Auger effect in medicine

1
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 L-shell 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

2
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 L-shell that will
be filled with M-shell electrons
The two M-shell electrons can emit two photons,
which can then knock out two more M-shell
electrons
Incident photon hits the K-shell
The L-shell electron then emits a Ka photon,
which can leave as fluorescence, or knock out
another L-shell electron
The vacancy in the K shell is filled with an
L-shell electron, creating a new vacancy
The electron gets ejected, leaving a vacancy
Electron absorbs the photon
3
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