Near infrared/MR system for imaging brain oxygenation

我们将设计并构建用于脑氧合研究的近红外（NIR）和磁共振（MR）联合成像系统，并将其应用于脑缺氧/缺血的研究。大脑的正常功能，以及诸如中风、出生窒息、肿瘤、脑积水和癫痫等疾病都会引起氧合的改变。能够提供有关脑氧合的高时空信息的成像方法将具有重要意义。该近红外/磁共振成像仪将提供脑氧利用、提取、血容量和血饱和度的空间分辨率数据。主要目的是表明，通过使用来自MRI的结构信息，可以约束近红外数据的重建以获得真正的近红外图像。然后，我们可以将这些氧合图像与任何MR成像模式共同配准，包括扩散、灌注和BOLD（血氧水平依赖成像）。近红外提供了血红蛋白含量和饱和度的准确信息，但是，没有我们提出的发展，近红外数据很难重建成图像。我们将在一系列研究直径范围内验证NIRS重建算法。然后，我们将构建与NIBS成像系统兼容的核磁共振硬件，并将两者结合起来，形成混合成像模式。我们将在幽灵和动物模型上进行测试。在开发系统之后，我们有两个假设驱动的目标，旨在展示成像仪的潜力，以及提供缺氧/缺血的独特数据。我们将验证海马体在正常缺氧时具有高氧提取能力，而在缺氧时增加提取能力降低的假设。这种提取的差异可能是海马缺氧敏感性增加的机制之一。我们还假设，在低体温缺血后的再灌注过程中，大脑的提取和脑血流量减少。这种氧合模式与体外循环后的神经损伤有关。另一方面，这是缺血后氧化损伤增加的时期，因此在某些情况下，再灌注时减少氧合可能是有益的。我们将评估脑组织氧合和血流（使用磁共振灌注成像）在缺血/再灌注在低氧和低温。这项资助将产生一种新的成像方式，可以无创地监测脑氧合、结构和血流。

We will design, and construct a combined near infrared (NIR) and magnetic resonance (MR) imaging system for studying brain oxygenation, and apply it to the study of brain hypoxia/ischemia. Normal function of brain, as well as pathologies such as stroke, birth asphyxia, tumors, hydrocephalus and epilepsy all induce changes in oxygenation. Imaging methods which provide high spatial and temporal information concerning brain oxygenation would be of significant use. This NIR/MR imager will provide spatially resolved data on cerebral oxygen utilization, extraction, blood volume and blood saturation. The main goal is to show that, by using structural information from the MRI, one can constrain the reconstruction of NIR data to obtain true NIR images. We can then co-register these oxygenation images with any MR imaging modality including diffusion, perfusion and BOLD (blood oxygen level dependent imaging). NIR provides accurate information on hemoglobin content and saturation but, without the developments which we propose, NIR data are difficult to reconstruct into an image. We will verify NIRS reconstruction algorithms for a range of study diameters. Then we will construct appropriate NMR hardware compatible with the NIBS imaging system and combine the two to create the hybrid imaging modality. We will test this on phantoms and on animal models. After developing the system, we have two hypothesis driven aims designed to show the potential of the imager, as well as to provide unique data on hypoxia/ischemia. We will test the hypothesis that the hippocampus has a high oxygen extraction during normoxia, and reduced capacity to increase extraction during hypoxia. This difference in extraction may be one of the mechanisms of increased hypoxia sensitivity in the hippocampus. We also hypothesize that the brain has a reduced extraction, and cerebral blood flow during reperfusion after hypothermic ischemia. Such a pattern of oxygenation has been implicated in neurological impairment after cardiopulmonary bypass. On the other hand, this is the period of increased oxidative damage post-ischemia, and so reduced oxygenation during reperfusion may be beneficial under some situations. We will assess brain tissue oxygenation and blood flow (using MR perfusion imaging) during ischemia/reperfusion during normoxia and hypothermia. This grant will produce a novel imaging modality which can non-invasively monitor cerebral oxygenation, structure, and blood flow.