1. A method for determining an abort criterion during acquisition of a plurality of two-dimensional images of a three-dimensional subject, comprising the steps of: irradiating a subject with x-rays from an x-ray source at a plurality of positions of said x-ray source relative to the subject and, for each position of said x-ray source, acquiring two-dimensional image data of the subject corresponding to attenuation of the x-rays by the subject, with a radiation detector at a plurality of positions of the radiation detector respectively correlated to the position of the x-ray source; using the respective positions of the x-ray source and the radiation detector, automatically electronically determining, as said two-dimensional image data are acquired for the respective positions, whether a three-dimensional image reconstruction of the subject is possible from an accumulated amount of said two-dimensional image data; and electronically determining an abort criterion, which ceases irradiation of the subject, to be fulfilled as soon as said three-dimensional image reconstruction of the subject is possible.