Spatial resolution, measuring time, and fast visualization of hidden deep phantoms in diffusion optical tomography of extended scattering objects

We present the results of testing a prototype of an optical tomograph (a co ntinuous-wave diode laser with a wavelength of 775 nm and a power of 15-20 mW) and fast algorithms for the I reconstruction of the internal structure of extended (with linear sizes up to 150 mm) strongly scattering objects. M odel experiments (with absorption coefficients of 0.005-0.015 and scatterin g coefficients of 1.4 mm(-1)) have demonstrated that the distributions of t he probability that detected photons pass through such objects (projections ) can he described in terms of the coefficient of relative trajectory lengt hening, whose value is independent of the arrangement of a light source and a detector. This experimental finding, confirmed by Monte Carlo numerical simulations, allows a simple scaling of projections in the case when the di stance between the light source and the detector changes, thus providing an opportunity to implement fast real-time approximate statistical nonlinear algorithms for the solution of inverse and direct problems of optical tomog raphy. Experimental testing of the prototype and the developed algorithms h as shown that, for a model object with a diameter of 140 mm within the stud ied range of optical parameters, the coefficient of relative trajectory len gthening ranges from 1.2 to 1.9, and the reconstruction of an image of a st rongly absorbing inclusion with a diameter of 1-2 mm requires no more than 0.5-1 min.