Research of the system response of neutron double scatter imaging for MLEM reconstruction

A Maximum Likelihood image reconstruction technique has been applied to neutron scatter imaging. The response function of the imaging system can be obtained by Monte Carlo simulation, which is very time-consuming if the number of image pixels and particles is large. In this work, to improve time efficiency, an analytical approach based on the probability of neutron interaction and transport in the detector is developed to calculate the system response function. The response function was applied to calculate the relative efficiency of the neutron scatter imaging system as a function of the incident neutron energy. The calculated results agreed with simulations by the MCNP5 software. Then the maximum likelihood expectation maximization (MLEM) reconstruction method with the system response function was used to reconstruct data simulated by Monte Carlo method. The results showed that there was good consistency between the reconstruction position and true position. Compared with back-projection reconstruction, the improvement in image quality was obvious, and the locations could be discerned easily for multiple radiation point sources.