An x-ray CT apparatus has an x-ray source which emits an x-ray beam which is displaceable relative to an examination subject, the x-ray source emitting x-rays in the form of one or more pulses during the registration of a projection. An arrangement for modulating the x-ray power sets the duration of the pulses dependent on an angle attenuation profile of the examination subject for the individual projections, such that the mAs product applied for the individual projections correspond to the curve of the angle attenuation profile.