106. MRI SAFETY Flashcards
1
Q
- Is MRI considered a safe Modality?
A
- yes
- it does not make use of any ionising radiation
HOWEVER:
- it is on all the time
- it is on for 24 hours for every day of the year
2
Q
- In which aspects do we assess the safety of MRIs?
A
- Operational Activities
- Personnel Training
3
Q
- What are the important Bio-effects and Safety Issues that we consider when we deal with MRIs?
A
- The presence of Strong Magnetic Fields
- The Radio Frequency Energy
- Time-Varying Magnetic Gradient Fields
- Cryogenic Liquids
- Claustrophobia
- High Noise levels of the Operation
4
Q
- What are Cryogenic Liquids?
A
- they are liquids that are used in Super Conducting
Magnets - they consist of Helium
- this helps to cool down the temperatures
5
Q
- Why would patients tend to feel Claustrophobic in an MRI machine?
A
- it is a Confined Imaging Device
6
Q
- Which kinds of patients need to be very carefully screened?
A
PATIENTS WITH:
- implants
- prostheses
- aneurysm clips
- pacemakers
- heart valves
NB:
- they need to check if the materials of these objects are
MRI compatible
7
Q
- What is the issue with a patient having a non-metallic implant on them?
A
- these implant materials can heat up significantly
- this is caused by the rapidly changing gradient fields
8
Q
- What kind of technical problem do certain materials bring about?
A
MATERIALS THAT ARE NOT MRI SAFE:
- can distort the final image
- they can add artefacts to it
- this can lead to a misdiagnosis
9
Q
- What is the issue with bringing Ferromagnetic materials into the MRI Imaging Room?
A
- they can become a deadly projectile
- they have caused patient deaths before
10
Q
- List the materials that cannot be brought into the MRI Scanning Room.
A
IMPLANTS:
- Metals
- Ferromagnetic materials
- Metallic Foreign Body in the eye
- Shrapnel Bullets
- Metallic Ocular Implants
ELECTRICAL DEVICES:
- Pacemakers
- Pacing Wires
- Neurostimulators
- Cochlear Implants
11
Q
- List the metals that are MRI Compatible.
A
- Titanium
- Aluminium
- Brass
12
Q
- What does this sign mean?
A
- the material is Mr Safe
- these objects are wholly non-metallic
13
Q
- What does this sign mean?
A
- the material is MR Conditional
- the objects may or may not be safe
- further investigation is necessary to make a conclusion
14
Q
- What does this sign mean?
A
- the material is not MR safe
- this is placed on all ferromagnetic materials
- it is also placed on many conducting materials
15
Q
- What can we do to the MRI in extreme emergencies?
A
- the Superconducting magnet can be turned off
- this is accomplished manually
IT IS DONE BY USING THE:
- quench procedure
16
Q
- What is the Quench procedure?
A
- the Superconducting magnet is exposed to a 260°
temperature difference - this happens in a short period of time
17
Q
- What happens if the Quench Procedure is performed too quickly?
A
- there will be major physical damage to the magnet
18
Q
- What kind of risks are associated with the manual Quench Procedure?
A
THERE ARE RISKS TO:
- the personnel
- the equipment
- the physical facilities
19
Q
- What causes Uncontrolled Quenching?
A
- a sudden loss of Superconductivity in the main
magnetic coils
HELIUM IS RELEASED INTO THE ROOM:
- this removes the magnetic properties of the
Superconducting magnet
20
Q
- What does Uncontrolled Quenching out at risk?
A
- it risks the safety of those in the room
- it risks the safety of those in adjacent areas
21
Q
- What happens if there is not enough gas outflow when a Quench Procedure takes place?
A
- the oxygen in the room can be displaced
- this can build up the pressure in the room
- this makes it extremely difficult for the doors to open
- people cannot leave the room
22
Q
- In which circumstances is MRI considered safe?
A
- when it is used within the Regulatory Guidelines
- these are required by the manufacturers
23
Q
- In which circumstances is MRI considered unsafe?
A
- when the Static and Magnetic fields are much stronger
than they need to be for diagnostic imaging
THIS LEADS TO:
- serious bio-effects
24
Q
- What can be said about the effects felt at Lower Magnetic Field Strengths?
A
- there have not been any deleterious or permanent
Biological effects to the individuals
25
Q
- What issues does an individual experience when they are exposed to Static Magnetic field strengths that are greater than 2.5 Teslas?
A
- patient heating
- headaches
- fatigue
- hypotension
- irritability
- disorientation
26
Q
- What issues does an individual experience when they are exposed to Static Magnetic field strengths that are greater than 20 Teslas?
A
- enzymatic changes
- increased membrane permeability
- altered biopotentials
27
Q
- What Magnetic Field strengths do we use for Human Imaging?
A
- we use Static Magnetic Field strengths of up to 8 Teslas
