Cardiac and Respiratory Motion Correction for Simultaneous Cardiac PET/MR

Abstract

Cardiac PET is a versatile imaging technique providing important diagnostic information about ischemic heart diseases. Respiratory and cardiac motion of the heart can strongly impair image quality and therefore diagnostic accuracy of cardiac PET scans. The aim of this study was to investigate a new cardiac PET/MR approach providing respiratory and cardiac motion-compensated MR and PET images in less than 5 min. Methods: Free-breathing 3-dimensional MR data were acquired and retrospectively binned into multiple respiratory and cardiac motion states. Three-dimensional cardiac and respiratory motion fields were obtained with a nonrigid registration algorithm and used in motion-compensated MR and PET reconstructions to improve image quality. The improvement in image quality and diagnostic accuracy of the technique was assessed in simultaneous 18 F-FDG PET/MR scans of a canine model of myocardial infarct and was demonstrated in a human subject. Results: MR motion fields were successfully used to compensate for in vivo cardiac motion, leading to improvements in full width at half maximum of the canine myocardium of 13% 6 5%, similar to cardiac gating but with a 90% 6 57% higher contrast-to-noise ratio between myocardium and blood. Motion correction led to an improvement in MR image quality in all subjects, with an increase in sharpness of the canine coronary arteries of 85% 6 72%. A functional assessment showed good agreement with standard MR cine scans with a difference in ejection fraction of 22% 6 3%. MR-based respiratory and cardiac motion information was used to improve the PET image quality of a human in vivo scan. Conclusion: The MR technique presented here provides both diagnostic and motion information that can be used to improve MR and PET image quality. Reliable respiratory and cardiac motion correction could make cardiac PET results more reproducible.

Hybrid Imaging: Instrumentation and Data Processing

“…Recent studies have been performed to evaluate the performance of these three methodologies [196,197]. More advanced methods, that use the synergistic information derived from the simultaneous PET and MR data acquisition, have been proposed to estimate [198] and to correct for motion in both PET and MR images [189]. Other attempts focused on the implementation of joint MoCo and PVC approaches to further improve the PET quantification of small lesions in regions that are susceptible to motion [199,200].…”

“…Specifically, the use of parametric imaging [section Kinetic Modeling and Image Derived Input Function (IDIF)] of data from PET/MR systems can help to shed new light on the mechanisms that underlie structural changes in the brain through the use of targeted radio-labeled tracers in combination with gadolinium-based contrast enhancement of MR [262]. Likewise, the combination of PET and MR images has proven to add prognostic value for assessments of myocardial examinations [189,263,264], while the value of the multi-parametric images obtained for oncological studies is still under evaluation [265].…”

“…Recently, the use of data-driven methods has gained substantial interest for both stand-alone and multi-modality imaging systems [185][186][187][188]. Continuous motion tracking can be used for motion compensation of PET and MR images [189,190]. In thoracic PET imaging, several motion detection techniques have been proposed, through builtin readout of the respiratory position and special radial-self gating sequences, respectively [186,187,191].…”

Respiratory‐ and cardiac motion‐corrected simultaneous whole‐heart PET and dual phase coronary MR angiography

“…Recently published approaches for cardiac and respiratory motion correction of PET data have proposed the use of 8–12 cardiac phases, whereas our approach considers motion correction only between the 2 extreme cardiac phases to ensure good coronary MR depiction in at least one of the cardiac phases. Preliminary results obtained from a simulation study suggest that accurate quantification of size and degree of transmurality of myocardial viability defects by PET can be obtained when correcting for cardiac motion using only the systolic and diastolic cardiac phases.…”

“…Recently, a novel approach where the motion estimated from MR is used to simultaneously correct both PET and MR images has been introduced . The method proposed in Munoz et al corrects for respiratory motion in both modalities and enables the simultaneous acquisition of myocardial viability PET and coronary MR angiography (CMRA) images.…”