DYNAMIC 3-D TAGGED MRI OF THE CARDIAC CYCLE IN ISCHEMIA

缺血性心脏病的检测一直受到一些问题的阻碍 这是常规成像中固有的，因此导致：（1）在常规成像中的大重叠。 梗塞区域之间的功能的图像衍生参数， 缺血和非缺血性功能障碍。(2)观察到的相关性较差 这些参数之间的范围和程度的透壁性 梗塞另外，内皮细胞是心肌层最 受缺血影响，但没有成像方法可以单独评估 内膜增厚有证据表明， 早期收缩和早期舒张可能是一个更敏感的指标， 舒张末期（艾德）与收缩末期（ES）比较， 是最常用的。传统成像的一个主要局限是， 被认为是，至少部分，负责这些缺陷，是 缺乏实用的方法（缺少植入物理标记）， 在空间和时间上跟踪心肌中的特定点。的 复杂刚体运动、变形和时间不均匀性 因此，心脏在其收缩序列期间所表现出的 目前的成像方法。在 没有人提出这种 方法，一个主要的未解决的问题是要知道心脏成像是否 由于内在生理重叠， 正常和缺血心肌或是否可以获得更好的测量 如果目前心脏成像的局限性得到纠正。 我们建议 用基于心肌组织概念的方法来解决这个问题 MRI标记。这种方法允许动态三维映射的整个左 心室，每个切片有8到12个体积元素，细分为 心内膜和心外膜区域，从而允许全面分析 局部变形的时间分辨率为25至50毫秒。我们将 确定该方法是否能提供更好的检测指标， 与局限于艾德的常规分析相比， ES测量。待检验的主要假设是， 从动态3D标记MRI导出的局部功能指数可以（1） 更有效地区分缺血性心肌和正常心肌，以及（2）更多 有效地与缺血大小、位置和程度相关， 梗死或非缺血性功能障碍，而不是基于 二维艾德/ES分析。如果这些假设得到证实， 将这种非侵入性方法应用于缺血性心脏病， 伙计

The detection of ischemic heart disease has been hampered by problems inherent in conventional imaging, thus leading to: (1) Large overlap in image-derived parameters of function between regions of infarction, ischemia, and nonischemic dysfunction. (2) Poor observed correlation between these parameters and the extent and degree of transmurality of infarction. Additionally, the endocardium is the myocardial layer most affected by ischemia, yet no imaging method can separately assess endocardial thickening. Evidence indicates that regional asynchrony in early systole and early diastole may be a more sensitive indicator of ischemia than end diastolic (ED) to end systolic (ES) comparisons, which are the most commonly used. A major limitation of conventional imaging, thought to be, at least in part, responsible for these deficiencies, is the lack of a practical method (short of implanting physical markers) to spatially and temporally track specific points in the myocardium. The complex rigid body motion, deformation, and temporal heterogeneity exhibited by the heart during its contractile sequence are therefore not accounted for by current imaging approaches. In the absence of such a method, a major unresolved question is to know whether cardiac imaging is fundamentally limited because of intrinsic physiologic overlap between normal and ischemic myocardium or whether better measures can be obtained if the current limitations of cardiac imaging are corrected. We propose to address this issue with a method based on the concept of myocardial tissue tagging by MRI.This method permits dynamic 3-D mapping of the entire left ventricle with 8 to 12 volume elements per slice subdivided into endocardial and epicardial regions, thus allowing a comprehensive analysis of local deformation with a temporal resolution of 25 to 50 ms. We will determine whether this method can provide better indices for detecting and quantifying regional ischemia than conventional analyses limited to ED and ES measurements. The main hypotheses to be tested are that time-dependent indices of regional function derived from dynamic 3-D tagged MRI can (1) more effectively discriminate ischemic from normal myocardium and (2) more effectively correlate with size, location, and extent of ischemia, infarction, or nonischemic dysfunction than conventional methods based on 2-D ED/ES analyses. If proven, these hypotheses would make possible the application of this noninvasive methodology to ischemic heart disease in man.