医用回旋加速器生产正电子核素^(18)F条件分析与优化

Analysis and optimization of production conditions for ^(18)F production using a medical cyclotron

分析医用回旋加速器正电子核素18F的照射条件和轰击参数对生产的影响,优化生产条件并给出最佳的轰击参数以期获得高效的生产产额。使用Origin 9.0软件绘制核素18F产量随不同质子束流强度和轰击时间的变化趋势曲线,以蒙特卡罗方法建立回旋加速器质子辐照靶室模型,分析不同质子能量、Havar膜和靶水厚度等对核素18F产量的影响,并给出18F生产最佳的束流强度、轰击时间和质子能量等生产参数。回旋加速器运行期间束流应充分聚焦于照射靶室中心位置,最大化的利用束流以引发足够多的核反应;根据质子束流的能量选择合适的Havar膜和靶水厚度,20 Me V质子束流轰击生产正电子核素18F的靶室系统使用Havar膜总计厚度60μm,靶水厚度3 mm,可获得最佳18F产量。总体而言,18F的产量随束流强度而增大,轰击时间越长18F产量越大,但随着轰击时间的延长增长趋势变缓,轰击时间建议60 min左右。正电子核素18F的生产需要选择合适的Havar膜和靶水厚度(当质子能量为20 Me V时,推荐Havar厚度60μm,靶水厚度3 mm),轰击时间建议60 min左右,开机启动稳定一段时间后再开始照射。

[Background] Positron emission tomography/computed tomography （PET/CT） is a routine diagnostic method of particular importance for treatment evaluation and management in oncology. It is very important for PET/CT diagnosis to produce good quality and quantity positron nuclides using medical cyclotron. [Purpose] The effect of irradiation conditions and bombardment parameters on positron nuclide 18F production was analyzed to acquire the optimized production conditions and optimum bombardment parameters. [Methods] Origin 9.0 software was used to analyze the change of 18F yield with different proton beam current and bombardment time. Monte Carlo method was applied to establish the target chamber model of proton irradiation, and the proton energy, thicknesses of Havar foils and the 18O water were analyzed to obtain the optimum conditions of beam current, bombardment time and the proton energy, etc. [Results] Proton beam should thoroughly irradiate on target chamber center to make the best of beam current for triggering as much as nuclear reaction. When 20-MeV proton beam was used to produce 18F, the thicknesses of Havar foil and the target water were recommended to be 60 μm and 3 mm, respectively. Usually, the yield of 18F increases with the beam current. The longer the bombardment time was, the higher the yield of 18F. But with bombardment time increased, the trend of yield became slower. The bombardment time was suggested approximately 60 min. [Conclusion] It is necessary to select the appropriate thicknesses of Havar foil and the 180 water for positron radionuclide 18F production （this paper shows that the thicknesses of Havar foil and the 180 water should be 60 μm and 3 mm when the proton energy is 20 MeV）. The irradiation time was suggested approximate 60 min to obtain high yield of 18F. Furthermore, irradiation should be started after the cyclotron run for a period of time for stabilization.