Synopsis

Keywords: Vessels, Myocardium, Coronary magnetic resonance angiography

Atherosclerotic lesions in coronary vessels cause vascular lumen stenosis or obstruction, resulting in myocardial ischemia, hypoxia or necrosis, which is an important cause of coronary heart disease. This study was designed to evaluate the performance of coronary magnetic resonance angiography(CMRA) sequence in volunteer subjects. The ability visualization of coronary Main Branch segments were no statistically significant difference in MRA coronary quality scores compared with CTA(p＞0.05) with sensitivity, specificity for per patient were 86%, 85%, respectively. The coronary artery visualization by CMRA can be used to detect clinically significant coronary artery stenosis in patients with suspected coronary heart disease.

Introduction

Coronary artery disease (CAD) is the leading cause of morbidity and mortality worldwide[1]. However, a substantial minority of patients referred for CAD are found not to have clinically significant coronary stenosis (defined as a reduction in the luminal diameter of at least 50%)[2]. Therefore, accurate assessment of coronary stenosis is critical. The current reference standard for diagnosing CAD is X-ray coronary angiography, which is costly, patients to ionizing radiation and associated with the risk of serious complications. CMRA could potentially offer a safe, non-invasive, contrast-free and ionizing radiation-free alternative for the anatomical assessment of CAD. Researches recently introduced a novel 3D free-breathing, non-contrast, ionizing radiation-free whole-heart coronary CMRA，which can reinvigorate the clinical potential of coronary CMRA[3]. The aim of this study is to investigate the feasibility of using Dixon water-fat separation and compressed SENSE (CS-SENSE)-accelerated 3.0T non-contrast enhancement to visualize coronary arteries in healthy subjects with free-breathing, while computed tomography angiography (CTA) was used as the reference standard.

Methods

All CMRA acquisitions were performed on a 3.0T MR system (Ingenia CX, Philips Healthcare, the Netherlands) and coronary CTA imaging (Siemens SOMATOM Force) within 24 hours. With diaphragm navigation and free breathing, high time resolution cine imaging of four chamber was performed. The relative quiescent period of the right coronary artery was selected as the acquisition basis. The Dixon water-fat separation technology was used to acquire the original data by axial coronary imaging. In this sequence, the diaphragmatic navigation and free breathing were used to detect respiratory movement, and the coronary signal was collected at the end of expiratory phase. T2prep was used to prepare the pre-pulse and to increase the tissue contrast, and Compressed SENSE (CS) was used to reduce scan time. Scanning parameters were as follows: TR/TE 4.3/1.4ms, FOV 265×300mm, acquisition spatial resolution 1.5×1.5×1.5mm, reconstruction resolution 0.75×0.75×0.75mm. CMRA and CTA datasets were independently reviewed by two observers with 15 and 7 years of experience in cardiac imaging, respectively. Image quality of every coronary segment was graded visually in consensus by these two readers on the basis of a four point scaled[4].The accuracy of CMRA for detecting a 50% reduction in diameter was determined using CTA as the reference method[5]. All statistical analyses were performed using SPSS version 27.0.0 (IBM Corporation, Armonk, NY, USA). Categorical variables as numbers (percentage), continuous variables are presented as mean±standard deviation and assessed using a two-tailed t-test. Data showing no Gaussian distribution were analyzed with the Wilcoxon matched-pairs test. Interobserver agreement for the ratings was assessed by means of Intraclass Correlation Coeffificients (ICC) and interpreted as follows: <0.2 = poor, 0.2―0.4 = acceptable, 0.41―0.6 = moderate, 0.61―0.8 = good, and >0.8 = excellent agreement. Sensitivity, Specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated on both a per-patient and per-vessel basis for the respective coronary artery segments. In all analyses, p < 0.05 was considered statistically significant.

Results

3 volunteers were excluded due to insufficient image quality of all participants. 48 volunteers (60.3±8.1 years old, 27 males) successfully completed the CMRA and CA, including 14( 29%) volunteers with significant coronary artery stenosis as shown in Table 1. The ratings for LM、RCA、LAD、LCX coronary artery visualization were comparable (P=0.026、0.036、0.025、0.012) when compared between CMRA and CTA. However, the visualization of coronary D1 and PDA segments were rated significantly higher for CTA compared to MRA (p <0.05) (Table 2 and Figure 2). There were excellent agreement between the CMR observers for image quality scoring (ICC = 0.89―0.93). The sensitivity, Specificity, positive predictive value, negative predictive value and diagnostic accuracy were: (86%, 85%, 70%, 93% and 85%) (as shown in Table 3) for per patient.

Discussion

In our study, we have demonstrated the feasibility of 3.0 T non-contrast-enhanced whole-heart CMRA using Dixon water-fat separation method. Our results showed that CMRA scan allowed for acceptable visualization of the RCA, LM, LAD, and LCX when compared to CTA. 3.0 T non-contrast-enhanced CMRA method may be useful in ruling out stenosis, which was consistent with the result that coronary CMRA approach demonstrated a high specificity and NPV per patient (88% and 97%)[6]. However, the visualization of distal branches D1 and PDA segments were rated significantly higher for CTA compared to MRA. Therefore, contrast-enhanced CTA remains the superior imaging currently in terms of diagnostic confidence and visualization of distal coronary artery branches and characterization of subtle anatomical detail such as intramural coronary course [7]. The limitation is the sample size in the current single-center study was relatively small. We only focused on volunteer who had significant coronary artery stenosis, and the low-to-intermediate risk subjects who were not evaluated in this study. Therefore, further studies including patients with suspected severe CAD.

Conclusion

The 3.0 T noncontrast whole-heart scan with Dixon water-fat separation and compressed sensing (CS-SENSE) acceleration has good feasibility in displaying coronary arteries under free breathing, which may provide a method to detect clinically significant coronary artery stenosis in patients with suspected coronary heart disease.

Acknowledgements

No acknowledgement found.