Evaluation of Transversely Isotropic Muscle Phantoms Using Ultrasonic Rotational and Rocking Shear Wave Elastography...

Area of Science:

• Biomedical Engineering
• Ultrasound Imaging
• Materials Science

Background:

• Muscle stiffness relates to physiological and pathological states, assessable by ultrasound shear wave elastography (SWE).
• Standard SWE assumes isotropic properties, limiting its use for skeletal muscles, typically modeled as transversely isotropic (TI).
• Full TI material characterization needs both shear horizontal (SH) and shear vertical (SV) wave modes; SV mode quantification is underdeveloped.

Purpose of the Study:

• To compare four TI phantoms with varying fiber analogs (PE, nylon, polyester, ex-vivo tissue) for muscle characterization using SWE.
• To assess SH and SV wave speeds, signal quality, shear anisotropy, and the impact of push width (F#) in these TI phantoms.
• To establish a foundation for optimizing TI phantom properties and imaging for SV mode detection.

Main Methods:

• Fabrication of four TI phantoms using different fiber analogs (PE, nylon, polyester, ex-vivo tissue) in a polyvinyl alcohol matrix.
• Application of ultrasonic rotational and rocking SWE imaging to evaluate wave propagation.
• Quantification of shear wave speeds (SH and SV modes), signal quality, and shear anisotropy, alongside analysis of push width effects.

Main Results:

• High variability in shear anisotropy was observed across phantoms; PE fibers showed the highest, followed by ex-vivo tissue.
• Nylon fiber phantoms exhibited anisotropy similar to resting muscle; polyester phantoms were nearly isotropic.
• SH mode was quantified in all phantoms; SV mode was detected only in ex-vivo tissue and nylon phantoms at specific F# values (1.2 and 2.5).

Conclusions:

• The study successfully developed and evaluated TI phantoms mimicking muscle tissue for advanced SWE applications.
• Optimizing phantom properties and imaging conditions is crucial for enabling SV mode detection in anisotropic tissues.
• This research advances muscle tissue characterization using SWE, potentially enhancing clinical assessment of muscle function, physiology, and pathology.