Imaging coronary plaques using 3D motion-compensated [¹⁸F]NaF PET/MR.

Area of Science:

• Medical Imaging
• Radiochemistry
• Cardiovascular Disease

Background:

• Cardiac Positron Emission Tomography (PET) with [18F]NaF aids in imaging coronary atherosclerosis and vulnerable plaques.
• Physiological motion (cardiac and respiratory) and resulting artifacts degrade image quality in cardiac PET.
• Accurate imaging of coronary atherosclerosis is crucial for risk stratification and treatment planning.

Purpose of the Study:

• To apply a novel MR-based motion compensation framework to [18F]NaF PET data.
• To improve the resolution and quality of cardiac PET and MR images by compensating for motion.
• To enhance the visualization and characterization of vulnerable coronary plaques.

Main Methods:

• Acquired free-breathing 3D Dixon MR data, retrospectively binned into motion states.
• Generated a non-rigid cardiorespiratory motion model and motion-resolved attenuation map from dynamic MR reconstructions.
• Applied the MR-based motion and attenuation models to [18F]NaF PET data for compensation.

Main Results:

• MR-based motion compensation successfully reduced motion blurring and attenuation correction mismatches in PET and MR images.
• Significant improvements observed in target-to-background ratio (7 ± 7%) and contrast-to-background ratio (26 ± 38%) for plaques.
• Plaque diameter measurements decreased by -22 ± 18%, indicating improved delineation.
• Dynamic attenuation correction effectively mitigated artifacts, even with stent-related signal voids.

Conclusions:

• The MR-based motion correction framework enhances the target-to-background, contrast-to-background, and width of focal tracer hotspots in coronary arteries.
• Dynamic attenuation correction effectively reduces artifacts at the lung-soft tissue boundary.
• This approach enables more reproducible and reliable plaque localization in cardiac PET imaging.