Quantitative MicroSPECT Imaging of Myocardial Blood Flow in Mice

这项建议的目的是开发和评估心肌血流量的MicroSPECT测量 (MBF)在小鼠体内。MBF是微血管健康状况的衡量指标，是心血管疾病的独立预测指标 发病率和死亡率。微血管功能障碍通常称为冠状动脉微血管病(Cmvd)。 并已成为一种日益公认的心脏病理。然而，尽管有越来越多的临床证据表明 由于其重要性，目前缺乏对CMVD的机制认识和靶向治疗。可得性 众多基于疾病和遗传的模型，以及遗传操作的简便性使小鼠模型 非常适合研究心血管疾病及其治疗。为了在小鼠身上开发非侵入性MBF措施，我们 计划考虑将99mTc标记的Sestamibi和201Tl作为示踪剂；每种都有自己的流动依赖示踪剂提取 组分(EXF)，可以是物种特定的。因此，在目标1中，我们将映射放射性示踪剂之间的关系 两种示踪剂在正常小鼠中的摄取，由K1和MBF测量。我们将验证微球的使用 作为我们通过测量左心室注射的不确定度来测量小鼠MBF的金标准 (LV)和左心房(LA)，其中后者是理想的，以便在手术前与血液更均匀地混合 微球是从左心室喷出的，但由于LA和它的小尺寸，技术上更具挑战性 很薄的墙。同样，我们将使用剂量校准器来测量示踪剂在切除的患者体内的摄取浓度 心。与这些金标准进行比较，我们将开展MI上的MicroSPECT MBF定量 实验室使用独特的体模和有针对性的动物研究进行U-SPECT，以开发定量校正和 优化(目标2)。该系统具有较高的灵敏度，分辨率可达~0.35 mm。幽灵将会 用于研究心肌摄取与输入功能之间的串扰关系，AS 以LV为单位测量。我们将使用这个体模优化我们的动态拟合程序，并确定 考虑到系统空间分辨率的溢出效应的适当的定量校正。这将是 在我们的评估(目标3)中进行了测试，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 纵向研究将与微球MBF和毛细血管密度的组织学测量相补充。 我们预计该项目的结果将是：(1)微球MBF在小鼠中的验证和不确定性的确定； (2)Sestamibi和201Tl在正常小鼠体内的EXF曲线；(3)MBFR较好示踪剂的测定 在小鼠身上的测量；(4)在转基因模型中验证示踪剂的EXF曲线；(5)开发和 小鼠体内MBF/MBFR准确测量的验证；(6)基于成像的MBF/MBFR的验证 基因激活的转基因小鼠的下降；以及(7)成像和微球MBF/MBFR与 毛细血管密度。在小鼠身上开发这种成像技术，结合一种独特的疾病模型，可以 调控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.