Medical Physics Department, Perugia General Hospital, Perugia, Italy; Physics Department, University of Turin, Turin, Italy.
Medical Physics Unit, Azienda Usl Toscana sud est, San Donato Hospital, Arezzo, Italy.
Phys Med. 2020 Oct;78:150-155. doi: 10.1016/j.ejmp.2020.09.025. Epub 2020 Oct 6.
[F]Fluoromethylcholine ([F]FMCH) is a radiopharmaceutical used in positron emission tomography (PET) imaging for the study of prostate, breast, and brain tumors. It is usually synthesized in cyclotron facilities where F is produced by proton irradiation of [O]HO through O(p,n)F reaction. Due to the activation of target materials, the bombardment causes unwanted radionuclidic impurities in [O]HO, that need to be removed during the radiopharmaceutical synthesis. Thus, the aim of this study is to quantify the radionuclide impurities in the F production process and in the synthesized [F]FMCH, demonstrating the radionuclidic purity of this radiopharmaceutical.
Long-lived radionuclide impurities were experimentally assessed using high-resolution gamma and liquid scintillation spectrometries, while short-lived impurities were monitored analyzing the decay curve of the irradiated [O]HO with an activity calibrator. As spectrometric radionuclide library, a Geant4 Monte Carlo simulation of the F-target assembly was previously performed.
H, Mn, Co, Tc, Cd, and Re were found in the irradiated [O]HO, but no radionuclide was found in the non-irradiated [O]HO neither in the final [F]FMCH solution with an activity concentration greater than the minimum detectable activity concentration. A total impurity activity <6.2 kBq was measured in the irradiated [O]HO, whereas a [F]FMCH radionuclide purity >99.9999998% was estimated. Finally, the decay curve of the irradiated [O]HO revealed a very low maximum of N activity (<0.03% of F) even immediately after the end of bombardment.
This study demonstrated the radionuclidic purity of [F]FMCH according to the EU Pharmacopeia.
[F]氟甲基胆碱([F]FMCH)是一种放射性药物，用于正电子发射断层扫描(PET)成像，用于研究前列腺、乳房和脑肿瘤。它通常在回旋加速器设施中合成，其中 F 通过质子辐照[O]HO 通过 O(p,n)F 反应产生。由于靶材料的活化，轰击会导致[O]HO 中产生不需要的放射性核素杂质，这些杂质需要在放射性药物合成过程中去除。因此，本研究的目的是量化 F 生产过程中和合成的[F]FMCH 中的放射性核素杂质，证明这种放射性药物的放射性核素纯度。
使用高分辨率伽马和液体闪烁谱仪实验评估长寿命放射性核素杂质，而使用放射性活度校准器分析辐照[O]HO 的衰变曲线来监测短寿命杂质。作为光谱放射性核素库，之前对 F-靶组件进行了 Geant4 蒙特卡罗模拟。
在辐照的[O]HO 中发现了 H、Mn、Co、Tc、Cd 和 Re，但在未辐照的[O]HO 中以及放射性活度浓度大于最小可检测活度的最终[F]FMCH 溶液中均未发现放射性核素。在辐照的[O]HO 中测量到的总杂质活度<6.2kBq，而估计[F]FMCH 的放射性核素纯度>99.9999998%。最后，辐照的[O]HO 的衰变曲线显示，即使在轰击结束后立即，N 活度的最大值也非常低(<0.03%的 F)。
根据欧盟药典，本研究证明了[F]FMCH 的放射性核素纯度。
