The Pennsylvania Patient Safety Authority received about 150 reports describing events in which patients with certain implanted objects or in which patients were not screened properly for metallic items were scheduled for MRI scans. These events resulted in some patients going into the MRI scanning room with implanted pacemakers and other metallic objects. The magnetic field of the MRI scanner may exert forces on certain implanted objects that are susceptible to the effects of the magnetic field, potentially causing the object to move within the body, which could result in serious harm. The most frequently reported problem involved sixty-eight reports (about 46%) of patients with implanted heart devices (e.g. pacemakers, heart defibrillators) getting past the safeguard of the screening process and entering into the MRI scan room or being stopped from entering the scan room by the final screening process. Other reports identified MR screening forms with incorrectly or inadequately answered questions. Many reports described miscommunication between facility departments (e.g. medical/surgical and radiology departments). Patients can protect themselves from possible injury by understanding the screening process prior to an MRI scan and by providing as much information as possible during the screening process.
The MR Safety Screening Process - What you Should Know
The screening process for an MRI scan is often a multi-level process consisting of the following:
A preliminary question-and-answer interview with you via a telephone call when the appointment is scheduled by non-MR personnel.
At the time of the appointment in the reception room, an MR screening form is filled out by you or a representative if you are unable to do so.
A more thorough screening is performed by MR personnel before you enter the MRI scanning room. Questions are asked to determine your medical history and metal exposure history in relation to the MRI scan.
If your medical history cannot be obtained and if the MRI scan cannot be rescheduled, then MRI personnel should physically examine you for signs of scars or other marks that may show that you’ve had an object implanted.
If a question remains regarding an implant or potential implant, an MR safety director should decide whether or not to proceed with the MRI scan.
Make sure you answer all questions on the screening form as accurately as possible to avoid confusion or
misunderstanding as to any implants you have received.
Don’t be embarrassed to ask or answer any question. For example, one report submitted to the Authority put a patient at risk because he/she did not initially disclose they were wearing a “house arrest” ankle bracelet.
If you experience any discomfort during your MRI scan, you should alert the MR technician right away.
The American College of Radiology (ACR) developed the “ACR Guidance Document for Safe MR Practices” which is widely used by the healthcare industry. The guidance recommends a four-zone model for the screening process. Each zone in the model represents a different safety level of magnetic field exposure for the general public. The four zones are as follows:
- Patients can roam freely in Zone 1. These areas include all areas just outside the MR environment such as corridors and entrances.
- Zone 2: Includes the area between the public accessible Zone 1 and the more strictly controlled MR environments
of Zones 3 and 4. Zone 2 areas typically include the reception, waiting and patient dressing and holding rooms. The general public is usually not free to move throughout Zone 2 without the supervision of MR personnel.
- Zone 3: This area is restricted to unscreened non-MR personnel and metal objects or equipment. Serious injury or
death could result in Zone 3 due to interactions between the individuals, objects or equipment and the MR environment’s static and magnetic fields. Supervision is under the control of the appropriate MR personnel. Access to Zone 3 should be physically restricted from the general public through the use of a locking system.
- Zone 4: This is the area containing the MRI scanner and it has the strongest magnetic fields. Zone 4 should be clearly
marked as being potentially dangerous due to strong magnetic fields. Zone 4 should also be marked with a red light and lighted sign stating “Magnet Is On.”
Table. Many ferromagnetic and non-ferromagnetic objects could be present on or in the body. Ferromagnetism refers to the process by which certain materials such as iron become permanent magnets or show strong interactions with magnets
Table. List of Items Found On or In Patients and Frequency of Reports
Pacemaker/implanted cardiac device/heart valve
Bullet/BB pellet/gunshot wound
Hearing aid/ear implant
Orbit (eye) metal
Abdominal aortic aneurysm stent
Inferior vena cava filter
“House-arrest” ankle bracelet
Pain pump (implanted)
Sweater (with 18% metal fabric)
Face mask (with metal nose piece)
For more information on the MRI scan data or to view excerpts from reports and to go to the 2009 March Pennsylvania Patient Safety Advisory article,