Diffraction correction for focused transducers in attenuation measurements in vivo

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Acoustics

Background:

• Diffraction effects introduce errors in ultrasound attenuation estimation in biological tissues.
• Inconsistent in vivo attenuation values necessitate calibration and correction for diffraction, especially with varied transducers.

Purpose of the Study:

• To present experimental results for in vivo calibration and correction of diffraction effects in focused ultrasound transducers.
• To numerically investigate the diffraction filter in time-frequency representation for focused probes.

Main Methods:

• Numerical analysis of the diffraction filter in a time-frequency domain.
• Experimental calibration using a foam phantom and in vivo muscle tissue.
• Development of in vivo calibration and correction methods for focused transducers.

Main Results:

• Identified a time-frequency domain region for focused probes where the diffraction filter's frequency slope is time-invariant.
• Demonstrated that specific probe distances and frequency limits can yield unbiased attenuation estimates.
• Confirmed numerical findings through experimental calibration on phantoms and in vivo muscle.

Conclusions:

• Accurate in vivo ultrasound attenuation estimation requires correction for diffraction effects.
• A method is presented to select optimal parameters for unbiased attenuation measurements using focused transducers.
• The findings facilitate more reliable and comparable ultrasound-based tissue characterization.