Table 1.
Summary of limitations and challenges in using ultrasound for assessing muscle health
| Challenge or Limitation | Description of Challenge or Limitation |
|---|---|
| Identification of landmarks | • Appropriate training is needed for consistent identification of landmarks. |
| • Standardized protocols on how to identify anatomical landmarks for measurement are lacking. | |
| • Reporting standards (in publications) are lacking for landmarking. | |
| • Reliability testing for landmarking is either lacking or included within the entire data acquisition process (i.e., probe placement, image analysis). | |
| Reliability testing | • Reporting on reliability testing is often lacking. |
| • Standardization on how a reliability test is performed and what is included in the testing procedure is lacking. | |
| • Intra- and interreliability tests are either both lacking or only one of the two tests is performed using ultrasound and published in research studies. | |
| Muscle site | • Different muscles are often measured across different studies (rectus femoris vs. vastus lateralis, upper limb vs. lower limb, or a combination). |
| • Different methods are used for muscle quantity assessment (i.e., cross-sectional area vs. muscle layer thickness). | |
| • Best site to capture muscle groups consistently are unclear (i.e. mid-thigh versus 2/3 femur length versus 3/5 femur length) | |
| Image acquisition and analysis | • Form of analysis varies across studies (i.e., muscle layer thickness, cross-sectional area, echogenicity). Some studies use a combination of these methods. |
| • Different body composition phenotypes present distinct challenges (e.g., obese individuals may have indistinguishable fascial boundaries, fatty infiltration may affect muscle thickness). | |
| • Fluid status may affect measurements: use of minimal versus maximal compression. | |
| Equipment use | • Appropriate use and reporting of curvilinear versus linear probes |
| • Identification of a minimal level of resolution for echogenicity | |
| • Software choice for image analysis varies | |
| Normative data and interpretation of results | • Limited studies that provide a healthy, homogeneous cohort for comparison |
| • Measurement reporting is essential for longitudinal evaluation but is currently missing in the literature. | |
| • Identification of the smallest detectable change for clinically meaningful longitudinal analysis is needed. |