Reconstruction from Fan-beam Projections

Abstract

The limitations of CT scanner projection systems that used parallel beams of radiation had become a major obstacle to the development of computed tomography. In order to overcome these growing technical barriers, engineers searched for solutions that used a single X-ray tube in which the radiation was collimated into a narrow beam in the shape of a fan (a fan-beam). This increased the speed with which each projection was carried out, as it eliminated unnecessary lateral movement of the tube-detector system. At the same time, it made more efficient use of the power emitted by the tube; the beam angle of the radiation was significantly increased compared to previous designs resulting in a shorter radiation exposure time for the patient and the distortions due to patient movement were minimised. This solution represents essentially a compromise between the simplicity of the projection system and an increase in the speed of the scanner.