CHAPTER 2. PHYSICAL CHARACTERISTICS AND
2.22. INDIUM-111
2.22. INDIUM-111 Half-life: 2.83 d.
Decay mode
Indium-111 decays by electron capture. There are two prominent gamma rays, one at 171.3 keV and one at 245.4 keV.
Uses
Indium-111 as a lipophilic complex (e.g. 111In oxine) is used for labelling blood cells. Indium-111 octreotide, a radiolabelled somatostatin analogue, binds to somatostatin receptors, which are very common in several cancers.
Indium-111 may, therefore, be useful for the visualization of metastases in cancer patients.
Electron emission products of 111In
Fraction Energy (MeV)
0.001814 0.244620
0.002450 0.170510
0.007849 0.241370
0.010499 0.167260
0.050384 0.218680
0.084090 0.144570
0.157720 0.019300
1.002700 0.002720
Photon emission products of 111In
This table is also continued on the next page.
Nuclear reactions
Nuclear reactions such as Cd(p, xn)111In, Cd(d, xn)111In and
109Ag(a, 2n)111In are used to produce 111In for medical use. The yield of 111In from the nuclear reaction on silver is much lower than that from the irradiation of cadmium targets with protons [2.22.1]. However, 111In obtained from a silver target is free from long lived 114mIn (T1/2 = 49.5 d), which emits high energy gamma radiation, whereas variable amounts of 114mIn are always present in
111In derived from the cadmium route [2.22.1–2.22.3]. There is really only one reaction that is used commercially to produce 111In: the proton reaction on natural cadmium. The two reactions possible are the 111Cd(p, n)111In and
112Cd(p, 2n)111In reactions [2.22.4].
Excitation functions
The excitation functions for 111In are shown in Figs 2.22.1–2.22.3.
Fraction Energy (MeV)
0.000028 0.150810
0.070853 0.003130
0.145970 0.026100
0.236280 0.022984
0.445810 0.023174
0.902400 0.171280
0.940000 0.245390
2.22. INDIUM-111
Cross-section (mb)
Incident energy (MeV)
FIG. 2.22.1. Excitation function for the 109Ag(a, 2n)111In reaction.
Cross-section (mb)
Particle energy (MeV)
FIG. 2.22.2. Excitation function for the 111Cd(p, n)111In reaction.
Thick target yields
The following table is taken from IAEA-TECDOC-1211 [2.22.5].
This table is also continued on the next page.
Energy
FIG. 2.22.3. Excitation function for the 112Cd(p, 2n)111In reaction.
2.22. INDIUM-111
Target materials
The target material is natural cadmium, enriched 112Cd or natural silver. It can be either electroplated or pressed as a powder into a target holder (see target preparation below).
Target preparation
Internal irradiation can be carried out on a hemispherical copper target head [2.221.6]. The outer surface of the copper target is electroplated with 80 mm thick cadmium metal. The target head is irradiated tangentially with a 20 MeV, 10–40 mA proton beam.
An external target is constructed as follows: cadmium metal (ª2 g) is first melted into a groove (15 mm diameter by 1 mm deep) cut into an aluminium disc. The molten cadmium is then pressed with an aluminium plate, ensuring complete filling of the cavity. The surface of the cadmium is then carefully polished, finally cleaned with soap and water, and dried. The target is mounted on a target holder, which can be fixed in the beam line. The rear of the target is cooled with a jet of low conductivity water [2.22.7]. The beam current is much lower for the external target than for the internal target.
Target processing
The separation of the 111In from the cadmium target plates has been accomplished by two different methods. Both ion exchange chromatography and solvent extraction have been used. These methods give similar recoveries of 111In [2.22.8]. The solvent extraction method is described here.
Irradiated 112Cd target is dissolved in concentrated HBr, and 111In is extracted in DIPE. The enriched 112Cd remains in the acid aqueous layer.
Indium-111 is then back-extracted into a small volume of 8M HCl, followed by evaporation to dryness. Indium-111 is redissolved in 0.05M HCl.
16.0 3.44 22.0 17.0 28.0 27.7 34.0 32.1
16.5 4.33 22.5 18.2 28.5 28.3 34.5 32.3
17.0 5.31 23.0 19.3 29.0 28.8 35.0 32.5
a A2 is the saturation activity of 1 mA irradiation.
Energy
Recovery of enriched materials
Cadmium-112 solution pooled from several irradiated targets with a manageable radiation level is boiled to remove residual DIPE, and a sufficient volume of 5N NaOH is added to precipitate 112Cd (pH > 12). The resulting precipitate is dissolved by gradual addition of NaCN (ª2.0 g/g of 112Cd).
Cadmium-112 is precipitated in sulphide form with sodium sulphide solution (2M), followed by dissolution in concentrated HCl. Cadmium is then repreci-pitated as Cd(OH)2 with 5M NaOH. If desired, hydroxide can be converted to oxide by heating at 90–130°C.
Specifications
The main impurity resulting from preparation from a natural cadmium target is 114mIn. The gamma spectrum of the final product will allow identifi-cation of the impurity. The chemical impurities of the target material (either cadmium or silver) must be separated along with the other target holder materials such as copper, aluminium and iron. Other radionuclidic impurities must also be separated using either solvent extraction or ion exchange chromatography.
Quality assurance tests for [111In]InCI3
Physicochemical tests can be carried out to check the quality of the final product. The radionuclidic purity of the final product is checked by gamma ray spectroscopy. Radiochemical purity is assessed by paper chromatography using Whatman No. 1 paper and a solvent system composed of 10% ammonium formate: methanol: 0.2M citric acid in the ratio 2:2:1 [2.22.9]. The chemical purity of the final product is tested by checking for the presence of Cu, Fe and Al by the ferric-iron–thiosulphate reaction, aa¢-dipyridyl reagent and Alizarin-S reagent tests, respectively.
REFERENCES TO SECTION 2.22
[2.22.1] MacDONALD, N.S., et al., Methods for compact cyclotron production of indium-111 for medical use, Int. J. Appl. Radiat. Isot. 26 (1975) 631–633.
[2.22.2] DAHL, J.R., TILBURY, R.S., The use of a compact, multi-particle cyclotron for the production of 52Fe, 67Ga, 111In and 123I for medical purposes, Int. J. Appl.
Radiat. Isot. 23 (1972) 431–437.
2.22. INDIUM-111
[2.22.3] ZAITSEVA, N.G., et al., Excitation functions and yields for 111In production using 113,114,nat.Cd(p, xn)111In reactions with 65 MeV protons, Appl. Radiat. Isot.
41 (1990) 177–183.
[2.22.4] NORTIER, F.M., MILLS, S.J., STEYN, G.F., Excitation functions and produc-tion rates of relevance to the producproduc-tion of 111In by proton bombardment of
natCd and natIn up to 100 MeV, Int. J. Radiat. Isot. 41 (1990) 1201–1208.
[2.22.5] INTERNATIONAL ATOMIC ENERGY AGENCY, Charged Particle Cross-section Database for Medical Radioisotope Production: Diagnostic Radio-isotopes and Monitor Reactions, IAEA-TECDOC-1211, IAEA, Vienna (2001).
[2.22.6] DAS, M.K., RAMAMOORTHY, N., 67Ga-gallium citrate I: Production experi-ence at Variable Energy Cyclotron Centre, Calcutta, Ind. J. Nucl. Med. 10 (1995) 63–66.
[2.22.7] DAS, M.K., RAMAMOORTHY, N., SARKAR, B.R., MANI, R.S., Yield of
52Fe by a-particle reaction on natural chromium at 70 MeV, Radiochim. Acta 47 (1989) 173–175.
[2.22.8] SZELECSÉNYI, F., et al., “Excitation functions of proton induced nuclear reactions on 111Cd and 112Cd: Production of 111In”, Nuclear Data for Science and Technology (QAIM, S.M., Ed.), Springer-Verlag, Berlin (1992) 603–605.
[2.22.9] PAIK, C.H., et al., Radiolabeled products in rat liver and serum after adminis-tration of antibody-amide-DTPA-indium-111, Int. J. Radiat. Appl. Instrum. B 19 (1992) 517–522.
BIBLIOGRAPHY TO SECTION 2.22
CHATTOPADHYAY, S., DAS, M.K., SARKAR, B.R., RAMAMOORTHY, N., Radiochemical separation of high purity 111In from cadmium, copper, aluminium and traces of iron: Use of a cation exchange resin with hydrobromic acid and hydrochloric acid, Appl. Radiat. Isot. 48 (1997) 1063–1067.
DAS, M.K., CHATTOPADHYAY, S., SARKAR, B.R., RAMAMOORTHY, N., A cation exchange method for separation of 111In from inactive silver, copper, traces of iron and radioactive gallium and zinc isotopes, Appl. Radiat. Isot. 48 (1997) 11–14.
TAKÁCS, S., TÁRKÁNYI, F., HERMANNE, A., PAVIOTTI DE CORCUERA, R., Validation and upgrading of the recommended cross section data of charged particle reactions used for production of PET radioisotopes, Nucl. Instrum. Methods Phys. Res.
B 211 (2003) 169–189.
2.23. INDIUM-114m