OBJECTIVE: To provide useful information for the further production and application of this novel radio-nuclide for potential clinical application. METHODS: ¹²⁴Te (p,n) ¹²⁴I nuclide reaction was used for the ¹²⁴I production. Firstly, the target material, ¹²⁴TeO₂ (200 mg) and Al2O3 (30 mg) mixture, were compressed into the round platinum based solid target by tablet device. HM-20 medical cyclotron was applied to irradiate the solid target slice for 6-10 h with helium and water cooling. Then, the radiated solid target was placed for 12 h (overnight) to decay the radioactive impurity; finally, ¹²⁴I was be purified by dry distillation using 1 mL/min nitrogen for about 6 hours and radiochemical separation methods. Micro-PET imaging studies were performed to investigate the metabolism properties and thyroid imaging ability of ¹²⁴I.After 740 kBq ¹²⁴I was injected intravenously into the tail vein of the normal mice, the animals were imaged with micro-PET and infused with CT. The micro-PET/CT infusion imaging revealed actual state ¹²⁴I's metabolism in the mice. RESULTS: It was been successfully applied for 200 mg ¹²⁴TeO₂ plating by the tablet device on the surface of platinum. It showed smooth, dense surface and without obviously pits and cracks. The enriched ¹²⁴Te target was irradiated for 6 to 10 hours at about 12.0 MeV with 20 μA current on HM-20 cyclotron. Then 370-1 110 MBq ¹²⁴I could be produced on the solid target after irradiation and 370-740 MBq high specific activity could be collected afterdry distillation separation and radio-chemical purification.¹²⁴I product was finally dissolved in 0.01 mol/L NaOH for the future distribution. The gamma spectrum of the produced ¹²⁴I-solution showed that radionuclide purity was over 80.0%. The micro-PET imaging of ¹²⁴I in the normal mice exhibited the thyroid and stomach accumulations and kidney metabolism, the bladder could also be clearly visible, which was in accordance with what was previously reported. To the best of our knowledge, it was the first production of ¹²⁴I report in China. CONCLUSION In this study, the preparation of ¹²⁴TeO₂ solid target was successfully carried out by using the tablet device. After irradiation of the ¹²⁴TeO₂ solid target and radio-chemical purification, we successfully produced 370-740 MBq high specific activity ¹²⁴I by a cyclotron for biomedical application, and micro-PET imaging of ¹²⁴I in normal mice exhibited the thyroid accumulations. Also, slight uptake in stomach were also monitored with almost nonuptake in other organs in the micro-PET imaging. The production of ¹²⁴I is expected to provide a new solid target radionuclide for the scientific research and potential clinical application of our country.
Animals ; China ; Cyclotrons ; Iodine Radioisotopes/standards* ; Mice ; Positron Emission Tomography Computed Tomography ; Quality Control ; Radiochemistry ; Radiopharmaceuticals/standards* ; Thyroid Gland/diagnostic imaging* ; Tomography, Emission-Computed

OBJECTIVETo study the immunoactivity,biodistribution and metabolic pattern of (131)I-Herceptin in rabbits.

METHODSHerceptin was radiolabelled with (131)I and its radiochemicalpurity (RCP) measured by size-exclusion high-pressure liquid chromatography (HPLC). The binding rate to BT-474 cells was measured to evaluate the immunoactivity of (131)I-Herceptin. (131)I-herceptin (2.0 mCi/kg) was injected intravenously into New Zealand rabbits. Scintigraphy on emission computed tomography was performed at 3 h, 1, 3 and 5 days after injection, and the radiocounts of the heart, liver and kidney etc. were compared with that of the muscle to calculate the organ-to-muscle activity ratio (O/M). On the fifth day,the rabbits were killed and the blood, myocardium, lung and other organs were obtained for measuring the radiocounts on gamma-counter to calculate the uptake percentage per gram tissue (ID%/g).

RESULTSThe labeling rate of (131)I-herceptin was 93% with RCP of 95% and binding rate to BT-474 cells of 36.9%. After injection of (131)I-herceptin, the heart, lung and liver displayed dense radioactive regions but not the muscles and intestines. Three hours after injection, the O/M ratio of the heart was significantly higher than that of the lung, kidney and intestine (P<0.05), but decreased significantly one day after injection (t=10.817, P<0.001) with further decrement on days 3 and 5 (P<0.05). The O/M ratio of liver on day 1, 3, and 5 reduced significantly in comparison with that at 3 h (P<0.05). The uptake percentage was higher in the blood (11.3 ID/g%) than in the liver (2.8 ID/g%) and the myocardium (1.8 ID/g%).

CONCLUSIONS(131)I-herceptin possesses high immunoactivity which distributes mainly in the blood, liver and kidney, but with low uptake in the myocardium.

Animals ; Antibodies, Monoclonal ; administration & dosage ; metabolism ; pharmacokinetics ; Antibodies, Monoclonal, Humanized ; Antineoplastic Agents ; administration & dosage ; pharmacokinetics ; standards ; Binding, Competitive ; Cell Line, Tumor ; Chromatography, High Pressure Liquid ; Female ; Humans ; Injections, Intravenous ; Iodine Radioisotopes ; administration & dosage ; metabolism ; pharmacokinetics ; Male ; Quality Control ; Rabbits ; Time Factors ; Tissue Distribution ; Trastuzumab