Abstract
Quantitative myocardial perfusion can be achieved without contrast agents using flow‐sensitive alternating inversion recovery (FAIR) arterial spin labeling. However, FAIR has an intrinsically low sensitivity, which may be improved by mitigating the effects of physiological noise or by increasing the area of artifact‐free myocardium. The aim of this study was to investigate if systolic FAIR may increase the amount of analyzable myocardium compared with diastolic FAIR and its effect on physiological noise. Furthermore, we compare parallel imaging acceleration with a factor of 2 with compressed sensing acceleration with a factor of 3 for systolic FAIR. Twelve healthy subjects were scanned during rest on a 3 T scanner using diastolic FAIR with parallel imaging factor 2 (FAIR‐PI2D), systolic FAIR with the same acceleration (FAIR‐PI2S) and systolic FAIR with compressed sensing factor 3 (FAIR‐CS3S). The number of analyzable pixels in the myocardium, temporal signal‐to‐noise ratio (TSNR) and mean myocardial blood flow (MBF) were calculated for all methods. The number of analyzable pixels using FAIR‐CS3S (663 ± 55) and FAIR‐PI2S (671 ± 58) was significantly higher than for FAIR‐PI2D (507 ± 82; P = .001 for both), while there was no significant difference between FAIR‐PI2S and FAIR‐CS3S. The mean TSNR of the midventricular slice for FAIR‐PI2D was 11.4 ± 3.9, similar to that of FAIR‐CS3S, which was 11.0 ± 3.3, both considerably higher than for FAIR‐PI2S, which was 8.4 ± 3.1 (P < .05 for both). Mean MBF was similar for all three methods. The use of compressed sensing accelerated systolic FAIR benefits from an increased number of analyzable myocardial pixels compared with diastolic FAIR without suffering from a TSNR penalty, unlike systolic FAIR with parallel imaging acceleration.
Highlights
Arterial spin labeling (ASL) allows quantification of myocardial perfusion without the use of potentially toxic gadolinium-based contrast agents, which are commonly used for first-pass perfusion CMR.[1]
Introducing a time delay between the labeling pulses and the image acquisition allows the labeled blood to reach the myocardium in the field of view (FOV), which yields a modulation in measured signal relative to the amount of blood received in the tissue
In this work we have investigated the merits of systolic image acquisition to increase the amount of analyzable myocardium of flow-sensitive alternating inversion recovery (FAIR) ASL
Summary
Arterial spin labeling (ASL) allows quantification of myocardial perfusion without the use of potentially toxic gadolinium-based contrast agents, which are commonly used for first-pass perfusion CMR.[1]. An implementation of myocardial ASL, flow-sensitive alternating inversion recovery (FAIR), involves the acquisition of two sets of magnetization-prepared images: one “control” image preceded by a slice-selective inversion pulse overlapping the FOV and one “tagged” image with a nonselective inversion pulse.[3,4,5] An additional M0 image is acquired to enable perfusion quantification. To achieve high perfusion sensitivity, a delay time of the order of 1 to 2 seconds is required This may introduce cardiac motion-related artifacts due to the difference in cardiac phase between the sliceselective inversion pulse and the following image acquisition, this can be minimized by performing the inversion pulse in the same cardiac phase but in the preceding cardiac cycle relative to the image acquisition.[6]
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