磁共振成像的电磁安全与限值标准

磁共振成像(MRI)是一种将外源电磁能量输入人体后产生物理效应并转换为医学图像信息的技术,包括静磁场、射频场、梯度场共3种电磁场。这3种电磁场均对生物体产生效应,并且在足够的强度下会对人体产生健康危险,如梯度场的神经刺激、射频场(RF)的热效应等电磁危险性。近10年来,美国食品药品监督管理局(FDA)发出MRI检查导致带动脉夹患者死亡的警告、MRI对带植入性神经刺激器患者伤害的通告、MRI对带金属背衬经皮给药帖片患者带来灼伤的通告。然而,当电磁场强度被限制在一定范围内时,MRI仍然是安全的。分析这3种电磁场主要的生物效应和健康危险,讨论国内外有关MRI电磁安全的限值标准。

Electromagnetical Safety and Limited Standard of Magnetic Resonance Imaging

Magnetic Resonance Imaging(MRI),comprising of static magnetic fields,radio-frequency(RF) fields and time-varying gradient magnetic fields,is a diagnostic technique that a physical-effect is being transformed an image information for human after the immigrated electromagnetic energy imports ones.The electro magnetic fields may possibly have some risks for human health,such as nerve stimulation of gradient fields and thermal-effects of RF fields.During recently decades,FDA of USA has given a safety alert of MRI related death of patients with aneurysm clip,a public health notification of MRI-caused injuries in patients with implanted neurological stimulators and an advisory of risk of burns during MRI scans from transdermal drug patches with metallic backings.Nevertheless,MRI can be safe under a limited intensity electromagnetic fields.This review reports the bio-effects and health risk associated with three fields and some national and international standards about the limited electromagnetic fields in MRI.