Pellets and Bullets

The majority of pellets and bullets tested in the MR environment were found to be composed of nonferromagnetic materials. Ammunition that proved to be ferromagnetic tended to be manufactured in foreign countries and/or used for military applications. Shrapnel typically contains steel and, therefore, presents a potential hazard for patients undergoing MR procedures.

Because pellets, bullets, and shrapnel are frequently contaminated with ferromagnetic materials, the risk versus benefit of performing an MR procedure should be carefully considered.

Additional consideration must be given to whether the metallic object is located near or in a vital anatomic structure, with the assumption that the object is likely to be ferromagnetic and can potentially move.

In an effort to reduce lead poisoning in "puddling" type ducks, the federal government requires many of the eastern United States to use steel shotgun pellets instead of lead. The presence of steel shotgun pellets presents a potential hazard to patients undergoing MR procedures and causes substantial imaging artifacts at the immediate position of these metallic objects.

In one case, a small metallic BB located in a subcutaneous site caused painful symptoms in a patient exposed to an MR system, although no serious injury occurred. In consideration of this information, MRI healthcare professionals should exercise caution when deciding to perform MR procedures in patients with pellets, bullets, shrapnel or other similar ballistic objects.

Smugar et al. conducted an investigation to determine whether neurological problems developed in patients with intraspinal bullets or bullet fragments in association with MR imaging performed at 1.5-Tesla. Patients were queried during scanning for symptoms of discomfort, pain, or changes in neurological status.

Additionally, detailed neurological examinations were performed prior to MRI, post MRI, and at the patient's discharge. Based on these findings, Smugar et al. concluded that patients with complete spinal cord injury may undergo MR imaging if they have intraspinal bullets or fragments without concern for affects on their physical or neurological status. Thus, metallic fragments in the spinal canals of paralyzed patients are believed to represent only a relative contraindication to MR procedures.

REFERENCES

Shellock FG. Magnetic Resonance Procedures: Health Effects and Safety. CRC Press, LLC, Boca Raton, FL, 2001.

Shellock FG, Kanal E. Magnetic Resonance: Bioeffects, Safety, and Patient Management. Second Edition, Lippincott-Raven Press, New York, 1996.

Smugar SS, Schweitzer ME, Hume E. MRI in patients with intraspinal bullets. J Magn Reson Imaging 1999;9:151-153.

Teitelbaum GP. Metallic ballistic fragments: MR imaging safety and artifacts [Letter]. Radiology 1990;177:883.

Teitelbaum GP, Yee CA, Van Horn DD, et al. Metallic ballistic fragments: MR imaging safety and artifacts. Radiology 1990;175:855-859.