CONTINUOUS WAWE DIFFUSE OPTICAL TOMOGRAPHY SYSTEM TESTED ON PHANTOMS AND ANIMAL TISSUES

Diffuse Optical Tomography (DOT) can image spatial variations in highly scattering optical media. We have built a continuous-wave DOT system containing a spatially combined 2 laser diode sources (at 785 nm and 830 nm), one SiPD detector, a transimpedance amplifier and two lock-in amplifiers, which can acquire 128 independent measurements in less than 60 seconds through two time-division-multiplexed optical scheme with eight illumination fibers and eight detector fibers in the measuring head (optode). These data can then be processed using a specialised imaging algorithm. We first discuss the design of diffuse imaging equipment in general, and then describe our instrument, along with the technical issues that influenced its design. The technical challenges involved in performing DOT over large optode areas are discussed. We also present the parametric evaluation of the system with an optode diameter of 5 to 6 cm. The paper describes the technique used to reach > 80 dB dynamic range, < 1% nonlinearity and a crosstalk < 0.01% at a digital resolution of 16 bits, how to put in evidence the selective absorption and scattering for some different kind of phantoms and their reconstructed images.