MRI safety and procedures

44 Gulf Prometric Radiographer (DHA, DOH, MOH, SCFHS, QCHP) practice questions on MRI safety and procedures, part of MRI. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   A patient with a programmable ventriculoperitoneal shunt valve is scanned at 1.5 T under the valve's MR conditional labelling. What must be arranged after the scan?

   1. AA CT is done to confirm that the valve has not moved
   2. BThe shunt is tapped to test for infection
   3. CThe valve setting is checked and reset if needed
   4. DNo action, as an MR conditional scan needs no follow-up

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   Answer: C · The valve setting is checked and reset if needed

   Many programmable shunt valves are set by an external magnet, so the scanner's field can change the pressure setting. Their labelling allows scanning, but the setting must be checked, usually with a radiograph or a reading device, and reset by the neurosurgical team after MRI. An unnoticed change can cause over- or under-drainage of CSF.

   • A: The concern is a changed setting, not movement of the valve.
   • B: Tapping the shunt is an invasive test for infection and is not part of MRI care.
   • D: MR conditional means safe under conditions, which here include checking the setting afterwards.

   Remember this

   Check and reset programmable shunt valves after MRI.

2. Question 2 · Medium

   A metalworker is to have an orbital MRI. What screening is needed?

   1. AAn interview about drug allergies and previous contrast reactions only
   2. BNo screening is needed, because any metal in the eye would be non-magnetic
   3. COrbital radiographs or CT to look for metal, if there is a history of metalwork
   4. DA chest radiograph to look for metal that may be moved by the field

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   Answer: C · Orbital radiographs or CT to look for metal, if there is a history of metalwork

   Iron particles in the eye can move in the field and damage the retina or blind the patient. Radiographs or CT before MRI exclude intraocular metal in at-risk patients such as welders and grinders.

   • A: Food allergy is unrelated to the hazard.
   • B: Steel fragments are ferromagnetic.
   • D: A chest film does not show the orbit.

   Remember this

   Screen possible orbital foreign bodies with imaging before MRI.

3. Question 3 · Medium

   An unconscious trauma patient arrives for an MRI of the head and no history of implants can be obtained. What is the best approach?

   1. AScan only after the patient's clothing has been removed and checked
   2. BScan at once because screening is not needed in an emergency situation
   3. CUse records, relatives and imaging such as radiographs to exclude implants before scanning
   4. DScan at the lowest field strength available without further checks

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   Answer: C · Use records, relatives and imaging such as radiographs to exclude implants before scanning

   A patient who cannot give a history cannot be screened by questionnaire, so the radiology team gathers information from records, relatives and previous imaging, and may use radiographs or CT to look for metal. Scanning proceeds only after the risk is judged acceptable.

   • A: Removing clothes does not reveal internal implants.
   • B: An emergency does not remove the projectile and implant risks.
   • D: A lower field still exerts force on ferromagnetic implants.

   Remember this

   An unscreened patient must not enter Zone IV until the implant risk is assessed.

4. Question 4 · Hard

   An 18 kg child is to receive gadobutrol 1.0 mmol/mL at 0.1 mmol/kg. What volume is given?

   1. A18 mL
   2. B1.8 mL
   3. C0.18 mL
   4. D9 mL

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   Answer: B · 1.8 mL

   Dose = 0.1 mmol/kg x 18 kg = 1.8 mmol. At 1.0 mmol/mL the volume is 1.8 mL.

   • A: 18 mL is ten times too large.
   • C: 0.18 mL is ten times too small.
   • D: 9 mL would be the volume of a 0.2 mmol/mL agent at the same dose.

   Remember this

   With a 1.0 mmol/mL agent, the volume in mL equals weight x 0.1.

5. Question 5 · Hard

   A 70 kg adult is to receive gadoterate meglumine 0.5 mmol/mL at the standard dose of 0.1 mmol/kg. What volume is injected?

   1. A7 mL
   2. B35 mL
   3. C1.4 mL
   4. D14 mL

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   Answer: D · 14 mL

   Dose = 0.1 mmol/kg x 70 kg = 7 mmol. Volume = 7 mmol / 0.5 mmol per mL = 14 mL.

   • A: 7 mL forgets to divide by the concentration of 0.5 mmol/mL.
   • B: 35 mL multiplies instead of dividing.
   • C: 1.4 mL would be correct for a 1.0 mmol/mL agent at 0.02 mmol/kg.

   Remember this

   Volume = weight x 0.1 mmol/kg divided by the agent concentration in mmol/mL.

6. Question 6 · Easy

   Which of the four ACR MR safety zones contains the scanner magnet itself?

   1. AZone IV
   2. BZone II
   3. CZone I
   4. DZone III

   Answer and explanation in LearnFree account

7. Question 7 · Medium

   In normal operating mode, the whole-body SAR limit for MRI under IEC 60601-2-33 is:

   1. A0.2 W/kg
   2. B2 W/kg
   3. C200 W/kg
   4. D20 W/kg

   Answer and explanation in LearnFree account

8. Question 8 · Easy

   The SI unit of magnetic flux density used to describe the strength of an MRI magnet is the:

   1. AGray
   2. BTesla
   3. CHenry
   4. DBecquerel

   Answer and explanation in LearnFree account

9. Question 9 · Medium

   Where in the MRI department is the screening interview and the patient's metallic clearance usually done?

   1. AZone I
   2. BZone IV
   3. CThe control room only
   4. DZone II

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    To lower the risk of burns during MRI, the radiographer should:

    1. ALet the patient's thighs touch each other to keep the position steady
    2. BCoil the ECG leads on the chest so that they stay in place
    3. CAvoid skin-to-skin contact and conductive loops, and insulate cables with padding
    4. DPlace monitoring cables in a tight loop beside the patient's body

    Answer and explanation in LearnFree account

11. Question 11 · Medium

    Which group of sequences forms the core of an MRI stroke protocol?

    1. APost-contrast T1 imaging only, with a delay of 5 minutes
    2. BProton density imaging only, with fat saturation
    3. CT1 spin echo only, before and after contrast injection
    4. DDWI with ADC, FLAIR, a susceptibility sequence and MRA

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12. Question 12 · Medium

    MR cholangiopancreatography (MRCP) is obtained using which type of sequence?

    1. ADiffusion-weighted, with a high b-value for the ducts
    2. BT1 gradient echo, after an injection of gadolinium
    3. CProton density spin echo, with fat suppression
    4. DHeavily T2-weighted, with fluid bright and no contrast

    Answer and explanation in LearnFree account

13. Question 13 · Medium

    Which room feature protects staff from oxygen displacement if helium escapes into the scanner room?

    1. AA radiation badge worn by every member of the staff
    2. BA silent gradient mode used for the whole examination
    3. CAn oxygen monitor and a quench pipe with a vented exit
    4. DA lead-lined door that keeps gas inside the magnet room

    Answer and explanation in LearnFree account

14. Question 14 · Hard

    A pregnant woman at 28 weeks has right-sided abdominal pain. Ultrasound is non-diagnostic. Which next step is most appropriate?

    1. AMRI of the abdomen without gadolinium
    2. BNo imaging at all until the delivery
    3. CCT with oral and IV contrast first
    4. DMRI with gadolinium contrast

    Answer and explanation in LearnFree account

15. Question 15 · Easy

    Specific absorption rate (SAR) in MRI is expressed in:

    1. ATesla per second
    2. BDecibels
    3. CJoules per cubic metre
    4. DWatts per kilogram

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16. Question 16 · Medium

    The 0.5 mT (5 gauss) fringe-field line around a magnet is used mainly to:

    1. AShow where the RF field ends outside the shielded scanner room
    2. BDefine the position of the helium vent on the roof of the building
    3. CMark the limit of acoustic noise from the gradient coils in the room
    4. DKeep people with pacemakers and other implanted devices outside the line

    Answer and explanation in LearnFree account

17. Question 17 · Medium

    Which item must be removed before MRI because it may contain a metal backing that can heat the skin?

    1. AA plastic hair tie without metal
    2. BA transdermal drug patch
    3. CA cotton bandage
    4. DA paper wristband

    Answer and explanation in LearnFree account

18. Question 18 · Medium

    An implant is labelled 'MR conditional'. This means that the item:

    1. AIs safe in any scanner at any field strength and with any sequence
    2. BIs attracted by the magnet and must always be kept out of the room
    3. CPoses no known hazard in an MR environment under specified conditions of use
    4. DIs safe only if it is kept outside Zone IV during the examination

    Answer and explanation in LearnFree account

19. Question 19 · Medium

    A patient with an eGFR of 25 mL/min/1.73 m2 needs a contrast-enhanced MRI. Which agent class has the lowest NSF risk?

    1. AOral barium suspension
    2. BGroup II macrocyclic agents
    3. CGroup I linear agents
    4. DIodinated contrast media

    Answer and explanation in LearnFree account

20. Question 20 · Medium

    A patient has an intracranial aneurysm clip of unknown type. What is the correct action?

    1. AScan if the clip looks like titanium on the scout image
    2. BDo not scan until the make and model of the clip are confirmed as MR safe or conditional
    3. CScan in the prone position to keep the clip away from the bore wall
    4. DScan with a low SAR setting to prevent any heating of the clip

    Answer and explanation in LearnFree account

21. Question 21 · Hard

    A patient has a pacemaker labelled MR conditional for 1.5 T only, and the hospital has 1.5 T and 3 T scanners. What is the right plan?

    1. AUse the 1.5 T scanner within the labelled SAR limit, with the device in MRI mode and monitoring
    2. BUse either scanner, as the field strength does not matter for conditional devices in a monitored patient
    3. CUse the 3 T scanner to shorten the scan time and the exposure of the patient
    4. DUse 3 T with the lowest flip angle that gives a useful image

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22. Question 22 · Easy

    What is the most important reason that all ferromagnetic oxygen cylinders must stay outside Zone IV?

    1. AThey increase the SAR delivered to the patient on the table
    2. BThey cause the magnet to quench as soon as they enter the room
    3. CThey change the image contrast by altering the field in the bore
    4. DThey can become projectiles pulled into the magnet

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23. Question 23 · Medium

    Which description matches an object classified as 'MR unsafe'?

    1. AIt has been tested and shows no heating or force under any conditions
    2. BIt is made of non-conducting, non-magnetic material and is safe in all fields
    3. CIt poses a hazard in all MR environments, such as a ferromagnetic oxygen cylinder
    4. DIt is safe at 1.5 T only and must be kept away from higher field systems

    Answer and explanation in LearnFree account

24. Question 24 · Medium

    Gadolinium retention in the brain after repeated injections has been seen mainly in the:

    1. ADentate nucleus and globus pallidus, with linear agents
    2. BPituitary gland only, with both classes of agent
    3. CCerebral cortex only, with macrocyclic agents
    4. DSpinal cord only, with all gadolinium agents

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25. Question 25 · Easy

    Which is the first measure for a claustrophobic patient before the scan?

    1. APosition the patient with the eyes closed and leave the room until finished
    2. BCancel the scan at once without any further discussion with the patient
    3. CExplain the procedure and offer reassurance, and let the patient hold the call bell
    4. DGive a sedative to the patient without any assessment by a doctor

    Answer and explanation in LearnFree account