Shear Wave Elasticity Imaging Using Nondiffractive Bessel Apodized Acoustic Radiation Force

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Acoustics

Background:

• Focused acoustic radiation force impulse (ARFI) is standard for transient shear wave elasticity imaging (SWEI).
• Focused ARFI yields limited image quality outside its focal zone due to depth of focus and diffraction limitations.
• This restricts the field of view and diagnostic utility of SWEI.

Purpose of the Study:

• To evaluate the feasibility of Bessel apodized ARFI for SWEI.
• To enhance image quality and extend the depth of focus in SWEI.
• To improve shear wave speed (SWS) estimation accuracy and enlarge elastogram field of view.

Main Methods:

• Simulations and experiments were conducted using tissue-mimicking phantoms and ex vivo liver tissue.
• Bessel apodized ARFI beams were implemented and compared against focused ARFI beams.
• Image quality metrics, depth of field, and SWS estimation accuracy were measured and analyzed.

Main Results:

• Bessel apodized ARFI significantly improved image quality, depth of field, and SWS estimation accuracy.
• Signal-to-noise ratio (SNR) improved by 26% in homogeneous phantoms compared to focused ARFI.
• Contrast-to-noise ratios (CNRs) for inclusions in heterogeneous phantoms increased by up to 8.79 dB.
• Bessel SWEI demonstrated superior SWS accuracy and higher SNR (8.1%) compared to supersonic shear imaging (SSI).

Conclusions:

• Bessel apodized ARFI enhances SWEI by improving image quality and extending the field of view.
• This technique offers more accurate SWS estimation and better visualization of tissue structures.
• Bessel SWEI provides a promising alternative to conventional methods, achieving higher quality elastograms with reduced energy consumption.