D. Habs, P. G. Thirolf, C. Lang, M. Jentschel, U. Köster, F. Negoita, V. Zamfir
We study the production of radioisotopes for nuclear medicine in
(gamma,gamma') photoexcitation reactions or (gamma,xn + yp) photonuclear
reactions for the examples of ^195mPt, ^117mSn and ^44Ti with high flux [(10^13
- 10^15) gamma/s], small beam diameter and small energy band width (Delta E/E ~
10^-3 -10^-4) gamma beams. In order to realize an optimum gamma-focal spot, a
refractive gamma-lens consisting of a stack of many concave micro-lenses will
be used. It allows for the production of a high specific activity and the use
of enriched isotopes. For photonuclear reactions with a narrow gamma beam, the
energy deposition in the target can be reduced by using a stack of thin target
wires, hence avoiding direct stopping of the Compton electrons and e^+e^-
pairs. The well-defined initial excitation energy of the compound nucleus leads
to a small number of reaction channels and enables new combinations of target
isotope and final radioisotope. The narrow-bandwidth gamma excitation may make
use of collective resonances in gamma-width, leading to increased cross
sections. (gamma,gamma') isomer production via specially selected gamma
cascades allows to produce high specific activity in multiple excitations,
where no back-pumping of the isomer to the ground state occurs. The produced
isotopes will open the way for completely new clinical applications of
radioisotopes. For example ^195mPt could be used to verify the patient's
response to chemotherapy with platinum compounds before a complete treatment is
performed. In targeted radionuclide therapy the short-range Auger and
conversion electrons of ^195mPt and ^117mSn enable a very local treatment. The
generator ^44Ti allows for a PET with an additional gamma-quantum (gamma-PET),
resulting in a reduced dose or better spatial resolution.
View original:
http://arxiv.org/abs/1202.2238
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