ABSTRACT
When discussing computed tomography (CT), it is interesting and useful to review the evolution of this technology since its inception. In the early 1970s, axial scanners were first introduced. These scanners had large cables attaching the X-ray tube to the power supply (1-3). This limitation resulted in intermittent X-ray exposures (eventually as short as two seconds) and incremental table motion. With these scanners, it was difficult to obtain more than about 10 slices per minute and slices were typically on the order of 10mm in thickness. As a result, imaging of the chest and abdomen, for example, was primarily performed during the longer and more sustaining venous and/or equilibrium phases. Furthermore, since the chest and upper abdomen was scanned during multiple breath-holds, respiratory misregistration was a significant problem.
