MRI SAFETY Flashcards
MRI Facility Zones
Zone I (Uncontrolled zone)
All areas that are freely accessible to the general public.
Zone II
This area is the interface between the publicly accessible, uncontrolled Zone I and the strictly controlled Zones III and IV.
Typically, patients are greeted in Zone II and are not free to move throughout Zone II at will, but are rather under the supervision of MR personnel. It is in Zone II that the answers to MR screening questions, patient history etc. are typically obtained
Quenching
This is a process of sudden loss of the absolute zero of temperature in the magnet coils so that they cease to be superconductive and become resistive.
Helium escapes from the cryostat very fast.
A quench can cause irreparable damage to the magnet so should only be performed in extreme cases with the knowledge of the engineer and with a physician.
This process can also be a result of an accident such as a earthquake.
Systems should have a vent for the helium to escape outside the room.
NSF
Nephrogenic systemic fibrosis is a serious adverse reaction that may occur in patients that has received MRI contrast (gadolinium).
“Common symptoms of NSF include:
Burning, swelling, itching and hardening of the skin.
Reddened or darkened patches on the skin.
Raised yellow spots on the whites of the eyes.
Inability to properly straighten the arms, hands and legs.
Muscle weakness.
Deep hip bone or rib pain.”
SAR
Specific Absorption Rate)
The FDA limit for RF exposure is either an increase in body temperature or RF absorption that can be expressed in SAR watts per kilogram (W/kg).
RF Antennae Effects
Due to electrical currents that can be produced in conductive loops, significant burn hazards can result, because of the RF fields.
Never allow for any electrically conductive material such as a coil cable to form a conductive loop or to touch the patient.
Clothing or tissue can potentially ignite by un-insulated cables.
Fringe Fields
The stray magnetic field outside the bore of the magnet can be a secondary concern of the main magnetic field and can have fatal effects.
It has no constraints (doors, ceilings and floors) and care must be taken siting the magnet.
General public must be protected by the stray magnetic field.
Acoustic Noise
Acoustic noise is created as current is passed through the gradient coils.
This noise can cause reversible as well as irreversible effects such as hearing loss and impairment.
