Optical tomograph with photon counting and projective reconstruction of the parameters of absorbing 'phantoms' in extended scattering media

A highly sensitive detection system with time-resolved photon counting was developed for modulation optical tomography (diode laser with a power of 15 -30 mW, modulation frequency 100 MHz) of extended scattering objects. Exper iments with model objects (linear dimensions up to 140 mm, absorption coeff icients of 0.005-0.015, scattering coefficients of 1.4 mm(-1)) showed that the propagation of optical radiation in such media is described by a relati ve path-lengthening coefficient which varied in the range 1.2-4.2, dependin g on the absorption coefficient and on the size of the object. A rapid proj ection algorithm for the solution of the inverse problem was used in the re construction of images of strongly absorbing inclusions known as 'phantoms' (cylinders 10-23 mm in diameter). An algorithm was developed for the solut ion of the direct problem, which made it possible to reduce the solution ti me to 5-10 min.