North D L, Shearer D R, Hennessey J V, Donovan G L
Department of Medical Physics, Rhode Island Hospital, Providence 02903, USA.
Health Phys. 2001 Sep;81(3):325-9. doi: 10.1097/00004032-200109000-00013.
The oral administration of radioactive 131I is a standard treatment for thyroid carcinoma. One consideration for this therapy is assuring that other people do not receive significant radiation exposure. In particular, federal and state regulatory authorities stipulate that no individual should receive more than 5 mSv (500 mrem) effective dose-equivalent from the released patient. Patients receiving more than 1.11 GBq (30 mCi) of 131I were traditionally confined as in-patients by regulation until their burdens of radioactivity fell below that level or until the external dose rates were less than 50 microSv (5 mrem) per hour at 1 m. Recent regulatory guidance recommends the use of biological elimination as well as physical decay in calculating the confinement time to keep the effective dose-equivalent to members of the public less than 5 mSv. Analysis of a database of more than 250 administrations of 131I for thyroid cancer shows a median effective half-life of at least 14 h, with substantial variation. Thus, discharge criteria for radiation safety purposes should be calculated on the basis of individual measurements. The release of these patients should not always be as prompt as the guidance indicates. The results also challenge some long-used assumptions regarding iodine excretion in this patient population.
口服放射性131I是甲状腺癌的标准治疗方法。这种治疗需要考虑的一个因素是确保其他人不会受到大量辐射照射。特别是，联邦和州监管机构规定，任何个人从出院患者那里接受的有效剂量当量不应超过5毫希沃特（500毫雷姆）。传统上，接受超过1.11吉贝可（30毫居里）131I的患者按规定要作为住院病人进行隔离，直到其放射性负担降至该水平以下，或者直到在距离患者1米处的外照射剂量率低于每小时50微希沃特（5毫雷姆）。最近的监管指南建议在计算隔离时间时使用生物消除以及物理衰变，以使公众成员的有效剂量当量低于5毫希沃特。对250多例用于甲状腺癌的131I给药数据库的分析表明，有效半衰期中位数至少为14小时，且存在很大差异。因此，出于辐射安全目的的出院标准应根据个体测量结果来计算。这些患者的出院并不总是像指南所表明的那样迅速。研究结果还对有关该患者群体碘排泄的一些长期假设提出了挑战。
