Algebraic Reconstruction of Images of a Diffusive Medium Containing Strong Absorbers: Comparative Study of Different Illumination Schemes and the Effect of Restricted View Angle

H. L. Graberet al. (1995)


The quality of the answer computed by an image reconstruction algorithm could significantly depend on certain details of the data collection and analysis procedures. We describe some of the decisions that must be taken during both of these steps, e.g., the geometry, number, and locations of both sources and detectors, selection of a set of time windows or modulation frequencies, and whether to process the data in a simultaneous or sequential manner. Because there is no set of choices is self-evidently optimal, we chose to use one comprehensive set of internal light intensity distributions and detector readings, both computed from Monte Carlo simulations, as a standard for tests of different varieties of image reconstruction algorithms applied to different subsets of detector readings. The reference medium in all cases was a densely scattering homogeneous,infinitely long cylinder. The three targets consisted of the same cylinder with the addition of either a single black rod parallel to the axis, or thirteen black absorbing rods distributed in the form of an "X". Time-resolved detector responses and internal collision densities were computed directly, and from these time-independent and frequency domain data were subsequently calculated. Images were reconstrcuted using algebraic algorithms medium. Results shown compare images obtained using data from different domains and different sets of source locations. The quality of the one-absorber images is very good to excellent. The quality of the images of the thirteen-absorber target, for which the weak perturbation premise is very strongly violated, is only fair. Sources of random and systematic erros are identified, and the effects of both types is discussed.