A direct-converting x-ray radiation detector is disclosed for detecting x-ray radiation, in particular for use in a CT system. In an embodiment, the detector includes a semiconductor material used for detecting the x-ray radiation; at least one collimator; and at least one radiation source, to irradiate the semiconductor material with additional radiation. In at least one embodiment, the at least one collimator includes at least one reflection layer on a side facing the semiconductor material, on which the additional radiation is reflected to the semiconductor material. In another embodiment, a CT system including the direct-converting x-ray radiation detector, and a method for detecting incident x-ray radiation via a direct-converting x-ray radiation detector, in particular for use in a CT system, are disclosed.