Partial scan with shifted detector: A novel weighting function for high temporal resolution in CT

摘要

The size of the field of measurement (FOM) in computed tomography is limited by the size of the x-ray detector. To enlarge the FOM one may laterally shift the detector by up to 50% of its size and apply well-known weighting functions to the rawdata prior to convolution and backprojection. In this case a full scan is required to obtain complete data though there is a small region, the inner FOM, that is covered redundantly and where a partial scan reconstruction may be sufficient. We propose a new weighting function that allows to reconstruct partial scans in that inner FOM while it reconstructs full scan or overscan data for the outer FOM that contains no redundancies. Thereby we can achieve a high temporal resolution in the inner FOM while maintaining truncation-free images for the outer part. Our approach is evaluated with simulated data using the geometry of a dual source micro-CT scanner with rotating gantry. The result is a doubled temporal resolution in the inner FOM without loss of image quality due to truncation or transition artifacts. Noise and spatial resolution in the inner FOM are equal to reconstructions using a detector that fully covers the FOM. The partial scan window can be arbitrarily shifted in the angular direction, which corresponds to shifting the temporal window of the data shown in the inner FOM. This feature allows dynamic CT studies with high temporal resolution and shifted detector and to reduce patient dose.