Particle induced X-ray emission (PIXE)

The principle of particle induced X-ray emission (PIXE) analysis and its medical application are described. Accelerated charged particles induce X-ray emission from the irradiated target atom due to the ionization of its inner orbital electron. Elemental analyses can be done by the characteristic X-rays, which differing from element to element. Particles such as protons are accelerated usually by the cyclotron or Van de Graaff accelerator. Emitted X-rays are measured by Si(Li) semiconductor detector which gives X-ray spectra of the target element atoms. PIXE analysis, highly sensitive to heavy elements, metals, P, S, K and Cl, is used for characterization of blood for aging and diseases and of rat tissues under normal and cancerous conditions. Micro-PIXE camera is a recent fruit, which gives the image of the distribution of intracellular elements by scanning with <1 μm particle beam. The micro-beam is produced by the static electric type accelerator, micro-slit system and quadrupolar magnets. Examples of the image of bovine endothelial cells (K, S, P and Br) and of Br kinetics given as Br-deoxyuridine are presented. The molecular imaging will be further developed from micro- to nano-PIXE. (N.I.)