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One of the main problems in neutron imaging is the scattered radiation that accompanies the direct neutrons that reach the imaging detectors and affect the image quality. We have developed a dedicated collimator for 14.2 MeV fast neutrons. The collimator optimizes the amount of scattered radiation to primary neutrons that arrive at the imaging plane. We have used different materials within the collimator in order to lower the scattered radiation that arrives at the scanned object. The image quality and the signal to noise ratios that are measured show that a mixture of BORAX (Na 2 B 4 O 7 •10H 2 O) and water in the experimental beam collimator give the best results. We have used GEANT4 to simulate the collimator performance, the simulations predict the optimized material looking on the ratios of the scattered to primary neutrons that contribute in the detector. We present our experimental setup, report the results of the experimental and related simulation studies with neutrons beam generated by a 14.2 MeV D-T neutron generator.

In multi-slice CT (MSCT), as the coverage becomes wider, the scattering contribution along the longitudinal direction (z) to the detectors' signal increases. The scattering results in image artifacts, appearing as dark shadows between highly attenuating objects. In this work we measure the scattering level systematically, using phantoms of various sizes, shapes, and materials. We study the dependencies and their effect on the scattering amount.We derive an empirical function for the scattering fraction, based on the maximal attenuation at each rotation angle. The function contains a single constant (SC). The variation of SC as a function of the different phantoms is analyzed, showing a clear dependence on the minimal water equivalent axis of each phantom.The strong dependence of the scattering fraction on the maximal attenuation along each view is shown. This phenomenon can be correlated to a single scatter process along the z axis in the presence of an anti-scatter grid along the direction of the detectors. The dependence of SC on the minimal axis indicates an additional significant scatter process.The results validate that the scattering level estimation can be achieved using the derived function, with a minimal variation in the solution parameters. Hence, enabling the introduction of this scatter estimation into an MSCT scattering correction scheme.

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