MRIs employ very strong magnets that can cause damage if any magnetic responsive metals are worn or equipment that could be driven by strong magnetic fields are used near them. That is why special MRI safe products are needed.
The Power of MR Magnets:
The magnet of the a magnetic resonance (MR) machine has a magnetic field that usually extends over the entire MR room, and beyond if not appropriately shielded. The magnetic field of a 1.5 Tesla machine is about 30,000 times stronger than the earth’s magnetic field.
Any magnetic or ferromagnetic material that is close to the MR machine will be subjected to great forces. That includes metallic implantations inside the patients themselves. Common objects can turn into deadly projectiles. Loose objects like cell phones, pins, clips, and keys can be a potentially deadly hazard. The magnets of the MR machine are always on, even when the machine itself is turned off. In every case, safety guidelines must be strictly observed.
A trained MR safety officer should be at hand at all times outside the MR room to assure that no unsafe objects can enter, even in times of emergencies. First responders or emergency personnel should not be admitted into the MR room without pre-screening. They should carry no magnetically sensitive materials into the room. Non-ferrous fire extinguishers need to be available inside the room.
The MR room is especially marked with zones of nearness to the machine. Each proximity zone should have its own limits as to the kinds of objects allowed in them. Staff should be well trained in recognizing objects or equipment that are unsafe for each zone.
The use of MR imagers require a special MR safety culture. Any personnel with access to the MR room should be carefully oriented in it. The MR safety officer should conduct regular training and training updates to keep all the stakeholders on their toes at all times.
All patients who are to be examined with the MR equipment and staff who work with the MR imagers have to go through screening before entry to be assured that their bodies contain no pacemakers, stents, implants, or other devices that are responsive to high magnetic fields.
Risks from intense MRI magnets:
- A study of 362,090 MRI examinations made between 2006 and 2012 gives an estimate of the real danger when the MR rooms are well administered. During that time, 1,290 MR-related accidents were reported. Only 2 out of the all the incidents resulted in death, but 8 resulted in permanent or major harm to the patient, and 307 caused temporary injury.
- In 2015, a 13-year-old boy lost his thumb during a routine MRI examination in France. He had been left in the MRI machine with a blood pressure monitoring device attached to his thumb. The device reportedly burned and the boy’s thumb was burned to the bone.
- A 6-year-old boy was reportedly killed when the machine’s powerful magnetic field jerked a metal oxygen tank across the room crushing the child’s head.
- Even the ink used in making tattoos may metallic. People with tattoos may experience short-term first and second degree burns from an MRI machine. Larger tattoos containing more ink may result in more serious effects. Deep red ink tends to contain more metallic compounds and may cause more burns. Facial tattoos or “permanent makeup” may be particularly painful. Older tattoo inks were made less stringently than newer inks and may pose a greater burn risk.
- Lens implants and lens implants may contain ferromagnetic elements. The Fatio eyelid spring and the retinal tack are made from Martensic, a ferromagnetic stainless steel. The Troutman magnetic ocular implant and the Unitek round wire eyelid spring show magnetic field interactions in an MR machine. Certain color contact lenses may contain iron oxide or other metals that may be problematic for MRI investigations or may distort MRI readings. Certain ocular shunt tubes, glaucoma drainage implants, magnetically activated devices, and the Scleral Buckle may be at risk.
What are MR safe tools and devices?
All tools, machines, tables and carts big and small within the MR room have be made of non-magnetic materials. Even non-ferrous metal tools, when part of a motor or moving device can cause distortions in the magnetic resonance image.
MR safe devices and tools are made with non-ferrous (not magnetically responsive) ceramics or other materials. Titanium is a metallic element with only very weak magnetic reactivity. Even though it is weakly responsive to magnetic fields, MRI tools are often made of titanium which is advertised as an MRI compatible.
Aluminum, and copper are non-ferrous metals used in making MR safe tools. Bronze (a copper-tin alloy) and brass (a copper-zinc alloy) are used as well. Some stainless steel can be de-magnetized, so equipment made of non-ferrous stainless steel can be used in MR rooms, unless these non-stainless steel materials get damaged or bent in which case they can become magnetically sensitive again. The final test of the magnetic properties of metal tools is to check them, pre-MR, with a permanent magnet or a ferromagnetic detector.
Ceramic materials are also used in making MR safe tools like scissors, knives and blades. Some boast the cutting capability of diamond.
Pneumatically-driven Ferrite-free motors have been developed to power equipment when MRIs are used simultaneously with surgery. One ceramic motor prototype can rotate at 14,000 rpm and achieve 36 watts of power. There are no magnetically sensitive components in these motors.
Starting in the business of manufacturing lenses for eyeglasses in 1905, Phillips Safety Products has grown into the manufacture of safety products. Our non-magnetic MRI prism glasses allow patients to see outside of the MRI machine during the MRI scan. Please contact us to learn more about our products.