Frequency dependence of average phase shift from human calcaneus in vitro

Area of Science:

• Biomedical Engineering
• Ultrasound Physics
• Materials Science

Background:

• Ultrasound velocity measurements in cancellous bone are vital for assessing bone health.
• Phase shift errors can arise from weak, linear dispersion in materials.
• Accurate dispersion and velocity measurements are essential for reliable material characterization.

Purpose of the Study:

• To investigate the impact of constant phase shift on ultrasound velocity and dispersion measurements in cancellous bone.
• To develop and validate a method for suppressing constant phase shift effects.
• To improve the accuracy of phase velocity and dispersion estimations in through-transmission experiments.

Main Methods:

• A single-wave model was applied to in vitro ultrasound measurements of 30 human calcaneus samples.
• A novel method was used to suppress the effects of constant phase shifts.
• Phase velocity and dispersion were calculated with and without phase shift correction.
• Complex transfer functions were analyzed to assess model conformity.

Main Results:

• Without correction, phase velocity was 1516+/-6 m/s and dispersion was -24+/-4 m/s MHz at 500 kHz.
• Correction reduced mean velocity by 4-9 m/s and mean dispersion magnitude by 50%-100%.
• A single-wave, linearly dispersive model accurately represented the data (1.9%+/-1.0% RMSE).

Conclusions:

• Constant phase shifts significantly affect ultrasound velocity and dispersion measurements in cancellous bone.
• The developed method effectively suppresses these errors, enhancing measurement accuracy.
• Accurate characterization of bone properties using ultrasound is improved by accounting for phase shift effects.