Advanced Processing Methodologies Improve Neutron Radiograph Image Quality

We propose a novel processing protocol framework for neutron radiograph image quality improvement. Neutron radiographs were collected at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) CG-1B imaging station utilizing a 2.35 Å cold neutron beam with flux ~107 n/cm2/sec. A 100 micron thick ZnS(Ag)/6LiF scintillator was coupled via mirror to a second generation sCMOS camera system with 2k x 2k spatial resolution. We address image quality degradations due to random spuriously detected gamma rays (spikes), camera dark current and readout noise (background), detection system resolution fall-off with increasing spatial frequency, and Gaussian noise due to detection counting statistics. The background is estimated and subtracted out. Gaussian noise is estimated and removed via 3D transform-domain collaborative filtering to minimize effects of spatial resolution degradation. Spikes are removed via an adaptive morphological filter. Capitalizing upon the resultant low noise images produced, Metz restoration filtering is employed to significantly improve image sharpness with increasing spatial resolution. The order of operations for filtering is important, and we restore very low noise images with ~70 micron resolution using our processing protocol.

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