Hindié Elif, Köster Ulli, Champion Christophe, Zanotti-Fregonara Paolo, Morgat Clément
Department of Nuclear Medicine, University Hospital of Bordeaux, Bordeaux, F-33076, France.
University of Bordeaux, UMR CNRS 5287, INCIA, Talence, F-33400, France.
EJNMMI Phys. 2024 Nov 22;11(1):98. doi: 10.1186/s40658-024-00699-z.
Targeted radionuclide therapy with Lu-labelled small conjugates is expanding rapidly, and its success is linked to appropriate patient selection. Companion diagnostic conjugates are usually labelled with Ga, 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 (I) ≥ 15% and compared them to Ga. The radiometals included: Sc, Sc, Ti, Co, Cu, Cu, Ga, Y, Y, Nb, La, Tb and Tb. La (7.2% I) was also examined because it was recently discussed, in combination with La, as a possible diagnostic match for Ac.
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.
For each annihilation process useful for PET imaging, the total energy released (MeV) is: Ti (1.5), Sc (1.6), Cu and Cu (1.8), Ga (1.9), Sc and La (2.9), Co (3.2), Y (3.3), La (4.8), Tb (6.5), Tb (7.1), Nb (8.6), and Y (13.6). Significant amounts (≥ 10%) of ≈0.5 MeV photons that may fall into the acceptance window of PET scanners are emitted by Co, Ga, Y, Y, La, and Tb. Compton background from more energetic photons would be expected for Sc, Co, Ga, Y, Nb, La,Tb, and Tb. The mean positron ranges (mm) of Cu (0.6), Y (1.0), Ti (1.5), La (1.6), Sc and Cu (1.7), Co (2.1), Sc and Y (2.5), and Nb (2.6) were lower than that of Ga (3.6). DOTA chelation is applicable for most of the radiometals, though not ideal for Cu/Cu. Recent data showed that chelation of Ti with DOTA is feasible. Nb requires different complexing agents (e.g., DFO). Finally, they could be economically produced by proton-induced reactions at medical cyclotrons.
In particular, Sc, Ti, and Cu have overall excellent β decay-characteristics for theranostic applications complementing Lu-labelled small conjugates, and they could be sustainably produced. Like Lu, Sc, Ti and to a lesser extent Cu could be labelled with DOTA.
用镥标记的小分子偶联物进行靶向放射性核素治疗正在迅速发展，其成功与合适的患者选择有关。伴随诊断偶联物通常用镓标记，在注射后约2小时内提供良好的成像。然而，最佳的肿瘤与背景比值通常在更晚的时候才能达到。本研究考察了半衰期在3小时至24小时之间且β射线强度（I）≥15%的有前景的正电子发射放射性金属，并将它们与镓进行比较。这些放射性金属包括：钪、钪、钛、钴、铜、铜、镓、钇、钇、铌、镧、铽和铽。还对镧（I为7.2%）进行了研究，因为最近有人讨论它与镥结合作为锕的一种可能的诊断配对物。
研究了每次衰变和每个正电子的总电子和光子剂量；可能产生干扰的γ射线发射；同日成像所需注射的典型活度；正电子射程；以及可用的生产路线。
对于PET成像有用的每个湮灭过程，释放的总能量（MeV）为：钛（1.5）、钪（1.6）、铜和铜（1.8）、镓（1.9）、钪和镧（2.9）、钴（3.2）、钇（3.3）、镧（4.8）、铽（6.5）、铽（7.1）、铌（8.6）和钇（13.6）。钴、镓、钇、钇、镧和铽会发射大量（≥10%）能量约为0.5 MeV的光子，这些光子可能落入PET扫描仪的接受窗内。钪、钴、镓、钇、铌、镧、铽和铽预计会产生来自能量更高光子的康普顿本底。铜（0.6）、钇（1.0）、钛（1.5）、镧（1.6）、钪和铜（1.7）、钴（2.1）、钪和钇（2.5）以及铌（2.6）的平均正电子射程（mm）低于镓（3.6）。DOTA螯合适用于大多数放射性金属，不过对铜/铜不太理想。最新数据表明钛与DOTA的螯合是可行的。铌需要不同的络合剂（如DFO）。最后，它们可以通过医用回旋加速器的质子诱导反应经济地生产出来。
特别是，钪、钛和铜对于与镥标记的小分子偶联物互补的治疗诊断应用具有总体优异的β衰变特性，并且它们可以可持续生产。与镥一样，钪、钛以及程度稍低的铜可以用DOTA标记。
