Measuring guided waves in long bones: modeling and experiments in free and immersed plates

Area of Science:

• Biomedical Engineering
• Materials Science
• Ultrasound Physics

Background:

• Guided waves, specifically the A0 Lamb mode, have been observed in bone structures.
• Previous velocity measurements used line fitting, limiting dispersion analysis and susceptible to wave mode interference.

Purpose of the Study:

• To develop and validate robust signal processing techniques for accurate guided wave analysis in bone.
• To improve the identification of wave modes and the determination of phase velocities and bone thickness.

Main Methods:

• Utilized fast Fourier transform (FFT) signal processing to overcome limitations of line fitting.
• Addressed spatial resolution limitations of FFT for enhanced mode precision.
• Developed an inversion scheme to calculate plate thickness from measured velocity.
• Conducted experiments on free and immersed plates simulating bone with and without overlying tissue.

Main Results:

• Achieved reliable identification of wave modes using group velocity filtering.
• Obtained precise phase velocity and thickness measurements.
• Demonstrated the effectiveness of the methods, particularly for immersed plates.

Conclusions:

• The developed FFT-based signal processing and inversion scheme provide a more robust method for guided wave analysis in bone.
• These techniques are crucial for accurate in vivo bone assessments, overcoming limitations of previous methods.