MR Screening

How do you screen patients for implants and foreign bodies prior to MRI?  
The American College of Radiology (ACR) has defined four safety zones (labeled I - IV) in and around a magnetic resonance imaging facility. All patients and non-MR personnel entering Zone III must undergo screening for implants and foreign bodies that may put them at risk in the magnetic environment. The recently published ACR Manual on MR Safety provides numerous excellent guidelines and suggestions for screening subjects.
​At least two separate screenings should be performed for non-emergent patients. The first level of screening should take place when the examination is ordered. The MR employee scheduling the exam should have basic training in MR safety and have ready a brief set of screening questions for the referring health care provider ordering the study. At a minimum, these questions should include: a) whether the patient has any implanted cardiac devices (pacemakers, wires, defibrillators) or other active devices (cochlear implant, neurostimulators, infusion pumps); b) a cerebral aneurysm clip; and c) any known metal fragments in critical locations like the eye.  Alternatively, if the examination is ordered through the electronic medical record, these questions can be programmed in with “hard stops” requiring an answer before allowing final scheduling. Although these questions are not exhaustive, they do cover a large fraction of common implants that potentially could create risk for the patient.
The second level of screening takes place when the patient presents to the MR Center for their exam. Conscious, non-emergent patients should complete a detailed written screening form like that pictured below. For children or patients with altered levels consciousness, history obtained from a source (parent, spouse, guardian) deemed reliable is acceptable. A technologist or other safety-trained staff member should then review the form in detail, with both parties signing it. 

For patients with altered consciousness for whom no reliable medical history is available, we review all recent imaging studies available, supplemented by plain film x-rays of the head and neck, chest, abdomen and pelvis as needed.
Picture
Sample MR Safety Screening Form provided by the ACR. Click on image to download the entire form as a pdf.
If a family member or other caretaker wishes to accompany the patient into Zone III and IV, they must undergo the same complete screening as the patient.
The above discussion applies to patient screening for devices and foreign bodies inside the body. Of course, a wide range of potentially dangerous objects (which might cause burns or act as projectiles) may be on the surface of the patient's body or in their clothes. We therefore recommend all patients change into MR-safe gowns, remove all jewelry, watches, hearing aids, piercings, hair pins, metallic drug delivery patches, and eye makeup before entering Zone III. Final screening by a ferromagnetic metal detector is recommended by the ACR, but this should not replace fastidious personal evaluation by the technologist.

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References
     ACR Committee on MR Safety. ACR Manual on MR Safety, version 1.0. American College of Radiology, 2020. [Direct Link]     
     Elster AD, Link KM, Carr JJ. Patient screening prior to MR imaging: a practical approach synthesized from protocols at 15 U.S. medical centers. AJR Am J Roentgenol 1994; 162:195-199.  [DOI Link]
Related Questions
     Should MRI facilities screen patients with metal detectors? 
     Which types of metal are the most dangerous around a magnetic field? 
     What are the ACR Safety Zones?​