Fluorescence Lifetime Imasing Based on Heterodyne Detection Techinique

基于外差检测的荧光寿命成像系统采用了二维光电探测器。采用图像增强器（I.I.）和图像反射管（IDT）作为二维光电探测器。利用门控电感管内通道电子倍增器的增益控制特性，利用低压控制信号实现外差检测。外差调制荧光和参考信号在多通道板的i.i.t管提供高达几百兆赫的高频响应。ii管的P20荧光屏（衰减常数约为100 mus）作为外差信号的低通滤波器，抑制高频成分。采用电子快门低至100 μ m的CCD相机，以100 μ m的时间间隔和快门持续时间与外差荧光图像的时间序列相耦合，并将其存储在个人计算机的存储器中。根据存储的数据计算出相位分辨图像，即终身图像。系统的时间分辨率约为1ns。在相位分辨荧光图像检测和比值法计算的基础上，提出了一种新的组分模式分析方法。荧光寿命的差异，提供相应的相关系，被积极地用来估计每个成分的空间分布。

Fluorescence lifetime imaging systems based on heterodyne detection using two dimentional photo-detectors have been developed. An image intensifier (I.I.) and an image dessector tube (IDT) were used as the two dimensional photo-detector.The gain control characteristics of the channel electron multiplier in the gated I.I.tube are utilized to allow heterodyne detection with low-voltage control signal. Heterodyning the modulated fluorescence and reference signals at the multichannel plate of the I.I.tube provides high-frequency response up to several hundred MHz.The P20 fluorecsence screen (decay constant of about 100 mus) of the I.I.tube behaves as a low pass filter for the heterodyned signal, rejecting hi-frequency components. A CCD camera with electronic shutter down to 100 mus coupled to the I.I.slices at the time interval and shutter duration of 100 mus the time sequence of the heterodyned fluorescence image and stores them in the memory of a personal computer. The phase resolved image, i.e.the llife time image is calculated the stored data. The time resolution of the system is about 1 ns.A new technique has also been developed for component pattern analysis based on phase resolved fluorescence image detection and a ratio method calculatin. Differences in fluorescence lifetimes, providing corresponding phase retadations, are positively utilized to estimate the spatial distribution of each component.