Guided ultrasonic waves in long bones: modelling, experiment and in vivo application

Area of Science:

• Biomedical Engineering
• Materials Science
• Orthopedics

Background:

• Current ultrasound methods for tibia assessment rely on the first arriving signal, reflecting bulk longitudinal velocity.
• Human long bones, as hollow tubes, theoretically support complex guided wave propagation, like Lamb waves.
• Guided waves offer potential for richer information on bone properties and architecture.

Purpose of the Study:

• To investigate the behavior of guided waves in bone using Lamb wave theory and numerical simulations.
• To experimentally validate the presence and characteristics of guided waves in bone-like structures.
• To assess the potential of guided waves as a sensitive indicator for osteoporosis detection.

Main Methods:

• Applied Lamb wave theory and numerical simulations to model wave propagation in bone.
• Utilized a prototype low-frequency axial pulse transmission device for experimental measurements.
• Conducted a pilot study comparing healthy and osteoporotic subjects.

Main Results:

• Confirmed the existence of two distinct wave types: a fast first-arriving wave and a slower second wave consistent with the lowest order Lamb antisymmetrical (A0) mode.
• Observed significant differences in the velocity of the second wave between healthy and osteoporotic individuals.
• Found no significant difference in the velocity of the first-arriving wave between the groups.

Conclusions:

• Guided wave measurements, specifically the second wave's velocity, show promise as a more sensitive indicator for osteoporosis than traditional methods.
• Ultrasonic characterization of long bones can be enhanced by incorporating guided wave analysis.
• This approach may lead to improved diagnostic tools for bone health assessment.