The invention provides a switchable photomultiplier switchable between a detecting state and a non-detecting state including a cathode upon which incident radiation is arranged to impinge. The photomultiplier also includes a series of dynodes arranged to amplify a current created at the cathode upon detection of photoradiation. The invention also provides a detection system arranged to detect radiation-emitting material in an object. The system includes a detector switchable between a detecting state in which the detector is arranged to detect radiation and a non-detecting state in which the detector is arranged to not detect radiation. The system further includes a controller arranged to control switching of the detector between the states such that the detector is switched to the non-detecting state while an external radiation source is irradiating the object.