Auger effect in medicine • The Auger effect refers to the ejection of electrons from an atom following ionization of inner-shell electrons • It is usually initiated by X-ray photoionization of K-shell or Lshell electrons. • In heavy high-Z atoms up to 20 Auger electrons may be ejected (see Table 5.3 of Atomic Astrophysics and Spectroscopy (AAS) Pradhan and Nahar, Cambridge University Press, 2011) • Special cases of Auger transitions are known as Coster-Kronig and Super-Coster-Kronig transitions (see Fig. 5.11 of AAS , as animated in the second slide) • It may be highly effective in cancer treatment using high-Z material or nanoparticles delivered to the tumor and irradiated by X-rays (animated in the third slide) • Auger electrons from high-Z atoms can kill malignant cells Auger Radiation and Electron cascades (“Atomic Astrophysics and Spectroscopy”, Anil Pradhan & Sultana Nahar, Cambridge U. Press 2011) This leaves us with four vacancies in the M-shell that will continue this increasing cascade of electron ejection throughout the atom We now have 2 vacancies in the LThe two M-shell electrons shell that will be can emit two photons, which filled with M-shell can then knock out two more electrons M-shell electrons Incident The vacancy Theinelectron photon hits the K shellgets is filled ejected, the K-shell with an L-shell leaving a electron, creating vacancy a new vacancy Electron absorbs the photon The L-shell electron then emits a Kα photon, which can leave as fluorescence, or knock out another L-shell electron Monoenergetic X-Ray Irradiation of High-Z Nanoparticles for Imaging and Therapy: “Resonant Nano-Plasma Theranostics (RNPT)” (Pradhan et. al., Proc. XVth Int. Conf. Comp. Rad., V.2, p89, 2007) Particles return to the ground state and emit light Burst of monochromatic x-rays Particles absorb X-rays and excite/ionize X-rays that are transmitted are detected