The system of pixel detectors can be arranged in layers forming a 3D matrix of sensitive elements - voxels. Such voxel detector can effectively record tracks of energetic particles. By proper analysis of these tracks it is possible to determine the type, direction and energy of the primary particle. The primary application of such device is localization and identification of gamma and neutron sources in the environment. This method can be used also for emission and transmission radiography and it is applicable in many fields where image integrating devices are currently utilized. This method improves qualitative properties of current methods such as: spatial resolution, efficiency, direction sensitivity, energy sensitivity and selectivity (background suppression). The work will be performed in collaboration with foreign partners involved in design of pixel detectors.