Stimulated positron emission for 3-D tomographic imaging and bone studies. I. Method feasibility and system considerations

The feasibility and inherent performance parameters of a novel method of 3-D tomographic imaging have been studied analytically. A cross section in the patient´s body is excited by high-energy X-rays ( hv>1.022 MeV) to produce positron-electron pairs. The resulting annihilation quanta are detected in coincidence by two detectors placed on opposite sides of the irradiated slice. Following a coincidence, the annihilation point is determined as the intersection of the line defined by the annihilation pair and the irradiated plane. Since the photon cross section for pair production interactions is proportional to the square of the atomic number of the absorber the image thus formed will be sensitive to atomic number and density of tissues in the irradiated slice. This technique is unique among other tomographic imaging modalities in its direct 3-D imaging capability. The application of the technique has been studied for imaging using contrast agents, and bone studies; in particular, osteoporosis and ostemalacia