Technical Development of Diagnostic Cardiovascular MRI

国家心脏、肺和血液研究所（NHLBI）/郊区医院心血管MRI研究项目的总体目标是开发新的方法，用MRI技术评估心血管疾病患者。 1)急性冠状动脉综合征的MRI检测和表征。 除了我们对诊断非ST段抬高急性冠状动脉综合征的灵敏度和特异性的初步临床研究（Kwong RY等，Circulation 2003; 107：538-544），我们已经将注意力集中在对心肌水肿敏感的MRI方法在评估心肌危险区域中的作用上。 这项工作导致了亮血T2加权方法的技术发展，提高了诊断的确定性，超越了商业成像方法。 2)用MRI表征心肌梗死和存活性。 我们继续使用成像心肌梗塞的相敏重建方法（Kellman P等人，Magnetic Resonance in Medicine 2002;47：372-383和Kellman等人，Magn Reson Med 2004;51：408-12）和用于量化这些和类似图像的计算机算法的变体（Hsu L等人，J Magn Reson Imaging. 2006; 23（3）：309-14; Hsu L等人J Magn Reson Imaging 2006;23：315-22）。非刚性运动校正成像方法已经传播到许多其他应用，包括T2加权成像和灌注成像。我们最近证实，钆基造影剂在接近细胞水平的分辨率下与梗死相关的纤维化相关（Schelbert E等人，Circ血管成像。2010; 3（6）：743-752）。 3)我们一直致力于通过仔细的定量分析来改善首过心肌灌注成像。 我们在绝对心肌灌注的分析方面取得了重大进展，超过了我们在亚克大小的心肌块中验证的初始方法（Christian TF等人，Radiology 2004; 232：677-84）。 最近，我们证明了MR首过灌注图像可以量化到像素水平，因此在相当于约32微升心肌的区域中（Hsu L等人，JACC CV IMaging 2012）。这些方法正在研究表征“暗边伪影”和用于诊断目的。我们记录了用于校正B1不均匀性的质子密度加权图像的问题和潜在的后处理改进（米勒CA et al. JCMR 2015）。我们最近改进了用于校正B1场不均匀性的质子密度加权图像的质量（Nielles-Vallespin et al. JCMR 2015）。 4)心肌异常的表征。 除了梗塞和缺血，许多疾病过程改变心肌的特性。 我们已经开发了用于分离心脏MR图像中的水和脂肪的方法，以改善致瘤性右心室发育不良的诊断（Kellman P等人，Magn Reson Med.2009;61：215-21）。 这些技术具有广泛的临床应用（Kellman P等人，Curr血管成像报告，2010; 3（2）：83-91），并且是明年由国际医学磁共振学会主办的专门研讨会的主题。 5)心肌细胞外容积（ECV）成像。在过去的两年中，我们研究了大量患者的细胞外容积分数，发现在远离梗死心肌的正常心肌中存在微妙但有趣的异常。 我们还发现ECV随着年龄的增长而增加，这与心肌纤维化的年龄相关性增加一致。 由于心肌T1的测量是心肌ECV的基本决定因素，我们研究了不同T1标测方法的准确性和一致性（Nacif MS等人，J Magn Reson Imaging. 2011年9月23日发布）。这些方法已得到广泛应用。已经公布了指导方针，以帮助广泛传播这些方法。

The overall aim of the National Heart, Lung and Blood Institute (NHLBI)/Suburban Hospital Cardiovascular MRI Research Project is to develop new approaches in assessing patients with cardiovascular disease with MRI technology. 1) Detection and characterization of acute coronary syndrome with MRI. Beyond our initial clinical studies of sensitivity and specificity for diagnosing non-ST elevation acute coronary syndrome (Kwong RY et al. Circulation 2003; 107:538-544) we have focused attention on the role of MRI methods sensitive to myocardial edema in evaluating the myocardial area at risk. This work has resulted in technical developments of bright blood T2-weighted methods that improve diagnostic certainty beyond those of commercially imaging methods. 2) Characterizing myocardial infarction and viability with MRI. We have continued to use the phase sensitive reconstruction method of imaging myocardial infarction (Kellman P et al. Magnetic Resonance in Medicine 2002;47:372-383 and Kellman et al. Magn Reson Med 2004;51:408-12) and variants of the computer algorithm used to quantify these and similar images (Hsu L et al. J Magn Reson Imaging. 2006; 23(3):309-14; Hsu L et al. J Magn Reson Imaging 2006;23:315-22) in almost all of our clinical and preclinical studies. The non-rigid motion corrected imaging methods have propagated to many other applications including T2 weighted imaging and perfusion imaging. We recently validated that gadolinium based contrast agents correlate with infarct-related fibrosis at resolutions approaching a cellular level (Schelbert E et al. Circ Cardiovasc Imaging. 2010; 3(6): 743-752). 3) We have been working on improving first pass myocardial perfusion imaging through careful quantitative analysis. We have made a major advance in the analysis of absolute myocardial perfusion beyond our initial methods which were validated in sub-gram sized pieces of myocardium (Christian TF et al. Radiology 2004; 232:677-84). Most recently, we demonstrated that MR first pass perfusion images can be quantified down to a pixel level and thus in regions equivalent to about 32 microliters of myocardium (Hsu L et al. JACC CV IMaging 2012). These methods are understudy for characterizing "dark rim artifacts" and for diagnostic purposes. We documented issues and potential post-processing improvements to the proton density weighted images used to correct for B1 inhomogeneity (Miller CA et al. JCMR 2015). We recently improved the quality of proton density weighted images used to correct for B1 field inhomogeneity (Nielles-Vallespin et al. JCMR 2015). 4) Characterization of myocardial abnormalities. Beyond infarction and ischemia, many disease processes alter the characteristics of myocardium. We have developed methods for separating water and fat in cardiac MR images to improve the diagnosis of arrhythmogenic right ventricular dysplasia (Kellman P et al. Magn Reson Med. 2009;61:215-21). These techniques have a wide range of clinical applications (Kellman P et al. Curr Cardiovasc Imaging Rep. 2010; 3(2):83-91) and are the subject of a dedicated workshop sponsored by the International Society of Magnetic Resonance in Medicine next year. 5) Myocardial Extracellular Volume (ECV) Imaging. We have studied the extracellular volume fraction in a large number of patients over the past two years and found subtle but intriguing abnormalities in normal myocardium remote from infarcted myocardium. We have also found the ECV increases with age consistent with an age-related increase in myocardial fibrosis. Since measurements of myocardial T1 is an fundamental determinant of myocardial ECV, we have studied the accuracy and agreement of different T1 mapping methods (Nacif MS et al. J Magn Reson Imaging. Electronically published 2011 Sep 23). These methods have achieved widespread utilization. Guidelines have been published to help disseminate these methods widely.