Abstract: An apparatus for measuring the density or the like of an object from the level of transmission through the object of gamma rays having different energy levels which are transmitted at the object by a gamma source having a predetermined solid angle of transmission. A collimator collimates gamma transmitted through the object and a scintillator generates light corresponding to the output of the collimator. Plural photomultipliers generate position-dependent electrical signals corresponding to the light generated by an incident gamma ray photon to the scintillator. A calculating circuit generates a density spectrum for the object from the position-dependent electrical signals by integrating the position-dependent electrical signals corresponding to each of the incident gamma ray photons to the scintillator.

Abstract: Apparatus for measuring the density of vertebrae or the like, comprises gamma ray emission means for emitting gamma rays within a predetermined target area; detecting means for detecting the gamma rays passing through the target area; and rotatable positioning means between the emission means and the detecting means for supporting a subject and exposing the subject to the gamma rays in the target area at a plurality of different angles.