Buchli R, Boesiger P, Meier D
Institute of Biomedical Engineering, University of Zurich, Switzerland.
Magn Reson Med. 1988 Jul;7(3):255-61. doi: 10.1002/mrm.1910070302.
Magnetic radiofrequency fields applied in magnetic resonance imaging examinations induce electrical currents in metallic implants. These eddy currents may heat up the implants and thus may be capable of causing localized tissue heating. The rf power deposition and the joule heating of the implant can be calculated by solving Maxwell's equations for the specific problem. First, extreme in vitro worst-case experiments were performed with a large and very thin aluminum sheet, which was placed in a 1.5-T MRI device in a position parallel to the magnetic rf field. In agreement with the theoretical results the temperature rise of a thermally insulated sheet amounted to only 0.08 degrees C after a 15-min MRI examination at 64 MHz. No temperature rise in the aluminum sheet could be measured for a sheet immersed in a saline solution. Second, in vitro experiments with a hip joint prosthesis and an osteosynthetic plate were performed to confirm the theoretical results, which predict nearly no temperature rise in the metallic implants. No temperature rise in the implants could be measured.
磁共振成像检查中施加的射频磁场会在金属植入物中感应出电流。这些涡电流可能会使植入物升温，从而可能导致局部组织发热。通过针对特定问题求解麦克斯韦方程组，可以计算出植入物的射频功率沉积和焦耳热。首先，用一块大而薄的铝板进行了极端的体外最坏情况实验，该铝板被放置在1.5-T磁共振成像设备中与射频磁场平行的位置。与理论结果一致，在64兆赫兹下进行15分钟的磁共振成像检查后，隔热铝板的温度仅升高了0.08摄氏度。对于浸泡在盐溶液中的铝板，未检测到温度升高。其次，用髋关节假体和接骨板进行了体外实验，以证实理论结果，该结果预测金属植入物几乎不会升温。未检测到植入物温度升高。
