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MED 107- MEDICAL PHYSICS II > 106. MRI SAFETY > Flashcards

106. MRI SAFETY Flashcards

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1
Q
  1. 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

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2
Q
  1. In which aspects do we assess the safety of MRIs?
A
  1. Operational Activities
  2. Personnel Training
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3
Q
  1. What are the important Bio-effects and Safety Issues that we consider when we deal with MRIs?
A
  1. The presence of Strong Magnetic Fields
  2. The Radio Frequency Energy
  3. Time-Varying Magnetic Gradient Fields
  4. Cryogenic Liquids
  5. Claustrophobia
  6. High Noise levels of the Operation
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4
Q
  1. 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
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5
Q
  1. Why would patients tend to feel Claustrophobic in an MRI machine?
A
  • it is a Confined Imaging Device
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6
Q
  1. 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

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7
Q
  1. 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
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8
Q
  1. 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

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9
Q
  1. 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
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10
Q
  1. 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

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11
Q
  1. List the metals that are MRI Compatible.
A
  1. Titanium
  2. Aluminium
  3. Brass
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12
Q
  1. What does this sign mean?
A
  • the material is Mr Safe
  • these objects are wholly non-metallic
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13
Q
  1. 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
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14
Q
  1. 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
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15
Q
  1. 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

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16
Q
  1. 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
  1. What happens if the Quench Procedure is performed too quickly?
A
  • there will be major physical damage to the magnet
18
Q
  1. 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
  1. 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
  1. 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
  1. 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
  1. In which circumstances is MRI considered safe?
A
  • when it is used within the Regulatory Guidelines
  • these are required by the manufacturers
23
Q
  1. 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
  1. 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
  1. 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
  1. 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
  1. What Magnetic Field strengths do we use for Human Imaging?
A
  • we use Static Magnetic Field strengths of up to 8 Teslas

MED 107- MEDICAL PHYSICS II (108 decks)

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