磁共振扫描中受检者电磁辐射现状与防护对策

Electromagnetic Radiation and Protection in Magnetic Resonance Scanning

[目的]研究不同部位累积射频能量吸收剂量(CSAD),分析受检者在磁共振扫描中的电磁辐射现状,探讨相应的防护措施。[方法]采用美国GE公司的signa EXITE HD 1.5T TwinSpeed扫描仪,头颅8通道高分辨线圈,腹部8通道相控阵线圈,根据机器自动计算出的峰值射频能量吸收率和每个序列的扫描时间分别计算得到各序列的射频能量吸收剂量(SAD),从而得到头颅和腹部常规序列(包括平扫和增强)扫描时的CSAD。[结果]头颅前10min内平扫扫描CSAD修正后为2.5489W/kg。第二个10min内,轴位三维扰相位快速梯度回波增强扫描时为1.2915W/kg;普通矢状位、冠状位、轴位增强扫描时为2.7146W/kg,为前者的2.1倍。腹部扫描前5min内CSAD修正后为1.5071W/kg,第二个5min内为0.8940W/kg。[结论]受检者在1.5T磁共振行头颅和腹部扫描的CSAD均未超过美国食品药品管理局制定的安全阈值,但是采用不同的脉冲序列扫描时电磁辐射剂量相差很大。合理选择并优化扫描脉冲序列,缩短检查时间,可有效降低受检者的电磁辐射剂量,防范受检者可能受到的潜在电磁辐射危险。

[ Objective ] To identify appropriate protective approaches to magnetic resonance scanning by evaluating the cumulative specific absorption dose （CSAD） of different body parts. [ Methods ] A signa EXITE HD 1.5 Tesla TwinSpeed magnetic resonance system （GE, US） with 8-channel high resolution brain coil and 8-channel abdominal phased array coil was applied in this study. CSADs of conventional head and abdomen sequences （including plain and enhanced） were estimated by peak specific absorption rate provided by the system and scanning time of each sequence. [ Results ] The first-lO-min adjusted CSAD in head was 2.548 9 W/kg in plain scanning and the second-lO-min was 1.291 5 W/kg in axial 3D FSPGR enhanced scanning （2,714 6 W/kg for conventional position enhanced scanning, 2.1 times that of the former）. The first-5-min CSAD in abdomen was 1.507 1 W/kg and the second-5-min was 0.8940 W/kg. [ Conclusion ] Both head and abdominal CSADs by 1.5 T magnetic resonance scanning are within the FDA safety limit, but electromagnetic radiation dose varies significantly using different pulse sequences. It is advisable to make a reasonable optimization on pulse sequence selection to shorten examination time and effectively reduce electromagnetic radiation doses and potential hazards subsequently.