CHARACTERIZATION OF THE RESPONSE OF HEXAG ONAL PARALLEL-HOLE COLLIMATORS OF SCINTILLATION CAMERAS

This paper presents a formulation of the frequency response of hexagon al parallel-hole collimator scintillation cameras. To describe this re sponse, we propose an equation determined semi-empirically from a grea t number of simulations. The utility of the equation is that it enable s the simple calculation of the response from collimator characteristi cs by taking into account the collimator's hexagonal structure. Becaus e the equation does not assume translation invariance, the results can be directly compared with experimental measurements obtained with a p oint source. It is particularly interesting for collimators with large holes, like the medium-resolution ones used for high-energy radiation . Quality control and physical performance measurements are thus facil itated for this kind of collimator. Also, we present a new parameter t hat gives a quantitative assessment of the importance of partition pen etration. This parameter is measured directly from the collimator freq uency response. It has been studied by simulation, taking into account gamma photon attenuation in collimator partitions. The experimental m easurements that have been made are in accord with the proposed equati ons.