A miniature X-ray source (10) for high dose rate brachytherapy that can be operated in a wide range of operating directions (76) in the presence of a strong magnetic field (B), such as, for instance, the static magnetic field (B) of an MR scanner, with at least one anode (12) and at least one cathode (14), wherein in an operative state, an electric field (18) between the anode (12) and the cathode (14) is essentially spherically symmetric in at least a continuous solid angle of more than π/2 sr about a center (16) of the cathode (14) a brachytherapy system, comprising at least one said miniature X-ray source (10), and a method for generating a beam (82) of X-ray radiation inside an outer magnetic field (B) or an operative MR scanner with said miniature X-ray source (10).
