A radiation detector assembly is provided that includes a semiconductor detector, a collimator, plural pixelated anodes, and at least one processor. The collimator has openings defining pixels. Each pixelated anode is configured to generate a primary signal responsive to reception of a photon and to generate at least one secondary signal responsive to reception of a photon by at least one surrounding anode. Each pixelated anode includes a first portion and a second portion located in different openings of the collimator. The first portion is configured as a collecting portion having a collecting area, and the second portion is configured as a non-collecting portion having a non-collecting area that has a different size from the collecting area. The at least one processor is configured to determine a location for the reception of a photon using a primary signal and at least one secondary signal.