Quantitative MicroSPECT Imaging of Myocardial Blood Flow in Mice

本提案的目的是发展和评价心肌血流的microSPECT测量 (MBF)对小鼠MBF是微血管健康的量度，并且是心血管疾病的独立预测因子。 发病率和死亡率。微血管功能障碍通常被称为冠状动脉微血管疾病（CMVD） 并且已经成为越来越被广泛认可的心脏病理学。然而，尽管有越来越多的临床证据表明， 由于其重要性，对CMVD的机制理解和靶向治疗缺乏。的可用性 许多基于疾病和遗传的模型和遗传操作的容易性使得小鼠模型 是研究心血管疾病及其治疗的理想选择。为了在小鼠中开发非侵入性MBF测量，我们 计划考虑99 mTc标记的sestamibi和201 Tl作为示踪剂;每种都有自己的流量依赖示踪剂提取 组分（EXF），其可以是物种特异性的。因此，在目标1中，我们将绘制放射性示踪剂之间的关系 在正常小鼠中，两种示踪剂的摄取，如通过K1和MBF测量的。我们将验证微球的使用 通过测量左心室注射的不确定性， (LV)和左心房（LA），其中后者对于在注射前与血液更均匀地混合是期望的。 微球从左心室射出，但由于左心房尺寸小， 薄墙类似地，我们将使用剂量校准器来测量切除组织中示踪剂的摄取浓度。 心利用这些金标准进行比较，我们将开发MI的microSPECT MBF定量 实验室U-SPECT+使用独特的体模和目标动物研究来开发定量校正， 优化（目标2）。该系统可实现~0.35 mm的分辨率和高灵敏度。幻影会 用于研究心肌摄取与输入函数之间的串扰关系，如 在LV中测量。我们将使用该体模优化动态拟合程序， 适当的定量校正，说明由于系统的空间分辨率的溢出。这将是 在我们的评估中进行了测试（目标3），我们将比较纵向心肌血流储备（MBFR） 在野生型小鼠和转基因小鼠中，微血管功能障碍的程度可以调节。这些 纵向研究将补充微球MBF和毛细血管密度的组织学测量。 我们期望该项目的成果是：（1）微球MBF在小鼠中的验证和不确定度测定; (2)正常小鼠的SESTAMIBI和~（201）Tl的EXF曲线：（3）MBFR较佳示踪剂的确定 在小鼠中的测量;（4）在转基因模型中验证示踪剂的EXF曲线;（5）开发和 在小鼠体内准确测量MBF/MBFR的验证;（6）基于成像的MBF/MBFR的验证 基因激活转基因小鼠中的下降;和（7）成像和微球MBF/MBFR与 毛细管密度在小鼠中开发这种成像技术，结合一种独特的疾病模型， Regulated将为冠状动脉微血管疾病的研究提供强有力的工具。

This proposal’s objective is to develop and evaluate the microSPECT measurement of myocardial blood flow (MBF) in mice. MBF is a measure of microvasculature health and is an independent predictor of cardiovascular morbidity and mortality. Microvasculature dysfunction is often called coronary microvascular disease (CMVD) and has become an increasingly well-recognized cardiac pathology. Yet, despite mounting clinical evidence of its importance, there is a dearth of mechanistic understanding and targeted therapies for CMVD. The availability of numerous disease-based and genetic models and the ease of genetic manipulations makes the mouse model ideal for studying cardiovascular disease and its treatment. To develop non-invasive MBF measures in mice, we plan to consider 99mTc-labeled sestamibi and 201Tl as tracers; each has its own flow-dependent tracer extraction fraction (EXF), which can be species-specific. Thus, in Aim 1, we will map the relationship between radiotracer uptake, as measured by K1, and MBF for both tracers in normal mice. We will validate the use of microspheres as our gold-standard measure for MBF in mice by measuring the uncertainty of injections into the left-ventricle (LV) and left atrium (LA), where the latter is desirable for the more uniform mixing with blood before the microspheres are ejected from the LV, but is more technically challenging due to the small size of the LA and its thin wall. Similarly, we will use a dose calibrator to measure the tracer’s uptake concentration in the excised heart. With these gold standards for comparison, we will develop microSPECT MBF quantification on the MI Labs U-SPECT+ using a unique phantom and targeted animal studies to develop quantitative corrections and optimizations (Aim 2). This system can achieve resolution of ~0.35 mm with high sensitivity. The phantom will be used for studying the crosstalk relationship between uptake in the myocardium and the input function, as measured in the LV. We will optimize our dynamic fitting procedures using this phantom and determine appropriate quantitative corrections that account for spillover due to the system’s spatial resolution. This will be tested in our evaluations (Aim 3) where we will compare the longitudinal myocardial blood flow reserve (MBFR) in wild-type mice and transgenic mice in which the degree of microvascular dysfunction can be regulated. These longitudinal studies will be complemented with microsphere MBF and histological measures of capillary density. We expect the project’s outcomes to be: (1) microsphere MBF validation in mice and uncertainty determination; (2) EXF curves for sestamibi and 201Tl in normal mice; (3) determination of the better tracer for MBFR measurements in mice; (4) validation of that tracer’s EXF curve in a transgenic model; (5) development and validation of accurate in vivo MBF/MBFR measurements in mice; (6) validation of imaging-based MBF/MBFR decline in transgenic mice with gene activation; and (7) correlation of imaging and microsphere MBF/MBFR with capillary density. Developing this imaging technique in mice combined with a unique disease model that can be regulated will provide a powerful tool for research into coronary microvasculature disease.