Abstract: The invention provides a device for the detection and mapping of radiation, the device comprising a polymeric core (18) located within an external shell material (1), wherein the polymeric core comprises a plurality of stacked polymeric sheets comprising at least one radiation sensitive component which is sensitive to said radiation emitted by said radioactive materials and the external sheath comprises a collimation sheath (1). Preferably, the polymeric core comprises a cubic, cylindrical, spherical or truncated spherical shape which is encased within the external shell. The external shell is preferably comprised of a metal, most preferably tungsten.