Quantifying Backscatter Anisotropy Using the Reference Phantom Method.

Area of Science:

• Biomedical Ultrasound
• Acoustic Imaging
• Tissue Characterization

Background:

• Acoustic properties are key to evaluating tissue microstructure.
• Current methods often assume tissue homogeneity and isotropy.
• Scattering in biological tissues is complex and can be anisotropic.

Purpose of the Study:

• To develop and validate novel acoustic parameters for quantifying anisotropy in biological tissues.
• To assess the ability of these parameters to detect and measure anisotropy in complex media.
• To evaluate the impact of speed of sound mismatch on parameter accuracy.

Main Methods:

• Development of three novel parameters to quantify anisotropy in backscattered echo signal power.
• Utilized the reference phantom method with electronic beamsteering of a linear array transducer.
• Tested parameters in isotropic phantoms, anisotropic phantoms, and in vivo human bicep muscle.

Main Results:

• The developed parameters successfully detected and quantified anisotropy in both phantom models and human muscle tissue.
• The parameters were sensitive to the presence and orientation of anisotropic scatterers.
• Bias in anisotropy parameters due to speed of sound mismatch was minimal (<0.2 dB) within a ±20 m/s range.

Conclusions:

• The novel acoustic parameters effectively address isotropy/anisotropy in backscattered signals.
• These parameters offer a valuable tool for challenging the assumption of isotropy in ultrasound.
• The findings provide a more detailed understanding of microstructural sources of backscatter in biological tissues.