A time-gated near-infrared spectroscopic imaging device for clinical applications.

Abstract

A time-resolved, spectroscopic, diffuse optical tomography device was assembled for clinical applications like brain functional imaging. The entire instrument lies in a unique setup that includes a light source, an ultrafast time-gated intensified camera and all the electronic control units. The light source is composed of four near infrared laser diodes driven by a nanosecond electrical pulse generator working in a sequential mode at a repetition rate of 100 MHz. The light pulses are less than 80 ps FWHM. They are injected in a four-furcated optical fiber ended with a frontal light distributor to obtain a uniform illumination spot directed towards the head of the patient. Photons back-scattered by the subject are detected by the intensified CCD camera. There are resolved according to their time of flight inside the head. The photocathode is powered by an ultrafast generator producing 50 V pulses, at 100 MHz and a width corresponding to a 200 ps FWHM gate. The intensifier has been specially designed for this application. The whole instrument is controlled by an FPGA based module. All the acquisition parameters are configurable via software through an USB plug and the image data are transferred to a PC via an Ethernet link. The compactness of the device makes it a perfect device for bedside clinical applications. The instrument will be described and characterized. Preliminary data recorded on test samples will be presented.

Time-resolved diffuse optical tomography using fast-gated single-photon avalanche diodes

“…This capability was already explored using both single [30] and multi-distance measurements [31]. Time gated instruments can improve this intrinsic features of time-domain techniques [32,33]. Differently from the previous works here a time-gated instrument based on a solid state detector, thus able to efficiently reject early photons, was employed giving the possibility to increase the injected power, reduce the interfiber distance and consequently improve the achievable signal to noise ratio.…”

Time-Resolved Diffuse Optical Spectroscopy and Imaging Using Solid-State Detectors: Characteristics, Present Status, and Research Challenges

“…An excellent way to distinguish between early and late photons is to use very fast time gating circuits that can record the arrival times of each photon. In the recent years, several types of detectors were used for fast TG-TR-DOI prototypes, such as ICCDs [ 9 , 70 ] and streak cameras [ 71 ]. However, these detectors are hindered by the huge numbers of early photons which significantly increase the noise and saturate the detectors [ 43 , 67 ].…”

Non-contact acquisition of brain function using a time-extracted compact camera

“…Two-dimensional image acquisition has also been demonstrated by scanning 11 the illumination spot. Time-gated measurements using an intensified CCD camera have also been adopted to detect absorption changes in deep tissues 15–23 , and two-dimensional imaging 22 , and in vivo experiments 23 have also been performed.…”