The invention relates to a combined imaging detector for detection of gamma and x-ray quanta comprising an x-ray detector (31) for generating x-ray detection signals in response to detected x-ray quanta and a gamma detector (32) for generating gamma detection signals in response to detected gamma quanta. The x-ray detector (31) and the gamma detector (32) are arranged in a stacked configuration along a radiation-receiving direction (33). The gamma detector (32) comprises a gamma collimator plate (320) comprising a plurality of pinholes (321), and a gamma conversion layer (322, 324) for converting detected gamma quanta into gamma detection signals.