Novel MRI Assessment of Placental Structure and Function Throughout Pregnancy

胎盘是一个高度血管化的器官，负责母亲和发育中的胎儿之间的相互作用。 绒毛间隙中的母体血液和绒毛膜绒毛中的胎儿血液的紧密接触，使得 营养物质，如氧气，从母亲到胎儿和废物的清除。绒毛间隙的灌注可以 胎盘疾病，如先兆子痫。胎盘灌注受损会损害 母亲和胎儿血液之间的交换，对母亲和胎儿都有潜在的破坏性影响。 今天，没有诊断工具可以直接监测区域胎盘灌注，绒毛间流入，氧反应 和氧的状态。临床医生仍然依赖于胎盘健康的间接措施，如胎儿大小和脐 动脉血流速度引产仍然是大多数胎盘疾病的治疗选择。新的， 迫切需要有效的技术来监测体内局部胎盘健康。我们组建了一个 MR技术专家、计算研究人员、MR临床科学家、经验丰富的产科医生团队 和国际公认的胎盘生物学家，以满足临床相关技术的需求， 胎盘成像MRI的进展。在这里，我们将制定强有力的，定量的措施， 胎盘灌注，绒毛间流入，氧反应和氧状态，从第2个妊娠晚期到足月， 安全性分析和可行性测试，为延长至妊娠早期铺平道路。我们将驾驶飞机， 优化我们对典型妊娠（TP）和先兆子痫（PE）母亲的胎盘MRI测量， 确定我们的新MRI方法是否能被两组患者耐受，并评估其可行性和潜力 作为区分个体中PE和TP胎盘的临床工具。为此，我们提出以下建议： 具体目标：1.绘制胎盘灌注图并估计绒毛间流入：我们将开发一种新的模型， 弥散成像体素内非相干运动（IVIM）的胎盘灌注，并制定速度选择性 自旋标记（VSSL）方法来估计绒毛间流入。 2.标测T1和T2以表征 胎盘氧反应和氧状态：我们将开发2D MR指纹（MRF），以创建快速联合 高氧时胎盘氧反应的T1和T2图和3D MRF或多反转回波平面 MIEPI成像（MIEPI）来创建体积联合T1和T2图以确定胎盘氧状态。目标1 我们将TP和PE的多模式胎盘模式与局部胎盘组织病理学相关联 用我们的胎盘展平法做指导 3.在整个妊娠期间优化成像安全性， 温度模拟：我们将重点关注射频（RF）组织加热的主要安全问题， 怀孕的前三个月到后三个月。我们将建立在我们的解剖学现实的数字怀孕 身体模型和电磁模拟的专业知识，并制定准确的和怀孕特定的 热模型，以确定和实验验证整个过程中安全有效的射频暴露 怀孕

The placenta is a highly vascular organ, responsible for the interaction between mother and developing fetus. Close proximity of maternal blood, in intervillous spaces, and fetal blood, in chorionic villi, enables transport of nutrients, such as oxygen, from mother to fetus and removal of wastes. Perfusion of the intervillous spaces can be impaired by placental diseases, such as preeclampsia. Compromised placental perfusion impairs the exchange between maternal and fetal blood with potentially devastating impact on both mother and fetus. Today, no diagnostic tool can directly monitor regional placental perfusion, intervillous inflow, oxygen response and oxygen state. Clinicians still rely on indirect measures of placental health, such as fetal size and umbilical artery blood velocity. Induced delivery remains the treatment of choice for most placental disorders. New, effective technologies are desperately needed to monitor regional placental health in vivo. We assembled a team of technical MR experts, computational researchers, MR clinician scientists, experienced obstetricians and a internationally recognized placental biologist to address the need for clinically relevant technological advances in MRI for placental imaging. Here we will develop robust, quantitative measures of regional placental perfusion, intervillous inflow, oxygen response and oxygen state from late 2​nd trimester to term, with safety analysis and feasibility testing that pave the way for extension to late 1​st trimester. We will pilot and optimize our placental MRI measures in mothers with typical pregnancy (TP) and preeclampsia (PE) to determine if our novel MRI methods are tolerated by both groups and to evaluate their feasibility and potential as clinical tools to distinguish PE from TP placentas in individuals. Towards this end, we propose the following specific aims: ​1. Map placental perfusion and estimate intervillous inflow: We will develop a new model for diffusion imaging intravoxel incoherent motion (IVIM) for placental perfusion and develop a velocity selective spin labeling (VSSL) approach to estimate intervillous inflow. ​2. Map T1 and T2 to characterize changes in placental oxygen response and oxygen state​: We will develop 2D MR Fingerprinting (MRF) to create rapid joint T1 and T2 maps of placental oxygen response during hyperoxia and 3D MRF or multi-inversion echo planar imaging (MIEPI) to create volumetric joint T1 and T2 maps to determine the placental oxygen state. For Aims 1 and 2, we will correlate multimodal placental patterns in TP and PE with regional placental histopathology using our placental flattening method for guidance. ​3. Optimize imaging safety throughout pregnancy using temperature simulations​: We will focus on the major safety concern of radiofrequency (RF) tissue heating in the first-through-third trimester of pregnancy. We will build on our anatomically realistic numerical pregnant body models and expertise with electromagnetic simulations and develop accurate and pregnancy-specific thermal models to determine and experimentally validate safe and efficient RF exposure throughout pregnancy.