View as “PDF version”
Our April 2, 2019 Patient Safety Tip of the Week “Unexpected Events During MRI” had a fairly comprehensive discussion of some recent developments in MRI safety. But, since MRI safety made ECRI Institute’s annual Top 10 list for Health Technology Hazards for 2020 (ECRI 2019), we thought this is an opportune time for an another update on MRI safety. Item #8 on the ECRI list, “Missing Implant Data Can Delay or Add Danger to MRI Scans”, is also one we’ve discussed in multiple columns (see the list of our prior columns below). Because some implants can heat, move, or malfunction when exposed to an MRI system’s magnetic field, they must be screened for prior to the procedure. ECRI suggests that, akin to an allergy list, organizations develop an implant list that collects all relevant information in one easy-to-access location in the electronic medical record. We like that idea!
In fact, a recent artificial intelligence (AI) study (Valtchinov 2019) used natural language processing (NLP) to identify such implantable devices from radiology reports, emergency department (ED) notes, and other clinical reports (eg, cardiology, operating room, physician notes, radiology reports, pathology reports, patient letters). The proportion of radiology reports, ED notes, and other clinical reports retrieved containing implantable devices with high safety risks for MRI ranged from 1.47% to 1.88%. This is a very promising approach to developing comprehensive lists of implantable devices posing high safety risks for MRI.
The most recent update of ACR guidelines on MR safety (Greenberg 2019) has a section on screening for both patients and non-MR personnel. Particularly illuminating is the section on ferromagnetic materials in unexpected places that may pose a risk for thermal injury during MRI. In our September 2019 What's New in the Patient Safety World column “New MRI Hazard: Magnetic Eyelashes” we discussed the risks associated with a new phenomenon: magnetic eyelashes. But the ACR guideline update notes that clothing and other related products may have incorporated ferromagnetic and/or conductive materials (eg, antimicrobial silver and copper) that are not reliably disclosed in labeling. Examples given include sportswear (including underwear), brassieres, orthotic‐related items (eg, stump covers or stump shrinkers), and blankets, but there are likely others as well. As a result, the guideline recommends patients wear only MR‐Safe gowns or scrubs supplied by the imaging facility for areas in or around the volume of transmitted RF power. The 2013 updated guidelines also discuss issues related to tattoos and dermal adornments. It also discusses orbital X-rays for screening patients having a history of orbital trauma with possible metallic elements. And see below for recommendations on prisoners with metallic restraints or tracking devices.
A recent review of over 1500 reports over a decade of adverse events related to MR reported to FDA (Delfino 2019) categorized adverse events as thermal (59%), mechanical (11%,), projectile (9%), and acoustic (6%). Mechanical events included things like slips, falls, crush injuries, broken bones, and cuts; musculoskeletal injuries from lifting or movement of the device. The authors thought the majority of these were potentially preventable. There were 3 deaths, two involving MRI technicians and the third due to a pain pump malfunction caused by the magnetic field.
One factor contributing to many of the thermal injuries was the MRI coils used in the examination. They noted inadvertent contact with another coil, electrocardiogram electrodes or leads, patient clothing, or stereotaxic head frames in 28% of such cases and skin-to-skin contact in 16%. The most recent update of ACR guidelines on MR safety (Greenberg 2019) advises that to help safeguard against thermal injuries or burns, “insulating pads should be placed between the patient's skin and any transmit RF coil located behind the walls and ceiling of the bore of the magnet system, especially the area of the transmit RF body coil, to ensure spacing between the bore wall and the patient's skin”. It notes that a single‐layer bed sheet is insufficient insulation or spacing. Interestingly, it acknowledges that large conducting loops may be created within the patient's own tissues by points of skin‐to‐skin contact, such as thigh‐to‐thigh contact. So, providing insulation in such areas may also be required to prevent burns.
Another paper (Cross 2018) stresses the importance of training in prevention of adverse MRI events. The authors suggest tailoring the training in accord with how or how likely the staff person is to come in contact with the MRI unit. Comprehensive training would be given to those who routinely work in and around the MRI scanner. That would include radiologists (or others who may be involved in MRI, such as neurologists), technicians, physicists and engineers, radiology nurses, and anyone who routinely may be in the MRI suite. A lesser level of training might be given to those working near the MRI unit who might occasionally be in the unit (eg. other radiologists, nurses, etc.). Any other individuals would be screened before access to the MRI suite.
And, you have to plan for the unexpected. You want to make sure your MRI unit is secured after hours to prevent housecleaning or building maintenance staff from inadvertently stumbling into any zone of the MRI suite or the scanner room itself. The most recent update of ACR guidelines on MR safety (Greenberg 2019) states that the “entry door to Zone IV (MR system room) should be closed except when it must be open for patient care or room/MR system maintenance. During the times that the door to the MR system room must remain open, a "caution" barrier is recommended at the entry to Zone IV to inhibit unintended passage of personnel and/or materials from Zone III to IV. Examples of caution barriers include easily adjusted straps or plastic chains secured across the scanner room doorway.”
In several previous columns, we’ve noted another group that needs training: first responders. Specifically, your local fire and police departments need training (see, for example, our October 21, 2014 Patient Safety Tip of the Week “The Fire Department and Your Hospital”). You don’t want a fireman with an axe and an oxygen tank racing into a room with an active magnet. Nor do you want a policeman with a ferromagnetic weapon in that room. We recommend you conduct training with the fire and police departments at least annually. The problem is more complex in rural or other communities that rely on volunteer firemen. You need to make sure new volunteers get such training before the annual session.
The most recent update of ACR guidelines on MR safety (Greenberg 2019) has a section on management of prisoners and on prison or security personnel weapons (ie, firearms). “Ferromagnetic firearm weapons should not be permitted into Zone III unless deemed absolutely essential for maintenance of security due to the design of the facility. Furthermore, ferromagnetic firearms that are loaded pose a serious threat in Zone IV (the MR system room) due to the possibility of inadvertent discharge”. The 2013 update of ACR guidelines on MR safety (Kanal 2013) recommended that, “in cases where requested to scan a patient, prisoner, or parolee wearing RF bracelets or metallic handcuffs or anklecuffs, request that the patient be accompanied by the appropriate authorities who can and will remove the restraining device before the MR study and be charged with its replacement following the examination.”
The Cross article also describes the important roles played by the MRI medical director, safety officer, and safety expert.
The American College of Radiology (ACR) has published guidelines on MR safety, beginning in 2002 (Kanal 2002) with periodic updates, including major updates in 2013 (Kanal 2013) and most recently in 2019 (Greenberg 2019).
That most recent update (Greenberg 2019) also emphasizes the "full‐stop and final check" concept. “In instances where the patient is sedated or anesthetized, an inpatient, or an emergent case, a ‘full‐stop and final check’ performed by the MRI technologist along with support staff is recommended to confirm the completion of MR safety screening for the patient, support equipment, and personnel MR screening immediately prior to crossing from Zone III to Zone IV. ‘Full‐stop and final check’ may also be useful for nonsedated outpatients and inpatients prior to movement from Zone III to Zone IV. The purpose of this final check is to confirm patient name, ensure that all screening has been appropriately performed, and that there has been no change in patient and/or equipment status while in Zone III.” This is the equivalent of the surgical timeout. For years we have stressed the importance of timeouts outside the OR (see our June 6, 2011 Patient Safety Tip of the Week “Timeouts Outside the OR”).
The update also discusses some emerging issues in MR safety. Particularly of concern is that MR systems are increasingly being installed in environments outside of conventional diagnostic MR facilities (intraoperative/interventional MR, positron emission tomography (PET) MR, and MR‐guided radiation therapy). We refer you to that update for details of the many considerations in such “unconventional” sites.
Lastly, the update alerts us to the need for safety guidelines that will be related to 7T MR. The FDA has now cleared 7T MR for clinical use. It notes that many implants, devices, and foreign bodies, that don’t significantly overheat at lower strength MR, might heat excessively at 7T strength. And certain devices that may retain functionality at lower MR strengths might lose functionality at 7T. A very recent paper (Hoff 2019) outlines the safety risks and associated risk-avoidance strategies of clinical 7-T MRI. Of particular concern are metallic implants and the risk for thermal injury. They note that over 6,000 metallic devices that have undergone evaluation at 1.5- and 3-tesla imaging, but that only 300 or so metallic implants and RF transmit coils have been tested for safety at 7-tesla MRI. Hoff et al. are also concerned about patient bioeffects such as vertigo, dizziness, false feelings of motion, nausea, nystagmus, magnetophosphenes, and electrogustatory effects that are more common and potentially more pronounced at 7 T than at lower field strengths. They suggest that earplugs and headphones could help reduce acoustic noise and related inner-ear and vision abnormalities and that increasing the amount of time patients spend in the 7-tesla static magnetic field as they enter and exit the scanner might help alleviate any physical issues
7T MR will undoubtedly have some diagnostic advantages over lower strength MR units. But, as with any new technology, we need to be vigilant for unintended consequences.
Lastly, one unanswered MR patient safety issue has to do with use of gadolinium contrast agents. Studies have shown cumulative exposure to gadolinium leads to deposition in brain tissue. This is especially a concern in patient with known or suspected multiple sclerosis (MS), in whom multiple MRI’s are commonly part of management. The FDA issued an alert in 2017 (FDA 2017) about tissue retention of gadolinium-based contrast agents that called for MRI units to provide a Medication Guide to patients undergoing MRI with gadolinium-based contrast agents. It notes that, on the whole, benefits of use of gadolinium-based contrast agents probably outweigh the risks but that further investigation is needed. A recent study (Zivadinov 2019) confirmed cumulative retention of gadolinium in brain tissue in MS patients but found no clinical or radiologic correlates of more aggressive disease. The accompanying editorial (Haider 2019) notes that, although no evidence currently exists linking brain gadolinium deposits with clinical consequences, regulatory agencies both in the United States and Europe clearly caution that GBCA should only be administered when informative for patient care.
Some of our prior columns on patient safety issues related to MRI:
ECRI Institute. 2020 Top 10 Health Technology Hazards Executive Brief. October 2019
Valtchinov VI, Lacson R, Wang A, et al. Comparing Artificial Intelligence Approaches to Retrieve Clinical Reports Documenting Implantable Devices Posing MRI Safety Risks. Journal of the American College of Radiology 2019; Published online first August 16, 2019
Greenberg TD., Hoff MN, Gilk TB, et al. for the ACR Committee on MR Safety. ACR guidance document on MR safe practices: Updates and critical information 2019. J Magn Reson Imaging 2019; published online July 29, 2019
Delfino JG, Krainak DM, Flesher SA, et al. MRI‐Related FDA Adverse Event Reports: A 10‐Year Review. Medical Physics 2019; First published: 16 August 2019
Cross NM, Hoff MN, Kanal KM. Avoiding MRI-Related Accidents: A Practical Approach to Implementing MR Safety. Journal of the American College of Radiology 2018; 15(12): 1738-1744
Kanal E, Barkovich AJ, Bell C, et al for the Expert Panel on MR Safety. ACR guidance document on MR safe practices: 2013. J Magn Reson Imaging 2013; 37: 501-530
Kanal E, Borgstede JP, Barkovich AJ, et al. American College of Radiology White Paper on MR safety. AJR AM J Roentgenol 2002; 178: 1335-1347
Hoff MN, McKinney A, Shellock FG, et al. Safety Considerations of 7-T MRI in Clinical Practice. Radiology 2019 292: 3: 509-551
FDA (US Food and Drug Administration). FDA Drug Safety Communication: FDA warns that gadolinium-based contrast agents (GBCAs) are retained in the body; requires new class warnings. FDA 12/19/2017 and 5/16/2018 Update
Zivadinov R, Bergsland N, Hagemeier J, et al. Cumulative gadodiamide administration leads to brain gadolinium deposition in early MS. Neurology 2019; 93(6): e611-e623
Haider L, Naismith RT, Rovira A. Use of gadolinium for MRI diagnostic or surveillance studies in patients with MS. Neurology 2019, 93(6): 239-240
Print “PDF version”