Chapter 10 - MRI Safety Flashcards
What is SAR stand for and what is it?
Specific absorption rate
this is a way of measuring the USA food and drug administration limit for RF ( Rutherfordium chemcial) exposure.
How many safety zones are there in MRI?
4
If a patient is in the room with the magnet, this is considered what safety zone?
4
What does safety zone #1 entail?
all areas that are freely available to the public ( AKA the hallway outside of MRI at the hospital)
If a patient is answering their screening questions, they are likely in which safety zone?
2. This is where people are greeted and asked to do their screening.
If an MRI tech is not with a patient and is just hanging out, she is likely in which safety zone?
3.
If a patient is currently getting their scan done and are under the magnet, which safety zone is this?
4.
Safety zone #4 should be marked as dangerous with a RED light and lighting sign.
True
True, this is the area in which the magnetic on and the patient is in the scanner.
What is the difference between level 1 and level 2 MRI people?
Level 1- is like the front desk/office people ( like Ashely or Margaret) who are trained in the basic safety but not an actual MRI tech. They are even allowed in the safety zone #3 :O
Level 2- is a MRI tech or MD trained in safety.
An item that poses no threat to MRI machines is considered a MR _______.
Safe, Conditional or, unsafe
MRI Safe
A green square with the words MR in it means that an item is “MRI SAFE”
True or False
True
What is an example of something that is considered MRI safe?
something plastic like a Petri Dish
What does a yellow sign with the words MR stand for?
MRI Conditional
What are the five major factors that are considered to have an impact on whether patients will have any side effects after having an MRI done?
- Psychiological
- The spatially varying static magnetic field
- electromagnetic fields
- Cryogens
- Time-varying gradient magnetic fields.
Some studies have shown that patients who have a brain scan sometimes have anxiety due to the close proximity and will require sedation of some sort.
true/ false
True
The narrow bore of an MRI machine rarely causes patient’s anxiety.
True/ False
False. The narrow bore of a MRI machine plays a significant role in patient claustrophobia and anxiety when having a test done.
At what stage of the exam are most patients the most scared/anxious?
the beginning.
What are several ways we can help put the patient at ease during exam?
- Aromatherapy
- Wider machines
- In-Scanner video presentations that include remainder of time of scan
- Painting the ceiling tiles.
- Sedation :)
What are the 4 main implications for patient safety in regards to the static field?
1) transient biological effects
2) projectile hazards
3) Torque on implanted devices
4) Foreign bodies in static field.
What is the main magnetic field called?
B
o
The magnetic field is 160, 000 times more powerful than that of the earth.
True
True
What are two temporary symptoms that are related to stepping into a magnetic field of 3-7?
Metallic taste in mouth and vertigo.
What are symptoms that patients experience in fields of 7T and above?
Nausea, dizziness, vertigo, postural instability,
What is thought to be the reasoning of why patients sometimes feel they are moving in a curved motion?
Caused by an overcompensation of the vestibular system ( in charge of balance) of the inner ear.
This phenomenon causes the induction of an electrical current through a conductor that is moved through an external magnetic field. What is this called?
Faraday’s lay of electromagnetic induction.
The magnet in the machine is not always on. The techs turn them off at the end of their shifts.
True or False
FALSE FALSE!!
The magnet is ALWAYS ON.
What are some examples of an implanted medical device?
stents, clips, neurostimulators, pacemakers, hip replacements
What is the word TORQUE mean in regards to MRI?
it is a term to describe a rotational force that causes the alignment of an object to the lines of magnetic flux.
This happens often with ferromagnetic implants such as pacemakers.
if a patient has a hip replacement, is this likely to experience torque during the MRI?
no because they are anchored to the bone with screws and/or cement.
A law that states that the direction of an induced current is always such as to oppose the change in the circuit or magnetic field that produces it.
Lenz Law
What does the word “Ferromagnetic” mean?
something that has a high susceptibility to magnetization.
True or False.
MRI does not use radiation.
TECHNICALLY false!!
MRI uses “non-ionizing” radiation.
What does the word “quench/quenching” mean in MRI?
the sudden loss of the superconductivity of the magnetic coils so that the magnet becomes resistive.
If someone has “stochastic effects from a MRI” , what does that mean?
effects that increase the probability of the patient developing a radiation- induced cancer at some time in the future
What is a “deterministic effect”?
effects that can be shown to have a nonrandom cause and affect with the increased absorbed dose.
EX- erythema or hair loss.
Much of the energy deployed by the rutherfordium pulse is absorbed by the patient’s body tissues which can cause an increase in thermodynamic temp.
True or false?
True
Joules refers to the measurement of?
Energy
Which areas of the body are more susceptible to heating than others?
Ees and the germ cells of the male reproductive system.
What is the difference in 1st level controlled operating mode and 2nd level??
1st- mode of operation in which one or more outputs reach a value that may cause physiological stress which needs to be controlled.
2nd- mode of operation in which one more more outputs reach a value that can produced significant risks for subjects for which explicit ethical approval is required.
What can happen to a patient during scan if they put their hands together?
it may produce a burn because this creates a biological circuit through which induced current may flow.
GO back to antenna effect
jj
