EXACT CONE-BEAM CT WITH A SPIRAL SCAN

A method is developed which makes it possible to scan and reconstruct an object with cone beam x-rays in a spiral scan path with area detect ors much shorter than the length of the object. The method is mathemat ically exact. If only a region of interest of the object is to be imag ed, a top circle scan at the top level of the region of interest and a bottom circle scan at the bottom level of the region of interest are added. The height of the detector is required to cover only the distan ce between adjacent turns in the spiral projected at the detector. To reconstruct the object, the Radon transform for each plane intersectin g the object is computed from the totality of the cone beam data. This is achieved by suitably combining the cone beam data taken at differe nt source positions on the scan path; the angular range of the cone be am data required at each source position can be determined easily with a mask which is the spiral scan path projected on the detector from t he current source position. The spiral scan algorithm has been success fully validated with simulated cone beam data.