This device is a gamma imagery device including: a gamma camera with an observation field, a gamma spectrometry detector collimated with a collimator with an observation field extending around an axis and that is included in the observation field of the gamma camera beyond a given distance from it; a laser pointer with a line of sight, this laser pointer being located close to the gamma spectrometry collimator, such that the line of sight is substantially parallel to the axis of the observation field of the collimator and intersects the observation field of the collimator, means for localising a zone pointed at by the laser pointer.