Tomography with fast neutrons

Medical imaging typically makes use of x rays, magnetic fields, ultrasound, or radioactive isotopes. At the July meeting in Pittsburgh of the American Association of Physicists in Medicine, Duke University researchers presented the first three-dimensional transaxial tomographic pictures—of an inorganic test object—from a new technique called neutron stimulated emission computed tomography (NSECT), which employs neutrons having energies between 1 and 10 MeV. Neutrons are highly penetrating and can therefore image deeply buried structures, for example in humans: Neutrons excite the nuclei of atoms, which then emit characteristic gamma rays that can be used to both locate and identify the nuclei. Fast neutron analysis (FNA) has been used for more than 10 years to identify hidden substances, such as explosives or contraband, by their atomic composition. FNA, though, generally does not require 3D reconstructions. As a proof-of-principle that neutron tomography can distinguish between two elements, Carey Floyd presented reconstructed images of...