Use of an analytical model for optimizing the design of a small-animal PET scanner with DOI capability

The optimization of spatial resolution is a critical issue for small-animal PET scanners, and is often addressed by Monte-Carlo simulation. Analytical models, though less versatile are very fast and their simplicity allows a direct appreciation of the influence of different model parameters. The authors have developed an analytical model for multi-layer PET systems, which provides estimates of the radial and tangential resolution at different positions within the field of view. After a preliminary validation, this model was used to optimize the design of a small single-slice multi-layer PET scanner with depth of interaction capability. The authors found satisfactory agreement between the analytical model and Monte Carlo results for several scanner configurations. The dependence of the resolution on the crystal width, the number of layers, and the crystal layout was determined for a scanner with internal and external diameters at 74 mm and 114 mm respectively. Both simulation methods agreed perfectly on the influence of these parameters. In particular confirming the degree of resolution improvement obtained using multiple-layers of crystals. These results show that an analytical model can provide accurate estimates of the spatial resolution, and can be used to complement or cross-validate Monte Carlo simulations