The future of nuclear medicine would appear to be the paradigm of personalized medicine — targeted radionuclide therapy to spare healthy tissue, and theranostic medicine, which pairs an imaging isotope with a therapeutic isotope to provide simultaneous, real-time dose delivery and verification, leading to reductions in prescribed patient dose.

Candidate isotopes to meet these needs have been identified based on their chemical and radioactive decay properties. However, there are significant uncertainties in both the reactions used to produce these radionuclides and/or the intensities and energies of their decay radiation. The Bay Area Nuclear Data (BAND) Group is currently leading a series of campaigns to perform targeted, high-priority measurements of thin-target cross sections and thick-target integral yields, as part of a larger campaign to address deficiencies in nuclear data needs. These studies will serve to support the production of clinically-relevant quantities of radioactivity.

This campaign has two goals. Primarily, we have performed multiple measurements of thin-target cross sections for proton- (≤200 MeV), deuteron- (≤50 MeV), and alpha-induced (≤90 MeV) reactions. These measurements have focused on the production of high-priority emerging therapeutic radionuclides (^58mCo, ^193mPt), as well as diagnostic radionuclides for use in theranostic pairs (⁴⁴Sc, ⁸⁶Y, ¹³⁴Ce). Additionally, we are developing improved monitor reactions for use at high-energy isotope production facilities.

The second goal has been the development of intense energetic neutron sources, for use as alternative production pathways for medical radionuclides. Both quasimonoenergetic (Li(p,n)) and broad-spectrum (deuteron breakup) sources are available to suit production needs. These have been used to demonstrate the production of high-profile radionuclides, including ⁴⁷Sc, the ⁶⁴Cu/⁶⁷Cu theranostic pair, and ²²⁵Ac. Since the range of these energetic neutrons is far larger than for charged-particle beams, production yields may be trivially increased by scaling up target thickness. Notably, the primary deuteron beams used for producing these secondary neutrons offer the potential for “simultaneous production”, reacting the primary beam on a thin (<5 MeV) target to make a desired radionuclide via (d,xn) reactions. The unreacted beam emerges to undergo breakup, using the energetic secondary neutrons for production on a different target via (n,x) reactions.

Eric Matthews

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