The invention relates to a method of computed tomography wherein a radiation source moves relative to an examination zone along a helical trajectory and wherein the movement involves a rotation around a rotational axis and a shifting parallel to the rotational axis. During the movement, a detector unit acquires real measured values. Fictitious measured values are determined from the real measured values by solving John's equation for a virtual movement of the radiation source along an intersection ellipse. The intersection ellipse intersects the helical trajectory at an intersection point and is the intersection of a virtual cylindrical surface, on which the helical trajectory is situated, with an intersection plane that is defined by a tangent vector of the helical trajectory at the intersection point and a vector that is oriented perpendicular to the rotational axis. Finally, an image of the examination zone is reconstructed using the real and fictitious measured values.