title: Some optimisation studies relevant to the production of high-purity 124I and 120gI at a small-sized cyclotron.
abstract: 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.
authors.affiliation: Institut für Nuklearchemie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany. s.m.qaim@fz-juelich.de
authors.forename: S M
authors.initials: SM
authors.lastname: Qaim
authors.forename: A
authors.initials: A
authors.lastname: Hohn
authors.forename: Th
authors.initials: T
authors.lastname: Bastian
authors.forename: K M
authors.initials: KM
authors.lastname: El-Azoney
authors.forename: G
authors.initials: G
authors.lastname: Blessing
authors.forename: S
authors.initials: S
authors.lastname: Spellerberg
authors.forename: B
authors.initials: B
authors.lastname: Scholten
authors.forename: H H
authors.initials: HH
authors.lastname: Coenen
mesh_terms: D017357:Cyclotrons; D007457:Iodine Radioisotopes / Q000737:chemistry / Q000302:isolation & purification*; D011854:Radiochemistry / Q000295:instrumentation / Q000379:methods; D011876:Radionuclide Generators; D019275:Radiopharmaceuticals / Q000737:chemistry / Q000302:isolation & purification*; D013691:Tellurium / Q000737:chemistry; D014055:Tomography, Emission-Computed
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013691:Tellurium