Myocardial perfusion magnetic resonance imaging using sliding-window conjugate-gradient highly constrained back-projection reconstruction for detection of coronary artery disease

State-of-the-Art Quantitative Assessment of Myocardial Ischemia by Stress Perfusion Cardiac Magnetic Resonance

Ischemic heart disease remains the foremost determinant of death and disability across the world. Quantification of the ischemia burden is currently the preferred approach to predict event risk and to trigger adequate treatment. Cardiac magnetic resonance (CMR) can be a prime protagonist in this scenario due to its synergistic features. It allows assessment of wall motility, myocardial perfusion, and tissue scar by means of late gadolinium enhancement imaging. We discuss the clinical and preclinical aspects of gadolinium-based, perfusion CMR imaging, including the relevance of high spatial resolution and 3-dimensional whole-heart coverage, among important features of this auspicious method.

Whole Left Ventricular Coverage Versus Conventional 3-Slice Myocardial Perfusion Magnetic Resonance Imaging for the Detection of Suspected Coronary Artery Disease

RATIONALE AND OBJECTIVES

Sliding-window conjugate-gradient highly constrained back-projection reconstruction (SW-CG-HYPR) allows whole left ventricular coverage, improved temporal and spatial resolution, and signal-to-noise ratio compared to the conventional 3-slice saturation recovery turbo-fast low-angle shot (SR-Turbo-FLASH) sequence. We prospectively compared the diagnostic value of whole leftventricular coverage myocardial perfusion magnetic resonance imaging (MRI) and conventional 3-slice technique in patients with suspected coronary artery disease (CAD).

MATERIALS AND METHODS

Thirty consecutive patients with suspected CAD who were scheduled for coronary angiography underwent myocardial perfusion MRI with both SW-CG-HYPR and SR-Turbo-FLASH in random order at 3.0 T. Perfusion defects were interpreted visually by two blinded observers and were correlated to x-ray angiographic stenoses ≥50%. Receiver-operating characteristic curve analysis was used to compare the diagnostic performance of the two imaging techniques.

RESULTS

The image quality score of SW-CG-HYPR was significantly higher than that of SR-Turbo-FLASH (3.4 ± 0.6 vs 3.0 ± 0.7, respectively; p < 0.05). In the per-patient analysis, SW-CG-HYPR provided a higher sensitivity (94% vs 89%), specificity (83% vs 75%), and diagnostic accuracy (90% vs 83%) for the detection of CAD than SR-Turbo-FLASH. In the per-vessel analysis, the diagnostic performance of SW-CG-HYPR was significantly greater than that of SR-Turbo-FLASH for the overall detection of CAD (area under receiver-operating characteristic curve: 0.96 ± 0.02 vs 0.90 ± 0.03, respectively; p < 0.05).

CONCLUSION

Whole left ventricular coverage myocardial perfusion MRI has higher diagnostic accuracy compared to conventional 3-slice technique for the detection of suspected CAD.

Data on diagnostic performance of stress perfusion cardiac magnetic resonance for coronary artery disease detection at the vessel level

Stress perfusion cardiac magnetic resonance (CMR) has been proposed as an important gatekeeper for invasive coronary angiography (ICA) and percutaneous coronary interventions (PCI) in patients evaluated for possible coronary artery disease (CAD) (Fihn et al., 2012; Montalescot et al., 2013) [1], [2]. Several meta-analyses have evaluated the accuracy of stress perfusion CMR to diagnose CAD at the vessel level (Danad et al., 2017; Dai et al., 2016; Jiang et al., 2016; Takx et al., 2015; Li et al., 2015; Desai and Jha, 2013; Jaarsma et al. 2012; Hamon et al., 2010; Nandalur et al. 2007) [3], [4], [5], [6], [7], [8], [9], [10], [11]. However, they included in the same analysis studies with different definitions of significant CAD (i.e. fractional flow reserve [FFR] < 0.75 and < 0.80 or coronary stenosis ≥ 50% and ≥ 70%), magnetic field strength (1.5 or 3 Tesla [T]), and study protocol (integration or not of late gadolinium enhancement [LGE] into stress perfusion protocol). Data of 34 studies (6091 arteries) have been pooled with the aim of analyzing the accuracy of stress perfusion CMR for the diagnosis of ischemic heart disease at the vessel level according to different definitions of significant CAD, magnetic field strength and study protocol (Arnold et al., 2010; Bettencourt et al., 2013; Cheng et al., 2007; Chiribiri et al., 2013; Cury et al., 2006; De Mello et al., 2012; Donati et al., 2010; Ebersberger et al., 2013; Gebker et al., 2008; Greulich et al., 2015; Hussain et al., 2016; Ishida et al., 2005, 2003; Kamiya et al., 2014; Kitagawa et al., 2008; Klein et al., 2008; Klem et al., 2006; Klumpp et al., 2010; Krittayaphong et al., 2009; Lockie et al., 2011; Ma et al., 2012; Merkle et al., 2007; Meyer et al., 2008; Mor-Avi et al., 2008; Pan et al., 2015; Papanastasiou et al., 2016; Pons Lladó et al., 2004; Sakuma et al., 2005; Salerno et al., 2014; Scheffel et al., 2010; van Werkhoven et al., 2010; Walcher et al., 2013; Watkins et al., 2009; Yun et al., 2015) [12–45]. This article describes data related article titled “Diagnostic Performance of Stress Perfusion Cardiac Magnetic Resonance for the Detection of Coronary Artery Disease” (Kiaos et al., submitted for publication) [46].

Sparse Reconstruction Techniques in Magnetic Resonance Imaging: Methods, Applications, and Challenges to Clinical Adoption

The family of sparse reconstruction techniques, including the recently introduced compressed sensing framework, has been extensively explored to reduce scan times in magnetic resonance imaging (MRI). While there are many different methods that fall under the general umbrella of sparse reconstructions, they all rely on the idea that a priori information about the sparsity of MR images can be used to reconstruct full images from undersampled data. This review describes the basic ideas behind sparse reconstruction techniques, how they could be applied to improve MRI, and the open challenges to their general adoption in a clinical setting. The fundamental principles underlying different classes of sparse reconstructions techniques are examined, and the requirements that each make on the undersampled data outlined. Applications that could potentially benefit from the accelerations that sparse reconstructions could provide are described, and clinical studies using sparse reconstructions reviewed. Lastly, technical and clinical challenges to widespread implementation of sparse reconstruction techniques, including optimization, reconstruction times, artifact appearance, and comparison with current gold standards, are discussed.

Cardiac MRI assessment of myocardial perfusion

Coronary artery disease is the most common cause of mortality and morbidity around the globe. Assessment of myocardial perfusion to diagnose ischemia is commonly performed in symptomatic patients prior to referral for cardiac catheterization. Among other noninvasive imaging modalities, cardiac MRI (CMR) is emerging as a highly sensitive and specific test for myocardial ischemia and infarction. Resting perfusion on CMR is used to evaluate for microvascular obstruction, which is shown to predict adverse left ventricular remodeling and cardiac events after acute myocardial infarction. This article summarizes the current understanding of CMR perfusion.

Adenosine stress cardiovascular magnetic resonance with variable-density spiral pulse sequences accurately detects coronary artery disease: initial clinical evaluation

BACKGROUND

Adenosine stress cardiovascular magnetic resonance perfusion imaging can be limited by motion-induced dark-rim artifacts, which may be mistaken for true perfusion abnormalities. A high-resolution variable-density spiral pulse sequence with a novel density compensation strategy has been shown to reduce dark-rim artifacts in first-pass perfusion imaging. We aimed to assess the clinical performance of adenosine stress cardiovascular magnetic resonance using this new perfusion sequence to detect obstructive coronary artery disease.

METHODS AND RESULTS

Cardiovascular magnetic resonance perfusion imaging was performed during adenosine stress (140 μg/kg per minute) and at rest on a Siemens 1.5-T Avanto scanner in 41 subjects with chest pain scheduled for coronary angiography. Perfusion images were acquired during injection of 0.1 mmol/kg Gadolinium-diethylenetriaminepentacetate at 3 short-axis locations using a saturation recovery interleaved variable-density spiral pulse sequence. Significant stenosis was defined as >50% by quantitative coronary angiography. Two blinded reviewers evaluated the perfusion images for the presence of adenosine-induced perfusion abnormalities and assessed image quality using a 5-point scale (1 [poor] to 5 [excellent]). The prevalence of obstructive coronary artery disease by quantitative coronary angiography was 68%. The average sensitivity, specificity, and accuracy were 89%, 85%, and 88%, respectively, with a positive predictive value and negative predictive value of 93% and 79%, respectively. The average image quality score was 4.4±0.7, with only 1 study with more than mild dark-rim artifacts. There was good inter-reader reliability with a κ statistic of 0.67.

CONCLUSIONS

Spiral adenosine stress cardiovascular magnetic resonance results in high diagnostic accuracy for the detection of obstructive coronary artery disease with excellent image quality and minimal dark-rim artifacts.

Improved quantification of myocardial blood flow using highly constrained back projection reconstruction

PURPOSE

To improve quantification of myocardial blood flow using a fast T1 mapping technique using highly constrained back projection reconstruction (HYPR)-accelerated acquisition.

METHODS

A major source of error in the measurement of myocardial blood flow (MBF) using MRI is the nonlinear relationship between image signal intensity and contrast agent (CA) concentration. HYPR-accelerated radial acquisition was used to generate pixel-wise T1 maps with a temporal resolution of one heartbeat. HYPR produces images with a temporal footprint of 40 ms and four images within 188 ms. T1 values were converted into CA concentrations by the known linear relationship between CA concentration and T1 . The T1 mapping technique was used to quantify MBF in 10 healthy subjects and compared with MBF found using image signal intensity as well as MBF reported in the literature.

RESULTS

The MBF measured using the proposed method was more consistent with that previously reported in the literature and was significantly lower (P = 0.002) than that calculated using image signal intensity (1.11 ± 0.27 mL/min/g versus 1.88 ± 0.45 mL/min/g, respectively).

CONCLUSION

We developed a fast T1 mapping method for MBF quantification using radial sampling and HYPR. Further validation is required to determine its clinical value in assessing myocardial perfusion deficit in coronary artery disease.

Imaging sequences in cardiovascular magnetic resonance: current role, evolving applications, and technical challenges

Cardiovascular magnetic resonance (CMR) has been established as a powerful and comprehensive imaging modality for studying the cardiovascular (CV) system. Shortly after invention of magnetic resonance imaging, CMR applications and developments started to emerge, and they continue to evolve up to the present day. CMR has the advantages of high spatial resolution, enhanced tissue contrast, superior safety profile, and the plethora of physiological parameters that can be obtained. In the near future, CMR is expected to be the gold standard modality for comprehensive CV imaging. Specifically, CMR imaging sequences are increasingly growing in parallel with advancements in scanner hardware. Not only do CMR imaging sequences provide detailed anatomical information, but they also provide functional, perfusion, viability, hemodynamic, and metabolic information about the CV system. In this article, an up-to-date review of different CMR imaging sequences is presented. Each sequence is described along with typical imaging parameters, necessary image processing steps, derived CV parameters, and potential applications. The article then addresses advanced CMR imaging techniques and emerging applications. Finally, the challenges facing CMR imaging are discussed along with its expected future role.