A radiation detector is disclosed, including a plurality of detector elements arranged adjacent to one another in a planar manner. In an embodiment, for the purpose of radiation detection, a semiconductor layer with an upper side and a lower side is present, the semiconductor layer on one of the sides including an electrode embodied so as to extend across a number of detector elements and electrodes subdivided into individual electrodes being arranged on the other side of the semiconductor layer so that by applying voltage between the electrodes of the two sides, an electrical field is generatable and each individual electrode is assigned an effective volume so as to collect charge in the semiconductor layer. In an embodiment, the individual electrodes are alternately connected to at least two different voltage potentials. Furthermore, a medical diagnostic system is disclosed, including at least one such radiation detector.