Fast visualization of internal structure of multiple-scattering objects by diffusion optical tomography

Abstract

Fast (i.e. able to a real-time operation) approximate statistical nonlinear algorithm ofthe diffusion optical tomography inverse problem solution has been described. Results ofthis algorithm approbation by the example of reconstruction of a rather complicated (up to 3 strongly absorbing inclusions with the size 5 mm) internal structure of strongly scattering and weekly absorbing (with scattering and absorption constants about 1 .4 and 0.005 ÷ 0.01 5 mm' correspondingly) large-size (up to 140 mm) model objects have been presented. CW radiation oflow-power (with input power < 20 mW) diode lasers of near JR (wavelengths in the range 770 ÷ 820 nm) region has been used in experimental realizations. . INTRODUCTIONDui-ing about ten last years, a quite new direction of optical diagnostics -the optical tomography (OT)is of great interest. In OT, a diagnosed object (further the object) many times (for different positions i ofa light source and j of a detector) is examined with an input near-JR-range radiation with known characteristics. One must know power or energy of the input light pulse (in CW and pulsed regimes ofthe light source operation), this pulse duration and the <<switching on>> moment, and so on. For all the possible (i,j) values, power or energy ofthe output light pulse (in the same operation Recent development of so-called <<diffusion>> OT, where a full flux of the output photons is detected, enables one to simplify OT hardware and to reduce essentially its price. Increase of the output signal results to a sharp decrease of the measuring time and to increase of the maximal size of the diagnosed object. However, in this case, a main <<load>> in the