Abstract: A device and a method for determining the interaction position and energy measurement of a radiation detector. A plurality of waveshifting optical fiber are positioned on the surface of a scintillator which is subjected to incident radiation causing the release of photons of a first wavelength from the scintillator which are absorbed by the optical fiber with a portion of the released photons being reemitted from one end of the fibers. The reemitted photons are measured and the centroid of the distribution of these measured photons is determined in order to provide an indication of the interaction position of incident radiation. A measurement of photons generated by the incident radiation which pass through the fibers but which are not transported down said fibers provide an indication of the energy of the incident radiation.