S.A.S.T.A.S Department-Section of Protezionistica A.S.S.I, University of Messina, Viale Gazzi-Policlinico Universitario, Torre Biologica, 98125, Messina, Italy,
Radiol Med. 2014 Mar;119(3):208-13. doi: 10.1007/s11547-013-0324-5. Epub 2013 Dec 12.
In an attempt to evaluate the exposure level of magnetic resonance imaging (MRI) workers to static magnetic fields, the isotropic magnetic flux density values were integrated over time to produce the cumulative exposure. To protect occupational staff a further precautionary step is proposed by introducing a weighting function incorporating the limits imposed by the Italian legislation. The results obtained should be reported, at the end of each working day, on a special dose card, in order to record each worker's exposure to the static magnetic field. Moreover, this dose card could be an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site.
To conduct measurements, three Hall-sensor probes were used. The consistency of experimental data, tools and methodologies used was evaluated by performing the Kruskal-Wallis test. Finally, the weighted magnitude of the magnetic flux density was integrated over time to obtain global exposure.
Measurements were performed on different MRI scanners ranging from 0.25 up to 3.0 T. The results obtained were compared with the 200 mT·h, which represents the upper limit of the Italian regulation. In no case was the 200 mT·h per day exposure exceeded: however, when the strength of the magnetic field was >200 mT the weighted function overestimated the exposure, so that it represents a highly precautionary measure taking into account possible acute and long-term effects. In addition, from the data recorded during patient positioning operations by MRI staff the dB/dt curve was obtained.
The areas obtained from the integral of the weighted static magnetic field strength over time can be indicative of the global exposure of the occupational staff. These values should be reported on a special dose card that could be considered as an important tool if long-term effects occur because it provides a complete history of the occupational exposure in an MRI site.
为了评估磁共振成像（MRI）工作人员暴露于静磁场的水平，通过对各向同性磁通密度值随时间的积分，产生累积暴露。为了保护职业人员，建议引入一个权重函数，该函数包含了意大利法规规定的限制。应在每天工作结束时将结果报告在特殊的剂量卡上，以记录每个工作人员暴露于静磁场的情况。此外，如果出现长期影响，这种剂量卡可以成为一个重要的工具，因为它提供了 MRI 场所职业暴露的完整历史。
为了进行测量，使用了三个霍尔传感器探头。通过执行 Kruskal-Wallis 检验来评估实验数据、工具和使用的方法的一致性。最后，通过随时间对磁通密度的加权幅度进行积分来获得总暴露量。
在从 0.25 到 3.0 T 的不同 MRI 扫描仪上进行了测量。将获得的结果与 200 mT·h 进行了比较，200 mT·h 是意大利法规的上限。在任何情况下，都没有超过每天 200 mT·h 的暴露量：然而，当磁场强度>200 mT 时，加权函数高估了暴露量，因此它是一种非常谨慎的措施，考虑到可能的急性和长期影响。此外，还从 MRI 工作人员进行患者定位操作时记录的数据中获得了 dB/dt 曲线。
随时间对加权静磁场强度的积分所获得的区域可以指示职业人员的总暴露量。这些值应报告在特殊的剂量卡上，如果出现长期影响，这种剂量卡可以作为一个重要的工具，因为它提供了 MRI 场所职业暴露的完整历史。
