Research On Dynamic Diffuse Optical Tomography System In Photon Counting Mode

Diffuse Optical Tomography(DOT)is a new optical imaging technique. As one of the tissues'optical features is high scattering and low absolution in the near-infrared spectroscopy, DOT can detect distribution of tissue optical parameters related to important physiology and provide information on anatomical and physiological features at the same time. This method has been widely used in imaging of breast, neonatal cerebral oxygen status and blood oxygen kinetics observed by its features such as continuous real-time, completely non-invasive, high time resolution, reasonable space resolution and others.Nowadays, DOT systems can be divided into three categories: the continuous wave system, the time resolved system and the frequency domain system. In continuous wave DOT system, a traditional way to realize detection of faint light is to utilize the photon counting techniques. Output of a photon detector is discrete by nature, which makes it possible to extract the weak signal by methods of pulse amplitude discrimination and digital counting techniques.Continuous wave DOT image reconstruction algorithms need that signals under each source location and detector location can be separated, so it can get right signal by encoding multiple sources. Most currently used source coding in DOT is optical time-division multiplexing technology, which utilizes the optical switch to switch light into optical fiber of different locations. In this way, it can decode any measured data of the corresponding source - detector from multiple combinations of source and detector.In this paper, a dynamic DOT system in photon counting mode is preliminary established by optical time-division multiplexing technology for continuous wave system, including a continuous laser, a 1:8 optical switch, four 1:4 optical switches, four photon counting heads and the photon counter. My main work contains three sections.1. A 8-channel boxcar photon counter based on programmable logic technology is designed. It can accumulate single-photon pulses and control the optical switches.2. The computer software interface is designed based on LabVIEW, which can control the operation of the whole system. 3. Build the whole system , then standardize it, and make some experiments to test and verify the function of the system.