Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with $\gamma$ Beams of High Intensity and Large Brilliance

摘要

We study the production of radioisotopes for nuclear medicine in$(\gamma,x{\rm n}+y{\rm p})$ photonuclear reactions or ($\gamma,\gamma'$)photoexcitation reactions with high flux [($10^{13}-10^{15}$)$\gamma$/s], smalldiameter $\sim (100 \, \mu$m$)^2$ and small band width ($\Delta E/E \approx10^{-3}-10^{-4}$) $\gamma$ beams produced by Compton back-scattering of laserlight from relativistic brilliant electron beams. We compare them to (ion,$x$n$+ y$p) reactions with (ion=p,d,$\alpha$) from particle accelerators likecyclotrons and (n,$\gamma$) or (n,f) reactions from nuclear reactors. Forphotonuclear reactions with a narrow $\gamma$ beam the energy deposition in thetarget can be managed by using a stack of thin target foils or wires, henceavoiding direct stopping of the Compton and pair electrons (positrons).$(\gamma,\gamma')$ isomer production via specially selected $\gamma$ cascadesallows to produce high specific activity in multiple excitations, where noback-pumping of the isomer to the ground state occurs. We discuss in detailmany specific radioisotopes for diagnostics and therapy applications.Photonuclear reactions with $\gamma$ beams allow to produce certainradioisotopes, e.g. $^{47}$Sc, $^{44}$Ti, $^{67}$Cu, $^{103}$Pd, $^{117m}$Sn,$^{169}$Er, $^{195m}$Pt or $^{225}$Ac, with higher specific activity and/ormore economically than with classical methods. This will open the way forcompletely new clinical applications of radioisotopes. For example $^{195m}$Ptcould be used to verify the patient's response to chemotherapy with platinumcompounds before a complete treatment is performed. Also innovative isotopeslike $^{47}$Sc, $^{67}$Cu and $^{225}$Ac could be produced for the first timein sufficient quantities for large-scale application in targeted radionuclidetherapy.