**Milán Magdics and László Szirmay-Kalos
Department of Control Engineering and Information Technology, Technical University of Budapest,
Budapest, Magyar tudósok krt. 2, H-1117, HUNGARY;
szirmay@iit.bme.hu
**

**Abstract:**

This paper presents a fast algorithm to simulate inter-crystal scattering to increase the accuracy of Positron Emission Tomography (PET). Theoretically, inter-crystal scattering computation would require the solution of a particle transport problem, which is quite time consuming. However, most of this calculation can be ported to a pre-processing phase, taking advantage of the fact that the structure of the detector is fixed. Pre-computing the scattering probabilities inside the crystals, the final system response is the convolution of the geometric response obtained with the assumption that crystals are ideal absorbers and the crystal transport probability matrix. This convolution is four-dimensional which poses complexity problems as the complexity of the naive convolution evaluation grows exponentially with the dimension of the domain. We use Monte Carlo method to attack the curse of dimension. We demonstrate that these techniques have just negligible overhead.

**Keywords:**

Positron Emission Tomography, Detector modeling, GPU, CUDA.