Comparative analysis of positron emitters for theranostic applications based on small bioconjugates highlighting 43Sc, 61Cu and 45Ti
EJNMMI Phys. 2024-11-22; 11(1):
DOI: 10.1186/s40658-024-00699-z
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1. EJNMMI Phys. 2024 Nov 22;11(1):98. doi: 10.1186/s40658-024-00699-z.
Comparative analysis of positron emitters for theranostic applications based on
small bioconjugates highlighting (43)Sc, (61)Cu and (45)Ti.
Hindié E(1)(2)(3), Köster U(4), Champion C(5), Zanotti-Fregonara P(6), Morgat
C(7)(8).
Author information:
(1)Department of Nuclear Medicine, University Hospital of Bordeaux, Bordeaux,
F-33076, France.
(2)University of Bordeaux, UMR CNRS 5287, INCIA, Talence, F-33400, France.
(3)Institut Universitaire de France (IUF), Paris, F-75000, France.
(4)Institut Laue-Langevin, Grenoble, F-38042, France.
(5)University of Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et
Applications), UMR 5107, Talence, F-33405, France.
(6)Perceptive Inc, Needham, MA, USA.
(7)Department of Nuclear Medicine, University Hospital of Bordeaux, Bordeaux,
F-33076, France. .
(8)University of Bordeaux, UMR CNRS 5287, INCIA, Talence, F-33400, France.
.
BACKGROUND: Targeted radionuclide therapy with 177Lu-labelled small conjugates
is expanding rapidly, and its success is linked to appropriate patient
selection. Companion diagnostic conjugates are usually labelled with 68Ga,
offering good imaging up to ≈2 h post-injection. However, the optimal
tumor-to-background ratio is often reached later. This study examined promising
positron-emitting radiometals with half-lives between 3 h and 24 h and β+
intensity (Iβ+) ≥ 15% and compared them to 68Ga. The radiometals included: 43Sc,
44Sc, 45Ti, 55Co, 61Cu, 64Cu, 66Ga, 85mY, 86Y, 90Nb, 132La, 150Tb and 152Tb.
133La (7.2% Iβ+) was also examined because it was recently discussed, in
combination with 132La, as a possible diagnostic match for 225Ac.
METHODS: Total electron and photon doses per decay and per positron; possibly
interfering γ-ray emissions; typical activities to be injected for same-day
imaging; positron range; and available production routes were examined.
RESULTS: For each annihilation process useful for PET imaging, the total energy
released (MeV) is: 45Ti (1.5), 43Sc (1.6), 61Cu and 64Cu (1.8), 68Ga (1.9), 44Sc
and 133La (2.9), 55Co (3.2), 85mY (3.3), 132La (4.8), 152Tb (6.5), 150Tb (7.1),
90Nb (8.6), and 86Y (13.6). Significant amounts (≥ 10%) of ≈0.5 MeV photons that
may fall into the acceptance window of PET scanners are emitted by 55Co, 66Ga,
85mY, 86Y, 132La, and 152Tb. Compton background from more energetic photons
would be expected for 44Sc, 55Co, 66Ga, 86Y, 90Nb, 132La,150Tb, and 152Tb. The
mean positron ranges (mm) of 64Cu (0.6), 85mY (1.0), 45Ti (1.5), 133La (1.6),
43Sc and 61Cu (1.7), 55Co (2.1), 44Sc and 86Y (2.5), and 90Nb (2.6) were lower
than that of 68Ga (3.6). DOTA chelation is applicable for most of the
radiometals, though not ideal for 61Cu/64Cu. Recent data showed that chelation
of 45Ti with DOTA is feasible. 90Nb requires different complexing agents (e.g.,
DFO). Finally, they could be economically produced by proton-induced reactions
at medical cyclotrons.
CONCLUSION: In particular, 43Sc, 45Ti, and 61Cu have overall excellent β+
decay-characteristics for theranostic applications complementing 177Lu-labelled
small conjugates, and they could be sustainably produced. Like Lu, 43Sc, 45Ti
and to a lesser extent 61Cu could be labelled with DOTA.
© 2024. The Author(s).
DOI: 10.1186/s40658-024-00699-z
PMCID: PMC11582248
PMID: 39572444
Conflict of interest statement: Declarations. Competing interests: The authors
have no conflict of interest to disclose, financial or otherwise.