Assessment of Lower Limb Muscle Volume Using 3D Ultrasonography: Validity and Reliability Compared to MRI.

Area of Science:

• Biomechanics
• Medical Imaging
• Musculoskeletal Research

Background:

• Muscle volume is a critical indicator of neuromuscular health and strength.
• Magnetic Resonance Imaging (MRI) is the gold standard for muscle volume assessment but is costly and time-consuming.
• Three-dimensional ultrasonography (3DUS) presents a more accessible alternative requiring validation for accuracy.

Purpose of the Study:

• To investigate the validity and reliability of a custom 3DUS setup for measuring lower limb muscle volumes.
• To compare 3DUS measurements against MRI in a cohort of participants.
• To assess the impact of protocol adaptations on measurement accuracy.

Main Methods:

• Fifteen participants underwent repeated 3DUS and single MRI scans of lower limb muscles (tibialis anterior, vastus lateralis, gastrocnemii, biceps femoris).
• A motion capture system integrated with ultrasonography was used, along with phantom models for calibration.
• Scanning protocols were adapted after initial scans, and data were analyzed using 3D Slicer.

Main Results:

• 3DUS demonstrated excellent test-retest and inter-rater reliability (ICC: 0.97-0.99).
• 3DUS systematically underestimated muscle volumes compared to MRI (biases: -10.0% to 33.0%), with variations based on muscle location.
• Protocol adaptations reduced mean differences between 3DUS and MRI by approximately 70%.

Conclusions:

• Custom 3DUS exhibits high reliability for lower limb muscle volume assessment.
• While underestimating volumes relative to MRI, 3DUS is a promising, cost-effective tool for longitudinal muscle change monitoring.
• The open methodology facilitates wider adoption and further research.