Explaining the Effect of a Grid by Using an Optical Analog to an X-ray Radiographic Imaging System

Compton scattering and diffuse scattering degenerate the contrast in radiographic images. To avoid such scattering effects, a grid, between the patient and the film is currently used to improve the image quality. Teaching this topic to medical physics students requires demonstration experiments. In this paper, an optical analog to an x-ray radiographic imaging system is described. The setup is inexpensive and is easy to be mounted. A He-Ne laser and a set of lenses (objective lens from a microscope + glass magnifier) were employed to direct a huge parallel beam at the sample. A washer glued onto pinhead-frosted glass was used as a sample. The ceramic part of a catalytic converter was used as a grid. The images, acquired by using a photographic digital camera, show the effect of a grid in cleaning the image (higher contrast): the washer, not seen in the image without the grid, is clearly seen in the image with the grid. (Contains 4 figures.)