Correction of respiratory and cardiac motion in cardiac PET/MR using MR-based motion modeling
Philip M Robson1,2, MariaGiovanna Trivieri1,3, Nicolas A Karakatsanis4
1Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave Levy Pl, New York, NY 10029, United States of America.
Abstract:
Cardiac positron emission tomography (PET) imaging suffers from image blurring due to the constant motion of the heart that can impact interpretation. Hybrid PET/magnetic resonance (MR) has the potential to use radiation-free MR imaging to correct for the effects of cardio-respiratory motion in the PET data, improving qualitative and quantitative PET imaging in the heart. The purpose of this study was (i) to implement a MR image-based motion-corrected PET/MR method and (ii) to perform a proof-of-concept study of quantitative myocardial PET data in patients. The proposed method takes reconstructions of respiratory and cardiac gated PET data and applies spatial transformations to a single reference frame before averaging to form a single motion-corrected PET (MC-PET) image. Motion vector fields (MVFs) describing the transformations were derived from affine or non-rigid registration of respiratory and cardiac gated MR data. Eight patients with suspected cardiac sarcoidosis underwent cardiac PET/MR imaging after injection of 5 MBq kg-1 of 18F-fluorodeoxyglucose (18F-FDG). Myocardial regions affected by motion were identified by expert readers within which target-to-background ratios (TBR) and contrast-to-noise ratios (CNR) were measured on non-MC-non-gated, MC-PET, and double respiratory and cardiac gated PET images. Paired t-tests were used to determine statistical differences in quantitative uptake-measures between the different types of PET images. MC-PET images showed less blurring compared to non-MC-non-gated PET and tracer activity qualitatively aligned better with the underlying myocardial anatomy when fused with MR. TBR and CNR were significantly greater for MC-PET (2.8 ± 0.9; 21 ± 22) compared to non-MC-non-gated PET (2.4 ± 0.9, p = 0.0001; 15 ± 13, p = 0.02), while TBR was lower and CNR greater compared to double-gated PET (3.2 ± 0.9, p = 0.04; 6 ± 3, p = 0.004). This study demonstrated in a patient cohort that motion-corrected (MC) cardiac PET/MR is feasible using a retrospective MR image-based method and that improvement in TBR and CNR are achievable. MC PET/MR holds promise for improving interpretation and quantification in cardiac PET imaging.
Insights
Motion-corrected cardiac PET/MR imaging reduces blurring caused by heart movement. This technique improves image quality and quantitative accuracy for cardiac PET scans, aiding in better diagnosis and interpretation.
Area of Science:
- Medical Imaging
- Cardiovascular Imaging
- Nuclear Medicine
Background:
- Cardiac PET imaging is often blurred by heart motion, hindering accurate interpretation.
- Hybrid PET/MR systems offer potential for motion correction using radiation-free MR data.
- Cardio-respiratory motion significantly impacts the quality of PET images of the heart.
Purpose of the Study:
- To implement and validate an MR image-based motion correction method for cardiac PET/MR.
- To assess the feasibility of quantitative myocardial PET data using this motion-corrected technique in patients.
- To improve the qualitative and quantitative aspects of cardiac PET imaging.
Main Methods:
- Developed a method to create motion-corrected PET (MC-PET) images by spatially transforming gated PET data using MR-derived motion vector fields.
- Utilized affine or non-rigid registration of cardiac and respiratory gated MR data to derive motion vector fields.
- Evaluated the method in eight patients with suspected cardiac sarcoidosis using 18F-FDG PET/MR.
Main Results:
- MC-PET images exhibited reduced blurring compared to non-motion-corrected PET images.
- Tracer activity in MC-PET images showed better alignment with myocardial anatomy when fused with MR.
- Significantly improved target-to-background ratio (TBR) and contrast-to-noise ratio (CNR) were observed in MC-PET compared to non-MC-non-gated PET.
- MC-PET demonstrated a lower TBR but greater CNR compared to double-gated PET images.
Conclusions:
- MR image-based motion correction for cardiac PET/MR is feasible in a patient cohort.
- The implemented method significantly enhances TBR and CNR, leading to improved image quality.
- Motion-corrected cardiac PET/MR shows promise for advancing the interpretation and quantification of cardiac PET imaging.
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