Development of novel positron emitters for medical applications: nuclear and radiochemical aspects

Abstract

AbstractIn molecular imaging, the importance of novel longer lived positron emitters, also termed as non-standard or innovative PET radionuclides, has been constantly increasing, especially because they allow studies on slow metabolic processes and in some cases furnish the possibility of quantification of radiation dose in internal radiotherapy. Considerable efforts have been invested worldwide and about 25 positron emitters have been developed. Those efforts relate to interdisciplinary studies dealing with basic nuclear data, high current charged particle irradiation, efficient radiochemical separation and quality control of the desired radionuclide, and recovery of the enriched target material for reuse. In this review all those aspects are briefly discussed, with particular reference to three radionuclides, namely64Cu,124I and86Y, which are presently in great demand. For each radionuclide several nuclear routes were investigated but the (p,n) reaction on an enriched target isotope was found to be the best for use at a small-sized cyclotron. Some other positron emitting radionuclides, such as55Co,76Br,89Zr,82mRb,94mTc,120I,etc., were also producedviathe low-energy (p,n), (p,α) or (d,n) reaction. On the other hand, the production of radionuclides52Fe,73Se,83Sr,etc.using intermediate energy (p,xn) or (d,xn) reactions needs special consideration, the nuclear data and chemical processing methods being of key importance. In a few special cases, a high intensity3He- orα-particle beam could be an added advantage. The production of some potentially interesting positron emittersviagenerator systems, for example44Ti/44Sc,72Se/72As and140N d/140Pr is considered. The significance of new generation high power accelerators is briefly discussed.