studies that additionally assessed muscle quality, a strong correlation was observed between CT and US measurements.
Conclusion: Our results suggest that US can be used to perform high quality assessments of lower extremity muscles and muscle mass in healthy individuals and patients with mild or moderate disease. In the future, high quality research on the tongue is needed for application to the field of dentistry.