The effects of collimation on image formation in Anger gamma cameras

The effects that collimators have on gamma camera images in nuclear medicine studies at 140 keV has been studied. A Monte Carlo simulation of photon transport through a multihole collimator was written to determine the average collimator point source response function. The code allows different dimensions, hole misalignments and alternative structures to be modelled. Images of source distributions using the various response functions are produced. The effects on the response functions and images of scattered photons and septal penetration is determined. Collimator hole angulations of up to 10 are simulated and images produced using collimator simulations with random angulations over the collimator. The effects of angulation on the spatial resolution and linearity are found. Laminated collimator structures are proposed as a means of producing robust, lightweight collimators. The images produced compare favourably with those from a conventional lead collimator. Alternative collimator materials have also been considered. The greater absorption properties of uranium, for example, allows a smaller septal thickness, and therefore greater efficiency, with no increase in photon penetration.<>