Critical Considerations in MRI Safety

Safety is critical when performing MRI procedures in veterinary practice. Safety issues related to the magnetic fields, radiofrequency energy, patient care, staff safety, and environmental concerns are crucial considerations in the MRI environment.

1. Magnetic Field Safety

The magnet in an MRI scanner is a powerful attractant for ferrous metal. The magnet of a 3T MRI is 60,000 times stronger than the Earth’s magnetic field. Any object containing ferrous metal can literally become a flying missile, potentially injuring a technician or the patient. Consequently, all objects within a calibrated distance from the scanner, called the Gauss Line, must be without ferrous metal or MRI safe. All patient monitors, anesthesia machines, IV poles, and patient support equipment must also be MRI safe.

• Personal Screening
  Since all ferrous materials in the MRI environment can become projectiles, it is imperative that all watches, cell phones, and jewelry be removed prior to entry. Wallets and credit cards need to be removed since the strong magnetic field can erase credit cards with a magnetic strip.
• Patient Screening
  It is imperative that each patient be assessed for any metallic implants such as joint replacements or surgical hardware, as they can cause tissue burns and image distortion. Most modern implants are titanium or stainless steel, which are MRI compatible; however, some older implants are contraindicated.
• Monitoring Equipment
  All patient support equipment, such as patient monitors, IV poles, and anesthesia equipment, must be MRI compatible.

A patient bed was literally “sucked” into an MRI scanner. Fortunately, no one was hurt.

2. Radiofrequency Energy Safety

Radiofrequency (RF) energy is used in MRI to create diagnostic images. This RF energy can interact with devices in close contact with the patient, as well as surgical implants that have ferrous metals, causing heating in the surrounding tissue.

To further prevent tissue injury, it is important not to have any direct contact of the patient’s skin with the coil of the MR system. The MRI Safe – ConRad Thermal Blanket, in addition to preventing hypothermia, also acts as an excellent “insulator” between the patient’s skin and the coil to prevent tissue injury.

3. Anesthesia Safety

The majority of MRI scans take 1½ to 2 hours, during which the patient cannot move. Consequently, every veterinary patient requires general anesthesia. This necessitates that the anesthetic machine, patient monitors, IV poles, and other equipment in the room be MRI safe.

Anesthesia during MRI presents its unique set of challenges:

• Limited Access:
  The patient is sequestered inside the circle of the magnet for 1½ to 2 hours and is virtually inaccessible. Dislodgement of an endotracheal tube may not be detected until vital signs change on the monitor.
• Hypothermia Risk:
  General anesthesia causes vasodilation of peripheral blood vessels, leading to shunting of warm core blood to the periphery. This, coupled with the large surface area to mass ratio of veterinary patients, makes hypothermia a perpetual problem in MRI.
• After 1½ to 2 hours in an MRI scanner, it is not uncommon for patients to be 2 to 3 degrees Fahrenheit below normal body temperature.
• Active warming devices containing ferrous metals cannot be used in MRI environments.

The MRI Safe – ConRad Thermal Blanket has proven to be an effective solution for combating hypothermia. The blanket circumferentially wraps the patient, maintaining body temperature and preventing deleterious effects of hypothermia.

4. Staff Safety

Veterinary staff working with MRI machines must follow strict safety protocols to mitigate risks associated with the strong MRI magnetic field.

• Training:
  All personnel working in the MRI environment must receive appropriate training, including understanding magnetic field hazards, system operation, emergency procedures, and maintaining a safe MRI environment.
• Magnetic Field Exposure:
  MRI technicians and veterinarians must follow guidelines regarding personal items, such as watches, cell phones, keys, jewelry, and credit cards, which can be damaged or pose risks in the MRI environment.
• Pregnant Staff:
  Pregnant MRI staff are advised to avoid the MRI environment during the first trimester. While MRI is generally considered safe in the second and third trimesters, it should still be approached cautiously due to limited conclusive evidence regarding early pregnancy safety.

5. Patient Positioning Safety

Patients undergoing MRI scans can remain in the scanner for several hours. Improper positioning can lead to joint pain, muscular injury, and soft tissue pressure sores.

The MRI Safe – HUG-U-VAC Positioners provide:

• Precise anatomical positioning for high-quality imaging.
• Prevention of postoperative joint pain and soft tissue injuries through vacuum activation, conforming to the patient’s anatomy.

6. Environmental Safety

MRI environments present unique challenges:

• Temperature Control:
• Optimal magnet operation requires an ambient room temperature of 18°C and very low humidity (45%), which hastens body heat loss.
• Cooling fans blow through the magnet, further contributing to patient heat loss.

One study showed that 63% of patients became hypothermic (less than 36°C) during MRI scanning.

• Shielding:
  MRI suites are frequently shielded to contain the magnetic field and prevent interference with nearby electronics. Only MRI-compatible equipment should be used to prevent malfunctions, equipment damage, and staff injuries.

The MRI Safe – ConRad Thermal Blanket is a proven, effective solution for maintaining patient warmth and ensuring safety in the MRI environment.

Summary

Safety in the MRI environment requires diligent management of magnetic fields, radiofrequency energy, anesthesia, staff protocols, patient positioning, and environmental conditions. Following strict safety protocols, using MRI-compatible equipment, and providing appropriate training can mitigate risks and ensure safety for both patients and staff.