Imaging aperture artifacts

Figure 3.16 Example of an imaging artifact. Left object consisting of an opaque specimen except for a 12 p,m diameter circular aperture. Right calculated transmission image for a single (nonconfocal) Schwarzschild objective with NA = 0.65 and for k = 6 p,m. Note the dark patch in the center, suggesting the presence of absorbing material inside the hole.

Figure 3.17 Imaging artifact for a specimen consisting of a thin uniform layer except for a 12 pm diameter hole (aperture), using a nonconfocal 32 x Schwarzschild objective (NA = 0.65) and X = 6 pm. Solid line calculated absorption profile through the diameter of the hole. Solid circles measured absorption profile for an actual specimen. Note the poor absorption contrast (—50%) and bump at the holes center (15 pm location).

Abstract— It is well known that contamination of CT data with scattered radiation rednces reconstrncted CT numbers and introduces cupping artifacts in the reconstructed images. This effect is more pronounced in multi detector CT scanners with extended detector aperture mostly using cone-heam configurations, which are much less immune to scatter than fan-heam and single-slice CT scanners. Accurate... 

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