Near Field Corrections for Coded Aperture Imaging in Scintimammography

In this work we study the form of artifacts arising with near-field imaging geometries associated with using coded apertures for scintimammography (SM) using a combination of Monte Carlo simulation (MCS), pseudo-ray tracing (PRT) and a new, but simple approach called binary mask shift. The latter method predicted the shape artifacts that are due to off-axis sources and finite size of the object but ignores the effect of varying the angle of incidence of the gamma-rays. The background artifact pattern produced by uniform 2D and 3D source objects of different sizes using a PRT method compared with the corresponding data obtained with MCS suggest that both methods produce striking similarities. From these results we are encouraged to believe that the so-called near field distortion observed with distributed planar and 3D sources, as might be found in SM using coded apertures, can be easily predicted and corrected.