Monte Carlo image reconstruction of a mammographic phantom

The aim of this study is the development of a methodology to reconstruct via Monte Carlo techniques the radiographic image of the CIRS 11 A (MAMMO PHANTOM SPOT) phantom. This phantom is used in image quality assessment during quality control tests in breast screening locations and other health centers. The mammographic phantom is comprised of a reference point, a glandular tissue step wedge, contrast and resolution targets, and groups of microcalcifications and fibers. The MCNP radiation transport code (version 4c2) has been modified and recompiled to let use of a large number of tallies and detectors per input file, and an azimuthal directional source biasing. The output surface air kerma (OSAK) delivered by the X-rays has been scored employing a rectangular matrix of point detectors (F5 tally) under the phantom, simulating the image system. Some variance reduction techniques have been implemented to ensure that photons reach the detectors and that weight fluctuations were reduced. The characteristic curve of the film-scanner imaging system combination has been obtained throughout several experimental measures with an aluminium sensitometric wedge and Monte Carlo simulations. The reconstructed images agree with the range of values, indicating that this method would be suitable for training purposes, phantom designing or dose calculations.