3-D image reconstruction of physical magnitudes inside bodies - creating position-electron pairs and reconstructing annihilation photon emission point from detection coordinates

摘要

Obtaining a 3-d image of physical magnitudes, partic. density within an object uses a beam of photons of energy E gamma >=1.022 MeV to create positron-electron pairs within the object. The positrons lose their energy and are annihilated on cassation. The two annihilation photons are emitted and can be detected in coincidence. The procedure allows the point of emission of the photons to be reconstructed in space from the detection coordinates. Knowing the path of the positrons in the body construction of 3-D image which gives information about the chemical compsn. and the density in the body. The appts. incorporates a cylindrical beam of gamma-photons of dia. 5 mm, a system which allows relative movement of object and beam and a system of two photon detectors. The technique is partic. of value in the medical field, giving information on the localisation and physical properties of tissues, normal or pathological. The technique gives good performance in that it gives a 3-D image of the density of tissues with a resolution 1 mm, an image reconstruction time 1 min, a local radiation does 0.5 rad and in the case of lungs, increased contrast and the possibility of observing the dynamics of breathing.