Bolliger Stephan A, Thali Michael J, Gascho Dominic, Poschmann Sebastian A, Eggert Sebastian
Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, 8057, Zurich, Switzerland.
Int J Legal Med. 2017 Sep;131(5):1363-1368. doi: 10.1007/s00414-017-1574-x. Epub 2017 Mar 16.
The fact that ferromagnetic bullets can move in air or gelatine when subjected to magnetic resonance (MR) units is well known. A previous study showed that the movement of 7.5-mm GP 11 Suisse bullets also depends on their orientation toward the gantry. In order to compare the movement in gelatine to that in real tissue, we decided to measure the movement of these bullets, as well as 9-mm Luger bullets, in the brain and liver.
The GP 11 and 9-mm Luger bullets were inserted into the fresh calf brain or pig liver either vertically or horizontally in the x- or z-axis to the gantry. Before and after exposure to a 3-T MR unit, their position was documented by CT.
GP 11 bullets rotated more readily and in general proved to be more mobile than the 9-mm Luger. All GP 11 bullets and a large amount of the 9-mm Luger bullets exited the brain. Sliding toward the gantry was easier for 9-mm Luger bullets in the brain than in the liver.
The orientation of a ferromagnetic object influences its mobility in a strong magnetic field. Tipping is easier than sliding for longish ferromagnetic projectiles, probably due to the lesser tissue resistance. The bullets moved more readily in biological tissue, especially brain tissue, compared to gelatine, thus implying that gelatine is not a suitable substitute for soft tissues when examining the movement of ferromagnetic objects in MR units.
铁磁性子弹在受到磁共振（MR）设备作用时能在空气或明胶中移动，这一事实已为人熟知。先前的一项研究表明，7.5毫米GP 11瑞士子弹的移动也取决于它们相对于扫描架的方向。为了比较子弹在明胶中的移动与在真实组织中的移动情况，我们决定测量这些子弹以及9毫米鲁格子弹在脑和肝脏中的移动。
将GP 11和9毫米鲁格子弹沿与扫描架的x轴或z轴垂直或水平方向插入新鲜的小牛脑或猪肝中。在暴露于3-T MR设备之前和之后，通过CT记录它们的位置。
GP 11子弹比9毫米鲁格子弹更容易旋转，总体上移动性更强。所有GP 11子弹和大量9毫米鲁格子弹都穿出了脑。9毫米鲁格子弹在脑中比在肝脏中更容易向扫描架滑动。
铁磁性物体的方向会影响其在强磁场中的移动性。对于较长的铁磁性射弹，翻转比滑动更容易，这可能是由于组织阻力较小。与明胶相比，子弹在生物组织尤其是脑组织中移动得更顺畅，因此这意味着在研究铁磁性物体在MR设备中的移动时，明胶不是软组织的合适替代品。
