Details

Autor(en) / Beteiligte

• Habs, D.
• Köster, U.

Titel

Production of medical radioisotopes with high specific activity in photonuclear reactions with γ-beams of high intensity and large brilliance

Ist Teil von

• Applied physics. B, Lasers and optics, 2011-05, Vol.103 (2), p.501-519

Ort / Verlag

Berlin/Heidelberg: Springer-Verlag

Erscheinungsjahr

2011

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We study the production of radioisotopes for nuclear medicine in ( γ , x n+ y p) photonuclear reactions or ( γ , γ ′) photoexcitation reactions with high-flux [(10 13 –10 15 ) γ /s], small diameter ∼(100 μm) 2 and small bandwidth (Δ E / E ≈10 −3 –10 −4 ) γ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion, x n+ y p) reactions with (ion = p,d, α ) from particle accelerators like cyclotrons and (n, γ ) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow γ -beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). However, for ions with a strong atomic stopping only a fraction of less than 10 −2 leads to nuclear reactions resulting in a target heating, which is at least 10 5 times larger per produced radioactive ion and often limits the achievable activity. In photonuclear reactions 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 γ excitation may make use of the fine structure of the Pygmy Dipole Resonance (PDR) or fluctuations in γ -width leading to increased cross sections. Within a rather short period compared to the isotopic half-life, a target area of the order of (100 μm) 2 can be highly transmuted, resulting in a very high specific activity. ( γ , γ ′) isomer production via specially selected γ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground state occurs. We discuss in detail many specific radioisotopes for diagnostics and therapy applications. Photonuclear reactions with γ -beams allow to produce certain radioisotopes, e.g. 47 Sc, 44 Ti, 67 Cu, 103 Pd, 117 m Sn, 169 Er, 195 m Pt or 225 Ac, with higher specific activity and/or more economically than with classical methods. This will open the door for completely new clinical applications of radioisotopes. For example 195 m Pt could be used to verify the patient’s response to chemotherapy with platinum compounds before a complete treatment is performed. Also innovative isotopes like 47 Sc, 67 Cu and 225 Ac could be produced for the first time in sufficient quantities for large-scale application in targeted radionuclide therapy.