Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Chemical separation of theranostic radionuclide 111 Ag produced innat
Pd(d, x)111 Ag reactions
K. Ooe,∗1,∗2 T. Watabe,∗1,∗2 Y. Shirakami,∗2 D. Mori,∗3 T. Yokokita,∗3 Y. Komori,∗3 H. Haba,∗3 andJ. Hatazawa∗2,∗4

∗1
∗2
∗3∗4

1 M HNO3 Conc. HNO350
Eluted radioactivity/%

Silver-111 (111 Ag, T1/2 = 7.45 d) is a candidate
radionuclide for theranostics (therapeutics + diagnosis). The nuclide emits β-particles (maximum β energy:1036.8 keV), which can be applied to tumor therapy,and γ-rays with energies of 342 keV (branching ratio:7%) and 245 keV (branching ratio: 1.33%), which canbe used for imaging by single photon emission computed tomography (SPECT). However, 111 Ag has beenrarely applied in the ﬁeld of nuclear medicine. Toward
the nuclear medical use of 111 Ag, we previously measured the production cross sections of nat Pd(d, x)111 Ag
reactions.1) The energy at the peak of the excitation
function of the nat Pd(d, x)111 Ag reactions was approximately 9 MeV with a cross section of approximately
40 mb, which is consistent with the reported results.2–4)
In this study, 111 Ag was chemically separated froma metallic nat Pd target through anion-exchange chromatography for future nuclear medical application of111
Ag.
111
Ag was produced by irradiating a stack of 6 metallic nat Pd foils (purity: 99.95%, thickness: 0.10 mm, Nilaco Corp., Japan) with a 24-MeV deuteron beam fromthe RIKEN K70 AVF Cyclotron. The average beam intensity was approximately 200 nA, and the irradiation
time was 30 min. After irradiation, one of the irradiated nat Pd targets was dissolved in a mixed HNO3and HCl solution. After evaporation to dryness, theresidue was dissolved in 1 M HNO3 solution and thenfed into an anion exchange column (Muromac 1 × 8,
200–400 mesh, NO−3 form, Φ10 mm × 11 cm). Firstly,111
Ag was eluted by 1 M HNO3 solution. According tothe literature,5) Ag shows no adsorption in 1 M HNO3
solution on an anion-exchange resin, while Pd adsorbs
on the resin. After the elution of 111 Ag, nat Pd wasstripped by concentrated HNO3 solution. Each eluted
fraction (approximately 1 mL) was subjected to γ-ray
spectrometry with a Ge detector for determining 111 Ag
radioactivity by using the 342-keV γ peak of 111 Ag. Because this γ peak was partly overlapped by the 345-keVγ peak of 105 Ag (T1/2 = 41.29 d), which was simultaneously produced in the nat Pd(d, x) reactions, the area of
the 342-keV γ peak of 111 Ag was calculated by Gaussian ﬁtting. The elution behavior of nat Pd was checkedusing the 172-keV γ peak of 111m Pd (T1/2 = 5.5 h),which was also produced in the nat Pd(d, x) reactions.
Figure 1 shows the elution curves of 111 Ag andDepartment of Nuclear Medicine and Tracer Kinetics, Osaka
University Graduate School of Medicine
Institute for Radiation Sciences, Osaka University
RIKEN Nishina Center
Research Center for Nuclear Physics, Osaka University- 196 -Ag-111
Pd-111m

4030201000102030
Elution volume/mL40Fig. 1. Elution curves of 111 Ag and 111m Pd in anionexchange chromatography.
111m

Pd obtained in this study. The elution of 111 Ag by
1 M HNO3 solution started from fraction #11 and almost ﬁnished at fraction #16 before the start of elutionof 111m Pd, showing the clear separation of 111 Ag fromthe nat Pd target. By changing the eluent to concentrated HNO3 after fraction #20, the elution of 111m Pdstarted from fraction #28. Very little 111 Ag and 111m Pd
radioactivities remained on the anion-exchange column
after completion of the separation. The recovery yieldsof 111 Ag and 111m Pd were approximately 99% and 98%,
respectively. This high yield for 111 Ag is quite suitable
for nuclear medical use, which requires large radioactivity for tumor therapy. Because many radioactive isotopes of Ag are produced in the nat Pd(d, x) reactions,the use of an enriched 110 Pd target is essential for theselective production of 111 Ag in the 110 Pd(d, 2n)111 Ag
reactions. However, enriched 110 Pd targets are quite
expensive, and it is important to recycle the 110 Pd target after the separation of 111 Ag. Therefore, the highrecovery yield for 111m Pd obtained in this study is alsofavorable for the separation of 111 Ag in medical use.
The present results will lead to preclinical studies oftherapeutic eﬀects with 111 Ag.
References
1) K. Ooe et al., RIKEN Accel. Prog. Rep. 52, 195 (2019).
2) A. Hermanne et al., Nucl. Instrum. Methods Phys. Res.
B 217, 193 (2004).
3) N. Ukon et al., Nucl. Instrum. Methods Phys. Res. B
426, 13 (2018).
4) F. Ditrói et al., Nucl. Instrum. Methods Phys. Res. B
270, 61 (2012).
5) J. P. Faris, R. F. Buchanan, Anal. Chem. 36, 1157
(1964).