Respiratory-resolved MR-based attenuation correction for motion-compensated cardiac PET-MR

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Cardiovascular Imaging

Background:

• Respiratory motion during cardiac PET scans causes image blurring and quantification errors, particularly due to misalignment of attenuation correction (AC) maps and PET data.
• Standard PET-MR methods often assume accurate alignment between breath-hold MR-based AC maps and free-breathing PET emission data, which is not always guaranteed.

Purpose of the Study:

• To develop and evaluate a novel 75-second free-breathing MRI acquisition for cardiac PET-MR.
• To generate respiratory-resolved attenuation correction maps (AC_Dyn) and non-rigid respiratory motion information.
• To improve PET quantification accuracy and reduce motion-induced artifacts in free-breathing cardiac PET-MR scans.

Main Methods:

• A 75-second free-breathing 3D multi-echo MR acquisition was performed in six patients.
• Respiratory-resolved dynamic AC maps (AC_Dyn) and non-rigid respiratory motion fields were extracted from the MR data.
• Motion-corrected image reconstruction (MCIR) was applied to both MR and PET data.

Main Results:

• The AC_Dyn approach provided accurate AC values for different breathing phases, ensuring precise attenuation correction for free-breathing PET data.
• Motion-corrected image reconstruction (MCIR) significantly improved PET tracer uptake signal recovery by 24% (p < 0.05) and PET image resolution by 20% (p < 0.05).
• Improvements were most pronounced in patients with significant misalignment between standard AC maps and PET emission data.

Conclusions:

• The proposed 75-second free-breathing MR acquisition efficiently provides accurate motion information and AC values for cardiac PET-MR.
• This AC_Dyn-MCIR technique significantly enhances PET quantification accuracy and image quality, reducing artifacts caused by respiratory motion.
• The short scan time facilitates easy integration into standard clinical PET-MR protocols.