Rapid cardiac cine imaging using MACH
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KeywordsAcceleration Factor Ringing Artifact SSFP Cine Sparse Factor Axis Acquisition
Previously, we developed a sparsely distribute k-space-time sampling approach termed BRISK, Block Regional Interpolation Scheme for K-space . This approach allowed a nominal acceleration factor of 4 with good quality and low artifact. Others have developed alternative k-space-time sampling schemes, such as KT-BLAST and SLAM [2, 3]. We note that even at high acceleration factors, KT-BLAST/SLAM allowed a smooth transition from frame to frame, while BRISK experienced ringing artifacts. From these considerations we isolated key features that contribute to a successful k-space-time sparse sampling scheme:
1) Update of k-space should be rapid near the center and lower near the periphery (as in BRISK) to capture highly dynamic features.
2) Update of k-space should smoothly vary over time (as in KT-BLAST/SLAM) avoiding sudden transitions between k-space regions to result in smoother transition between frames.
Simulations were performed using fully acquired stead-state-free-precession (SSFP) cine image data to allow direct comparison of MACH and KT-BLAST/SLAM when using the same acceleration factors. Further, MACH was implemented on a 1.5 T scanner (GE, Milwaukee, WI). Using the SSFP cine acquisition, long and short axis acquisitions were acquired using the conventional examination and MACH applied with a net sparse factors ranging from 2 to 5, with matrices ranging from 224 to 336. Comparable cine acquisitions were acquired of the heart in 10 volunteers. The end-diastolic and end-systolic phases were identified and areas were planimetered and compared between the conventional and the MACH accelerated scans.
In sparse k-space-time acquisition strategies, rapidly updating the central region of k-space is known to be important. We note that MACH achieves this condition very efficiently while also achieving a smooth transition of update rate between each region of k-space since MACH does not use a uniform or even a regular update rate. MACH was successfully implemented and shown to accurately represent cardiac regions with good fidelity.
This article is published under license to BioMed Central Ltd.