18F Production Research Articles

18F production in the 19F(γ, n) reaction

A race-track microtron is used to measure the yield of 18F in the reaction 19F(γ, n) at an energy of the electron beam of 55 MeV. 18F is widely used in positron emission tomography for high-sensitivity diagnostics. The currently available data are not sufficient to make accurate estimates of the yield of 18F in isotope production experiments using the reaction (γ, n). The value of σ−1 estimated in this work is (1.7 ± 0.1) mb.

Isγ-Ray Emission from Novae Affected by Interference Effects in theF18(p,α)O15Reaction?

The (18)F(p,α)(15)O reaction rate is crucial for constraining model predictions of the γ-ray observable radioisotope (18)F produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, (19)Ne, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J(π)=3/2(+) states near the proton threshold (S(p)=6.411 MeV) and a broad J(π)=3/2(+) state at 665 keV above threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the (19)F((3)He,t)(19)Ne reaction. In stark contrast to previous assumptions we find at least 3 resonances between the proton threshold and E(cm)=50 keV, all with different angular distributions. None of these are consistent with J(π)=3/2(+) angular distributions. We find that the main uncertainty now arises from the unknown proton width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects (18)F production by at least a factor of two in the model considered.

Estimation of thermal neutron flux in pet cyclotron rooms by means of radioactive analysis of bolts in the rooms

Abstract Short-lived radionuclides for positron emission tomography (PET) examinations in medicine are produced mainly using on site small cyclotrons. The operation of the cyclotron generates a significant quantity of neutrons, which will activate the cyclotron and surrounding materials. A new technique is proposed to estimate the neutron fluxes in the cyclotron rooms, in which small bolts in the cyclotron rooms were used as surrogates for neutron detectors. The measurements were carried out at four PET cyclotrons. The induced radioactivity of the bolts was analyzed by gamma-ray spectroscopy and elemental analysis. A gold foil activation method was applied to compare the results. The neutron fluxes in the PET cyclotron rooms were in the range of 105∼106 cm−2 s−1 during 18F production. In the brass bolts, 69mZn, 65Zn, 64Cu, 58Co, and 60Co were detected. In the iron bolts, 56Mn, 54Mn, 59Fe, 60Co, 69mZn, and 65Zn were detected. In the stainless steel bolts, 58Co, 60Co, 56Mn, 54Mn, and 59Fe were detected. Neutron fluxes estimated from the activities of 56Mn agreed well with those by the Au foil method. The feasibility of estimating the neutron fluxes in cyclotron rooms by means of radioactive analysis of bolts in the rooms was proven.

Thermal performance of batch boiling water targets for 18F production

Batch boiling targets are commonly used in cyclotrons to produce Fluorine-18 by proton bombardment of Oxygen-18 enriched water. Computational models have been developed to predict the thermal performance of bottom-pressurized batch boiling production targets. The models have been validated with experimental test data from the Duke University Medical Cyclotron and the Wisconsin Medical Cyclotron. Good agreement has been observed between experimental measurements and model predictions of average target vapor fraction as a function of beam current and energy.

Distribution of Thermal Neutron Flux Around a PET Cyclotron

The number of positron emission tomography (PET) examinations has greatly increased world-wide. Since positron emission nuclides for the PET examinations have short half-lives, they are mainly produced using on-site cyclotrons. During the production of the nuclides, significant quantities of neutrons are generated from the cyclotrons. Neutrons have potential to activate the materials around the cyclotrons and cause exposure to the staff. To investigate quantities and distribution of the thermal neutrons, thermal neutron fluxes were measured around a PET cyclotron in a laboratory associating with a hospital. The cyclotron accelerates protons up to 18 MeV, and the mean particle current is 20 μA. The neutron fluxes were measured during both 18F production and C production. Gold foils and thermoluminescent dosimeter (TLD) badges were used to measure the neutron fluxes. The neutron fluxes in the target box averaged 9.3 × 10(6) cm(-2) s(-1) and 1.7 × 10(6) cm(-2) s(-1) during 18F and 11C production, respectively. Those in the cyclotron room averaged 4.1 × 10(5) cm(-2) s(-1) and 1.2 × 10(5) cm(-2) s(-1), respectively. Those outside the concrete wall shielding were estimated as being equal to or less than ∼3 cm s, which corresponded to 0.1 μSv h(-1) in effective dose. The neutron fluxes outside the concrete shielding were confirmed to be quite low compared to the legal limit.

A water target with beam sweep for routine fluorine-18 production

Fluorine-18 ( 18F) production with 18O-enriched water targets is well established world-wide. Heat transfer is still a critical point, however, when high beam currents are used to increase the amount of radioactivity per batch within an adequate irradiation period. The technique of beam sweep formerly used in Hannover for all targets has been adapted for this water target again. A titanium target with a beam sweep of up to 3 cm in the horizontal plane was designed to keep the total amount of enriched water low (2.06 ml), to allow beam currents of 30 μA for 1 h on a daily schedule and thereby to extend maintenance periods to more than 6 months. The design had to take into account that the target must be mounted on a target ladder with five additional positions and that the beam is carried by a 5.50 m beam line from a variable energy, multi-particle cyclotron (mc35, Scanditronix) to the target. The target has been in use for more than 130 consecutive runs with beam currents of about 30 μA at a target pressure of up to 15 bar without any maintenance. The mean value of the recovered radioactivity has reached 91.9±7.7% of the theoretically expected value at the end of bombardment (EOB).

A practical production of no-carrier-added 18F from natural water via the 16O( 3He,p) 18F reaction, using an ultra-compact in-house cyclotron

No-carrier-added 18F production via the 16O( 3He,p) 18F reaction was evaluated using a natural water target and low energy, 12–19 MeV, 3He particles accelerated by a 74 cm ultra-compact cyclotron, to see whether this method is practical for PET 18F radiotracer preparations. With 3He particles of 19 MeV, 2 h-irradiation yielded 11 mCi 18F/μA, which could allow 2–3 18F synthesis for PET studies. Radionuclidic contamination with 15O, 7Be or other nuclides from the activated foil, was practically negligible due to either shorter half-life or 10 −5 to 10 −7 times the activity of 18F. In 30–40 min after end of bombardment (EOB), the radionuclidic purity was higher than 99.99%. Radionuclidic impurities from the activated foil could be minimized by choosing an appropriate target foil material. A simple target pressure control system consisting of a pressure monitoring device and an electric valve which degassed the target before the pressure reached to a critical point worked satisfactorily without a catalyzing device. These results suggest that simple and inexpensive 18F productions are feasible with an ultra-compact in-house cyclotron installed for PET radiotracer preparations.

Cyclotron production of PET radionuclides: 18F (109.77 min; β + 96.9%; EC 3.1%) from high-energy protons on natural magnesium targets

The production of no-carrier-added (NCA) 18F (109.77 min) from proton induced reactions on Mg targets of natural isotopic composition was investigated in the 67.5-13.7-MeV energy range. In Mg targets, 22Na (2.602 a) and 24Na (15.04 h) were detected as radionuclide impurities. In 0-containing targets [i.e. Mg(OH) 2], 7Be was also detected and measured. The total cross section (mbarn) for the production of 18F and single and cumulative yields (mCi/μAh) for the production of 18F, 22Na, 24Na and 7Be were measured and are reported here. The total cross section for 18F reached a peak value of 22.8 ± 0.2 mbarn in the 60–70-MeV energy region. In the full energy range covered in this work, the cumulative 18F yield (67.5-13.7 MeV) was measured as 27.0 ± 2.7 mCi/ μAh. However, for practical reasons, only a 18F yield of 24.9 ± 2.5 mCi/ μAh in the 67.6-40-MeV energy range needs consideration. Based upon these results, targetry aspects and the potential for the large-scale 18F production from Mg targets are discussed. These results are also compared to a previously reported study of the potential of Al targets for producing 18F with high-energy protons.

Labelling of a new serotoninergic ligand : [18F]ritanserin

AbstractRitanserin has been labelled with 18F to visualize the serotoninergic receptors by Positron Emission Tomography (PET). The synthesis was carried out by a nucleophilic substitution of a nitro substituent of a nitrophenylketone by 18F− and then addition of a Grignard reagent to the ketone followed by dehydration of the tertiary alcohol so formed.The total time to have [18F]ritanserin ready for injection into a patient was 150 minutes (after the end of bombardement for the 18F production [18O (p,n) 18F]).The labelling technique described was used to obtain 1.1 to 1.5 GBq (30 to 40 mCi) of [18F]Ritanserin with a specific activity of 44 GBq/μmol (1.2 Ci/μmol) starting from 18.5 GBq (500 mCi) 18F.

18F]Fluoride from a small cyclotron for the routine synthesis of [ 18F]2-Fluoro-2-deoxy- d-glucose

[ 18F]Fluoride was produced via the 18O (p, n) 18F reaction using a low volume stainless steel 18O-water target in a small cyclotron. The average 18F production rate for 60 runs was about 720 μCi/μA-min. A typical bombardment time of 20 min produced 120 mCi of 18F-fluoride. [ 18F]2-Fluoro-2-deoxy- d-glucose ([ 18F]2FDG) was prepared using the procedure developed by Tewson [ J. Nucl. Med. 24, 718 (1983)] involving a protected cyclic sulfate glucose derivative as precursor. The routine synthesis and quality testing of [ 18F]2FDG required 1 h and, typically, yields of 30–35 mCi of > 95% HPLC-pure product were obtained.

Photonuclear production of 18F from F, Ne and (metallic) Na

Cross sections per equivalent quantum (σ q) have been measured for photonuclear reactions yielding 18F from LiF, SF 6, CF 4, Ne and metallic Na targets, in the energy range 77–125 MeV. The σ q values for LiF and Na are conformable with known data, whilst the σ q values for SF 6 and CF 4 are found to be 10% lower than for LiF. The utility of metallic Na as a target for 18F production has been demostrated by a nucleophilic substitution reaction with (C 2H 5) 4N 18F, formed after dissolution of irradiated Na in absolute C 2H 5OH.

A series target system for the rapid, sequential production of [ 15O]H 2O and O 2, and [ 18F]F 2

A two chambered, series target was developed for use in the rapid, sequential production of [ 15O]H 2O and O 2, and [ 18F]F 2 using an FN-6 tandem van de Graaff accelerator. The 15O labeled tracer gases are produced on a continuous flow basis in an aluminum target chamber using the 14N(d,n) 15O reaction on 5% H 2 in N 2 and 2% O 2 in N 2, respectively. Fluorine-18 labeled F 2 is produced on a batch basis using the 20Ne(d,α) 18F reaction on 0.1% F 2 in Ne in a high pressure, polished nickel chamber. The two target chambers are separated by an aluminum-nickel foil sandwich, and the 15O target is evacuated during 18F production. Switching between 15O target gases as well as choice of 18F or 15O production is completely remote. System performance is comparable to that obtained previously using individually mounted targets.

Target Systems for Radioisotope Production

A high power target, to hold plated radioisotope target material for irradiation by an external particle beam, has been designed and tested. This paper describes the design and use of the target and its handling system, the External Target System with Isorabbit Transport. The target has been shown to dissipate up to 6.4 kW of beam power over an area of approximately 15 cm2 while maintaining the target surface temperature below 160°C. The target design was optimized by using finite difference analysis of various cooling fin geometries; close correlation is observed between predicted and measured target heat transfer properties. Important radiation safety features were incorporated in the mechanical design of the External Target System with Isorabbit Transport. Also described are high yield and high specific activity, shortlived, radioisotope production systems using protons as the bombarding particle. These include a system for 15O, 13N, and 11C gas production; a system for 13N-ammonia production by proton irradiation of water; and a system for 18F production by irradiation of 18O gas.

Oxygen content of selected coals as determined by charged particle activation analysis

Coal samples are irradiated with 3He ions to produce 11C, 13N, and 18F via the following nuclear reactions: 12C( 3He, 4He) 11C; 12C( 3He, d) 13N; 16O( 3He, p) 18F. By comparing the 11C to 18F production, a direct comparison of the amounts of carbon and oxygen present in the coal samples can be obtained. The 13N production provides an internal check for the amount of carbon present. In preference to calculating the yield of C-11 and F-18 on an absolute basis, organic standards with known oxygen-to-carbon ratios can be irradiated which provide a direct correlation between the 18F 11C produced and the 16O 12C originally present in the sample. By using this ratio method, the necessity for accurately known reaction cross-sections and beam fluxes is eliminated. If the standards and samples can be irradiated simultaneously, corrections for differences in saturation can be eliminated.

Cyclotron isotopes and radiopharmaceuticals—XXIII: Novel anhydrous 18F-fluorinating intermediates

The 20Ne( d, α) 18F reaction and a high purity nickel target passivated with an anhydrous film of nickel fluoride were utilized for the preparation of anhydrous 18F-labeled fluorinating reagents. A recovery yield of ∼8.8 mCi/μAh of 18FF 2 was obtained with 11 MeV deuterons incident on neon and F 2 carrier at a pressure of 2.63 atm. 18FF 2 was obtained at a production rate of 11.8 mCi/μAh with the 19F( p, pn) 18F and 19 F(p, 2n) 18 Ne → 18 F nuclear reactions at 31.7 MeV on 11.5 mmole of F 2. The 20 Ne( 3 He, x) 18 F and 18 Ne 1.5 s 18 F nuclear reactions (ifx = 3p2n, αn, 3 He2n and 2p3n, 3 Hepn , respectively) with 55.7–10 MeV 3He and the 20 Ne(α,α2n) 18 Ne 1.5 s 18 F and 20Ne( α, αpn) 18F reactions at 45-33 MeV were evaluated. At the 3He beam energies available on all but the smallest compact cyclotrons the 18F production rate was ∼ 70% of that obtainable for the ( d, α) reaction on a given accelerator. The methodology and targetry for the production of 18FF 2, 18FCF 4, H 18F, NO 18F and Cl 18F are described.

Preparation of 18F in a Nuclear Reactor

Summary 18F has been produced irradiating LiN03 in the Ispra 1 reactor, by 16O(t, n)18F reaction using tritons from 6Li(n, t)4He reaction. A simple method is proposed for the purification of 18F, based on the adsorption on anionic alumina in OH- form and elution with NaF solution. Also the adsorption of 18F on magnesium oxide has been experimented. Several other salts containing lithium and oxygen have been irradiated. Some remarks are reported on the dependence of the 18F production yields from the chemical composition of the irradiated compounds.