Title: Cyclotron production of 44Sc - new tracer for PET technique
Publication Year: 2011
JRC N°: JRC68732
ISSN: 0362-4803
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC68732
Type: Articles in periodicals and books
Abstract: Objectives: Two isotopes of scandium, 47Sc and 44Sc, are perspective radionuclides respectively for radiotherapy and diagnostic imaging. 47Sc decays with the half-life of 3.35 days and maximum β- energy of 600 keV. It also emits low-energy γ-radiation (Eγ = 159 keV) suitable for simultaneous imaging. The other scandium radionuclide - 44Sc (t1/2 = 3.92h) is an ideal β+-emitter in PET diagnosis. It can be used instead of 68Ga, because 44Sc has longer half-life and forms stable radiobioconjugates with a structure similar to 90Y and 177Lu, what is important in planning radionuclide therapy [1]. 44Sc can be obtained as a daughter radionuclide of long-lived 44Ti (t1/2 = 60.4y) from 44Ti/44Sc generator or can be produced by nuclear reaction 44Ca (p, n) 44Sc in small cyclotrons. The aim of our work was to find optimal parameters for 44CaCO3 target irradiation in order to maximize production of 44Sc with minimal impurities of longer-lived 44mSc and development of simple chemical procedure for separation of 44Sc from the calcium target. Methods: The irradiation of enriched 44CaCO3 Isoflex (Russia) was performed with the Scanditronix MC 40 Cyclotron Joint Research Centre (Ispra, Italy). In stack target, 2mg of enriched CaCO3 in aluminum foil envelop were used together with Cu disk as beam current monitor. The copper monitor was positioned in entrance of the stack which allowed to have an accurate measurement of the proton beam current by measuring the 44Sc activity. The stack-foil target was irradiated in aluminum capsules inserted in a holder that allowed direct water cooling from the rear and the front side. Longer-lived 46Sc was used instead of 44Sc in the separation procedure. The CaCO3 target (10 mg) was dissolved in 1 ml of 0.1 M HCl. Next, the solution was passed through the small column filled with iminodiacetic resin Chelex-100. After adsorption of 46Sc the column was washed with 30 ml of 0.01 M HCl and the effluent containing enriched calcium was collected for further irradiations. The 46Sc was quantitatively eluted with 1 M HCl in the second 0.5 ml fraction. Results: The 44CaCO3 target was irradiated by protons in the range of 5.5-23MeV. The analysis of several irradiations indicate that the amount of 44Sc obtained is maximal with minimal (0.16%) 44mSc impurity in the energy range of 9-10MeV. 46Sc was separated from the target on iminodiacetic resin with efficiency of more than 95%, eluted in volume of 0.5 ml. The recovery of the calcium target is nearly quantitative. The level of Ca2+ in 46Sc fraction is less than3 g/ml. Conclusions: The low-energy irradiation of 44Ca gives opportunity to produce Ci level activities of 44Sc. The separation process proposed of 44Sc from the target is simple and fast. The 44Sc obtained can be used instead of 68Ga in PET diagnosis and planning radionuclide receptor therapy.. Research Support: This work was carried out as a part of the project of the Ministry of Science and Higher Education of Poland DWM/N166/COST/2007 and COST Action D38. References: [1] A.Majkowska, A.Bilewicz, J.Inorg.Biochem. 105 (2011) 313–320.
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