Refraction correction in 3D transcranial ultrasound imaging

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Biomedical Engineering

Background:

• Refraction significantly distorts ultrasound images, especially during transcranial imaging due to skull bone.
• Existing ultrasound systems lack effective methods to correct for acoustic refraction.
• This limitation reduces image quality, spatial resolution, and diagnostic accuracy.

Purpose of the Study:

• To develop and validate the first method for correcting refraction in 3D ultrasound imaging.
• To improve image quality and diagnostic capabilities for transcranial ultrasound applications.
• To quantitatively assess the impact of refraction correction on lesion visualization and image brightness.

Main Methods:

• An iterative approach was used, tracing acoustic propagation paths through a two-layer tissue model and applying Snell's law in 3D.
• The method was adapted for real-time 3D transcranial ultrasound by precomputing delays for various skull thicknesses.
• Phased array imaging was performed with user-selectable delay sets for efficient correction.

Main Results:

• Simulations predicted increased sensitivity, reduced beam steering errors, and restored spatial resolution, especially at large steering angles.
• In phantoms, corrected images restored lesions to 93.6% of their original lateral diameter and 98.1% of their original shape.
• In vivo imaging of volunteers showed an 8.3% increase in mean image brightness without spatial dependency.

Conclusions:

• The developed refraction correction method is effective for 3D ultrasound imaging, particularly transcranial applications.
• The technique significantly improves the accuracy of lesion size and shape representation in ultrasound images.
• Refraction correction enhances image brightness and holds promise for improving diagnostic accuracy in ultrasound examinations.