固体靶PET核素碘-124的制备、质控及甲状腺分子显像

Preparation,quality control and thyroid molecule imaging of solid-target based radionuclide ioine-124

目的:建立利用医用回旋加速器有效生产高放射性活度碘-124(^(124)I)的方法,以期为进一步制备和使用^(124)I提供参考。方法:采用124Te(p,n)^(124)I的质子核反应进行^(124)I的制备,首先通过压片装置将靶材料124Te O2压制在圆形铂金靶上,利用医用回旋加速器轰击靶片6~10 h,然后采用放置12 h的方法除去核不良反应可能产生的杂核素,最后采用碘升华-放射化学分离的方法收集得到^(124)I溶液。静脉注射740 k Bq的^(124)I生理盐水溶液至小鼠体内,观察^(124)I的正常生理分布,利用micro-PET/CT可见其在甲状腺有明显富集。结果:通过压片装置能够有效实现200 mg的124TeO_2在铂金靶片的压制。固体靶上124Te镀层平滑、均匀、致密,无明显凹坑和裂纹。采用医用回旋加速器以12.0 Me V能量,20.0μA质子束,轰击获得370~1 110 MBq的^(124)I,经放射化学分离纯化后可获得370~740 MBq的高放射性活度^(124)I,定容于45 000 Bq/μL的0.01 mol/L氢氧化钠中,核纯度大于80.0%。经过尾部静脉注射^(124)I生理盐水溶液到小鼠体内后,micro-PET/CT成像发现小鼠体内甲状腺部位具有明显的放射性信号浓聚,另在胃部也有富集,并观察到其从膀胱代谢,该代谢行为符合碘元素在生物体内的代谢规律。结论:通过压片装置成功地进行了^(124)I固体靶片的制备,并利用医用回旋加速器已成功进行了^(124)I的生产,通过碘升华纯化装置,获得370~740 MBq高放射性活度的^(124)I,并实现了模型动物甲状腺的micro-PET/CT分子显像。^(124)I的生产为我国科学研究和临床应用提供一种新的核素奠定了基础。

Objective:To provide useful information for the further production and application of this novel radio-nuclide for potential clinical application.Methods:124Te(p,n)124 I nuclide reaction was used for the 124 I 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,124 I 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 124 I.After 740 kBq 124 I 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 124 I’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 20μA current on HM-20 cyclotron.Then 370-1 110 MBq 124 I could be produced on the solid target after irradiation and 370-740 MBq high specific activity could be collected afterdry distillation separation and ra-dio-chemical purification.124 I product was finally dissolved in 0.01 mol/L NaOH for the future distribution.The gamma spectrum of the produced 124 I-solution showed that radionuclide purity was over 80.0%.The micro-PET imaging of 124 I 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 124 I 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 124 I by a cyclotron for biomedical application,and micro-PET imaging of 124 I 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 124 I is expected to provide a new solid target radionuclide for the scientific research and potential clinical application of our country.