HIGH-RESOLUTION MRI OF MYOCARDIAL DEFORMATION

该提案的总体目标是制定、实施和 评估高分辨率磁共振成像方法，特别是 心肌标记，用于获取局部应变的时间序列 对狗的心肌进行测量。这将第一次允许 心肌跨壁依赖性的时间、无创性测量 变形。缺乏这样的非侵入性方法一直是一个主要的问题 心脏力学领域的局限性。因为对当地的了解 为了研究纤维之间的关系，需要研究变形模式 在正常和疾病状态下，心脏缩短和心壁增厚， 研究人员已经求助于在人体内植入不透射线的标记阵列 心肌及其标记物运动的双平面追踪 电影放射摄影术。这是现在执行以下操作的标准方法 心肌应变的测量。随着一种 专门的探头、心肌标记脉冲序列和应变 计算算法，与应变测量值相同，如果不是更高的话 可以非侵入性地获得。因此，这项提案的具体目标 包括： (1)完善和验证高分辨率心肌标记技术。 这涉及到一个专门的探测器的设计和建造， 磁共振成像应变估计的优化和验证 在体模中进行了仿真和实验，并对所选的 方法体内实验。 (2)确定心肌取样所需的分辨率 收缩过程中的变形，允许计算 使用线性模型对心壁的局部区域进行检测。 (3)确定心肌变形是均匀的还是 左心室局部和远处的异质性。使用 在此应用程序中描述的技术，我们将进行应变估计 通过心壁，各向同性分辨率约为3mm3。 这些目标的实现将对研究产生重大影响 在心脏力学方面。最重要的是，第一次，调查人员 将有能力测量心肌局部力学 非侵入性收缩。

The overall objective of this proposal is to develop, implement, and evaluate high-resolution magnetic resonance imaging methods, specifically myocardial tagging, for acquiring a time series of localized strain measurements in the myocardium of the dog. This will allow, for the first time, noninvasive measurements of the transmural dependence of myocardial deformation. The absence of such a noninvasive method has been a major limitation in the field of cardiac mechanics. Because knowledge of local deformation patterns is required to study the relationship between fiber shortening and heart wall thickening in normal and diseased states, investigators have resorted to implanting arrays of radiopaque markers in the myocardium and tracking the motion of these markers with biplane cineradiography. This is now the standard method for performing measurements of strain in the myocardium. With the development of a specialized probe, myocardial tagging pulse sequences and strain calculation algorithms, equivalent, if not superior, measurements of strain may be obtained noninvasively. Thus the specific aims of this proposal are: (1) To refine and validate high-resolution myocardial tagging techniques. This involves the design and construction of a specialized probe, optimization and validation of MRI-derived strain estimates with simulations and experiments in phantoms, and the comparison of selected methods in vivo. (2) To determine the resolution required for sampling myocardial deformation during contraction that permits the calculation of strain in local regions of the heart wall using a linear model. (3) To determine whether myocardial deformation is homogenous or heterogeneous in local and remote regions of the left ventricle. Using the techniques described in this application, we will make strain estimates through the heart wall with an isotropic resolution on the order of 3 mm3. The accomplishment of these aims will have a significant effect on research in cardiac mechanics. Most important, for the first time, investigators will have the ability to measure the local mechanics of myocardial contraction noninvasively.