MRI の吸引力についての検討

Abstract

Magnetic Resonance Imaging（ MRI ）は被曝のない低侵襲の検査であるが，検査室内は常時強い磁場が発生しており注意が 必要である．MRI 装置への磁性体の吸引事故は海外では死亡事例も報告されており，その安全管理は重要である．近年導入す る施設が増えている 3 テスラ MRI 装置は高画質の画像が提供できる一方で，従来の 1.5 テスラ装置の倍の磁場が発生し，より 安全面への注意が必要である．今回，磁性体としてクリップを用いて当院の MRI 装置での静磁場中の金属の吸引力を検討した ところ，MRI 装置まで距離が近いほど吸引力は大きくなり，磁場の強さと磁性体の質量に比例して吸引力は大きくなった． 重大な吸着事故を予防するため，MRI 検査室に磁性体を持ち込まないように入室前の金属チェックが重要である．

Magnetic resonance imaging (MRI) is a minimally invasive examination, but the constantly strong magnetic field in the exam ination room requires caution. Incidents caused by attraction of magnetic objects to the MRI device including deaths have been reported. Therefore, adequate safety management is important. The new 3.0T MRI device now being introduced in many facilities provides an image with a higher contrast. On the other hand, the 3.0T MRI device has twice the magnetic field of the previous 1.5T MRI device. We examined the magnetic field of our instrument using a metal clip as a magnetic object, and measured the magnetic attraction of our MRI device. The magnetic attraction became stronger the closer the magnetic object was to the MRI device and the larger its mass. In order to prevent serious attraction incidents, it is important to check the patients for metal ob jects before they enter the room and make sure no metal objects are brought into the MRI examination room.