MRI Safety

MRI Scanner Information and Participant Limitations

The Rotman MRI has a Siemens PrismaFit 3 Tesla whole body MRI scanner, installed in December 2020 . The magnet has a bore diameter of 60cm and a table weight limit of 250 kg / 550 lbs. In actual practice, depending on the height and weight distribution of the participant, the practical weight cutoff is usually lower (approximately 100 kg / 220 lbs) to comfortably fit inside the 60cm bore, without feeling claustrophobic, and to be able to use response boxes or other research equipment. If the participant can tolerate being in a tight space, it will be safe to put them on the table. If you want to measure the participant to confirm fit, the available width from side to side is 58cm (i.e. width at shoulders and hips should be < 58cm), and from back to front is 40cm (i.e. participant’s back to front of stomach), when the participant is in a supine position. For more technical information on the MRI scanner and accessories, please refer to the Facility and Equipment page.

MRI Risks and Contraindications

The Rotman MRI operates a dedicated research scanner (no prescribed clinical imaging) with a heavy emphasis on functional neuroimaging techniques. When deciding whether to perform a particular examination on a research participant, we have a different level of risk tolerance compared to clinical sites. The benefit of research scans are most often to the research study and not to the participant. As a result, our contraindications are primarily based on eliminating and minimizing any risk to our research participants. Just because a participant has received a clinical MRI in the past, does not guarantee that they will be eligible for research scans.

The primary categories of concerns for MRI safety are:

The magnet is always on. Therefore the magnetic field is always present. The magnet does not turn off when the scanner is “shut down”, or during a power outage, or for any reason other than a controlled ramp-down or an emergency quench.
The introduction of ferrous material into the magnetic field. Any ferrous objects introduced to the magnetic field have the potential to become high speed projectiles, causing injury or damaging equipment.
The potential for heating of implanted devices / objects and or disruption of their function. Metallic devices implanted in the body may experience forces exerted on them by the magnetic field, or may heat up over time within the magnetic field. Electronic devices implanted in the body may become permanently destroyed or have their function disrupted by the magnetic field.

The most common specific contraindications for MRI Research Imaging are:

Cardiac Pacemaker – The magnetic field can cause movement of the pulse generator or leads, temporary or permanent modification of the function of the device, and inappropriate sensing or activation of the device. Changing gradients can cause excessive heating of the leads or induced currents in the leads. Although MRI Conditional pacemakers exist, they remain a contraindication here at the Rotman MRI Facility due to no available qualified personnel to manage the pacemaker during the MRI scan (ie. electrophysiologist, cardiologist) and emergency medical resources on standby in our non-clinical environment.
Aneurysm Clip – Certain types of intracranial aneurysm clips (e.g. those made from martensitic stainless steels such as 17-7PH or 405 stainless steel) are an absolute contraindication to the use of MR procedures because excessive, magnetically induced forces can displace these clips and cause serious injury or more likely, death.
Cochlear Implant – Cochlear implants are electronically-activated devices. Consequently, an MR procedure may be contraindicated for a participant with this type of implant because of the possibility of injuring the participant and/or altering or damaging the function of the device.
Pregnancy – Contraindicated by Research ethics.
Metal in the eye – Past penetrating metallic eye injury is a contraindication until proven otherwise. X-Rays of eyes can rule out the presence of metal prior to MRI. We will require a copy of the X-ray report indicating a negative result for metallic foreign bodies before the MRI is scheduled.

MRI Web Safety Resources

If you’re looking for an information resource covering MRI safety, bioeffects and participant management, please explore www.mrisafety.com. In particular “The LIST” is a great resource for checking the MRI compatibility status of many products and materials. Please keep in mind that the Rotman MRI has a 3 Tesla magnet. Pay close attention to the field strength in the product entries. Many products may only be rated safe at 1.5 Tesla (a common clinical MRI field strength). Individuals who have been scanned on a 1.5 Tesla magnet might not be able to be safely scanned on our 3 Tesla magnet depending on the make, model and year of implant or device they have.

The Rotman MRI also maintains a subscription to www.magresource.com. We use this database to validate the MRI compatibility of medical implants. If you have a participant with a medical implant, please forward the implant information (operative report obtainable from the medical records department from the institution where the device was implanted, not the doctor’s dictated report) to Garry for review before scheduling the participant.

Rotman MRI Screening Form

Our MRI Screening Form contains a list of potential risk factors. Although many of the items on the screening form may not be an absolute contraindication, they all represent possible risk factors that need to be addressed prior to having the MRI scan (i.e. removal of hearing aids or insulin pumps). The latest version of the form is available here.

Frequently asked questions

Dental metal (braces, retainers, dentures, implants)

There are no safety concerns with the items listed above.
However, metal braces are a NO. The metal artifact generated by the braces will radiate into the frontal, temporal and parietal areas of the brain.
Retainers are typically OK as the metal artifact generated by the retainers is confined to the mandibular area. Retainers behind the upper teeth may cause very small amounts of signal dropout in prefrontal regions.
Dental implants are typically OK. The artifact is usually confined to the mandibular area. You will need to check that the dental implant is not magnetically held. There is the possibility of the magnetically-held dental implants becoming demagnetized during/after the MRI scan.
Dentures are OK as they are removable. Denture cups are provided.

Tattoos

The risk of adverse heating of tattoos is very small, regardless of the location of the tattoo. Participants with tattoos may be included in research MRI studies. You must inform the participant of the small chance of heating to occur and that they have the emergency ball to squeeze if they start to feel any discomfort during the scan. The “Research MRI wording for consent forms” maintained on the Baycrest REB website contains the following recommended language regarding tattoos: “If you have a tattoo, there is a very small possibility that you will feel a tingling or burning sensation at the tattoo site.”

Makeup

Black eyeliner, black mascara, frosted eye shadow – Remove prior to arrival. Possible potential for heating due to possible iron oxide content.
Dark nail enamel – may have to be removed from the middle finger for studies requiring pulse ox placement as it can interfere with the light based signal.
Colored contact lenses – Contacts that change the color of your eyes must be removed prior to scanning due to possible iron oxide content. Regular contacts may be worn during the MRI exam.

MRI Suite Safety Zones

MRI Facilities are designed with four distinct zones to clearly identify and control access to areas with varying degrees of safety risk. References for the policies dictating these zones are found at the end of this section. The Rotman MRI Facility is divided into 4 Zones as follows:

Zone 1 – Basement Hallway

This zone is public access.
There is no safety risk from the MRI in this zone.
There are no restrictions on entering this zone.
Researcher Use: There is a small waiting area outside the MRI suite with a small table and two chairs for researcher use, e.g. early arrival, and filling of forms (consent & MRI screening). If you find this space in use by others before your scan time, please feel free to remind them it is reserved for MRI users, as indicated by the signage on the wall.

Zone 2 – Hallway with sink, Simulator Room, Interview Room, Change Room

This zone is controlled/limited access.
There is no safety risk from the MRI in this zone, but it acts as a buffer before the first zone containing direct risks to personnel and participants.
Access to this zone is restricted to Level 2 trained MRI Staff and select Level 1 trained researchers and safety trained hospital staff (e.g. Security, Housekeeping, Facilities).
Researcher Use: The Simulator Room can be booked and accessed independently for projects requiring its use. The Interview Room and Change Room will be accessed by the researcher and participant as part of the typical research flow process.

Zone 3 – MRI Control Room, MRI Technical Room

This zone is restricted access.
The MRI magnetic field can extend into this area, making it a severe risk to individuals with cardiac pacemakers or other implanted electronic devices. It also acts as a buffer before the magnet room which contains the greatest risks.
Access to this zone is restricted to Level 2 trained MRI Staff. Everyone else entering this area (participants, untrained researchers, Level 1 trained researchers, facilities staff, contractors, etc.) must have been screened by Level 2 trained MRI staff and must also be accompanied by Level 2 trained MRI Staff.
Researcher Use: The Control Room is where the researcher and the technologist will be during the scanning session. It contains the MRI Stimulus computer and equipment that you will use to run your experiments. The technologist operates the MRI from this room. Researchers will not access the MRI Technical Room.

Zone 4 – Magnet Room

This area is restricted access.
This is the 3 Tesla Magnet Room. This area can pose a risk to any individual who has not prepared for the extreme strength of the magnetic field. It is an extreme risk to any individual with electronic implants or certain metallic implants. Anyone in the room is at an extremely high risk if ferromagnetic objects are brought into the room.
Access to this zone is restricted to Level 2 trained MRI Staff. Everyone else entering this area (participants, untrained researchers, Level 1 trained researchers, facilities staff, contractors, etc.) must be accompanied by Level 2 trained MRI Staff. Another round of verbal checks will be conducted before entry.
Researcher Use: In the typical flow process, only the technologist and participant will enter Zone 4. The researcher should be prepared to enter Zone 4 if the technologist requires help setting up the participant, if the project uses any specialized equipment in zone 4, and in the event of an emergency as detailed during MRI Safety Training.

This information references the 2020 ACR MR Safety Document, 2011 CAR Standard for Magnetic Resonance Imaging. References:
https://www.acr.org/-/media/ACR/Files/Radiology-Safety/MR-Safety/Manual-on-MR-Safety.pdf
https://car.ca/wp-content/uploads/Magnetic-Resonance-Imaging-2011.pdf
https://mriquestions.com/acr-safety-zones.html

Cellular / Phone access

Depending on your cellular provider, there is limited cellular access in the basement of Baycrest. Baycrest/Rotman WiFi can also be weak in the Control room, but is typically better in the basement hallway. The phones located in the interview room and Simulator room may be utilized for brief calls by the researcher or participant. Please dial 9, prior to the area code for external access.