Search

Purpose: In recent years the use of 68 Ga (t 1/2  = 67.84 min, β + : 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of 68 Ga via the 68 Zn(p,n) 68 Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand., Methods: Irradiations of 1.7 Msolution of 68 Zn(NO 3 ) 2 in 0.2 N HNO 3 were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18. The proton beam energy was degraded to 12 MeV, in order to minimize the production of 67 Ga through the 68 Zn(p,2n) 67 Ga reaction. The product's activity was measured using a calibrated activity meter and a High Purity Germanium gamma-ray detector., Results: The saturation yield of 68 Ga amounts to (330 ± 20) MBq/µA, corresponding to a produced activity of 68 Ga at the EOB of (4.3 ± 0.3) GBq in a typical production run at 46 µA for 32 min. The radionuclidic purity of the 68 Ga in the final product, after the separation, is within the limits of the European Pharmacopoeia (>99.9%) up to 3 h after the EOB. Radiochemical separation up to a yield not lower than 75% was obtained using an automated purification module. The enriched material recovery efficiency resulted higher than 80-90%., Conclusions: In summary, this approach provides clinically relevant amounts of 68 Ga by cyclotron irradiation of a liquid target, as a competitive alternative to the current production through the 68 Ge/ 68 Ga generators., (Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Background: In medical cyclotron facilities, 11C is produced according to the 14N(p,α)11C reaction and widely employed in studies of prostate and brain cancers by Positron Emission Tomography. It is known from literature that the 11C-target assembly shows a reduction in efficiency during time, meaning a decrease of activity produced at the end of bombardment. This effect might depend on aspects which are still not completely known., Objective: Possible causes of the loss of performance of the 11C-target assembly were addressed by Monte Carlo simulations., Methods: Geant4 was used to model the 11C-target assembly of a GE PETtrace cyclotron. The physical and transport parameters to be used in the energy range of medical applications were extracted from literature data and 11C routine productions. The Monte Carlo assessment of 11C saturation yield was performed varying several parameters such as the proton energy and the angle of the target assembly with respect to the proton beam., Results: The estimated 11C saturation yield is in agreement with IAEA data at the energy of interest, while it is about 35% greater than the experimental value. A more comprehensive modeling of the target system, including thermodynamic effect, is required. The energy absorbed in the inner layer of the target chamber was up to 46.5 J/mm2 under typical irradiation conditions., Conclusion: This study shows that Geant4 is potentially a useful tool to design and optimize targetry for PET radionuclide productions. Tests to choose the Geant4 physics libraries should be performed before using this tool with different energies and materials., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)