PNNL

Abstract

High energy x-ray radiography is useful as a highly penetrating method for imaging through dense materials. However, the primary modes of interaction of x-raysat these energies involves scattering or the production of secondary high energy photons, which can interfere with the image. In addition, detector blurring, often resulting from scatter within the detector, can reduce image sharpness. Both of these processes can be mitigated with the use of convolution kernels, with the main challenge that the proper kernel to use is not known, particularly for the scatter contribution. By radiographing solid slabs of uniform attenuation, we show that point spread functions and materialspecific point scatter functions can be determined that significantly reduce the effect of detector blurring and object scatter. Constraining the fits to the slabs and uniform transmission within the slabs is sufficient to recover these functions. A functional form that reproduces the angular distribution of high-energy bremsstrahlung x-rays is presented for recovering point scatter functions. The method is applied to radiographs of objects from bremsstrahlung x-ray sources operating at 4 and 7.5 MV endpoint energies and a significant increase in sharpness is observed.