IMPROVEMENT OF DEPTH SENSITIVITY TO CEREBRAL HEMODYNAMICS W/ TIME GATED SYSTEM

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 通过记录光子飞行时间的分布，时间域(TD)系统本质上提供了比连续波(CW)系统更多的信息。特别是，它们能够在单源-探测器(SD)分离时实现深度辨别。这对脑功能成像特别有意义，因为皮层的激活通常被表面的全身反应所掩盖。我们的TD装置是基于钛宝石脉冲激光器和增强型CCD相机(ICCD)。我们开发了一种结合了深度敏感和2D成像的探头。它由两半组成，每半半球一个，每个半球有4？4个源和3？3个探测器，呈正方形(SD=2.5厘米)。每个探测器由7根不同长度的光纤组成，以7个延迟进行并行检测。所有126根光纤在ICCD阵列上并行成像。32个信号源按顺序照明，在同一个CCD帧期间打开4组8个信号源，而不会产生明显的串扰。这种源时分复用和并行检测允许整个头部的成像频率几乎为2赫兹。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. By recording the distribution of times of flight of photons, Time Domain (TD) systems intrinsically provide more information that continuous wave (CW) ones. In particular, they enable depth discrimination at a single source-detector (SD) separation. This is of particular interest for functional brain imaging, where cortical activation is often hidden by superficial systemic response. Our TD device is based on a Ti:Sapphire pulsed laser and an intensified CCD camera (ICCD). We have developed a probe combining depth sensitivity and 2D imaging. It consists in 2 halves  one per hemisphere  each with 4¿4 sources and 3¿3 detectors in a square geometry (SD = 2.5 cm). Each detector consists of 7 fibers of different lengths, for parallel detection at 7 delays. All 126 fibers are imaged in parallel on the ICCD array. The 32 sources are illuminated sequentially, with 4 sets of 8 sources that are turned on during the same CCD frame without causing significant cross-talk. This source time-multiplexing and the parallel detection allow for an imaging frequency of almost 2 Hz for the whole head.