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ABSTRACT

Purpose: To visualize x-ray scatter using the novel tomographic reconstruction (TR) camera based on circular penumbra analysis; to produce these visualizations at clinical x-ray doses.

Methods: The TR camera was constructed as a box made of 4.76 mm steel, with a hole several centimetres in diameter cut in the front to serve as the aperture. A CR plate was placed in the back of the camera, at an adjustable depth ranging from 1.5 to 5 cm. The camera was exposed to four point sources using a radiographic tube, with a different number of exposures at each point to produce differing relative intensities (at a distance of 300 cm with 73 kVp and 0.4 mAs per exposure). Reconstruction of the point sources served as proof of concept. Later, the camera was exposed to x-ray scatter using a fluoroscopy system with a torso phantom (at a distance of 1 m, with the system run until a DAP of 344 μGym² was reached). A pinhole camera was constructed similarly to the TR camera (with a 3 mm diameter aperture), and was also exposed to the x-ray scatter. For the TR camera, both the point sources and scatter sources produced raw CR data which appeared as circular penumbra images; these data were used to reconstruct images of the sources. The TR camera x-ray scatter reconstructions were overlaid with photographs taken from the point of view of the TR camera, to visualize the sources.

Results: Faithful reproductions of x-ray point sources and x-ray scatter were produced using the TR camera (including accurate relative intensities), and the scatter sources were visualized by overlaying them with photographs. In order to collect x-ray scatter data using the pinhole camera, the fluoroscopy system had to be run until it reached a DAP eight times greater than was required by the TR camera.

Conclusions: This work shows that circular penumbra tomographic reconstruction can be used to accurately visualize both x-ray point sources and x-ray scatter, and that reconstructions of x-ray scatter can be scaled to match photographs in order to visualize the sources.