Abstract
Pinhole SPECT imaging systems are widely used in small animal studies. The multi-pinhole system improves the low sensitivity while the helical trajectory system improves the field of view (FOV) size. Conventional system model for the pinhole system is based on ray-tracing (RT) algorithm including single-ray ray-tracing (SRRT) and multi-ray ray-tracing (MRRT).However, the RT series algorithm could not solve the finite aperture effect and depth effect in a pinhole SPECT system. Moreover, both SRRT andMRRT algorithm may cause missing information because of characteristic geometry of pinhole collimator. Here, we proposed a new system model called voxel-driven (VD) model to describe the emission and detection of photons. The VD model are calculated based on geometry and this model accounts for both depth effect and finite aperture for pinhole SPECT imaging system. The missing-information phenomenon caused by RT algorithm won’t happen in this model. The results show that using VD model can improve the reconstructed images’ quality and this model are also suitable to be applied in helical trajectory pinhole SPECT system. Multi-pinhole and helical trajectory pinhole SPECT is a high resolution and larger FOV imaging system, and VD model is not only suitable for this imaging system but also able to further improve the image quality.