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的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 通过记录光子的飞行时间分布，时域（TD）系统本质上提供了比连续波（CW）系统更多的信息。特别是，他们能够在一个单一的源检测器（SD）分离的深度歧视。这对于功能性脑成像是特别感兴趣的，其中皮层激活通常被表面系统反应所隐藏。我们的TD设备是基于钛：蓝宝石脉冲激光器和增强型CCD相机（ICCD）。我们开发了一种结合深度灵敏度和2D成像的探头。它包括两个半  每个半球一个  每个具有正方形几何形状的4 <$4个源和3 <$3个探测器（SD = 2.5 cm）。每个探测器由7个不同长度的光纤组成，用于以7个延迟并行检测。所有126根光纤在ICCD阵列上并行成像。这32个光源被依次照亮，其中4组8个光源在同一CCD帧期间被打开，而不会引起显著的串扰。这种源时间复用和并行检测允许整个头部的成像频率几乎为2 Hz。

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.