Quantitative contrast measurements in B-mode images comparison between experiment and theory

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Biomedical Engineering

Background:

• Quantitative image contrast is essential for accurate B-mode ultrasound diagnosis, particularly for identifying anechoic structures like cysts.
• Understanding factors affecting image contrast is critical for optimizing ultrasound system performance and image interpretation.

Purpose of the Study:

• To quantitatively measure image contrast in B-mode ultrasound for anechoic spheres within a scattering medium.
• To investigate the influence of different transducer geometries on image contrast.
• To compare experimental contrast measurements with theoretical calculations using simulation and numerical convolution.

Main Methods:

• Utilized four distinct transducer geometries (spherical and hybrid cones with varying f-numbers) in pulse echo mode.
• Performed quantitative contrast measurements on anechoic spheres in a random scattering medium.
• Employed 3D computer simulation and numerical convolution relating the point spread function (PSF) to image contrast for theoretical analysis.

Main Results:

• Experimental contrast measurements showed good agreement with both 3D simulation and numerical convolution methods.
• Image contrast was found to be influenced by factors beyond the full width at half maximum (FWHM) of the PSF.
• High-resolution (low f-number) axicons demonstrated significant contrast degradation due to far off-axis ultrasound beam contributions.

Conclusions:

• Image contrast in ultrasound B-mode imaging is a complex parameter influenced by multiple factors, not solely the PSF's central width.
• Off-axis beam characteristics play a significant role in degrading image contrast, especially with high-resolution imaging systems.
• The study validates theoretical models for contrast prediction while emphasizing the impact of beam profile on image quality.