Speaker
Description
Radiopharmaceuticals containing gamma-ray and beta(-)(alpha, Auger electron)-ray emitting radioisotopes are used to diagnose the dynamics of a medicine in the living body and kill targeted cancer cells, respectively. Using 99mTc (T1/2 = 6 h), the daughter nuclide of 99Mo (T1/2 = 66 h), about 0.9 million and 6 million diagnostic procedures per year are carried out in Japan and in EU, respectively.1,2) Japan imports all of its required 99Mo. Most 99Mo is produced by the fission reaction of enriched 235U in nine research reactors around the world.3) The supply chain of 99Mo is fragile owing to the unscheduled shutdown of some of the research reactors and natural disasters such as Iceland volcano eruptions. 90Y (T1/2 = 64 h, pure beta-ray emitter with E(max) = 2.3 MeV) radiopharmaceuticals is used for cancer therapy.4) 67Cu (T1/2 = 64 h, E(max) = 0.58 MeV) is believed to be a promising radionuclide to treat small distant metastases in radioimmunotherapy.5) 67Cu emits low-energygamma-rays, and therefore it can be used simultaneously for diagnostics and therapy. Establishing a proper production method of high quality 67Cu is a longstanding problem.5)
New routes were proposed to produce 99Mo and 67Cu via the 100Mo(n,2n)99Mo6) and 68Zn(n,np+d)67Cu7) reactions, respectively, using accelerator neutrons provided by the C(d,n) reaction at a deuteron energy of 40 – 50 MeV. In order to separate 99mTc from the 99Mo with a low specific-activity, a thermochromatography apparatus was developed.8) The quality control tests of the 99mTc-radiopharmaceuticals were shown to fulfill the United States Pharmacopeia regulatory requirements.9) We claim that about 30 – 50% of the demand for 99mTc in Japan would be met using a single accelerator of 40 MeV, 2 mA deuteron beams.10) The radionuclide purity, labeling efficiency, and specific activity of 67Cu, eluted from the 68ZnO sample irradiated with accelerator neutrons by using several ion exchange columns were measured.11) 67Cu chloride of 35 – 50 kBq dissolved in saline was injected into the colorectal tumor-bearing mice to determine the biodistribution, and a high uptake of 67Cu in the tumor was found.12) The result suggests that 67CuCl2 can be a potential radionuclide agent for cancer radiotherapy. Characteristic points of accelerator neutrons to produce a wide variety of medical radioisotopes of high quality will be discussed together with the results described above.
References
[1] Report by Japan Radiation Association, Isotope News 54, 723 (2016) [in Japanese].
[2] NuPECC Report “Nuclear Physics for Medicine”, 2014.
[3] The Supply of Medical Radioisotopes: Report by Nuclear Energy Agency (March 2016).
[4] Biogen Idec Inc. Zevalin (ibritumomab tiuxetan) (Biogen Idec Inc., San Deiego, CA, 2005).
[5] I. Novak-Hofer and P. A. Schubiger, Eur. J. Nucl. Med. 29, 821 (2002).
[6] Y. Nagai and Y. Hatsukawa, J. Phys. Soc. Jpn. 78, 2009, 033201-1
[7] T. Kin, Y. Nagai et al., J. Phys. Soc. Jp. 82, 2013, 034201-1
[8] Y. Nagai, M. Kawabata et al., J. Phys. Soc. Jpn. 83, 2014, 083201-1
[9] Y. Nagai, Y. Nakahara et al., J. Phys. Soc. Jpn. 86, 2017, 053202-1
[10] F. Minato, K. Tsukada et al., J. Phys. Soc. Jpn. 86, 2017, 114803-1
[11] M. Kawabata, K. Hashimoto et al., J.Radioanal. Nucl. Chem, 303, 2015, 1205
[12] Y. Sugo, K. Hashimoto et al., J. Phys. Soc. Jpn. 86, 2017, 023201-1
