The Medipix sensor is a pixel detector that uses LHC-style sensors and electronics to detect the position, time and energy of particles. One application is the ability to take colour X-rays. Another is in dosimetry, where UCD physicists in collaboration with St. Vincent's hospital are investigating its potential. The plot shows the (raw and corrected) energy spectrum obtained with Cobalt-57. The peak at 122 keV is due to gamma-ray emission from the nucleus.