Abstract
PurposeDynamic contrast enhanced MRI of the heart typically acquires 2–4 short-axis (SA) slices to detect and characterize coronary artery disease. This acquisition scheme is limited by incomplete coverage of the left ventricle. We studied the feasibility of using radial simultaneous multi-slice (SMS) technique to achieve SA, 2-chamber and/or 4-chamber long-axis (2CH LA and/or 4CH LA) coverage with and without electrocardiography (ECG) gating using a motion-robust reconstruction framework.Methods12 subjects were scanned at rest and/or stress, free breathing, with or without ECG gating. Multiple sets of radial SMS k-space were acquired within each cardiac cycle, and each SMS set sampled 3 parallel slices that were either SA, 2CH LA, or 4CH LA slices. The radial data was interpolated onto Cartesian space using an SMS GRAPPA operator gridding method. Self-gating and respiratory states binning of the data were done. The binning information as well as a pixel tracking spatiotemporal constrained reconstruction method were applied to obtain motion-robust image reconstructions. Reconstructions with and without the pixel tracking method were compared for signal-to-noise ratio and contrast-to-noise ratio.ResultsFull coverage of the heart (at least 3 SA and 3 LA slices) during the first pass of contrast at every heartbeat was achieved by using the radial SMS acquisition. The proposed pixel tracking reconstruction improves the average SNR and CNR by 21% and 30% respectively, and reduces temporal blurring for both gated and ungated acquisitions.ConclusionAcquiring simultaneous multi-slice SA, 2CH LA and/or 4CH LA myocardial perfusion images in every heartbeat is feasible in both gated and ungated acquisitions. This can add confidence when detecting and characterizing coronary artery disease by revealing ischemia in different views, and by providing apical coverage that is improved relative to SA slices alone. The proposed pixel tracking framework improves the reconstruction while adding little computational cost.
Highlights
Dynamic contrast enhanced MRI of the heart is becoming a more widespread tool to detect and characterize coronary artery disease
Full coverage of the heart during the first pass of contrast at every heartbeat was achieved by using the radial simultaneous multi-slice (SMS) acquisition
The proposed pixel tracking reconstruction improves the average signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) by 21% and 30% respectively, and reduces temporal blurring for both gated and ungated acquisitions
Summary
Dynamic contrast enhanced MRI of the heart is becoming a more widespread tool to detect and characterize coronary artery disease. ECG gating and breath-holding are commonly employed to suppress motion This acquisition suffers from limited coverage of the left ventricle myocardium, which can limit the sensitivity and confidence of detecting and quantifying ischemic regions. A 2D radial SMS approach was used to acquire 12 SA slices [4], and a 3D technique was used to acquire 8 SA slices, but at a lower spatial resolution [2] These studies were focused on increasing the number of SA slices rather than considering slices oriented differently such as LA slices. A recent retrospective study using SPECT perfusion images pointed out that a conventional three slice acquisition is likely to fail to detect ischemia in the apical myocardium [7], and another study concluded that whole left ventricle coverage (6 SA slices) improves the accuracy in detection of coronary artery disease compared with acquiring 3 SA slices [8]. Acquiring full left ventricle coverage by SA slices and LA slices is of great interest; LA slices can probe part or all of the apical myocardium and full coverage of the 17 myocardial segments suggested by the American Heart Association [9] can be achieved
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