Moro Luca, Alabiso Francesco, Parisoli Francesco, Frigerio Francesco
Servizio di Fisica Sanitaria, Fondazione Salvatore Maugeri - IRCCS, Istituto Scientifico di Pavia.
G Ital Med Lav Ergon. 2013 Jan-Mar;35(1):26-31.
The recent postponement until 31 October 2013 of the deadline for transposition of the EU Directive 2004/40/EC, concerning the minimum health requirementsfor the exposure of workers to the risks arising from electromagnetic fields between 0 and 300 GHz, keeps on suspending the Italian law which was aimed to implement the EU regulations on the occupational exposure to electromagnetic fields, including those generated by Magnetic Resonance Imaging (MRI) units. Waiting for the revision of the exposure limits proposed by the EU Directive taking into account results from new studies and evolution of knowledge, the time-weighted values of static magnetic field proposed by the Italian Ministry of Health (D.M 02/08/91) still survive as limits for worker's exposure. The comparison between the proposed thresholds and the time required to position patients allows to calculate how long the MRI staff can stay at different values of static magnetic field, i.e. the maximum workload of each worker. In order to evaluate more accurately how many time the members of MRI staff are near the magnet bore and the real value of worker's exposure to the static magnetic field during the handling of patients, a teslameter Metrolab THM1176-PDA was used. Personal exposure measurements on the radiologists and the radiographers who worked on a 3 T GE Healthcare Discovery 750 MR were carried out during the positioning of self-sufficient and collaborative patients. The sensor was worn at the chest level on the side that was nearest to the magnet bore. Results show wide variations occurring between individual working procedures concerning the handling of patients, especially during the initial position phase. The mean values of the time spent by radiographers inside the magnet room (B > 0.5 mT) to place the patient and to take him outside at the end of the exam were respectively 220 and 127 seconds. The mean value of the time spent by radiologists was 162 seconds when they had to insert a peripheral vein access (arm) and inject contrast medium. The time fraction spent in magnetic flux density above 200 mT was near 31% for radiographers and about 7% for radiologists. The maximum of the static magnetic field recorded was 1550 mT for radiographers and 409 mT for radiologists. The measuring system has proven to be useful in evaluating the compliance with time weighted exposure limit stated by Italian law and also to find the maximum magnetic flux density to which the staff is actually exposed. This is the quantity of significance in evaluating workers' exposure following international guidelines.
欧盟指令2004/40/EC涉及工人暴露于0至300吉赫兹之间电磁场产生风险的最低健康要求，其转换期限最近推迟至2013年10月31日，这使得旨在实施欧盟关于职业暴露于电磁场（包括磁共振成像（MRI）设备产生的电磁场）法规的意大利法律继续暂停。在等待欧盟指令根据新研究结果和知识演变对暴露限值进行修订期间，意大利卫生部（1991年8月2日部长令）提出的静磁场时间加权值仍作为工人暴露的限值。将提议的阈值与安置患者所需时间进行比较，可以计算出MRI工作人员在不同静磁场值下可以停留的时间，即每个工人的最大工作量。为了更准确地评估MRI工作人员在患者处理过程中靠近磁体孔的时间以及工人暴露于静磁场的实际值，使用了一台特斯拉计Metrolab THM1176 - PDA。在安置自理和协作患者期间，对在3T通用电气医疗集团Discovery 750 MR上工作的放射科医生和放射技师进行了个人暴露测量。传感器佩戴在最靠近磁体孔一侧的胸部位置。结果表明，在患者处理的各个工作程序之间存在很大差异，尤其是在初始定位阶段。放射技师在磁体室（B＞0.5毫特斯拉）内安置患者并在检查结束时将其带出磁体室所花费的平均时间分别为220秒和127秒。当放射科医生必须插入外周静脉通路（手臂）并注射造影剂时，所花费的平均时间为162秒。放射技师在磁通密度高于200毫特斯拉时所花费的时间比例接近31%，放射科医生约为7%。记录到的静磁场最大值，放射技师为1550毫特斯拉，放射科医生为409毫特斯拉。该测量系统已被证明有助于评估是否符合意大利法律规定的时间加权暴露限值，还能找出工作人员实际暴露的最大磁通密度。这是按照国际准则评估工人暴露情况时的重要量值。
