Optical Diffusion Tomography Data Acquisition System

Optical diffusion tomography (ODT) has recently found renewed interest by the scientific and medical community due to advances in imaging electronics, computer processing power, development of tumor marking dyes, and image reconstruction algorithms. The development of this technology may allow the use of near infra red and infra red light to image internal structures of tissue without the use of ionizing radiation, as in the case of X-Ray computed tomography (CT). Presently, a working ODT system has been constructed and is capable of measuring intensity changes due to light absorption data. The design of an ODT system capable of intensity measurement and phase measurement using intensity modulation is described in this thesis. A prototype ODT system has been built and tested to obtain phase and magnitude measurements of tissue phantoms with immersed absorbers. A semiconductor laser diode with a wavelength of 790 nm and power output of 5 milliwatts was modulated at the frequencies of 150 and 200 MHz. The system was capable of identifying absorbers of widths as small as 0.3 millimeters within slabs of 1% Intralipid tissue phantoms 5 centimeters thick. Thesis Supervisors: Prof. Charles G. Sodini, Department of Electrical Engineering and Computer Science, MIT. Guillermo Ferla, MIT '72, Engineering Fellow, Polaroid Corporation.