Analytical modeling of the sensitivity of cylindrical PET systems based on bulk materials and metascintillators

Positron emission tomography scanners are commonly characterized by their photon sensitivity. Scanner design often requires Monte Carlo simulations to probe different geometries and materials. However, the computational load of such simulations can be significant and costly. Furthermore, the applicability of the Monte Carlo approach in optimization loops is limited as each instance, such as source position or scanner dimensions, has to be simulated independently. In this work, Monte Carlo results have been accurately replicated by an analytical model that uses characteristics of the foreseen cylindrical scanner and returns the sensitivity profile following NEMA guidelines. BGO and LYSO bulk materials and several metascintillator scenarios have been used. The mean absolute error (MAE), mean absolute percentage error (MAPE) and standard deviation of the error (SDE) are as low as 0.49%, 2.22% and 0.26% when no energy window is used, respectively. With an energy window applied, the analytical model presents the lowest values of MAE and SDE, with MAPE value being 8.19%. A normalization factor has been used to compensate for the scattered events included in the 350-650 keV window. This work facilitates significantly the development of cylindrical scanners, allowing direct probing of their axial sensitivity profiles.