External fixation and braces are typically very carefully screened for contraindication for MRI examination, but what may not be as frequently screened is the clothing underneath. We’ve received a report of a patient who received a burn from the specialty T-shirt, worn under their brace! The T-shirt, which included electrically-conductive silver fibers, purportedly acted as an RF antennae and produced focal heating.

This incident, like so many others, goes to show how so many risks in the MRI environment, such as concealed ferromagnetic threats, can be difficult to find if you don’t have the proper tools and knowledge with which to look for them.

Every MRI provider should avail themselves of the latest MRI safety information, standards, recommendations and peer accounts of accidents and near-misses in order to deploy the greatest protections, both for their patients and for their own risk management. For burn risks, this means diligent screening of everything that accompanies the patient into the bore. For ferromagnetic (projectile) risks, this includes the use of ferromagnetic detection systems.

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The article describes how the boy was wrapped in a metallic ‘space blanket’ during the exam, and yet the 3rd degree burn was attributed (by the hospital administration) to ‘trapped heat’ in the cotton blanket that came from a blanket warmer.

Example of Space Blanket

Though it may have taken a little ‘nudging’ to get a formal commitment on the part of the hospital to cover the costs of all treatment associated with the burn, it is the least that should be done to offset the injury that was caused by a failure to follow industry standard screening protocols.

Hopefully this incident will also trigger a review of MRI protocols and procedures at this facility, too. Often the ‘it’ll never happen here’ attitude persists even after an incident (morphing, ever so smoothly, into ‘it’ll never happen here again‘), with little effectively done to reduce the risks of recurrence.

And as I am a firm believer in the gold-plated opportunity that is presented every time we learn of any mistake (our own or others’), I hope that MRI providers around the world look at this incident as one more validating event that periodic reviews of our safety policies is not just a good idea, it’s absolutely necessary in such a dynamic area as MRI.

Some insurance payers are beginning to refuse reimbursement for care that is necessitated by certain ‘never events’, and that list is likely to grow. And while they may not always result in patient injury, I’d like to propose my own list of 5 MRI ‘never events’ which should at least trigger an investigation…

#5 Unauthorized Access: If any person, patient, visitor or staff member, gains access to the restricted areas of the MRI suite (Zones III and IV) without having been appropriately screened and supervised, this should raise red-flags and be the impetus for a review of the physical protections and operational protocols. Too often, because these safety-symptoms don’t immediately result in injury, they are disregarded as harmless, which couldn’t be further from the truth. If unscreened people or equipment are making it into the controlled access areas of the MRI suite, it’s only a matter of time before one of them is involved in a real accident.

#4 NSF / Renal Function Screening: A year ago, this may have appeared as the #1 item on this list, but the fact is that, today, many facilities are doing a great job of this. Essentially, we need to provide, at a minimum, a renal function risk-factor screening for every patient prior to being administered Gadolinium-based contrast agents. And, minimally, for patients identified as falling within one of the higher-risk profiles, a calculated eGFR should be taken for verification of patient risk and to inform the treatment of that patient. As with the #5 never event above, the failure to provide effective screening, even if it doesn’t result in an adverse outcome, is enough to warrant a review of operational protocols.

#3 Contraindicated Implants: There are times when, as a concurrent result of poor patient history / records, and inconspicuous (or absent) indicators for medical devices, patients (or visitors) enter the MRI scanner room with contraindicated devices. Nobody expects MR Technologists to be omniscient about what is on or inside their patients, but it is critical that we provide an appropriately thorough screening for the circumstances to try and ascertain whether the patient has any of the potpourri of shunts, pacers, stimulators, clips, pins, plates, etc… that may be dangerous to them. Any failure to use the appropriate means available to identify contraindications should, minimally, spur an evaluation of policies & procedures.

#2 RF Burns: This one factor may be the fastest-growing source of patient injury in MRI. By verifying that unneeded coils and leads are removed, that remaining leads are appropriately positioned and insulated from the patient, that the patient’s body is not positioned to form large-caliber loops, and that there is appropriate distance / insulation between the patient and any transmitting RF coils are all integral, requisite elements to minimizing the risks of MR burns. A failure to follow the appropriate steps to protect the patient, even if the shortcut doesn’t result in a visible burn, should (as with the proceeding never events) trigger a review of operational procedures.

#1 Projectiles / Missiles: Screening protocols should do everything to make sure that ferromagnetic materials are not brought into the MRI scanner room. Any discovered ferromagnetic material inside the MRI room indicates a breakdown in screening and presents all of the ingredients for injury or equipment damage. Particularly for MRI providers that don’t gown all of their patients, the use of a ferromagnetic detector is more than just recommended, it is codified in the ACR Guidance Document for Safe MR Practices as a part of the MR safety best practice. And as with all of the MRI never events before #1, any discovery of a ferromagnetic threat inside the magnet room should trigger a review of existing protections, operations and protocols.

While these 5 don’t encompass all of MRI safety, they do clearly represent 5 of the most common (and most avoidable) hazards in the MRI environment. MRI providers should have rigorous protocols and protections to minimize these risks to patients, staff, visitors and, in the case of projectile accidents, millions of dollars of MRI equipment.

First, let’s get the issue of non-ferromagnetic metals taken care of.

Metals that aren’t attracted to magnets are non-ferromagnetic. However, even if they aren’t attracted to the magnet, non-ferromagnetic metals do still interact with the magnetic field. They can cause local distortions which can mess up MRI scans (making it very difficult to image anatomy close to any metallic implant or object). Orthodontic braces may make certain facial / brain scans difficult. Orthopedic implants may disrupt the MR imaging of areas right around the pin / plate / screw / rod. Different materials will have different disruptive properties, so never assume that you can’t be imaged simply because you have an orthopedic implant. Check with a radiologist.

Also, MR imaging makes use of radio frequency (RF) energy. Like magnetism, RF is non-ionizing (doesn’t break down DNA and give rise to cancers as X-ray energies have been shown capable of), and like magnetism RF interacts with electrically conductive materials. If an electrically conductive element is the right shape and/or size, the material may inadvertently serve as an antenna for the RF signal and the energy may disproportionately collect in the conductor. As you may remember from high school physics, energy doesn’t just ‘go away,’ it converts. in the case of RF energy, it converts to heat. If you have the ‘ideal’ antenna length and/or configuration for a particular radio frequency, it can cause remarkable heating and that heat can cause damage.

But just as with the issue of image disruption, don’t assume that the presence of an electrical conductor inside your body is an automatic contraindication for an MRI exam. Consult your radiologist.

For these reasons, it is important to identify all electrically conductive materials on or in the patient. But even with these real risks associated with non-ferromagnetic materials, the greatest threat, both in terms of numbers of incidents and fatalities, is ferromagnetic materials.

Now, let’s move on to ferromagnetic materials. Some of this may seem familiar to you if you’ve read my prior post on MRI and Metal, but work with me here and you’ll find that we delve a little deeper into what happens that makes ferromagnetic materials such a concern.

When a ferromagnetic material enters a magnetic field, it becomes a magnet itself. A ferromagnetic material accepts an induced magnetic field. Many ferromagnetic materials give up the field almost as easily as they accept it, so they aren’t significantly magnetized. Think of them in the same way as I’m a baseball fan… when surrounded by baseball fans, I can pretend to be interested. Away from other baseball fans, I have almost zero interest in the game.

So, if a ferromagnetic material becomes a magnet when exposed to another magnet, we now have two magnets, and we all know what happens when we bring two magnets together… [SNAP]

Actually, when we bring two magnets together, two distinct things happen. The first is that the two magnets work to align themselves to one another. We know that two like magnetic fields (positive-to-positive) will repel each other, but opposite polarity fields will attract. The natural action is that the magnets will work to rotate themselves in order to align their fields positive-to-negative. Compass needles are the living illustration of this as we count on them to rotate to align with the North Pole.

In the case of a ferromagnetic object brought near an MRI, let’s compare our two magnets. One weighs perhaps 12 tons and is bolted to the floor, the other is a pair of scissors that weigh a few ounces. Which of these two things is going to rotate to align itself? Right, the scissors.

So the smaller ferromagnetic objects that we wear, carry, or have placed within our bodies, are going to be subject to intense forces that will be working to align the magnetic polarity of the object to the massive (in weight and strength) magnetic polarity of the MRI magnet. This results in torque forces that can twist, turn and even tear whatever may be trying to hold them in place.

The other mechanical force that develops between two magnets is the one we’re all very familiar with… attractive force. As we bring two magnets that have aligned themselves to one another (or, as it the case of sticking a magnet to your fridge door, the non-magnetized large ferromagnetic material develops a localized magnetic domain in order to receive the fridge-door magnet you’re sticking to it), they snap together, often with startling speed and strength.

We describe this phenomenon in MRI as the ‘missile effect’ because ferromagnetic objects, propelled by enormous amounts of magnetic energy, can launch across the room with tremendous force towards an MRI. While magnetic projectiles may look as though they’ve been launched from a cannon, unlike ‘launched’ projectiles, these magnetic missiles don’t lose their inertia just because they hit something. Their singular mission in life is to reach the strongest part of that magnetic field and, if interrupted in their flight, they will incessantly continue applying pressure to try and push their way towards the peak of the magnetic field (typically the center of the MRI).

The torque from rotating ferromagnetic materials and the force of flying ferromagnetic materials have each killed people in the MRI, and caused many injuries, and done horrific damage to MRI machines and their components. This presents two major problems…

First, metal is everywhere. It’s in our shoes. It’s in the shiny filaments in our clothes. Our belt-buckles. It’s in the stuff in our pockets. It’s often in thing that are labeled ‘sand bags’. It’s in stuffed animals and even often in hospital pillows. Metal is an unavoidable part of modern life.

Second, as I described in my prior post on metal and MRI, it’s impossible to visually distinguish between magnetic and non-magnetic metals. Even if we know something is made out of wood, for example, doesn’t mean that we can be confident that it isn’t held together with steel screws or reinforced with a steel rod. So, not only is metal ubiquitous, but ferromagnetic metals are perhaps the most widespread types of metal used in contemporary life.

Because of the torque and attraction risks of ferromagnetic materials, many tools and devices made for use in the MRI environment that require the strength and durability of metal use of aluminum, titanium, brass and other non-magnetic materials.

It is the intersection of these concerns – that all types of metal are everywhere and that we usually want to admit non-ferromagnetic metals into the MRI room – that generates the need for a detection system that distinguishes only ferromagnetic material.

The name of this blog is the MRI Metal Detector for precisely this reason… while I frequently digress and discuss many things relevant to MRI safety, at the heart this forum is about the specific risks associated with ferromagnetic metals and, equally importantly, the contemporary tools that can be effectively deployed to help reduce those risks.

To help protect patients, staff, and millions of dollars of MRI equipment, I recommend (as do the VA, the ACR and others) that every MRI provider avail themselves of ferromagnetic detection to help more effectively screen people and equipment intended to enter the MRI suite.