Original Research Article
Production of therapeutic quantities of 64Cu using a 12 MeV cyclotron

https://doi.org/10.1016/S0969-8051(03)00024-6Get rights and content

Abstract

64Cu is a useful radiotracer for positron emission tomography (PET) and a promising radiotherapy agent for the treatment of cancer. Recently, 64Cu-labeled radiopharmaceuticals were reported to be useful for internal radiation therapy as well as PET monitoring of tumors.

64Cu was produced at the Fukui Medical University’s cyclotron using twelve MeV proton irradiation and the 64Ni(p,n) 64Cu nuclear reaction. A 64Ni target was electroplated on a gold disk at a thickness of 50 to > 100 μm. Electroplating was performed at 2.5 V, at currents between 5-15 mA, and was completed in 12-24 hr. The 64Ni target was bombarded with a 50 ± 3 μA proton current. After bombardment, 64Cu was separated from the 64Ni target and other contaminants using an anion exchange column. Target 64Ni was recovered and re-used. The yield of 64Cu was 0.6 to > 3.0 mCi/μA*h, and averaged 1.983 mCi/μA*h. The radionuclidic purity of 64Cu was over 99%. In this study, we obtained sufficient qualities and quantities of 64Cu for therapeutic application and dose monitoring using PET using an ultra-small cyclotron.

Introduction

64Cu, which is one of the most useful radio-copper radionuclides for internal radiation therapy, has an intermediate half-life (T0 1/2 = 12.7 hrs) and a multiple decay mode that involves β3 -, electron capture, and positron decay. These characteristics make 64Cu radiopharmaceuticals useful for radiotherapy [2], [3], [5] and for PET monitoring of tumors [1], [4], [8].

It has been shown that 64Cu can be produced using a small cyclotron and the 64Ni(p,n)64Cu nuclear reaction [9], [10]. We report here about the adaptation of this method for the production of 64Cu using the 12 MeV proton cyclotron in our facility and improvements in the 64Ni recycling method.

Section snippets

Materials

All reagents were metal-free. Glassware and other tools were pre-treated with 0.1 N HNO 3 for over 2 hrs, ensuring that contamination with metals was avoided, to prevent a decrease in the radionuclidic purity and specific activity of 64Cu. Enriched 64Ni (94.8%) was purchased from Trace Sciences International (Richmond Hills, Ontario, Canada). Gold disks (2.0 cm diameter x 0.1 cm thickness, 99.99%) and graphite rods (0.5 cm diameter, 99.99%) were obtained from Niraco (Japan). High purity H2SO4

64Ni target preparation

Target preparation was performed using the methods previously reported [6]. Between 9.380 and 25.27 mg of 64Ni was plated on the gold disk. Plating efficiencies were more than 60%.

Radionuclidic yield of 64Cu

In this study, the yield of 64Cu was 0.6 to > 3 mCi/μA*h, with an average of 1.983 mCi/μA*h. The yield was consistently > 3 mCi/μA*h, reaching up to 6.565 mCi/μA*h in the latest study, although they were lower than the predicted yields (Table 1). The yields of 64Cu reported previously using 11 MeV and 11.4 MeV proton

Conclusion

Sufficient qualities and quantities of 64Cu for therapeutic and diagnostic applications using PET can be obtained using an ultra-small cyclotron in a regular PET center. Collection of 64Cu and recycling of 64Ni can be accomplished with such a high efficiency that availability of 64Cu is dramatically improved in the therapeutic and/or diagnostic fields of oncology.

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