Clinical Applications Flashcards
Two metal objects are exposed to the static magnetic field. Object #1 weighs 4 pounds (1.8 kg) and is in the shape of a sphere and has a diameter of 6 inches (15.4 cm). Object #2 is 4 pounds (1.8 kg) and is in the shape of a rod measuring is 1 x 6 cm. Which object will have the greatest potential for torque in the magnetic field?
Object #1
Object #2
Neither will experience any torque
Both will experience equal torque
Object #2
Pillowcases or sheets placed between the patient and the bore provides appropriate protection against proximity burns. True or False?
True
False
False
The best way to ensure that an oxygen tank can be safely taken into the scan room is:
Look for the green top. Green means go.
Look for the silver sides. The silver is aluminum which is not magnetic.
Test the tank with a handheld magnet of at least 1,000G every time it is used.
Pick it up. If it is heavy, it should not go into the scan room.
Test the tank with a handheld magnet of at least 1,000G every time it is used.
If a patient is too large for manufacturer recommended padding to be placed between the patient and the bore, it is recommended to perform the scan and ask the patient to sign a consent form stating that they are aware of the associated thermal risk.
True
False
False
Clothing labels/tags always indicate the presence of silver fibers or treatments. True or False?
True
False
False
While researching a patient’s implant for safety, acceptable information can be gained from:
The patient’s surgical report
The patient’s billing records for the implant procedure
The patient’s medical records
The patient’s implant card
All of the above
The patient’s surgical report
The patient’s billing records for the implant procedure
The patient’s medical records
The patient’s implant card
All of the above
Items labeled ‘MR Safe’ are only safe in a specific MR environment. True or False?
True
False
False
In the U.S. if an oxygen tank has a green top with silver sides, what is known about it?
It is MR safe because green means go
It is MR conditional because it has silver sides
Nothing, other than it contains oxygen
It is MR unsafe. There is no such thing as an MR conditional oxygen tank
Nothing, other than it contains oxygen
A patient presents with a metallic implant having MR conditional labeling for spatial gradient max 720G/cm. The maximum spatial gradient (MSG) for the MR system is 2420G/cm. Based solely on this spatial gradient information, could the patient be scanned safely?
No, because the system’s MSG exceeds the labeling for the implant
Yes, because spatial gradient labeling doesn’t matter
Possibly, but the location of the implant while it is in the static field should be checked against the spatial gradient map for the system
What’s maximum spatial gradient?
Possibly, but the location of the implant while it is in the static field should be checked against the spatial gradient map for the system
Keeping all other factors the same, doubling the flip angle will have what effect on SAR?
There will be no effect
SAR will also double
SAR will increase by a factor of 4
SAR will be decreased
SAR will increase by a factor of 4
Providing patients with warm blankets during scanning will help them perspire and better dissipate heat. True or False?
True
False
False
When transmitting with the body coil, the best way to limit RF exposure to anatomy is:
Use the smallest receive coil possible
Use the body coil to receive also
Keep anatomy out of the area of RF deposition
Use a small field of view
Keep anatomy out of the area of RF deposition
If an implant has not been tested for MR safety, it is unsafe and should not be used in the MRI environment. True or False?
True
False
False
If an oxygen tank has a green top with silver sides, it is known to the MR conditional. True or False?
True
False
False
Nitinol is a non-ferrous nickel-titanium alloy. Because it is non-ferrous, it would be labeled MR Safe. True or False?
True
False
False
Patients should be permitted to wear their own clothing in the MRI scanner. True or False?
True
False
False
EKG changes may be observed with patient exposure to the static magnetic field, before imaging has begun. True or False?
True
False
True
When performing a risk/benefit analysis for a patient with an implant, all of these questions should be considered except:
Where is the implant within the patient?
Where are we depositing RF energy?
Did the ordering physician document that the implant is safe to scan?
Will the implant be exposed to each MR energy?
Is there a low resistance pathway (loop) bringing e-fields to the implant?
Did the ordering physician document that the implant is safe to scan?
The ways humans can handle or dissipate heat include all of the following EXCEPT
perspiration/evaporation
radiation
convection
conduction
hydration
hydration
When scanning with a receive only RF coil, what can be done to prevent unwanted RF irradiation to anatomy outside of the area of interest?
Use a smaller receive coil.
Use a smaller FOV
All anatomy within the body coil will receive RF, so if possible, position the patient so that the anatomy in question is outside the volume of the transmit coil.
Place a saturation band/region over the other anatomy
All anatomy within the body coil will receive RF, so if possible, position the patient so that the anatomy in question is outside the volume of the transmit coil.
Obese or pregnant patients may have difficulty dissipating heat because they have a decreased surface to volume ratio. True or False?
True
False
True
EKG perturbances can alter cardiac gating due to elevation of the ST segment of the EKG waveform. True or False?
True
False
True
Interactions between the static magnet field and active implants include all of the following EXCEPT:
motion/dislodgement
incapacitation of device
improved function
alteration of device function
improved function
What can be done to mitigate Lenz’s forces on a patient’s large metallic, conductive implant?
Nothing, just advance the patient to isocenter quickly to get it over with
Explain what is happening to the patient and advance them to isocenter slowly
Have the patient hold onto the implant so that it doesn’t move
Cancel the exam because the patient may feel burning
Explain what is happening to the patient and advance them to isocenter slowly
Nitinol is a non-ferromagnetic nickel-titanium alloy commonly used for self expanding stents. For MR safety purposes, nitinol would be labeled:
MR Safe
MR Conditional
MR Unsafe
MRI Compatible
MR Conditional
What type of matter lacks magnetic qualities?
Unmagnetic
Supermagnetic
Paramagnetic
Nonmagnetic
Nonmagnetic
A patient presents for an MR Brain and has a spherical metallic object in their pelvis. It has been determined that the object is MR conditional, so the patient has been cleared for scanning. If the patient is scanned using a Transmit/Receive head coil, what effect will RF have on the object?
It could heat, so a heat sink should be applied
It could experience torque, so it should be immobilized
Nothing, it will not be in the area of RF deposition
I would not scan this patient
Nothing, it will not be in the area of RF deposition
Which scenario has the most potential for a thermal injury due to induced voltage loops?
Patient with arms and legs crossed
Patient with arms at sides and fingers just touching bare lateral thighs
Patient with legs immobilized and pressed together hip to ankle
Patient with one arm above head and one arm at side
Patient with arms at sides and fingers just touching bare lateral thighs
All stainless steel is non-ferromagnetic and therefore MR conditional. True or False?
True
False
False
All stainless steel is ferromagnetic and therefore MR unsafe. True or False?
True
False
False
Most implants are not tested for MR safety because:
The manufacturers don’t care about MR safety
The implant wasn’t marketed for use in the MRI environment
It is too expensive
The implant wasn’t marketed for use in the MRI environment
A patient may interpret the vibration of nonferrous metallic jewelry or body modification as ‘burning’, especially in the periphery of the bore. True or False?
True
False
True
Of the following modifications, which one would change the anatomy exposed to RF?
Positioning the patient away from isocenter
Positioning the anatomy of interest at isocenter
Switching to a different transmit RF coil
Changing the scan FOV
Switching to a different transmit RF coil
Hearing protection should only be provided if the patient requests it. True or False?
True
False
False
_________ is a potential risk of gowning all MR patients. Using ________ can eliminate this risk.
Patient dissatisfaction/gift cards
Increase in skin to skin contact/appropriate positioning and padding
Patients being cold/lots of warm blankets
Infection/bleach wipes
Increase in skin to skin contact/appropriate positioning and padding
A patient arrives to the department for an MRI examination. The patient has 3x2mm retained piece of metal in the soft tissue. All are possible precautions that may be taken from a safety standpoint EXCEPT:
Adjust gradients to have increased duty cycle and lower ramp time
Review the area of the retained metal and what organs surround the area in case of translation and rotation
Review the coils being used and the potential for focal heating to the metal
If near the surface of the skin, a dry, cold compress can be used to compensate for focal heating
Adjust gradients to have increased duty cycle and lower ramp time
Decreasing TR will have what effect on SAR?
SAR will be increased
SAR will be decreased
SAR will be uneffected
SAR will be increased
Which is more important in preventing proximity burns?
The type of padding used between the patient and the bore
Ensuring that the appropriate distance between the patient and the bore is maintained
Ensuring that the appropriate distance between the patient and the bore is maintained
Patients should be changed into site provided gowns or scrubs. True or False?
True
False
True
Kissing burns can occur if the fabric between the body parts is wet, conductive, or contains metallic fibers. True or False?
True
False
True
If a patient already has hearing loss, it is acceptable to scan them without hearing protection. True or False?
True
False
False
A patient with permanent tattoo eyeliner experiences tingling around her eyes as she is advanced into the bore. This is due to _____ .
RF heating of the tattoo pigment
The tattoo pigment interacting with the magnetic field as the patient crosses flux lines
Time varying gradient causing peripheral nerve stimulation
The patient’s imagination because she is anxious
The tattoo pigment interacting with the magnetic field as the patient crosses flux lines
Which of these can be known to be a safe choice for a patient to wear during their MRI scan?
Clothing that is labeled 100% cotton
Clothing that the patient has worn during their other MRI scans
Scrubs provided by the MR department
Any clothing that does not contain zippers or snaps
Scrubs provided by the MR department
The three most commonly reported MR-related adverse events -unrelated to contrast- are:
Claustrophobia, anxiety, service complaints
Anxiety, temperature of the room, short staffing
Burns, projectiles, hearing loss
Wait times, nausea, claustrophobia
Burns, projectiles, hearing loss
It is correct for an IV pump approved to be used in MR Zone 4 to be labeled ‘MR Safe’. True or False?
True
False
False
Of these metallic objects, which one could be more likely to experience resonant circuitry heating, based on the shape of the object.
Hip stem
Row of surgical staples
BB
Mechanical heart valve
Hip stem
The color green for medical gas cylinders is always an indication for oxygen. True or False?
True
False
False
The most important function of the fan inside the bore is to:
Increase patient satisfaction scores
Remove the air that the patient has heated up through convection, evaporation, conduction, and radiation, replacing it with cooler air
Decrease patient anxiety
Remove the air that the patient has heated up through convection, evaporation, conduction, and radiation, replacing it with cooler air
If the ST segment of the EKG waveform is elevated during cardiac gating, this can be corrected by:
Asking the patient to hold their breath during the scan
Turning off cardiac gating
Repositioning the EKG leads
Cancelling the exam
Repositioning the EKG leads
Device conditions labeling indicates the maximum conditions used until the device failed. True or False?
True
False
False
Patients may feel a sensation in the area of a large implanted nonferrous device when being moved into or out of the bore. True or False?
True
False
True
Device conditions labeling indicates only how the device was tested and does not indicate where the device failed. True or False?
True
False
True
Infants have difficulty maintaining body temperature because they have a high surface to volume ratio. True or False?
True
False
True
A patient experienced redness, and pain on the left elbow during an MR exam of the right shoulder. A receive only shoulder coil was used. What is the probable cause of the patient’s injury?
Resonant frequency
Large caliber body loop
Near field/proximity
Too much padding between the patient and the bore
Near field/proximity
When using the body coil to transmit RF, it is only important to pad the patient on the sides/by their arms. True or False?
True
False
False
It is important to ensure padding/air gap between the patient and the bore:
Only between the anatomy being scanned and the bore
Only next to the patient’s arms
All the way around the patient, anywhere they could come into contact with the bore
If the patient asks for padding for comfort
All the way around the patient, anywhere they could come into contact with the bore
The reason why most implants are untested for MR safety is because their manufacturers know that there would be no safe conditions for MR scanning. True or False?
True
False
False
The reason why most implants are untested for MR safety is because their manufacturers know that there would be no safe conditions for MR scanning. True or False?
True
False
False
As long as the patient’s clothing is free of zippers or snaps, it will be safe in the scanner. True or False?
True
False
False
Without changing any other factors, doubling the flip angle will increase SAR by a factor of 4.
True
False
True
According to the ACR Guidance Document for MR Safe Practices, quenching the magnet in the event of a patient cardiac or respiratory arrest is not advised. This is because:
It can easily take over a minute for the static magnetic field to dissipate
Quenching the magnet can be hazardous and ideally the room should be evacuated for an intentional quench
Time should be used to initiate life saving measures while
removing the patient from Zone 4
All of the above
It can easily take over a minute for the static magnetic field to dissipate
Quenching the magnet can be hazardous and ideally the room should be evacuated for an intentional quench
Time should be used to initiate life saving measures while
removing the patient from Zone 4
All of the above
A patient with a dermal piercing on her cheek presents for an MR Brain. What is the best way to proceed?
Test the piercing with a hand held magnet
Reschedule the patient until she can remove the piercing
Have her sign a consent form that states you are not responsible for any possible injury
Put a piece of tape over the piercing like they do in surgery
Test the piercing with a hand held magnet
All other variable remaining the same, changing from 1.5T to 3T will have what effect on SAR?
There will be no effect
SAR will also double
SAR will increase by a factor of 4
SAR will decrease
SAR will increase by a factor of 4
The actual deflection angle of an object found to be MR Conditional or MR Unsafe could be useful information to have when making a clinical decision regarding an implant’s safety in the MR environment.
True
False
True
The magnetic properties of matter include:
paramagnetic, semimagnetic, ferromagnetic
unmagnetic, ferromagnetic, supermagnetic
nonmagnetic, paramagnetic, ferromagnetic, diamagnetic
nonmagnetic, paramagnetic, ferromagnetic, diamagnetic
Larger patients experience more problems with thermoregulation during MRI due to all of the following factors EXCEPT:
More obstruction of air flow within the bore
Decreased ability to perspire
Increased temperature in the bore resulting in lower rate of thermal exchange
Lower surface area to volume ratio
Decreased ability to perspire
The most commonly reported MR related, non-gadolinium related adverse event it:
Projectiles
Claustrophobia
Heating/Thermal injuries
Hearing loss
Dizziness
Heating/Thermal injuries
Although the patient claimed they had no implanted metal, upon running a localizer, there is a large area of susceptibility seen in the area of the anterior communicating artery. The radiologist decides to abort the scan and remove the patient. What is the best way to remove the patient?
Quickly move the patient table out of the bore to minimize torque and translational forces, sit the patient up, and escort the patient out of zone 4.
Slowly move the patient table out of the bore to minimize torque and translational forces, sit the patient up, and escort the patient out of zone 4.
Quickly move the patient table out of the bore to minimize torque and translational forces, keep the patient supine and transfer them to an MR safe stretcher, and remove the patient from zone 4.
Slowly move the patient table out of the bore to minimize torque and translational forces, keep the patient supine and transfer them to an MR safe stretcher, and remove the patient from zone 4
Slowly move the patient table out of the bore to minimize torque and translational forces, keep the patient supine and transfer them to an MR safe stretcher, and remove the patient from zone 4.
Disturbances to the patient’s EKG waveform can be caused by:
The static magnetic field
The time-varying gradient
magnetic field
The RF magnetic field
All of the above
The static magnetic field
The time-varying gradient
magnetic field
The RF magnetic field
All of the above
It is possible for a patient to be unaware of receiving an RF related burn because:
This is not possible, patients would feel burns
Patients are distracted by the gradient noise during scanning
It is thought that are no pain receptors in subcutaneous fat
Patients are embarrassed to say anything
It is thought that are no pain receptors in subcutaneous fat
A patient presents for an MR Brain and has a spherical metallic object in their pelvis. It has been determined that the object is MR conditional, so the patient has been cleared for scanning. In regards to the static magnetic field (B0), what effect do you expect the object to experience?
Translation
Torque
Resonant heating
Peripheral nerve stimulation
Resonant heating
Which of the following could be labeled ‘MR Safe’?
titanium hip prosthesis
platinum coronary stent
plastic biliary stent
clipped epicardial pacing wires
plastic biliary stent
If an object is made of surgical stainless steel, what is known about it?
The object is not magnetic and is therefore MR safe
The object is made out of stainless steel that is used in surgery
The object is very magnetic and should be removed from the MR department
The surgeon who left it in the department needs to come and pick it up
The object is made out of stainless steel that is used in surgery
Permanent hearing loss is possible after a patient with poorly fitted earplugs is exposed to the acoustic gradient noise.
True
False
True
Lenz’s forces on large nonferrous, conductive, implanted devices can be decreased by moving the patient into or out of the bore slowly.
True
False
True
If a patient has multiple MR Conditional implants, which implant conditions should be followed to ensure safety?
All of them
Only the conditions for the implant closest to the area of interest
The most restrictive conditions, taking into consideration all of the implants
It doesn’t matter. Patients with multiple conditional implants cannot be scanned safely.
The most restrictive conditions, taking into consideration all of the implants
For an object to be labeled ‘MR Safe’, it must be ALL of the following:
Nonmetallic, nonmagnetic, nonconductive
Nonferrous, noncorrosive, nonmagnetic
Conductive, nonmetallic, flexible
Nonreactive, nonmetal, nonmagnetic
Nonmetallic, nonmagnetic, nonconductive
Magnetically charged fluid in the semicircular canals can produce nausea for a person moving through the static magnetic field.
True
False
True
Exposure to the static magnetic field can alter the EKG readout by elevating the ST segment. What can be done to correct for this?
Nothing
Reposition leads to prevent the system from triggering off the elevated T wave
Ignore the EKG, it can’t be used for monitoring anyhow
Cancel the exam until the ST segment is normal
Reposition leads to prevent the system from triggering off the elevated T wave
Near field (proximity) burns are generally seen when transmitting with the body coil. What is the most effective way to prevent them?
Slip a pillowcase between the patient and the bore
Make sure the patient’s thighs are not touching
Use the manufacturer recommended thickness padding between the patient and the bore
Turn the fan on high to increase air circulation for large patients
Use the manufacturer recommended thickness padding between the patient and the bore
As the table is advanced into the magnet bore, your patient complains of a pulling sensation in the area of a nonferrous implant that has been labeled MRI conditional. What can you do to minimize this effect?
Nothing and cancel the exam immediately.
Explain to the patient that this is a normal occurrence and advance the table more slowly
Call your radiologist and ask for advice
Advance the table as fast as possible to get the patient through the discomfort
Explain to the patient that this is a normal occurrence and advance the table more slowly
What feature of a medical gas cylinder indicates that it is MR Conditional?
Green top
Silver sides
Information from your supervisor
An ‘MR Conditional’ label, but it should be double checked before being taken into Zone 4
An ‘MR Conditional’ label, but it should be double checked before being taken into Zone 4
Making sure your patient is well hydrated is an efficient way to help them dissipate heat during an MRI.
True
False
False
Energy deposition is affected by all of the following parameters EXCEPT:
TR
Echo train length
TE
Flip angle
# slices
TE
It is possible for an implant that has not undergone testing for MR safety to be safe in the MRI environment.
True
False
True
Without changing any other variables, changing from 1.5T to 3T will double SAR.
True
False
False
It is thought that subcutaneous fat contains pain receptors.
True
False
False
If an oxygen tank is labeled ‘MR Conditional’, that means that the regulator is MR Conditional also.
True
False
False
