Spectral-Encoding for Video-Rate Hemodynamic Tomography

描述(由申请人提供)： 近红外(NIR)光谱层析成像作为一种成像组织中基于血液的对比度的方法已经出现。这种成像方法的一个潜在优势是它可以非常快，基本上是实时的，类似于超声波，到目前为止还没有被充分利用。开发快速近红外断层成像系统的主要限制是需要顺序扫描光源，使得即使在并行检测的情况下，图像采集时间也被限制在几赫兹的帧速率。这项工作引入了一个新的概念，即在所有震源位置同时激活的情况下进行成像。这项技术使用了一组光源，这些光源在光谱上被纳米级的分数分开，但却聚集在很窄的带宽(4到5 nm)内。由于组织的光谱特征在如此窄的频带上没有显著变化，这些不同的激光源将对组织中相同的衰减和散射过程进行采样，然而在检测通道中，与每个源波长相关联的响应可以容易地由光谱仪分离，从而并行检测。这种方法避免了探测器的源饱和问题，同时允许在单个测量事件中并行检测所有源和所有探测器。这种类型的位置光谱编码是几种成像系统的核心，例如MRI，它允许从不同的无线电频率并行读出位置。该系统将实现在小动物的几何成像中，使用CCD和光电倍增管进行探测。通过组织体模和动物实验，将从硬件和软件两个方面论证其可行性。脑中脉动血流的血流动力学反应将在大鼠大脑中成像，以及吲哚青绿动力学。数据采集将以视频速率生成，从而允许动态的实时可视化。 在项目的R33阶段，相同的系统设计将扩展到多个并行检测器，允许对血氧饱和度和总血红蛋白进行定量光谱分析。该系统将用于现有的MRI-NIR成像系统，用于脑和肿瘤成像研究。组合的MRI-NIR成像系统将在模体中进行校准，并改进软件，以进行基于区域的靶向重建的快速动态定量血红蛋白成像。我们假设，总血红蛋白和血氧饱和度变化的动态成像将从根本上提供关于组织功能和代谢对刺激的反应的新信息。将在啮齿动物大脑中进行的对比研究将是功能激活研究，以及肿瘤成像将包括(I)固有的血液脉动流动(Ii)吲哚青绿的脉动流动和动力学，(Iii)血氧饱和度随吸入氧浓度的长期和瞬时变化而发生的动态变化，以及(Iv)葡萄糖通过克拉布特里效应引起的耗氧量的代谢变化。

DESCRIPTION (provided by applicant): Near-Infrared (NIR) spectroscopic tomography has been emerging as a method to image blood-based contrast in tissue. A potential strength of this imaging approach which has not been fully exploited to date is that it can be very fast, essentially real-time, similar to ultrasound. A major limitation in the development of fast NIR tomography systems has been the need to sequentially scan the light source, such that even with parallel detection, the image acquisition time is limited to frame rates of a few Hertz. This work introduces a new concept for imaging in parallel with all source locations simultaneously activated. The technique uses an array of light sources that are separated by fractions of a nanometer spectrally, yet clustered within a narrow (4 to 5 nm) bandwidth. Since the spectral features of tissue do not vary significantly over such a narrow band, these different laser sources will sample the same attenuation and scattering processes in tissue, yet in the detection channel the response associated with each source wavelength can readily be separated by a spectrograph, and thereby detected in parallel. This approach avoids the problem of source saturation of the detectors, while allowing parallel detection of all sources and all detectors in a single measurement event. This type of spectral encoding of the position is at the heart of several imaging systems such as MRI, where it allows parallel readout of the location from different radio frequencies. The system will be implemented in a small animal imaging geometry, using CCD and photomultiplier tube detection. Feasibility will be demonstrated in hardware and software through both tissue phantom and animal experiments. The hemodynamic response in terms of pulsatile flow in the brain will be imaged in the rat brain, as well as indocyanine green kinetics. The data acquisition will be generated at video rate, thereby allowing real-time visualization of the dynamics. In the R33 phase of the project, the same system design will be extended to multiple parallel detectors, allowing quantitative spectroscopy of oxygen saturation and total hemoglobin. The system will be used in existing MRI-NIR imaging systems for both brain and tumor imaging studies. The combined MRI-NIR imaging system will be calibrated in phantoms and software refined for rapid dynamic quantitative hemoglobin imaging with region-based targeting of the reconstruction. We hypothesize that dynamic imaging of total hemoglobin and oxygen saturation changes will provide fundamentally new information about tissue function and metabolic response to stimulus. The contrasts to be examined in rodent brain will be functional activation studies, as well as imaging of tumors will include (i) intrinsic blood pulsatile flow (ii) pulsatile flow and kinetics of indocyanine green, (iii) dynamic changes in oxygen saturation in response to long term and transient changes of inspired oxygen concentration, and (iv) glucose induced metabolic changes in oxygen consumption from the Crabtree effect.