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Patient Safety Tip of the Week

April 2, 2019   Unexpected Events During MRI


We’ve done quite a few columns on patient safety issues related to MRI scanning and safety issue in radiology departments in general (see the list at the end of today’s column). But unexpected events beyond just those related to patient safety may impact patient flow and efficiency within the MRI suite. A recent study of almost 35,000 MRI scans in a large multi-hospital system quantified the unexpected events encountered in patients having MRI scans (Sadigh 2017). The authors found that unanticipated events occurred in 16.7% of all scans.


Rates of unanticipated events for each of the following categories were:


Patient events unrelated to contrast included:


Other patient events unrelated to contrast included issues regarding body habitus, pregnancy, falls, inability to complete the exam, and code called for resuscitation.


The authors found that the rate of overall unanticipated events was significantly higher in university-affiliated sites than at community-affiliated sites (18% vs. 5%), in scans performed in the mixed outpatient/inpatient settings than those strictly outpatient settings (22.3% vs. 12.6%), and in scans performed during weekends/holidays than on business days (21.5% vs. 16.2%). The authors anticipated that patients at university-related sites were likely more complicated, hence more likely to experience unexpected events. However, the magnitude of the difference was quite striking. The higher weekend/holiday rate was largely driven by patient events unrelated to contrast.


Delays in performing MRI are not, per se, patient safety events. But they do become important because such delays lead to time pressures that can subsequently be factors contributing to other events that are true patient safety events. For example, in our December 11, 2018 Patient Safety Tip of the Week “Another NMBA Accident” we noted that a delay in recognizing a patient had claustrophobia and needed sedation led to time pressures that likely contributed to a fatal medication error. (That case involved PET scanning, not MRI scanning, but one can easily see how the same might happen with MRI).


We refer you back to some of our earliest columns on MRI safety and, in particular the work of Emanuel Kanal and Tobias Gilk (see our October 25, 2011 Patient Safety Tip of the Week “Renewed Focus on MRI Safety”).


And, of course, we’ll point out that the majority of adverse events in the MRI suite probably have little to do with MRI imaging itself. In our numerous columns on the radiology suite being a hazardous area (see, for example, our October 22, 2013 Patient Safety Tip of the Week “How Safe Is Your Radiology Suite?”), we’ve pointed out that patients coming for imaging studies often have complex medical problems and are often receiving multiple medications, have multiple IV lines and other catheter connections, and have multiple monitoring needs. The primary caregivers are often not attending the patient in radiology and communication breakdowns are common. Add to that certain features that are more common in the MRI suite: need to isolate the patient in a room, preclusion of certain types of equipment, and the frequent need for sedation.


Pediatric patients, in particular, often need sedation for an MRI scan. We have discussed procedural sedation in children in several columns (see our What’s New in the Patient Safety World columns for August 2016 “Guideline Update for Pediatric Sedation” and or Patient Safety Tips of the Week for January 17, ,2017 “Pediatric MRI Safety” and August 8, 2017 “Sedation for Pediatric MRI Rising”). A very interesting approach to reduce the need for sedation in young children comes from Denmark (Forrest 2018). Researchers developed an app that features animated characters that explain what to expect from the MRI scan on a level suited to the child's age and cognitive ability. It tells the young children (age 4 to 9) what to expect. For example, it lets them know the scan will make loud noise and that they have to hold still. Using the app, they were able to substantially reduce the number of children undergoing sedation for MRI.


New 2019 guidelines for safe provision of anesthesia in magnetic resonance units in the UK (Wilson 2019) have been published. These are outstanding guidelines that include provisions for safety of not only patients but also staff. The supplemental tables include a series of very useful checklists for MRI safety.


They divide MRI hazards into five broad categories:

1.     Displacement force from static magnetic field

2.     Induced currents from time‐varying magnetic fields

3.     Acoustic noise

4.     Heating from radiofrequency fields

5.     Helium escape


All patients must be screened for devices and implants that may contraindicate a safe scan. The UK guideline (Wilson 2019) has a checklist for such screening. It also has excellent sections on passive implanted medical devices (eg. vascular access ports, catheters, cardiovascular stents, heart valves, orthopedic, ocular and penile implants, tissue expanders, breasts implants) that may contain metal components that may either heat up during scanning, produce artefact of the image or discomfort for the patient if the implant moves during the MR scan itself.


The section on implanted cardiac devices is excellent. It notes that most prosthetic heart valves, mechanical or bioprosthetic, and all coronary stents are considered safe in the MR environment at field strength up to 1.5 T and many will be safe up to 3 T. While the presence of a pacemaker or internal defibrillator formerly was considered an absolute contraindication to performing an MRI scan, this is now considered a relative contraindication, as MR conditional pacemakers allow patients to have non‐cardiac MRI scans under controlled conditions. These conditions are always detailed by the device manufacturer. But, in some cases, the pacemaker needs to be turned off and then reprogrammed following the scan, so coordination with the patient’s cardiology team is needed. And, obviously, the patient needs monitoring during the scan. They note that implantable defibrillators are usually a contraindication for MR, but in some cardiac centers scanning is possible, with appropriate monitoring and resuscitation support.


Other devices covered in the guidelines are programmable shunts (for hydrocephalus), neurostimulators and implantable programmable devices, programmable pumps, and even self-implanted devices like RF chips.


The guidelines also have a section dealing with gadolinium, discussing risks and safety issues to be considered when deciding whether use of gadolinium contrast will add important information from the scan.


Acoustic damage is a threat from MRI scanning. The UK guidelines require that all people remaining in the scanner room are provided with MR Safe hearing protection (eg. earplugs, ear defenders or both), noting this is particularly important for anesthetised patients, who are unable to alert the operators to hearing discomfort. Temporary hearing loss may occur with stronger magnets so patients and staff should be warned. For anesthesia personnel, they note a set‐up allowing remote monitoring from the control room is ideal. But, if this is not possible, staff who remain within the examination room must wear ear protection and be aware that the noise may still make communication difficult.


Many of the adverse events affecting patients during MRI could have been prevented by appropriate monitoring. The UK guidelines have a detailed section on equipment and monitoring. They note that most units exclude all unlabeled or MR Unsafe equipment from the examination room, but they do describe unique cases where constraints like physical tethers have been used. They recommend use of fibreoptic pulse oximeters because standard oximeters have been associated with reports of burns caused by induction currents. Similarly, specific MR Safe ECG electrodes are needed to monitor the patient during anesthesia or sedation because of the risk of burns with standard ECG electrodes and leads. They also advise that care should be taken interpreting the ECG trace when the patient is being scanned. They also have specific recommendations regarding both non‐invasive and invasive blood pressure monitoring, capnography, temperature monitoring, and other devices, such as intracranial pressure monitors.


The guidelines, of course, include details about how sedation and/or anesthesia should be provided in the MRI unit. They also have comments on specific situations like pregnancy, pediatrics, patients from ICU’s, and intraoperative MRI.


The guidelines also have sections on layout and design, visibility, access control, personnel and workflow, training and supervision of staff, and emergency procedures. The reference list is extensive and the checklists in the supplemental materials are very useful. These guidelines are a “must read” not only for anesthesiologist and MRI unit staff but for anybody who sends patients for MRI scanning.


There have been other good recent references on MRI safety (Sammet 2016, Cross 2018). Sammet discusses the various MRI zones and the importance of training for anyone that might enter the various zones. Note also that we have recommended you also do training sessions with your local fire and police departments on responding to emergencies in the MRI suite (see our October 21, 2014 Patient Safety Tip of the Week “The Fire Department and Your Hospital”). That last thing you want is a first responder wielding an axe or metallic weapon entering a zone where a magnet is active.


A recent Pennsylvania Patient Safety Advisory (Field 2018) reported on the incidents in Pennsylvania involving over 1100 MRI screening events from 2009 to 2017. The article lists a myriad of medical and nonmedical devices and objects that were brought to MRI suites and discusses what sorts of objects are allowable in the specific MRI zones. More than a quarter of the events involved a device or object brought into the MR scanner room that was not considered safe for MRI. The most common objects or devices involved in MRI screening events were pacemakers (32.3%). 35.2% of events involved external objects, carried in by or attached to the patient or healthcare staff. Of the 1100+ incidents, there were only five serious events (one nonmedical object projectile, one thermal injury from an external medical device, and three malfunctions or displacements of internal medical devices).


Field identified the following factors as contributing to the MRI screening events:

·       Screening forms were not completed or not fully completed either because of an oversight, staff unfamiliarity with the form, or a poorly designed form.

·       Patients had known history of an internal medical device but there was either no investigation or not enough time to determine whether the medical device was MR-safe or MR-conditional.

·       Patients had a known history of exposure to metal (e.g., metal worker, welder) but preliminary radiology screening was not ordered or completed because of an oversight or an unfamiliarity with the process for screening prior to MRI.

·       Patients had internal or external medical devices but failed to disclose having a device during screening either due to poor recall or misunderstanding of the definition of terms such as "implant."

·       Patients failed to disclose having exposure to metal due to poor recall or lack of knowledge regarding having internal metal artifacts and/or foreign bodies.

·       External devices or objects reaching Zone III or Zone IV because the patient or non-MR personnel forgot they had ferromagnetic objects on them, were unaware of a device's or object's ferromagnetic properties or components, or did not understand the strength and potential impact of the magnet.

The article has a good discussion on the MRI screening process and recommendations for training/education of MRI personnel, non-MRI personnel, and patients, plus recommendations about the environment and medical equipment.


As noted above, implantable cardiac devices have historically been a major safety concern for patients undergoing MRI, resulting in many patients not getting MRI’s that might have provided important information about their medical problems. A recent study (Bhuva 2019) reported on development of a ‘one-stop’ service for MRI, whereby such devices could be reprogrammed and scans acquired at a single location and visit. They trained a team including administrators, physicians, cardiac physiologists and radiographers and developed a standard protocol. This resulted in increased provision of MRI to such patients and significantly reduced delays in patients getting MRI. Their protocols and checklists are available at That article also has an excellent bibliography.


See also our October 2016 What's New in the Patient Safety World column “MRI Safety: There’s an App for That!” that describes an app which attempts to determine whether an MRI can be performed in the presence of certain implants. It considers not only the type of implant but also its location, the type of MRI scan being done, the part of the body being imaged, the strength of the magnet and other issues of configuration of the MRI machine, and other considerations such as the location of the various energy sources relative to the patient’s location in the MRI suite.


The effects of electromagnetic energy may result in thermal injuries from tissue heating, particularly in areas where metallic elements are in contact with skin or organs. ECG leads and electrodes or cables have been implicated most often. But another concern has been transdermal drug patches (see our March 2009 What's New in the Patient Safety World column “Risk of Burns during MRI Scans from Transdermal Drug Patches”). Sometimes those items are ones we would not even thing about. The RF identification tag on certain breast implants can heat up during the MR scan (Wilson 2019). 


One concern over the years has been what to do with patients having tattoos. Many color pigments may contain ferrous particles that may interact with the magnetic resonance and many are conductive and could lead to burns. There have been isolated cases of adverse effects of MRI related to tattoos. With the prevalence of tattoos increasing substantially in recent years, many patients with tattoos may have been denied MRI scans. But a recent prospective study (Callaghan 2019) found that, in 330 persons who had one to seven tattoos, only one mild tattoo-related adverse reaction was detected during MRI. That patient had an unpleasant tingling sensation in the tattoo that disappeared within 24 hours. The results suggest a low risk among persons with tattoos when MRI is performed under these specific study conditions. But note that the researchers had strict criteria regarding the size of tattoos: a single tattoo was not allowed to exceed 20 centimeters and tattoos could cover no more than five percent of the body in total.


And, while this is a column on unexpected events during MRI, we’d be remiss if we did not comment on unexpected events after MRI. Of course, we are referring here to detection of incidental findings on the MRI. We always teach our residents to consider before ordering an MRI (or any diagnostic test) what they will do if the result is normal, if it shows what they expected, or if it shows something unexpected. A systematic review and meta-analysis (Gibson 2018) found a pooled prevalence of potentially serious incidental findings was 3.9% on brain and body MRI, 1.4% on brain MRI, 1.3% on thoracic MRI, and 1.9% on abdominal MRI. About half the potentially serious incidental findings were suspected malignancies (brain, 0.6%, thorax, 0.6%, abdomen 1.3%, brain and body 2.3%. Limited data suggested that relatively few potentially serious incidental findings had serious final diagnoses (20.5%). We also refer you to two articles about incidental findings found on MRI scans done for headache evaluations (Evans 2017, Evans 2018). What is not known is what unintended consequences arise from the further testing and interventions that may take place after incidental findings are reported. We must always be ready to deal with the problem of incidental findings any time we order an MRI scan.


Lastly, keep in mind that, as magnets get stronger and stronger, we may see effects not seen with weaker magnets. Last year one study showed that mercury was released from dental amalgams when patients were exposed to 7.0 Tesla MRI magnets (Yilmaz 2018). It’s not known whether any harm comes from such events. But the point is that we must remain vigilant for adverse consequences as imaging becomes more advanced.



Some of our prior columns on patient safety issues related to MRI:



Some of our prior columns on patient safety issues in the radiology suite:

·       December 11, 2018     “Another NMBA Accident”






Sadigh G, Applegate KE, Saindane AM. Prevalence of Unanticipated Events Associated With MRI Examinations: A Benchmark for MRI Quality, Safety, and Patient Experience. J Am Coll Rad 2017; 14(6): 765-772 Published online: March 26, 2017



Forrest W. Pediatric patients use app to prep for MRI scan. 2018; March 2, 2018



Wilson SR, Shinde S, Appleby I, et al. Guidelines for the safe provision of anaesthesia in magnetic resonance units 2019. Guidelines from the Association of Anaesthetists and the Neuro Anaesthesia and Critical Care Society of Great Britain and Ireland. Anesthesia 2019; First published: 03 February 2019



Sammet S. Magnetic Resonance Safety. Abdominal Radiology 2016; 41(3): 444–451

March 2016



Cross M, Hoff MN, Kanal KM. Avoiding MRI-Related Accidents: A Practical Approach to Implementing MR Safety. J Am Coll Radiol 2018; 15(12): 1738-1744



Field C. MRI Screening: What’s in Your Pocket? Pa Patient Saf Advis 2018; 15(4). December 19, 2018



Bhuva AN, Feuchter P, Hawkins A, et al. MRI for patients with cardiac implantable electronic devices: simplifying complexity with a ‘one-stop’ service model. BMJ Qual Saf 2019; Published Online First: 13 February 2019



Callaghan MF, Negus C, Leff AP, et al. Safety of Tattoos in Persons Undergoing MRI
N Engl J Med 2019; 380: 495-496 Jan 31, 2019



Gibson LM, Paul L, Chappell FM, et al. Potentially serious incidental findings on brain and body magnetic resonance imaging of apparently asymptomatic adults: systematic review and meta-analysis. BMJ 2018; 363: k4577



Evans RW. Incidental Findings and Normal Anatomical Variants on MRI of the Brain in Adults for Primary Headaches. Headache 2017; 57(5): 780-791



Evans RW. Headache MRI: What to Do With Incidental Findings. Medscape Medical News 2018; August 28, 2018



Yilmaz S, Adison MZ. Ex Vivo Mercury Release from Dental Amalgam after 7.0-T and 1.5-T MRI. Radiology 2018; Published Online:Jun 26 2018





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