Obtaining of the Zr-89 medical isotope in the (γ, αn)-reaction

Oct 13, 2020, 2:40 PM
25m
Online

Online

Oral report Section 8. Nuclear medicine. Section 8. Nuclear medicine

Speaker

Mr Pavel Remizov (Lomonosov Moscow State University)

Description

The modern medical method of nuclear visualization based on monoclonal antibodies, the new carriers of the radioactive label, is Immuno-PET. For its realization, it is necessary that the biological half-life of the molecule, the label carrier, coincides with the half-life of the radioactive isotope. The $^{89}$Zr isotope has optimal physical characteristics for Immuno-PET: it decays with a half-life of 78.41 hours by positron emission and electron capture to the intermediate state $^{89m}$Y, which decays to stable $^{89}$Y with half-life 15.7 s.
Traditionally, $^{89}$Zr is produced with cyclotrons in the ($p, n$)- and ($d$, 2$n$)-reactions. However, in both methods, the exclusion of $^{88}$Zr isotope impurities with a half-life of 83.4 days and its daughter $^{88}$Y isotope with a half-life of 106 days resulting from ($p$, 2$n$)- or ($d$, 3$n$)-reactions presents a significant problem.
Therefore, an urgent task is to study the $^{89}$Zr yield in various photonuclear reactions.
We irradiated a $^{94}$Mo enriched molybdenum target and a tantalum monitor target using an electron accelerator with a 20 MeV maximum electron energy.
The spectra of irradiated targets were measured by Canberra and Ortec gamma spectrometers with ultra-pure semiconductor detectors with a (15–40)% detection efficiency compared to a 3′×3″ NaI(Tl) detector. The energy resolution of the spectrometers was 1.8–2.0 keV on the 1332 keV $^{60}$Co γ-line. In the studied spectrum, γ-transitions from $^{89}$Zr decay are reliably identified. The bremsstrahlung spectrum was simulated using the Geant4 software code.
As a result, we obtained the integral cross-section for the $^{94}$Mo(γ, $n$)$^{89}$Zr reaction equal 4.5 mbn×MeV. The $^{89}$Zr yield is 5×10$^4$ Bq×μA×hour. Obtained data are discussed.

Primary author

Marina Zheltonozhskaya (Lomonosov Moscow State University)

Co-authors

Mr Pavel Remizov (Lomonosov Moscow State University) Dr Vladimir Iatsenko (A.I. Burnasyan Federal Medical Biophysical Center of Federal Medical Biological Agency, Moscow, Russia) Prof. Alexander Chernyaev (Lomonosov Moscow State University)

Presentation materials