Plantar Soft Tissue Characterization Using Reverberant Shear Wave Elastography: A Proof-of-Concept Study

Area of Science:

• Biomechanics
• Medical Imaging
• Biomedical Engineering

Background:

• Plantar soft tissue stiffness is crucial for understanding foot biomechanics.
• Monitoring foot elasticity aids in managing complex conditions like diabetic foot.
• Existing elastography techniques may have limitations in signal quality for plantar tissues.

Purpose of the Study:

• To investigate the reliability of reverberant shear wave elastography (RSWE) for assessing plantar soft tissue elasticity.
• To compare RSWE performance against a commercial shear wave elastography technique (Supersonic Imaging - SSI).

Main Methods:

• Shear wave speed (SWS) measurements were taken on the plantar soft tissue of five healthy volunteers at the first metatarsal head, third metatarsal head, and heel.
• Experiments were repeated for test-retest reliability analysis, with and without a gel pad, across a frequency range of 400-600 Hz.
• Statistical analysis was used to evaluate SWS estimation reliability and compare RSWE with SSI.

Main Results:

• Low coefficients of variation (median: 5.59% with gel pad, 5.83% without) indicate high test-retest reliability for RSWE.
• SWS measurements increased with higher frequencies, consistent with prior research.
• Significant differences (p<0.05) in SWS were found between anatomical locations (median: 2.42 m/s at 1st metatarsal head, 2.16 m/s at 3rd metatarsal head, 2.03 m/s at heel), demonstrating RSWE's ability to differentiate plantar regions.
• RSWE exhibited superior elastographic signal-to-noise ratios compared to SSI, with fewer artifacts.

Conclusions:

• RSWE is a reliable method for estimating plantar soft tissue elasticity.
• The technique shows promise for evaluating biomechanical changes in the foot, potentially aiding in the management of conditions like diabetic foot.
• RSWE's improved signal quality suggests it could be a valuable advancement in foot diagnostics.