Clinical Applications Flashcards by William Kerns

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

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Pillowcases or sheets placed between the patient and the bore provides appropriate protection against proximity burns. True or False?

True

False

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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.

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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

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Clothing labels/tags always indicate the presence of silver fibers or treatments. True or False?

True

False

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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

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Items labeled ‘MR Safe’ are only safe in a specific MR environment. True or False?

True

False

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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

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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

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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

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Providing patients with warm blankets during scanning will help them perspire and better dissipate heat. True or False?

True

False

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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

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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

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If an oxygen tank has a green top with silver sides, it is known to the MR conditional. True or False?

True

False

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Nitinol is a non-ferrous nickel-titanium alloy. Because it is non-ferrous, it would be labeled MR Safe. True or False?

True

False

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Patients should be permitted to wear their own clothing in the MRI scanner. True or False?

True

False

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EKG changes may be observed with patient exposure to the static magnetic field, before imaging has begun. True or False?

True

False

True

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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?

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The ways humans can handle or dissipate heat include all of the following EXCEPT

perspiration/evaporation

radiation

convection

conduction

hydration

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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.

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Obese or pregnant patients may have difficulty dissipating heat because they have a decreased surface to volume ratio. True or False?

True

False

True

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EKG perturbances can alter cardiac gating due to elevation of the ST segment of the EKG waveform. True or False?

True

False

True

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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

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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

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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

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