Scans with dynamically collimated beam and with non-coaxial field of view. Local tomography.Dynamic collimation Typically x-ray beam is collimated (restricted) such way that there are no direct rays missing the detector. However sometimes a required field of view is relatively small and in most cases is not coaxial with the axis of rotation. A requirement of illumination only field of view causes a necessity of moving collimator blades Dynamically collimated viewsDynamic collimationAngular dependent projection cropping Dynamic (angular dependent) collimation results into partially illuminated views where exposed area gets different positions from projections to projection. A direct utilization of such data causes major artifacts. To avoid this it is needed to involve information about exposed area position within every view. So the software might take it into account by internal cutting off (cropping) all non-relevant pixels. There are two .bin files in Cobra for describing this processing mode. Local tomography Dynamic collimation typically leaves a substantial part of the object outside field of view. This situation is well known in CT as object protrusion. Cobra incorporates a special algorithm Dynamic slice scale calibration to mitigate related artifacts |
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Describing a reconstruction task
Defining position dependent cropping