Evaluation of left ventricular ejection fraction using through-time radial GRAPPA

Abstract

BackgroundThe determination of left ventricular ejection fraction using cardiovascular magnetic resonance (CMR) requires a steady cardiac rhythm for electrocardiogram (ECG) gating and multiple breathholds to minimize respiratory motion artifacts, which often leads to scan times of several minutes. The need for gating and breathholding can be eliminated by employing real-time CMR methods such as through-time radial GRAPPA. The aim of this study is to compare left ventricular cardiac functional parameters obtained using current gold-standard breathhold ECG-gated functional scans with non-gated free-breathing real-time imaging using radial GRAPPA, and to determine whether scan time or the occurrence of artifacts are reduced when using this real-time approach.Methods63 patients were scanned on a 1.5T CMR scanner using both the standard cardiac functional examination with gating and breathholding and the real-time method. Total scan durations were noted. Through-time radial GRAPPA was employed to reconstruct images from the highly accelerated real-time data. The blood volume in the left ventricle was assessed to determine the end systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) for both methods, and images were rated for the presence of artifacts and quality of specific image features by two cardiac readers. Linear regression analysis, Bland-Altman plots and two-sided t-tests were performed to compare the quantitative parameters. A two-sample t-test was performed to compare the scan durations, and a two-sample test of proportion was used to analyze the presence of artifacts. For the reviewers´ ratings the Wilcoxon test for the equality of the scores’ distributions was employed.ResultsThe differences in EF, EDV, and ESV between the gold-standard and real-time methods were not statistically significant (p-values of 0.77, 0.82, and 0.97, respectively). Additionally, the scan time was significantly shorter for the real-time data collection (p<0.001) and fewer artifacts were reported in the real-time images (p<0.01). In the qualitative image analysis, reviewers marginally preferred the standard images although some features including cardiac motion were equivalently rated.ConclusionReal-time functional CMR with through-time radial GRAPPA performed without ECG-gating under free-breathing can be considered as an alternative to gold-standard breathhold cine imaging for the evaluation of ejection fraction in patients.

Assessment of Left Ventricular Function and Mass on Free-Breathing Compressed Sensing Real-Time Cine Imaging

“…23,24 CS real-time cine MRI is a useful approach in such patients because single-shot acquisition is inherently insensitive to motion artefacts caused by arrhythmia or breathing. 11, 12 We believe that the CS tech- Data given as mean ± SD. Abbreviations as in Tables 2,3.…”

“…10 To overcome this limitation, imaging data have been acquired over 2 heart beats, thus capturing the complete end-diastole between the first and second heart beats. 10 Given that CS cine MRI has the advantage of being inherently insensitive to respiratory motion because of single-shot acquisition, 11,12 it is suitable for free-breathing (FB) imaging. The purpose of this study was therefore to compare the accuracy of FB full cardiac cycle CS and BH standard cine MRI at 3.0 T for LV volume assessment in patients with cardiac conditions.…”

Recent advances in parallel imaging for MRI

“…SENSE with spiral sampling has been used to accelerate velocity-encoded MRI [81]. Through-time non-Cartesian GRAPPA has been used to collect real-time cardiac data without breathholds or electrocardiogram gating in 45ms per 2D frame with radial sampling (Figure 12) [70,82] and 35ms per frame with spiral sampling [71]. Non-Cartesian GRAPPA has also been applied for renal MRA [72], myocardial [83] and liver perfusion [84], and abdominal T 1 mapping [85].…”

Sparse Reconstruction Techniques in Magnetic Resonance Imaging

“…Techniques including the family of parallel imaging reconstruction methods 1–4 have been successful in reducing clinical MRI scan times by factors of two or four, or even higher in some applications 5–8 . These acceleration techniques have also been used to improve image quality or reduce artifacts while maintaining scan time 9,10 .…”