MRI-Compatible Diffuse Optical Tomography System

描述(申请人提供)：这项提案的总体目标是开发一种用于小动物血氧测定的三维光学断层扫描(OT)近红外成像系统。该系统将被设计为允许OT数据和磁共振(MR)成像数据的共同配准，但也可以用作独立的光学成像单元。虽然存在执行光学血液氧合监测的商业系统，但这些仪器尚未针对小动物研究进行优化，也没有与磁共振成像系统相结合。此外，现有的设备通常使用有限数量的源和探测器，不生成三维体图像，并且图像重建是使用基于扩散理论的算法来执行的。然而，众所周知，扩散理论没有完全考虑光在小生物介质(直径1-2厘米)中传播的影响，因为在这些维度上，更普遍适用的辐射传输理论的扩散近似不够准确。 这项拟议的工作试图克服目前的不足，并开发一种可与标准小动物磁共振扫描仪结合使用的近红外光学成像系统。该项目的主要假设是，目前光学层析成像的局限性可以通过实施基于辐射传递方程(ERT)的三维频域重建方案来解决。该算法将与商业频域测量系统(来自伊利诺伊州Urban-Champaign ISS的IAMGENT)一起实施和使用，该系统将适用于收集MR小型动物成像仪内的数据。通过共同配准光学和MR数据，人们可以结合MR的高空间分辨率和OT的高时间分辨率的优点，以及其分离氧合血红蛋白、脱氧血红蛋白和血液容量效应的能力。对于这个项目，我们将追求以下三个具体目标：(1)开发和数值验证用于漫反射光学层析成像的三维、基于传输理论的频域图像重建程序；(2)在小型动物磁共振成像仪上验证和评估光学层析成像系统(代码和仪器)；以及(3)比较频域和稳态、基于传输理论的光学层析成像和基于扩散理论的光学层析成像。这一比较将量化的优势和劣势 这些不同的光学成像模式。

DESCRIPTION (provided by applicant): The overall goal of this proposal is the development of a three-dimensional optical tomographic (OT) near-infrared imaging system for oximetry in small animals. The system will be designed to allow for co-registration of OT data and magnetic resonance (MR) imaging data, but may also be used as a stand-alone optical imaging unit. While commercial systems that perform optical blood-oxygenation monitoring exist, these instruments have not been optimized for small animal studies and have not been combined with MR imaging systems. Furthermore, the available devices often operate with a limited number of sources and detectors, do not generate three-dimensional volumetric images, and the image reconstruction is performed with diffusion-theory-based algorithms. It is well known, however, that diffusion theory does not fully account for the effects of light propagation in small biological media (diameter 1-2 cm), because at these dimensions the diffusion approximation to the more generally applicable theory of radiative transfer is not sufficiently accurate. The proposed work attempts to overcome the current shortfalls and develop a near-infrared optical imaging system that can be used in combination with standard small animal MR scanners. The main hypothesis of this project is that current limitations of optical tomographic imaging can be addressed by implementing a three-dimensional frequency-domain reconstruction scheme that is based on the equation of radiative transfer (ERT). This algorithm will be implemented and used in conjunction with a commercially available frequency-domain measurement system (IAMGENT from ISS, Urban-Champaign, IL), which will be adapted to collect data inside an MR small animal imager. By co-registering optical and MR data one can combine the benefits of MR's high-spatial-resolution, with OT's high temporal resolution and its capability of separating oxyhemoglobin, deoxyhemoglobin, and blood volume effects. For this project we will pursue the following three specific aims: (1) Develop and numerically validate of a three-dimensional, transport-theory-based, frequency-domain image reconstruction code for diffuse optical tomography; (2) Validate and evaluate the optical tomographic imaging system (code and instrument) in a small animal magnetic resonance imager; and (3) Compare frequency-domain and steady-state, transport-theory based optical tomography with diffusion-theory-based optical tomography. This comparison will quantify the advantages and disadvantages of these different optical imaging modalities.