Department of Biomedical Engineering & Physics, Amsterdam University Medical Centers, Amsterdam Cardiovascular Sciences, University of Amsterdam;
Department of Biomedical Engineering & Physics, Amsterdam University Medical Centers, Amsterdam Cardiovascular Sciences, University of Amsterdam; BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai.
J Vis Exp. 2021 May 24(171). doi: 10.3791/62595.
Mouse models have contributed significantly to understanding genetic and physiological factors involved in healthy cardiac function, how perturbations result in pathology, and how myocardial diseases may be treated. Cardiovascular magnetic resonance imaging (CMR) has become an indispensable tool for a comprehensive in vivo assessment of cardiac anatomy and function. This protocol shows detailed measurements of mouse heart left ventricular function, myocardial strain, and hemodynamic forces using 7-Tesla CMR. First, animal preparation and positioning in the scanner are demonstrated. Survey scans are performed for planning imaging slices in various short- and long-axis views. A series of prospective ECG-triggered short-axis (SA) movies (or CINE images) are acquired covering the heart from apex to base, capturing end-systolic and end-diastolic phases. Subsequently, single-slice, retrospectively gated CINE images are acquired in a midventricular SA view, and in 2-, 3-, and 4-chamber views, to be reconstructed into high-temporal resolution CINE images using custom-built and open-source software. CINE images are subsequently analyzed using dedicated CMR image analysis software. Delineating endomyocardial and epicardial borders in SA end-systolic and end-diastolic CINE images allows for the calculation of end-systolic and end-diastolic volumes, ejection fraction, and cardiac output. The midventricular SA CINE images are delineated for all cardiac time frames to extract a detailed volume-time curve. Its time derivative allows for the calculation of the diastolic function as the ratio of the early filling and atrial contraction waves. Finally, left ventricular endocardial walls in the 2-, 3-, and 4-chamber views are delineated using feature-tracking, from which longitudinal myocardial strain parameters and left ventricular hemodynamic forces are calculated. In conclusion, this protocol provides detailed in vivo quantification of the mouse cardiac parameters, which can be used to study temporal alterations in cardiac function in various mouse models of heart disease.
小鼠模型在理解健康心脏功能涉及的遗传和生理因素、干扰如何导致病理以及心肌疾病如何治疗方面做出了重大贡献。心血管磁共振成像（CMR）已成为全面评估心脏解剖结构和功能的不可或缺的工具。本方案展示了使用 7T CMR 对小鼠心脏左心室功能、心肌应变和血液动力学力进行详细测量。首先，展示了动物准备和在扫描仪中的定位。进行扫描以在各种短轴和长轴视图中规划成像切片。采集一系列前瞻性心电图触发的短轴（SA）电影（或 CINE 图像），从心尖到基底覆盖心脏，捕捉收缩末期和舒张末期相位。随后，在中隔 SA 视图中采集单张、回顾性门控 CINE 图像，以及在 2、3 和 4 腔视图中采集，使用定制和开源软件将其重建为高时间分辨率的 CINE 图像。使用专用的 CMR 图像分析软件对 CINE 图像进行后分析。在 SA 收缩末期和舒张末期 CINE 图像中描绘心内膜和心外膜边界，可计算收缩末期和舒张末期容积、射血分数和心输出量。在所有心脏时帧中描绘中隔 SA 的 CINE 图像，以提取详细的容积-时间曲线。其时间导数可用于计算舒张功能，即早期填充和心房收缩波的比值。最后，使用特征跟踪在 2、3 和 4 腔视图中描绘左心室心内膜壁，从中计算出纵向心肌应变参数和左心室血液动力学力。总之，本方案提供了对小鼠心脏参数的详细体内定量分析，可用于研究各种心脏病小鼠模型中心脏功能的时间变化。
