A computer tomograph, a method, and a computer program product are disclosed. A computer tomograph is disclosed for scanning an image of at least one examination region of a patient, including a scanning unit which can be rotated about a longitudinal axis. The scanning unit includes an X-ray detector and an X-ray emitter. The extension of an X-ray beam emitted by the X-ray emitter is controlled for scanning purposes along the longitudinal axis using at least one patient-dependent control signal. By controlling the extension of the X-ray beam, the dose applied to the patient is also controlled such that the dose can be used as efficiently as possible. The control further allows the pitch to be matched to the patient-dependent control signal while scanning in the spiral mode.
