Patent ID: 7978810
Filing Date: 2011-07-12
Classification: A61B,G06T

Abstract:
1. An imaging method for variable pitch spiral CT, comprising: spirally scanning an examination object lying on a patient table, with the aid of a beam emanating from at least one focus, and with the aid of a 2 dimensional detector arrangement lying opposite the focus, the detector arrangement supplying record data; rebinning the record data to output data, the output data being in parallel geometry and representing an attenuation of the beams during passage through the examination object; filtering the output data; weighted back-projecting the filtered output data; and visualizing at least one of a layer and a volume on a display unit based upon the weighted back projected output data, a non constant pitch of the spiral scanning being taken into account computationally during the back projection, and the non constant pitch being described in the form of a function that describes a location of the patient table as a function of a focus angle, and function being expressed by a mathematical relationship between a projection angle, a column coordinate of the detector arrangement and a radius of the spiral, the mathematical relationship being approximated via one of the following, a first approximation taking account of the actual position of a parallel projection and of the current pitch of the spiral and basing a local linearization of the spiral profile thereon, a second approximation taking account of the actual position of a parallel projection and of the current pitch of the spiral and basing an approximation of the spiral profile in the form of an average pitch thereon, or a third approximation being implemented by an approximation of the position of a parallel projection and of the current pitch of the spiral by way of an average pitch and an effective initial position of the focus angle.