S.M. Qaim

EXCITATION FUNCTIONS OF PROTON INDUCED NUCLEAR REACTIONS ON ENRICHED 61NI AND 64NI : POSSIBILITY OF PRODUCTION OF NO-CARRIER-ADDED 61CU AND 64CU AT A SMALL CYCLOTRON

Abstract Excitation functions were measured by the stacked-foil technique for 61Ni(p,n)61Cu and 61Ni(p,2n)60Cu nuclear reactions using 88.84% enriched 61Ni and for 64Ni(p,n)64Cu reaction using 95% enriched 64Ni from threshold up to 18.6 MeV. The optimum energy range for the production of both 61Cu and 64Cu was found to be 12 → 9 MeV. The calculated thick target yield of 61Cu amounts to 17.5 mCi (647 MBq)/γAh. At the given enrichment the yield was 15.5 mCi (573 MBq)/γAh and the expected level of 60Cu and 64Cu impurities at EOB reached 14.59 and 0.086%, respectively. For production of 64Cu the yield was 6.71 mCi (248 MBq)/γAh. At 95% enrichment of the target material the 64Cu yield amounts to 6.38 mCi (236 MBq)/γAh and the 60Cu and 61Cu impurities at EOB are 10.01 and 0.41%, respectively. An anion-exchange chromatographic technique for the separation of radiocopper from activated Ni target was developed. The 61Ni(p,n)61Cu and 64Ni(p,n)64Cu processes are suited for the production of 61Cu and 64Cu at a small cyclotron. The common production routes for 64Cu are briefly reviewed.

Excitation functions of 124Te(p, xn)124,123I reactions from 6 to 31 MeV with special reference to the production of 124I at a small cyclotron

Abstract Excitation functions were measured by the stacked-foil technique for (p, xn) reactions on highly enriched 124Te in the proton energy range of 6–31 MeV. Thin uniform films of 24Te on Ti-backing were prepared by an electrodeposition method. Above 17 MeV our data agree within experimental errors with the literature values, thus validating the 123I-yields and 124I-impurity levels associated with the 124Te(p, 2n)123I production process. Detailed measurements near the threshold of the 124Te(p, n)124I reaction, on the other hand, show that, contrary to the general assumption, the thick target yield of 124I is fairly high, amounting to 20 MBq (0.54 mCi)/μAh over the optimum energy range Ep = 13 → 9 MeV. A comparison of the three suggested routes for the production of 124I, viz. 124Te(d, 2n)-, 126Te(p, 3n)-, and 124Te(p, n)-processes, is given. The yield and impurity-level data suggest that the 124Te(p, n)124I reaction has a great potential for production at a small cyclotron.

PET quantitation and imaging of the non-pure positron-emitting iodine isotope 124I.

A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HRR+ operated in both 2D and 3D modes. No specific correction was applied for the gamma-rays emitted together with the positrons. As compared to 18F, in studies with 124I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of -6 +/- 13% (mean+/-SD) in respect of the phantom radioactivity as measured with gamma-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124I is feasible and may be improved by the development of specific corrections.

Production of the Positron Emitting Radioisotope 86Y for Nuclear Medical Application

The production of 86Y via the 86Sr(p,n)-reaction was studied. Samples of 96.3% enriched 86SrCO3 were irradiated using a 4 π water-cooled target system at nearly optimum proton energy ranges (14 → 10 MeV) at beam currents of 3–8 μA. Thick target yields calculated from the measured excitation functions were compared with results from production runs. A chemical separation procedure including the recovery of the enriched target material was developed. Activities of about 1.5 GBq (40 mCi) 86Y per batch with high radionuclidic and radiochemical purity were achieved and [86Y]citrate was prepared for pharmacokinetic studies using PET.

Some optimisation studies relevant to the production of high-purity 124I and 120gI at a small-sized cyclotron

Optimisation experiments on the production of the positron emitting radionuclides 124I(T(1/2) = 4.18d) and (120g)I (T(1/2) = 1.35 h) were carried out. The TeO(2)-target technology and dry distillation method of radioiodine separation were used. The removal of radioiodine was studied as a function of time and the loss of TeO(2) from the target as a function of oven temperature and time of distillation. A distillation time of 15 min at 750 degrees C was found to be ideal. Using a very pure source and comparing the intensities of the annihilation and X-ray radiation, a value of 22.0 +/- 0.5% for the beta(+) branching in 124I was obtained. Production of 124I was done using 200 mg/cm(2) targets of 99.8% enriched 124TeO(2) on Pt-backing, 16 MeV proton beam intensities of 10 microA, and irradiation times of about 8 h. The average yield of 124I at EOB was 470 MBq(12.7 mCi). At the time of application (about 70 h after EOB) the radionuclidic impurity 123I (T(1/2) = 13.2 h) was <1%. The levels of other impurities were negligible (126I < 0.0001%;125I = 0.01%). Special care was taken to determine the 125I impurity. For the production of (120g)I only a thin 30 mg target (on 0.5 cm(2) area) of 99.9% enriched 120TeO(2) was available. Irradiations were done with 16 MeV protons for 80 min at beam currents of 7 microA. The 120gI yield achieved at EOB was 700 MBq(19 mCi), and the only impurity detected was the isomeric state 120 mI(T(1/2) = 53 min) at a level of 4.0%. The radiochemical purity of both 124I and 120gI was checked via HPLC and TLC. The radioiodine collected in 0.02 M NaOH solution existed >98% as iodide. The amount of inactive Te found in radioiodine was <1 microg. High purity 124I and 120gI can thus be advantageously produced on a medium scale using the low-energy (p,n) reaction at a small-sized cyclotron.

Cross-section measurements of the nuclear reactions natZn(d,x)64Cu, 66Zn(d,α)64Cu and 68Zn(p,αn)64Cu for production of 64Cu and technical developments for small-scale production of 67Cu via the 70Zn(p,α)67Cu process

The radionuclides 64Cu (T1/2=12.7h) and 67Cu (T1/2=61.9h) are useful in internal therapy. In connection with production of 64Cu, excitation functions of the reactions natZn(d,x)64Cu, 66Zn(d,alpha)64Cu and 68Zn(p,alphan)64Cu were measured radiochemically using the stacked-foil technique. From the measured data, the thick target yields of 64Cu were calculated and compared with experimental data available in the literature. The three investigated processes are discussed in comparison to the commonly used 64Ni(p,n)64Cu reaction for the production of 64Cu. As regards 67Cu production, the technical feasibility of the 70Zn(p,alpha)67Cu process was investigated. An electroplated isotopically enriched 70Zn target was developed which can withstand slanting beams of 20MeV protons of currents up to 20 microA. Methods for chemical separation of 67Cu and efficient recovery of the enriched target material were worked out. The method is suitable only for small-scale production of 67Cu.

Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.

Evaluation of excitation functions of 100Mo(p,d+pn)99Mo and 100Mo (p,2n)99mTc reactions: Estimation of long-lived Tc-impurity and its implication on the specific activity of cyclotron-produced 99mTc

Excitation functions were calculated by the code TALYS for 10 proton-induced reactions on (100)Mo. For (100)Mo(p,d+pn)(99)Mo and (100)Mo(p,2n)(99m)Tc, calculations were also performed using the code STAPRE. Furthermore, for those two reactions and (nat)Mo(p,x)(96)Tc, evaluation of available experimental data was also carried out. The production of (99m)Tc via the (100)Mo(p,2n)-process is discussed. The ratio of atoms of long-lived (99g)Tc and (98)Tc to those of (99m)Tc is appreciably higher in cyclotron production than in generator production of (99m)Tc; this may adversely affect the preparation of (99m)Tc-chelates.

Measurements and nuclear model calculations on proton-induced reactions on 103Rh up to 40 MeV: evaluation of the excitation function of the 103Rh(p, n)103Pd reaction relevant to the production of the therapeutic radionuclide 103Pd

Excitation functions were measured by the stacked-foil technique for the reactions 103Rh(p,n)103Pd, 103Rh(p,3n)101Pd and 103Rh(p,4n)100Pd from their respective thresholds up to 39.6 MeV. The radioactivity of the activation products was determined by high-resolution X-ray and gamma-ray spectrometry. Statistical model calculations taking into account the precompound effects were performed for all reactions, and good agreement was found with our data. A critical evaluation of the existing and present data for the 103Rh(p,n)103Pd reaction was carried out. Recommended cross sections and integral yields for this reaction of key importance in the production of the widely used therapeutic radionuclide 103Pd are given.

Excitation functions of 85Rb(p, xn)85m, g, 83,82,81Sr reactions up to 100 MeV: integral tests of cross section data, comparison of production routes of 83Sr and thick target yield of 82Sr

The beta+ emitter 83Sr (T(1/2) = 32.4 h, Ebeta+ = 1.23 MeV, Ibeta+ = 24%) is a potentially useful radionuclide for therapy planning prior to the use of the beta+ emitter 89Sr (T(1/2) = 50.5 d). In order to investigate its production possibility, cross section measurements on the 85Rb(p,xn)-reactions, leading to the formation of the isotopes (85m,g)Sr, 83Sr, 82Sr and 81Sr, were carried out using the stacked-foil technique. In a few cases, the products were separated via high-performance liquid chromatography. For 82Sr, both gamma-ray and X-ray spectrometry were applied; in other cases only gamma-ray spectrometry was used. From the measured excitation functions, the expected yields were calculated. For the energy range Ep = 37 --> 30 MeV the 83Sr yield amounts to 160 MBq/microA h and the level of the 85gSr (T(1,2) = 64.9 d) and 82Sr (T(1/2) = 25.5 d) impurities to <0.25%. In integral tests involving yield measurements radiostrontium was chemically separated and its radioactivity determined. The experimental production data agreed within 10% with those deduced from the excitation functions. The results of the 85Rb(p,3n)83Sr reaction were compared with the data on the production of 83Sr via the 82Kr(3He,2n)-process. In the energy range E3Hc = 18 --> 10 MeV the theoretical yield of 83Sr amounts to 5 MBq/microA h and the 82Sr impurity to about 0.2%. The method of choice for the production of 83Sr is thus the 85Rb(p,3n)-process, provided a 40 MeV cyclotron is available. During this study some supplementary information on the yield and purity of 82Sr was also obtained.