Lin W Y, Tsai S C, Hsieh B T, Lee T W, Ting G, Wang S J
Department of Nuclear Medicine, Taichung Veterans General Hospital, Taiwan.
J Nucl Cardiol. 2000 Jan-Feb;7(1):37-42. doi: 10.1067/mnc.2000.102919.
Intravascular brachytherapy is an effective method for inhibiting coronary restenosis after percutaneous transluminal coronary angioplasty. A new concept for preventing restenosis is the use of a liquid-filled balloon containing a beta-ray-emitting radioisotope. Generator-produced rhenium-188 (Re-188) is a good candidate for intravascular brachytherapy. However, in the unlikely event of balloon rupture, release of Re-188 perrhenate may cause a high radiation dose to the thyroid and stomach. In this study, we compared the biodistributions of three Re-188 preparations (Re-188 perrhenate, Re-188 pentetic acid [DTPA], and Re-188 MAG3) to assess the radiation dose to organs in a rat model that mimicked balloon rupture.
After injection of Re-188 preparations intravenously, rats were killed at 10 minutes, 30 minutes, 60 minutes, 2 hours, and 6 hours (n = 5/group). Tissue concentrations were calculated and expressed as percent injected dose per gram or per milliliter. In addition, urine excretion and thyroid gland uptake were evaluated in rats (n = 5/group) with a gamma camera after administration of 37 MBq (1 mCi) of each agent. Our data showed all 3 agents were excreted primarily via urine. In the Re-188 MAG3 group, 82% was excreted within 1 hour, but in the Re-188 perrhenate group, only 28% was excreted. The biodistribution data for these agents revealed that radioactivity levels in the stomach and the thyroid gland were high in the perrhenate group but low in the Re-188 DTPA and Re-188 MAG3 groups. The concentration levels in other tissues including lung, liver, testis, muscle, and blood were low throughout this study for all 3 agents. The thyroid radiation values were 0.163, 0.0167, and 0.00728 mGy/MBq for Re-188 perrhenate, Re-188 DTPA, and Re-188 MAG3, respectively. The stomach radiation values were 0.127 mGy/MBq for Re-188 perrhenate, 0.013 mGy/MBq for Re-188 DTPA, and 0.0104 mGy/MBq for Re-188 MAG3.
In the event of balloon rupture, the release of Re-188 MAG3 or Re-188 DTPA results in lower radiation doses than release of Re-188 perrhenate, especially to the thyroid gland and the stomach.
血管内近距离放射治疗是抑制经皮冠状动脉腔内血管成形术后冠状动脉再狭窄的有效方法。预防再狭窄的一个新概念是使用含有发射β射线的放射性同位素的充液球囊。发生器产生的铼-188（Re-188）是血管内近距离放射治疗的良好候选物。然而，在球囊破裂这种不太可能发生的情况下，高铼酸盐Re-188的释放可能会给甲状腺和胃部带来高辐射剂量。在本研究中，我们比较了三种Re-188制剂（高铼酸盐Re-188、喷替酸Re-188 [DTPA]和巯基乙酰三甘氨酸Re-188 [MAG3]）的生物分布，以评估在模拟球囊破裂的大鼠模型中各器官的辐射剂量。
静脉注射Re-188制剂后，在10分钟、30分钟、60分钟、2小时和6小时处死大鼠（每组n = 5）。计算组织浓度，并表示为每克或每毫升注射剂量的百分比。此外，在给予每种制剂37 MBq（1 mCi）后，用γ相机评估大鼠（每组n = 5）的尿液排泄和甲状腺摄取情况。我们的数据显示，所有三种制剂主要通过尿液排泄。在Re-188 MAG3组中，82%在1小时内排泄，但在高铼酸盐Re-188组中，仅28%被排泄。这些制剂的生物分布数据显示，高铼酸盐组中胃部和甲状腺的放射性水平较高，而在Re-188 DTPA和Re-188 MAG3组中较低。在整个研究过程中，所有三种制剂在包括肺、肝、睾丸、肌肉和血液在内的其他组织中的浓度水平都很低。Re-188高铼酸盐、Re-188 DTPA和Re-188 MAG3的甲状腺辐射值分别为0.163、0.0167和0.00728 mGy/MBq。Re-188高铼酸盐的胃部辐射值为0.127 mGy/MBq，Re-188 DTPA为0.013 mGy/MBq，Re-188 MAG3为0.0104 mGy/MBq。
在球囊破裂的情况下，Re-188 MAG3或Re-188 DTPA的释放所导致的辐射剂量低于高铼酸盐Re-188的释放，尤其是对甲状腺和胃部。
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