Kz-accelerated variable-density stack-of-stars MRI.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Imaging Physics

Background:

• Standard stack-of-stars radial MRI can be limited by scan time and slice resolution.
• Motion artifacts, particularly respiratory motion, are a challenge in free-breathing liver MRI.

Purpose of the Study:

• To develop and evaluate a modified stack-of-stars sampling scheme (VD-stack-of-stars) for rapid, motion-robust 3D liver MRI.
• To assess if VD-stack-of-stars can improve slice resolution and image quality without extending acquisition time.

Main Methods:

• Developed a VD-stack-of-stars trajectory with variable-density undersampling along the kz dimension.
• Acquired free-breathing non-contrast-enhanced and dynamic contrast-enhanced (DCE) liver MRI data in volunteers using both standard and VD-stack-of-stars.
• Reconstructed images using motion-compensated compressed sensing techniques, extracting respiratory motion from radial data.

Main Results:

• VD-stack-of-stars achieved higher slice resolution or volumetric coverage compared to standard stack-of-stars.
• Images acquired with VD-stack-of-stars showed improved overall image quality, sharper liver edges, and enhanced hepatic vessel clarity.
• No increase in scan time was required for the improved performance.

Conclusions:

• The VD-stack-of-stars sampling scheme offers superior performance for free-breathing liver MRI, including DCE-MRI.
• This technique enables increased slice resolution and better image quality without prolonging scan duration.
• Reformatted coronal and sagittal images with improved slice resolution may offer significant clinical value.