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001 MRI > EXAM #10 — PHYSICS UNIT 03 > Flashcards

EXAM #10 — PHYSICS UNIT 03 Flashcards

1
Q

define the following term:

specific absorption rate (SAR).

A

a measure of energy (RF) dissipation in the body

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2
Q

define the following term:

time varying magnetic fields.

A

magnetic fields whose strength varies over time

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3
Q

define the following term:

exclusion zone.

A

the area around the MRI magnet where the field strength is 5 Gauss or stronger

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4
Q

identify the 3 types of electromagnetic fields that are used in MRI.

A

static field, gradient fields, RF

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5
Q

identify the maximum static magnetic field strength allowed by the FDA for clinical imaging of patients over 1 month old.

A

8 Tesla

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6
Q

discuss the risk of irreversible biological effects of static magnetic field strengths less than 2T.

A

no known risk of irreversible biological effects

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7
Q

identify the primary safety hazard associated with static magnetic fields.

A

interaction with metallic objects

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8
Q

identify the primary safety hazard associated with gradient magnetic fields.

A

induced electrical currents in conductors

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9
Q

identify 3 reversible, temporary biological effects associated with very rapidly
switching gradient magnetic fields.

A

visual flashes, skin sensation, and muscle contractions

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10
Q

identify the unit of measure of specific absorption rate (SAR).

A

Watts/kilogram (Wlkg)

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11
Q

identify the maximum SAR values for:

a. whole-body imaging in the US. ___ W/kg
b. head imaging in the US. ___ W/kg

A

identify the maximum SAR values for:

a. whole-body imaging in the US. 4.0 W/kg
b. head imaging in the US. 3.0 W/kg

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12
Q

discuss the primary potential biological response to RF in the MRI environment.

A

tissue heating

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13
Q

discuss the primary hazard associated with RF in the MRI environment.

A

burns or fires caused by the induction of electrical currents in conductors

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14
Q

state the patient information that directly affects SAR calculation.

A

weight and age

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15
Q

state 4 ways in which an implanted cardiac pacemaker is dangerous in the MRI environment.

A

deflection of pacemaker generator, reed switch malfunction, pacemaker reprogramming, induction of electrical current in pacemaker leads

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16
Q

identify 2 objects that are often present in an MRI site and have wires that can form conductive loops.

A

surface coils, patient monitoring equipment (EKG)

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17
Q

discuss 3 hazards associated with metallic implants and MR imaging.

A

deflection, heating, artifacts that can cause misdiagnosis

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18
Q

safe / unsafe / conditionally

cardiac pacemaker.

A

Unsafe

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19
Q

safe / unsafe / conditionally

intracranial aneurysm clip.

A

Conditionally safe (depends on specific model)

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20
Q

safe / unsafe / conditionally

intravascular filter or stent.

A

Conditionally safe (depends on time since implantation)

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21
Q

safe / unsafe / conditionally

vascular access port.

A

Conditionally safe (depends on specific model)

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22
Q

safe / unsafe / conditionally

prosthetic heart valve.

A

Safe

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23
Q

safe / unsafe / conditionally

otologic implant.

A

Conditionally safe (depends on specific model)

24
Q

safe / unsafe / conditionally

ocular implant.

A

Conditionally safe (depends on specific model)

25
Q

safe / unsafe / conditionally

bullet, pellet, or shrapnel.

A

Conditionally safe ( depends on location in body)

26
Q

safe / unsafe / conditionally

surgical staples in abdomen.

27
Q

safe / unsafe / conditionally

halo vest, external fixation device.

A 
Conditionally safe (depends on specific
model)
28
Q

safe / unsafe / conditionally

orthopedic internal fixation.

29
Q

safe / unsafe / conditionally

neurostimulator.

A

Conditionally safe (depends on several factors, must rely on specific manufacturer’s guidelines)

30
Q

safe / unsafe / conditionally

bone growth stimulator.

A

Conditionally safe ( depends on several factors, must rely on specific manufacturer’s guidelines)

31
Q

safe / unsafe / conditionally

intraocular metallic foreign body.

32
Q

safe / unsafe / conditionally

internal cardiac defibrillator.

33
Q

safe / unsafe / conditionally

internal drug infusion pump.

A

Conditionally safe (depends on several factors, must rely on specific manufacturer’s guidelines)

34
Q

deflection / current / malfunction

cardiac pacemaker.

35
Q

deflection / current / malfunction

intracranial aneurysm clip.

A

Deflection

36
Q

deflection / current / malfunction

intravascular filter or stent.

A

Deflection

37
Q

deflection / current / malfunction

vascular access port.

38
Q

deflection / current / malfunction

prosthetic heart valve.

A

Deflection, malfunction

39
Q

deflection / current / malfunction

otologic implant.

A

Deflection

40
Q

deflection / current / malfunction

ocular implant.

A

Deflection

41
Q

deflection / current / malfunction

bullet, pellet, or shrapnel.

A

Deflection, heating

42
Q

deflection / current / malfunction

surgical staples in abdomen.

A

Deflection

43
Q

deflection / current / malfunction

halo vest, external fixation device.

A

Deflection

44
Q

deflection / current / malfunction

orthopedic internal fixation.

A

Deflection

45
Q

deflection / current / malfunction

neurostimulator.

46
Q

deflection / current / malfunction

bone growth stimulator.

47
Q

deflection / current / malfunction

intraocular metallic foreign body.

A

Deflection

48
Q

deflection / current / malfunction

internal cardiac defibrillator.

49
Q

deflection / current / malfunction

internal drug infusion pump.

A

Deflection, malfunction

50
Q

state the fringe field strength that defines the exclusion zone.

51
Q

identify the most reliable source for MRl safety information on a specific implant.

A

implant manufacturer

52
Q

discuss the primary hazard associated with a superconducting magnet quench.

A

asphyxiation by gaseous helium in the magnet room

53
Q

discuss 2 safety issues related to the acoustic noise generated by MRl systems.

A

difficult patient/technologist communication, hearing loss

54
Q

discuss the US FDA guidelines for scanning pregnant patients.

A

the scanning of pregnant patients is neither recommended nor prohibited

55
Q

discuss the Society of Magnetic Resonance Imaging (SMRl) Safety Committee’s recommendation for scanning pregnant patients.

A

the risk of injury to the fetus should be weighed with the potential benefit to the mother and fetus

001 MRI (15 decks)

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