Optimization of 68Ga production at an 18 MeV medical cyclotron with solid targets by means of cross-section measurement of 66Ga, 67Ga and 68Ga.

The future development of personalized nuclear medicine relies on the availability of novel medical radionuclides. In particular, radiometals are attracting considerable interest since they can be used to label both proteins and peptides. Among them, the ß+-emitter 68Ga is widely used in nuclear medicine for positron emission tomography (PET). It is used in theranostics as the diagnostic partner of the therapeutic ß--emitters 177Lu and 90Y for the treatment of a wide range of diseases, including prostate cancer. Currently, 68Ga is usually obtained via 68Ge/68Ga generators. However, their availability, high price and limited produced radioactivity per elution are a major barrier for a wider use of the 68Ga-based diagnostic radiotracers. A promising solution is the production of 68Ga by means of proton irradiation of enriched 68Zn liquid or solid targets. Along this line, a research program is ongoing at the Bern medical cyclotron, equipped with a solid target station. In this paper, we report on the measurements of 68Ga, 67Ga and 66Ga production cross-sections using natural Zn and enriched 68Zn material, which served as the basis to perform optimized 68Ga production tests with enriched 68Zn solid targets.

Cross-section measurement of 44mSc,47Sc, 48Sc and 47Ca for an optimized 47Sc production with an 18 MeV medical PET cyclotron.

Novel medical radioisotopes for both diagnostic and therapy are essential for the future development of personalized nuclear medicine. Among them, radiometals can be used to label both proteins and peptides and encompass promising theranostic pairs. The optimized supply of radiometals in quantity and quality for clinical applications represents a scientific and technological challenge. 47Sc is a ß- emitter that forms a theranostic pair together with one of the ß+ emitters 43Sc or 44Sc. It can be produced at a medical cyclotron by proton bombardment of an enriched calcium oxide target. The parasite production of 48Sc undermines the 47Sc purity, which strongly depends on the energy of protons impinging the target and on the thickness of the target material. For this purpose, an accurate knowledge of the production cross-sections is mandatory. In this paper, we report on the measurement of the cross-section of the reactions 44Ca(p,n)44 mSc,48Ca(p,n)48Sc, 48Ca(p,2n)47Sc and 48Ca(p,pn)47Ca using natCaCO3 targets performed at the Bern University Hospital cyclotron laboratory. On the basis of the obtained results and of the isotopic composition of commercially available enriched target materials, the thick target yields and the purity were calculated to assess the optimal irradiation conditions.

Measurement of 43Sc and 44Sc production cross-section with an 18MeV medical PET cyclotron.

43Sc and 44Sc are positron emitter radionuclides that, in conjunction with the ß- emitter 47Sc, represent one of the most promising possibilities for theranostics in nuclear medicine. Their availability in suitable quantity and quality for medical applications is an open issue and their production with medical cyclotrons represents a scientific and technological challenge. For this purpose, an accurate knowledge of the production cross sections is mandatory. In this paper, we report on the cross section measurement of the reactions 43Ca(p,n)43Sc, 44Ca(p,2n) 43Sc, 46Ti(p,α)43Sc, and 44Ca(p,n)44Sc at the Bern University Hospital cyclotron. A study of the production yield and purity performed by using commercially available enriched target materials is also presented.

Experimental measurement and Monte Carlo assessment of Argon-41 production in a PET cyclotron facility.

In a medical cyclotron facility, (41)Ar (t1/2 = 109.34 m) is produced by the activation of air due to the neutron flux during irradiation, according to the (40)Ar(n,γ)(41)Ar reaction; this is particularly relevant in widely diffused high beam current cyclotrons for the production of PET radionuclides. While theoretical estimations of the (41)Ar production have been published, no data are available on direct experimental measurements for a biomedical cyclotron. In this work, we describe a sampling methodology and report the results of an extensive measurement campaign. Furthermore, the experimental results are compared with Monte Carlo simulations performed with the FLUKA code. To measure (41)Ar activity, air samples were taken inside the cyclotron bunker in sealed Marinelli beakers, during the routine production of (18)F with a 16.5 MeV GE-PETtrace cyclotron; this sampling thus reproduces a situation of absence of air changes. Samples analysis was performed in a gamma-ray spectrometry system equipped with HPGe detector. Monte Carlo assessment of the (41)Ar saturation yield was performed directly using the standard FLUKA score RESNUCLE, and off-line by the convolution of neutron fluence with cross section data. The average (41)Ar saturation yield per one liter of air of (41)Ar, measured in gamma-ray spectrometry, resulted to be 3.0 ± 0.6 Bq/µA*dm(3) while simulations gave a result of 6.9 ± 0.3 Bq/µA*dm(3) in the direct assessment and 6.92 ± 0.22 Bq/µA*dm(3) by the convolution neutron fluence-to-cross section.