Teitelbaum G P, Yee C A, Van Horn D D, Kim H S, Colletti P M
Department of Radiology, LAC-USC Medical Center 90033.
Radiology. 1990 Jun;175(3):855-9. doi: 10.1148/radiology.175.3.2343136.
The ferromagnetism of various bullets and shotgun pellets was tested in vitro. Magnetic deflection showed that four of 21 metallic specimens tested (all bullets) demonstrated marked ferromagnetism. Three of these four were made outside the United States; two of the four were known to contain steel, and the other two were reportedly either copper or copper-nickel-jacketed lead bullets (indicating that the ferromagnetism was due to impurities in the bullet jackets or cores). Ferromagnetic bullets readily rotated within a gelatin phantom in response to magnetic torque. Nonferromagnetic bullets and pellets demonstrated only mild to moderate metal artifact during spin-echo and gradient-echo magnetic resonance (MR) imaging. However, all four of the ferromagnetic bullets produced severe MR artifacts and image distortion. MR studies of seven patients with retained bullets, pellets, or shrapnel were reviewed. In six of the seven, only mild MR artifacts were seen. Only intracranial shrapnel (presumably steel) in one patient created significant artifact. All seven patients with retained bullets and shotgun pellets were imaged safely with MR. However, caution should be exercised with MR imaging in the presence of metallic foreign bodies, particularly if they are located near vital neural, vascular, or soft-tissue structures.
对各种子弹和霰弹进行了体外铁磁性测试。磁偏转显示，在测试的21个金属标本中（均为子弹），有4个表现出明显的铁磁性。这4个中的3个是在美国境外制造的；其中2个已知含有钢，另外2个据报道是铜或铜镍包覆铅弹（表明铁磁性是由于弹壳或弹芯中的杂质所致）。铁磁子弹在明胶模型中会因磁转矩而轻易旋转。非铁磁子弹和霰弹在自旋回波和梯度回波磁共振（MR）成像过程中仅表现出轻度至中度的金属伪影。然而，所有4颗铁磁子弹均产生了严重的MR伪影和图像失真。回顾了7例留有子弹、霰弹或弹片患者的MR研究。在这7例中的6例中，仅观察到轻度MR伪影。只有1例患者颅内的弹片（可能是钢质）产生了明显的伪影。所有7例留有子弹和霰弹的患者均通过MR安全成像。然而，在存在金属异物的情况下进行MR成像时应谨慎，特别是当它们位于重要的神经、血管或软组织结构附近时。
