Whole-Heart Myocardial Blood Flow Quantification Using MRI

描述（由申请人提供）：拟议项目的广泛，长期目标是改善由冠状动脉疾病（CAD）或冠状动脉微血管功能障碍（CMD）引起的心肌缺血患者的预后。冠心病引起的心肌缺血的早期诊断非常重要，因为冠状动脉血运重建术和药物治疗都可以显著降低发病率和死亡率。在没有阻塞性CAD的情况下，CMD是心肌缺血的主要原因，特别是在女性中，由于冠状动脉微循环异常。首次心肌灌注心脏磁共振（CMR）是一种非常有前途的检测局部缺血引起的局部血流缺陷的技术。它不需要电离辐射，并提供比核成像更高的空间分辨率。在静脉血管扩张剂压力下获得的动态图像描绘了与心肌缺血相关的区域。尽管有相当大的技术进步和临床经验，最近的一项多中心多供应商研究（MR-IMPACT II）显示，CMR检测CAD引起的缺血的敏感性优于SPECT(67%对59%)，特异性较差（61%对72%）。CMR的敏感性和特异性仍然相对较低，提示大量假阳性和假阴性诊断。几项MBF CMR研究表明，异常MBF可用于检测CMD引起的缺血。然而，这些研究仅显示出中等程度的诊断准确性，表明需要进行重大改进。MBF CMR导致CAD和CMD诊断不准确的主要技术限制包括：(i)图像伪影，如暗边缘伪影（DRA）和心脏和呼吸运动引起的伪影，这会降低图像质量和诊断准确性；（ii）用于评估总缺血性负荷的左心室覆盖不全；（iii）空间分辨率不足，无法可靠地检测心内膜下灌注缺陷；和(四)

DESCRIPTION (provided by applicant): The broad, long-term objective of the proposed project is to improve the prognosis of patients with myocardial ischemia caused by coronary artery disease (CAD) or coronary microvascular dysfunction (CMD). Early diagnosis of myocardial ischemia caused by CAD is important as both coronary revascularization and medical therapies can significantly reduce morbidity and mortality. CMD is a major cause for myocardial ischemia in the absence of obstructive CAD, particularly in women, due to abnormalities in coronary microcirculation. First- pass myocardial perfusion cardiac magnetic resonance (CMR) is a highly promising technique for detecting regional blood flow deficits caused by ischemia. It does not require ionizing radiation and provides higher spatial resolution than nuclear imaging. Dynamic images acquired during intravenous vasodilator stress delineate regions associated with myocardial ischemia. Despite considerable technical improvements and clinical experience, a recent multicenter multivendor study (MR-IMPACT II) shows that while the sensitivity of CMR to detect ischemia caused by CAD is superior to SPECT (67% vs 59%), specificity is inferior (61% vs 72%). Both sensitivity and specificity of CMR remain relatively low indicating substantial false positive and false negative diagnoses. Several studies using MBF CMR have shown that abnormal MBF can be used to detect ischemia caused by CMD. However, these studies have shown only moderate diagnostic accuracy, indicating the need for major improvements. Major technical limitations of MBF CMR that contribute to inaccurate diagnoses of CAD and CMD include: (i) image artifacts, such as dark rim artifact (DRA) and cardiac and respiratory motion-induced artifacts, which reduce the image quality and diagnostic accuracy; (ii) incomplete coverage of the LV for evaluating total ischemic burden; (iii) inadequate spatial resolution for reliable detection of subendocardial perfusion deficits; and (iv) errors in AIF estimation for flow quantification due to saturation of blood signal intensity at pea enhancement. In the proposed project, we will develop novel techniques to address these limitations (Aim 1). The techniques will be rigorously validated in animals using microsphere measurements as the reference (Aim 2). Finally, the techniques will be tested in CAD and CMD patients using PET and invasive coronary reactivity testing as reference, respectively (Aim 3). The end point of the project is the development and rigorous validation of a new myocardial perfusion quantification CMR method with whole-heart coverage, high isotropic resolution, cardiac phase-resolved acquisition, accurate arterial input estimation while without the requirements of ECG triggering or breath-hold. It is expected that such a technique will significantly improve image quality, reduce technical failures, increase the diagnostic accuracy, and facilitate the eventual adoption of myocardial perfusion CMR as the method of choice for detecting myocardial ischemia. .