Compressed‐sensing motion compensation (CosMo): A joint prospective–retrospective respiratory navigator for coronary MRI

Abstract

Prospective right hemi-diaphragm navigator is commonly used in free-breathing coronary MRI. The navigator results in an increase in acquisition time to allow for re-sampling of the motion-corrupted k-space data. In this study, we are presenting a joint prospective-retrospective navigator motion compensation algorithm called compressed-sensing motion compensation (CosMo). The inner k-space region is acquired using a prospective navigator; for the outer k-space, a navigator is only used to reject the motion-corrupted data without reacquiring them. Subsequently, those unfilled k-space lines are retrospectively estimated using compressed sensing (CS) reconstruction. We imaged right coronary artery (RCA) in 9 healthy adult subjects. An under-sampling probability map and sidelobe-to-peak ratio (SPR) were calculated to study the pattern of under-sampling, generated by navigator. RCA images were then retrospectively reconstructed using CosMo for gating windows between 3–10 mm and compared with the ones fully acquired within the gating windows. Qualitative imaging score and quantitative vessel sharpness were calculated for each reconstruction. The probability map and SPR show the navigator generates a random under-sampling k-space pattern. There were no statistically significant differences between the vessel sharpness and subjective score of the two reconstructions. CosMo could be an alternative motion compensation technique for free-breathing coronary MRI that can be used to reduce scan time.

3D late gadolinium enhanced cardiovascular MR with CENTRA-PLUS profile/view ordering: Feasibility of right ventricular myocardial damage assessment using a swine animal model

“…In this study, a conservative 3 mm gating window was used for the acquisition of the central 15% of the k-space region in the first ~1/6th of the scan, and the window was expanded to 5-7 mm for the remainder of the scan duration. The smaller gating window was employed for the central k-space data in this study, which concurs with recent approaches proposed for several coronary MR approaches that define inner and outer gating window separately (20,21). Such flexibility in navigator gating may allow for accelerated acquisition strategies that may suit clinical patient imaging that will have additional challenges in respiratory motion correction such as drifting respiratory motion during the scan.…”

Sparse Reconstruction Techniques in Magnetic Resonance Imaging

“…Parallel imaging is often incorporated into these techniques to further increase the data reduction factor and improve image quality 13,15,18 . Because motion, including cardiac and respiratory motion, can reduce the efficacy of compressed sensing reconstructions, a number of groups have incorporated navigator information 19–21 , image registration 22–24 , or even an additional motion dimension 25,26 , directly into the reconstruction.…”

“…Therefore, MR angiography (MRA) is a natural application for sparse reconstructions. Both contrast enhanced 99 and non-contrast enhanced MRA 100 have been examined in a variety of applications, including intracranial vasculature 101,102 , carotids 103,104 , coronaries 19 , and pulmonary veins 105 . Reducing the acquisition time enables the dynamic visualization of the flow of blood sequentially into arteries and then veins via repeated rapid imaging.…”

“…Pulmonary angiography, thoracic angiography, and coronary angiography are important representative techniques in which respiratory and cardiac motion pose major difficulties, necessitating ultrafast imaging 19,85,105,107–109 . Abdominal MR angiography poses the twin challenges of rapid contrast dynamics and a need for very large field of view coverage.…”

Motion Compensation Strategies in Magnetic Resonance Imaging

“…In whole-heart coronary MRA, CS can also be applied to overcome the strict constraints that are set by motion, thus allowing the acquisition of a whole-heart volume in one breath hold, 115 or it can be used to compensate for respiratory motion in free-breathing acquisitions. 116,117 …”