Use of Real Time MRI for Evaluation of Regional Myocardial Function

描述(由申请人提供)：心力衰竭是美国27万人死亡和每年340万人次住院的原因。在1999年(31.7%)至2008年(29.6%)之间，心力衰竭的风险调整后一年死亡率基本保持不变，尽管与急性心肌梗死相关的死亡率显著下降(男性每年10.7%)。最近通过新的药理学、干细胞和机械疗法预防梗塞后心力衰竭的尝试在动物实验中显示出了希望，但随后在患者身上的研究显示成功非常有限。这在一定程度上可以归因于缺乏高空间分辨率的方法来评估梗死和随后的治疗对局部收缩功能和心肌健康的影响。目前确定收缩功能的金标准方法包括压力-体积环和通过MRI测量应变。虽然MRI可以以高空间分辨率成像左心功能和应变，但它是一种多激发、多心跳采集，速度太慢，无法测量心肌工作中每搏一跳的变化。该项目的目标是开发实时MRI方法来测量梗死发展过程中局部心肌的工作密度和Frank-Starling关系，并在猪模型中用常规MRI和生化方法验证这些结果。为实现这一目标，(1)对RT-MRI方法进行改进和优化。压缩感知将进一步完善我们已经实现的亚奈奎斯特图像重建算法。此外，k空间采样轨迹的修改将改善伪影不一致性和算法性能。然后，(2)对心肌功能的区域估计进行验证。该方法跟踪心肌壁增厚和局部功密度以及Frank-Starling关系。SPAM标记的图像和传统的室壁运动电影成像将被用来产生可比较的值。最后，(3)初步的序列脑梗塞猪研究将被用来将观察到的基于RT-MRI的功能变化与组织学测试相关联。这将决定所提出方法的空间分辨率和时间精度。该提案开发了一种方法，允许在体内和纵向评估梗死后的心室重构。这种方法对于先进的设计和评估预防梗死性心力衰竭的新疗法是必要的。

DESCRIPTION (provided by applicant): Heart failure is the cause of 270,000 deaths in the U.S. and 3.4 million annual hospital visits. The risk-adjusted 1-year mortality of heart failure ha remained essentially unchanged between 1999 (31.7%) and 2008 (29.6%), despite a significant decrease in mortality associated with acute myocardial infarction (10.7% per year for men). Recent attempts to prevent post-infarction heart failure through novel pharmacologic, stem cell, and mechanical therapies have shown promise in animal studies but subsequent studies in patients showed very limited success. This can be partly attributed to the lack of high spatial resolution methods to evaluate the consequences of infarction and subsequent therapy on regional contractile function and myocardial health. Current gold-standard approaches to determine contractile function include pressure-volume loops and strain measurement via MRI. Although MRI can image LV function and strain with high spatial resolution, it is a multi- shot, multiple heartbeat acquisition that is too slow to measure beat-to-beat changes in myocardial work. The goal of this project is to develop real-time MRI methods to measure regional myocardial work density and Frank-Starling relations during infarct development and validate these results with conventional MRI and biochemistry in a porcine model. To achieve this goal, (1) the rt-MRI approach will be improved and optimized. Compressed sensing will further improve the current sub-Nyquist image reconstruction algorithm we have implemented. In addition, modification of the k-space sampling trajectory will improve artifact incoherence and algorithm performance. Then, (2) validation of regional estimates of myocardial function will be performed. The proposed method tracks myocardial wall thickening and regional work density and Frank-Starling relations. SPAMM-tagged images and conventional CINE imaging of ventricular motion will be used to generate comparable values. Finally, (3) an initial serial infart swine study will be used to correlate observed rt-MRI based changes in function to histological testing. This will determine the spatial resolution and temporal accuracy of the proposed method. The proposal develops a method to allow for in-vivo and longitudinal evaluation of post-infarction ventricular remodeling. Such a method is necessary for advanced design and evaluation of novel therapies for prevention of infarct-induced heart failure.