A VARIABLE-RESOLUTION ROTATE-ONLY COMPUTED-TOMOGRAPHY SCANNER

The Rotoscan is a computed tomography scanner that combines the advant ages of variable geometric resolution and adjustable size of measureme nt diameter of translate-rotate scanners with the improved speed of ro tate-only scanners. Because of the small number of only 26 detectors u sed for this scanner, a special data collection scheme of multiple rot ations with interleaved detector positions was employed. In order to a void angular data interpolation after reordering of the projections fr om the fan- to a parallel-beam geometry, the detectors were incrementa lly moved at a right angle to the centerline of the fan rather than ro tated about the source. The measurement time of 40 s for one cross-sec tion is comparable to that of second-generation systems. However, for longer measurement diameters, the measurement time for second-generati on systems increases, whereas that of the Rotoscan remains constant.