Patent ID: 7548603

Claim:
A computed tomography method which comprises the steps of: generating, using a radiation source, a conical radiation beam which traverses an examination zone or an object present therein, generating a relative motion of the radiation source about the examination zone, which relative motion comprises a rotation about an axis of rotation and a displacement parallel to the axis of rotation and is shaped as a helix, acquiring measuring values which are dependent on the intensity of the radiation beam that traverses the examination zone and is incident on a detector unit during the relative motions, and reconstructing a CT image of the examination zone from the measuring values, in which reconstruction of an exact 3D back projection comprising the following steps is carried out: determining the partial derivative of measuring values of parallel rays with different radiation source positions in conformity with the angular position of the radiation source, performing a weighted integration of the partial derivative of the measuring values along K lines, multiplying the integrated partial derivative of the measuring values by a first weighting factor which corresponds to the cosine of the cone angle of the ray associated with the measuring values and by a second weighting factor which corresponds to the reciprocal value of the cosine of a fan angle of the beam associated with the measuring values, and reconstructing the absorption of each object point by back projection of the weighted, integrated partial derivative of the measuring values.