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Positron emission tomography (PET) uses radiation emitted from tagged physiologically participative radiopharmaceuticals to provide detailed physiological images of in-vivo processes. The decay of these positron emitting tracer radionuclides injected into a subject provides two 511 keV annihilation gamma rays that can be detected and used to construct tomographic images. The most common radionuclides used to synthesize these tagged radiopharmaceuticals (11C., 13N, 15O and 18F) are short-lived and are made only by bombarding appropriate targets with accelerated ion beams. The most common ion beam used for this purpose is protons, although deuterons and 3He ion beams can also be used. Deuterons with modest energies (3 to 4 MeV) are most useful for the 14N(d, n)15O reaction, while higher energy deuterons have been used primarily for the 20Ne(d, α)18F reaction. The use of 3He ions at energies as low as 8 MeV to produce all four of the common PET isotopes is also a viable production technique. All of these ion beams can be generated by a class of new compact rf linear accelerator (linac) based on Radio Frequency Quadrupole (RFQ) technology. |
