Patent ID: 6240157
Filing Date: 2001-05-29
Classification: A61B,G06T

Abstract:
A method for three-dimensional tomographic imaging of long objects, including the steps of:subjecting the long object to be imaged to simultaneous translation and rotation relative to a cone-beam ray source and a two-dimensional detector limited to a window opposite to the cone-beam ray source, where this window is constrained to correspond to a surface area shaped as a parallelogram attached to a cylinder centered at an axis of rotation and passing through the cone-beam ray source,defining a height of the window measured along the length of the cylinder to equal a pitch of a helix and a width of the window such that a maximum width of the long object to be reconstructed is covered,determining an upper and lower boundary of the window to coincide with two consecutive turns of the source path relative to the fixed long object, andcarrying out a reconstruction procedure comprising the steps of:pre-weighting with a factor that depends on an angle of a ray that gave rise to a specific detector value,filtering with a ramp-filter horizontally or near horizontally across the detector, andback projecting with a magnification factor along the direction of a plurality of rays that gave rise to a plurality of original detector values,wherein the actual pre-weighting, the actual filter design, and the actual magnification factor depend on the physical embodiment given to the detector and a step of rebinning that has been employed with the detected data.