Radiology - MRI Safety
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The major risk of injury or harm due to a magnet quench is:
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The boiling off of cryogens that creates an asphyxiating steam
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The magnet becomes so warm that it may cause burns to patients in the bore
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There is no danger with a quench. It is how we shut down the machine for repair
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A blinding flash of light
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As you probably could have guessed, the science of radiology can be quite harmful to the human body given the high levels of radiation involved. What are the proper safety measures when handling an MRI? Let’s find out.
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- 2.
Patients with which of the following prosthetic devices may be safely scanned:
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Cardiac pacemaker
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History of having metal flakes in the eye
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Cochlear implant (inner ear prosthetic device)
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Total knee replacement
Correct Answer
A. Total knee replacementExplanation
The following items can NEVER be allowed into the scanning room:
cardiac pacemakers, cochlear (inner ear) implants, ferromagnetic or unidentifiable aneurysm clips of the brain, implanted neuro stimulators, metal or unidentifiable foreign bodies in the eyes, and implanted pumps to deliver medicine that cannot be removed.
If a subject works around metal and cannot say for sure they have never had any metal in their eyes the study should be canceled.Rate this question:
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- 3.
The emergency shutdown button should be used to immediately cut power to the scanner electrical system in each of the following situations EXCEPT:
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Loud popping noises and smoke come from the scanner
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Sprinklers go off in scan room, but there is no fire
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Scan room fire
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The subject in the scanner squeezes the emergency ball
Correct Answer
A. The subject in the scanner squeezes the emergency ballExplanation
Shutting power to the PDU may be required for life threatening situations such as:
Fire in the computer room, fire, sparks, loud noises emanating from the scan room, flooding or sprinkling system goes off, and catastrophic equipment failure. These reasons should be life threatening. It is important to remember that pressing the emergency stop button shuts the power to the scanner to but the magnetic field is still active.Rate this question:
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- 4.
In which of the following situations should you push the “Quench” button:
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A steel oxygen tank was brought into the scan room and has flown across the room and stuck to the magnet, pinning someone’s arm in a painful crush
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Scan room fire
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A janitor has entered the room with a large floor buffing machine which is now stuck to the magnet. No one is hurt, but he can’t pull the machine off the magnet
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All of the above
Correct Answer
A. A steel oxygen tank was brought into the scan room and has flown across the room and stuck to the magnet, pinning someone’s arm in a painful crushExplanation
An intentional quench is done in an emergency to run the magnetic field to zero. This is done in extreme emergencies only (ex- a projectile that is pinning a patient against the magnet, injuring them).Rate this question:
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- 5.
Which of the following is a likely consequence of forgetting to remove your wallet from your pocket before entering the scan room:
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There will likely be no adverse consequence
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The magnetic stripes on your credit cards and ATM cards are erased
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The wallet will heat up and may cause burns
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Because the ink on US currency is ferromagnetic, your wallet may become a projectile and fly into the magnet bore
Correct Answer
A. The magnetic stripes on your credit cards and ATM cards are erasedExplanation
The magnetic field can seriously damage or impair the following personal items:
Cameras, watches, credit and bank cards, hearing aids, hair accessories, belt buckles, shoes and I-pods just to name a few. Please remember to empty ALL of your pockets before entering the scanning room.Rate this question:
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- 6.
What is a Quench?
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Total power down of the computer system
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A ramping up of the magnetic field in which all of the cryogens are put into the bore thus making the scanner super conductive
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How the staff shuts the magnet down after hours, to ensure maximum safety
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A rapid boil off of cryogens and ultimate loss of a magnetic field
Correct Answer
A. A rapid boil off of cryogens and ultimate loss of a magnetic fieldExplanation
MR scanners are super cooled with inert gases such as helium. A quench is the rapid boiling off of these cryogens intentionally or unintentionally.Rate this question:
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- 7.
There are two real safety concerns with regard to the magnetic forces and how they interact with ferrous objects. They can be described as which of the following:
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Translation and Magnetization of the object
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Transverse and Rotation of the object
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Translation and Torque of the object
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Translation and Mutation of the object
Correct Answer
A. Translation and Torque of the objectExplanation
Translation describes the force that attracts ferrous objects to the center of the magnetic field. It is sometimes referred to as the projectile effect. Rotation is the term that relates to the force of the North and South poles and the orientation of the scanner’s magnetic field. Ferrous objects will attempt to align their long axes with this orientation and will rotate until they are aligned with the magnetic field.Rate this question:
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- 8.
To reduce the effects of peripheral nerve stimulation:
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Have the subject uncross their extremities
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Use immobilization pads
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Change the subject out of their street clothes and into a gown
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None of the above
Correct Answer
A. Have the subject uncross their extremitiesExplanation
When a patient crosses their legs or intertwines their fingers a circuit is formed and it is more likely to cause peripheral nerve stimulation.Rate this question:
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- 9.
The main hazard of the Static Field is:
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Nerve Stimulation
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Objects becoming projectiles
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Heat Deposition
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None of the above
Correct Answer
A. Objects becoming projectilesExplanation
Heat deposition and nerve stimulation are hazards of a varying magnetic field.Rate this question:
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- 10.
If there is ever a Quench in the scan room instead of the outside environment, you must remove the patient and all staff from the room immediately. What are the safety concerns?
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Asphyxiation and frost bite
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Explosion
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Convulsion
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Fire
Correct Answer
A. Asphyxiation and frost biteExplanation
If a quench occurs, everyone must be removed from the room immediately. The vapors and gases are very cold and can cause frostbite. They also often condense the moisture in air, creating a highly visible fog that can replace oxygen in the room.Rate this question:
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- 11.
What does SAR measure?
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The length of the scan time
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The amount of heat the patient will absorb during the scan
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The strength of the fringe field outside the bore of the magnet
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All of these answers are correct
Correct Answer
A. The amount of heat the patient will absorb during the scanExplanation
Dissipation of the absorbed RF energy is described in terms of Specific Absorption Rate (SAR), measured in watts/kg. SAR is calculated by the patient’s weight and the expected increase in body temperature for each imaging pulse sequence. The scanner will calculate how much heat the patient will be absorbed if it is too high the scan will not run.Rate this question:
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- 12.
If an object is considered safe to be used in a 1.5Tesla MR scanner, but has not been tested in a 3Tesla scanner, it should be labeled as:
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MR Safe
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Not sure, more research should be done
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MR Not Safe
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Does it matter?
Correct Answer
A. Not sure, more research should be doneExplanation
A 3T magnet is double the strength of a 1.5T unit. It is important to remember that objects that are clear for a 1.5T magnet cannot go into a 3T magnet. Mrisafety.com has the largest database of items that are cleared for the 3T environment.Rate this question:
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- 13.
Every subject can choose if they would like to wear ear plugs, head set, both or nothing during the scan. It's up to each individual.
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True
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False
Correct Answer
A. FalseExplanation
The MRI scanner produces very high acoustic noise, which can reach excess of 130 DbA. Everyone who is scanned must wear both ear plugs and headset during the exam.Rate this question:
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- 14.
A subject checks the box that they have tattoos, the next step is to:
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Cancel the study, tattoos are never allowed in the scanner
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Wrap the tattoo in a cold compress and continue with the study
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Nothing, tattoos are fine
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Explain that in rare cases tattoos can tingle or burn and let them know if they are not comfortable in continuing they can back out of the study
Correct Answer
A. Explain that in rare cases tattoos can tingle or burn and let them know if they are not comfortable in continuing they can back out of the studyExplanation
Since there have been documented cases of tattoos burning the skin you must let them know there is a small chance of this. At that time they can back out of the study if they want. If they do feel a strange sensation during the scan have them squeeze the emergency ball as soon as possible and apply a cold compress to the area. The study is complete at this time.Rate this question:
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- 15.
The magnetic field is contained entirely in the center of the bore, it does not extend to the outside environment
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True
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False
Correct Answer
A. FalseExplanation
All magnets have a fringe field that extends from the center of the magnet. Rooms are shielded as much as possible to contain this field but only people who have been cleared by the SCAN Center should be allowed in the controlled access areas of the center.Rate this question:
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- 16.
Name:
Correct Answer
N/A
Quiz Review Timeline (Updated): Mar 22, 2023 +
Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.
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Current Version
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Mar 22, 2023Quiz Edited by
ProProfs Editorial Team -
Jul 26, 2013Quiz Created by
Sergesic
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