A physics based model of pixellated semiconductor gamma camera

A solid state CdZnTe gamma camera simulator, taking into account the gamma-ray emission and attenuation in the examined phantom, a geometric collimator model and the CdZnTe semiconductor detector response, has been developed. In a first step, the energy dependent spectrometric response of the planar semiconductor pixels is computed from first physical principles (gamma-ray interaction with the crystal and charge collection in the semiconductor detector), as well as from specific acquisition parameters (front-end electronics signal filtering, pulses classification in a pulse height versus rise time biparametric spectrum and bi-dimensional window based pulses selection). In a second step, the uncollided and once scattered photon fluxes, incident to each gamma camera´s pixel, are computed by the means of ray tracing through the phantom´s CAD model. They are then combined with a geometric collimator model. The energy dependent pixel response is finally used to generate the simulated image. Each component of the model has been compared to experimental data. Finally, a correct qualitative agreement was found between simulated images and measurements performed on a prototype platform