Some experimental studies on ⁸⁹Zr production

Abstract

The radionuclide ⁸⁹Zr (T_1/2=78.4ߙh) is particularly attractive for in vivo assessment of biochemical proesses characterized by biological half times in the order of several hours. In the present study we assessed the feasibility of ⁸⁹Zr production via the ⁸⁹Y(p,n)⁸⁹Zr reaction. Irradiation tests were performed using a 16.5ߙMeV GE-PETtrace cyclotron. High purity (>99.9%) yttrium metallic foils (0.15ߙmm) were irradiated in a solid target station developed in our Institution. The literature cross section data of all the nuclear reactions possible in the energy range of interest were carefully studied to optimize the irradiation parameters. The irradiated target was dissolved in 1ߙN HCl and the activity of the sample was measured in a CRC-15 PET dose calibrator, setting different values for the calibration factor. The sample activity was then measured usin g a calibrated HPGe gamma ray detector. A comparison of the activity measurements allowed the evaluation of the calibration factor for the Capintec CRC-15 PET; for a 3ߙml syringe geometry, it was found 739±60. Saturation yields of ⁸⁹Zr were found to be 1150±110ߙMBq/μA for a single 0.15ߙmm thick disc irradiation (E_p=12.6→11.2ߙMeV) and 2400±220ߙMBq/μA for irradiation of two discs of total thickness 0.3ߙmm (E_p=12.6→9.5MeV). Total produced activities in the range of 200–400ߙMBq (according to target thickness) were repeatedly and safely obtained by 60ߙmin bombardments at 20ߙμA. Analysis of gamma ray spectra of all the samples showed a very high radionuclidic purity (>99.9995%).