Injuries associated with MR imaging: survey of safety records and methods used to screen patients for metallic foreign bodies before imaging

Abstract

Objective: The purpose of this study was to survey the methods used by academic institutions for identifying patients who might have metallic foreign bodies or other contraindications to MR imaging. We also sought to determine the types of MR-related injuries and any subsequent legal action that might have occurred at these institutions.

Materials and methods: A survey on these issues was mailed to 207 academic institutions listed in the American Medical Association's Directory of Graduate Medical Education Programs. Institutions that did not respond by mail were contacted by phone. The survey requested information on the use of questionnaires, plain radiography, CT, and metal detectors for screening potential MR imaging subjects, as well as on any MR-related injuries and subsequent legal action. Responses were entered into a data base and response percentages were calculated for each question.

Results: The overall response rate for the survey was 99% (206/207). These 206 institutions have a total of 368 MR imaging units, with a mean number of 1.8 MR units per department (range, none to nine). Data from a total of 205 different sites revealed that all patients are screened before MR imaging with a written questionnaire at 93% of all institutions (190/205). For selected indications, 85% of departments (174/205) screen with plain film radiography of the orbits. For selected indications, 41% of facilities (83/205) screen with CT of the orbits. Patients are sometimes screened with a metal detector or magnetometer in 12% of the departments (24/205). Ten departments reported serious injuries relating to MR imaging. The most serious injury occurred when an oxygen tank near the magnet became a missile and struck a patient's face. Most injuries (nine of 14) were burns. Two institutions also reported adverse reactions to gadopentetate dimeglumine. Injuries prompted legal action against four of the 10 institutions. No injuries were related to intraorbital foreign bodies, vascular clips, or pacemakers in patients.

Conclusion: These data demonstrate the lack of consensus on screening protocols before MR imaging. Accidents are uncommon, but most accidents that do occur are potentially severe and easily preventable. We recommend that all patients be screened by a written questionnaire followed by oral questioning before imaging to determine those who are at risk. Specific questions should investigate the possibility that patients have ferromagnetic foreign bodies or implants anywhere in the body that are electrically, magnetically, or mechanically activated. All facilities must maintain a high state of vigilance in an effort to prevent iatrogenic burns and injuries from ferromagnetic missiles.