Use of multiple CT scans to accommodate large objects and stretch dynamic range of detectability

摘要

Rotate-only X-ray CT scanners are preferred for their speed and dose utilization, but suffer from the restriction that the scanned object must fit within the radiation beam. In addition, the ratio of signals unattenuated by air paths to those penetrating thick, dense objects often exceeds the dynamic range of conventional X-ray detectors. Both of these disadvantages can be removed for objects larger than the X-ray beam by taking multiple scans, each of which exposes only part of the object. These partial data sets can then be merged to produce a complete data set. For most objects, it is also possible to separately expose regions in which the ratios between the extremes of attenuation are much lower than that between air and the maximum path length. It is therefore possible to use a higher flux to image denser regions, improving signal-to-noise ratios and yielding images superior to those of larger scanners having the same dynamic range.