Improved forward model for quantitative pulse-echo speed-of-sound imaging.

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Acoustics

Background:

• Computed ultrasound tomography in echo mode (CUTE) uses pulse-echo ultrasound to map tissue speed-of-sound (SoS).
• Current methods rely on a linear forward model based on straight-ray approximation for SoS reconstruction.
• Existing models do not fully account for phase shifts related to transmit/receive angles and echo position offsets.

Purpose of the Study:

• To enhance the accuracy of SoS reconstruction in CUTE by refining the forward model.
• To investigate the impact of incorporating specific phase shift detection and echo position correction features.
• To improve quantitative SoS imaging for applications like hepatic and cancer imaging.

Main Methods:

• Developed an advanced forward model for CUTE incorporating phase shift detection between mid-angle centered Tx/Rx pairs.
• Included compensation for additional phase shifts due to reconstructed echo position offsets.
• Validated the model using phantom studies mimicking liver and tumor tissues and preliminary volunteer data.

Main Results:

• The enhanced forward model accurately predicts echo phase shifts across various phantom geometries.
• Substantially improved quantitative SoS images were achieved compared to previous models.
• The necessity of both proposed model features for accurate SoS prediction was demonstrated.

Conclusions:

• The refined CUTE forward model significantly enhances the accuracy of quantitative SoS imaging.
• The findings are crucial for advancing ultrasound-based tissue characterization and diagnostic imaging.
• The improved model shows promise for clinical applications, as supported by preliminary volunteer results.