Myocardial first‐pass perfusion: Influence of spatial resolution and heart rate on the dark rim artifact

Abstract

Myocardial perfusion images can be affected by the dark rim artifact. This study aimed to evaluate the effects of the spatial resolution and heart rate on the transmural extent of the artifact. Six pigs under anesthesia were scanned at 1.5T using an echo-planar imaging/fast gradient echo sequence with a nonselective saturation preparation pulse. Three short-axis slices were acquired every heart beat during the first pass of a contrast agent bolus. Two different in-plane spatial resolutions (2.65 and 3.75 mm) and two different heart rates (normal and tachycardia) were used, generating a set of four perfusion scans. The percentage drop of signal in the subendocardium compared to the epicardium and the transmural extent of the artifact were extracted. Additionally, the signal-to-noise and the contrast-to-noise ratios were evaluated. The signal drop as well as the width of the dark rim artifact increased with decreased spatial resolution and with increased heart rates. No significant slice-to-slice variability was detected for signal drop and width of the rim within the four considered groups. signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) ratios decreased with increasing spatial resolution. In conclusion, low spatial and temporal resolution could be correlated with increased extent of the dark-rim artifact and with lower SNR and CNR. Magn Reson Med 66:1731-1738,

Towards elimination of the dark-rim artifact in first-pass myocardial perfusion MRI: Removing Gibbs ringing effects using optimized radial imaging

“…In addition to ringing effects, there may be other potential contributing factors to the DRA as listed in the Introduction. Furthermore, it is difficult to decouple the contribution of each factor [e.g., motion versus ringing (19,59)]. Nevertheless, the left-to-right pattern of the observed DRAs in Cartesian images matches the PE direction ( Fig.…”

“…Our studies were limited to rest perfusion scans (maximum imaged heart rate ¼ 78 beats per minute). Previous works have suggested that stress imaging is more prone to DRAs, which has been attributed to a higher degree of Gibbs ringing (7,10) and increased cardiac motion (19,59). The results of our phantom study suggest that, even for sharp signal-intensity discontinuities (6:1 ratio in Figure 5), the optimized radial imaging method effectively eliminated ringing-induced DRAs.…”

Myocardial perfusion MRI with an undersampled 3D stack‐of‐stars sequence

“…Greater spatial coverage makes it less likely to miss ischemic areas and allows for better sizing of ischemia. High spatial resolution can reduce the dark rim artifact [5][6][7] which can mimic subendocardial defects. 8 High temporal resolution can also be important in reducing dark rim effects and to accurately track signal intensity changes.…”

First-pass myocardial perfusion MRI with reduced subendocardial dark-rim artifact using optimized Cartesian sampling

“…With Cartesian sampling, the so‐called “k‐t” accelerated methods (k‐t BLAST/SENSE/PCA) utilize advanced model‐based reconstruction to achieve high spatiotemporal accelerations, thereby significantly improving in‐plane spatial resolution to reduce DRA . The underlying principle is that higher spatial resolution reduces the visual extent and severity of Gibbs ringing, one of the major causes of DRA . However, unlike conventional vendor‐provided schemes that reconstruct each frame independently using parallel‐imaging acceleration, “k‐t” methods require temporal acceleration and specialized reconstruction software/hardware that are not available across different MRI scanner platforms.…”

“…[8][9][10][11][12] The underlying principle is that higher spatial resolution reduces the visual extent and severity of Gibbs ringing, 8 one of the major causes of DRA. 5,8,13 However, unlike conventional vendor-provided schemes that reconstruct each frame independently using parallel-imaging acceleration, "k-t" methods require temporal acceleration and specialized reconstruction software/hardware that are not available across different MRI scanner platforms. Furthermore, established k-t accelerated imaging methods require a breath-hold scan, which can be difficult to achieve, especially during vasodilator stress studies.…”