Transcript Auger Effect in Biomedicine

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