背景：實施冠狀動脈擴張手術後之病人超過30%會發生心血管再狹症。利用錸-188-MAG3配合汽球擴張術對血管狹窄處進行局部輻射照射以預防再狹症復發，目前正進行IND試驗中。汽球破裂為這項治療可能發生的顧慮。本研究目的為評估錸-188-MAG3的放射化學安定性。萬一發生汽球破裂時，穩定的錸-188-MAG3會很快由腎臟排泄，確保全身輻射劑量低於可接受範圍。不安定的錸-188-MAG3則會使放射活性停滯在許多器官，對病人造成較高的輻射劑量。
方法：製備完成的錸-188-MAG3(3.7 GBq/ml)分成五組：包括控制組(不含維生素C或龍膽酸)、含25mg維生素C、含50mg維生素、含1 mg龍膽酸、含2 mg龍膽酸等；所有樣品均保存室溫下。每一樣品的體外安定性都以ITLC-SG/生理鹽水、TLC-SG 60/acetonitrile及Sep-Pak C18管柱(分別以0.001N HCI及乙醇-生理鹽水混合液淘洗)等分析系統在製備後0、3、6及24小時分析。
結果：控制組樣品的平圾放射化學純度在製備後3小時由原來的97%降為80%；6小時降為59%；24小時降為4%。樣品中含維生素C 25 mg或50 mg，錸-188-MAG3製備後24 小時的放射化學純度仍可以完整保留。樣品中若含龍膽酸1 mg或2 mg，錸-188-MAG3的放射化學純度可以保存至少6小時。

Backgrounds: following coronary angioplasty restenosis occurs in≧30% of cases. Local irradiation of the stenosed artery immediately after angioplasty using 188Re-MAG3 delivered into the diseased vessel via a balloon to prevent the restenosis is currently under investigation (IND). A potential complication of the procedure is balloon rupture. The aim of this study is to evaluate the radiochemical stability of 188Re-MAG3. stable 188 Re-MAG3, in unlikely event of balloon rupture, will be quickly eliminated via the kidneys, with a resultant acceptability low whole body radiation does. Unstable 188Re-MAG3, which is retained in various organs results in a greater rediation burden to the patient.
Methods: 188Re-MAG3 (3.7 GBq/ml) was prepared, and the product was evenly divided into 5 sample groups: control (without ascorbic or gentisic acid), with 25 mg of ascorbic acid, with 50 mg of ascorbic acid, with 1 mg of gentisic acid, and with 2 mg of gentisic acid. The samples were kept at room temperature. The in vitro stability of each sample was analyzed (N=3) by using ITLCSG/normal saline, TLC-SG 60/caetonitrile, and sep-Pak C18 column/ 0.001 N HCI, ethano/normal saline systems at 0, 3, 6 and 24 h after preparation.
Results: The results demonstrated that the mean radiochemical purity of the control sample decreased from 97% to 80% at 3 h, to 59% at 6 h, and to 4% at 24 h after preparation. In the presence of either 25 mg or 50 mg of ascorbic acid, the stability of 188Re-MAG3 was fully preserved after 24 h. in the presence of 1 mg or 2 mg of gentisic acid, the stability of 188Re-MAG3 was fully preserved up to 6 h after preparation.
Conclusion: The presence of ascorbic acid (25~50 mg) is needed to maintain in vitro stability of 188Re-MAG3.