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MRI Review Part A > MRI screening and safety > Flashcards

MRI screening and safety Flashcards

1
Q

family members and ancillary personnel accompanying the patient into the scan room

A

should be screened as if they are going through the procedure themselves

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2
Q

in preparatoin for the MRI examination patients should be encourage to

A

change into a hostpital gown or scrub suit provided by the imaging center and known to be MR safe

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3
Q

MRs jones has just been sent to the MRI department from the mergency room followoing a severe motor vehichle accident. She ahs suffered a fracture of C3 and her physicians are concerned about a cervical spinal cord compression at that level

select the best method for proceeding with this case

A

ask her and her family about the possibility of her having metal fragments in her body

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4
Q

persons should be educated about the effects of the static magnetic field especially in high field superconducting magnets include

A

nursing staff and code team

housekeeping

members of fire department

anesthesiologist and respiratory therapists

technologist and radiologist

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5
Q

accodring to the White Paper on MRI safety persons are identified into levels where by level 2 personnel include

A

persons with extensive training in MRI safety to include the broader aspects of MRI

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6
Q

according to the White Paper on MRI safety imaging centers should be separated into zones including all of the following

A

zone 1 freely accessible to any level MR personnel

Zone 2 interface between 1 and 3

zone 3 warm zone, generally console area and last stop before scan room

zone 4 the hot zone, scan room itself

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7
Q

a screening questionaire for patients about to undergo MRI should include information about

A

prior injuries

prior surgery and implants

pregnancy

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8
Q

the terminology for devices and implants in MRI was modified a few years ago, whereby the term MR compatible has been replace with all of the following

A

MR safe

MR unsafe

MR conditional

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9
Q

absolute contraindications to MRI include

A

intracranial vascular clips, unless they are KNOWN to be safe

cardia pacemakers, unless they are KNOWN to be safe

intraocular ferrous foreign bodies

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10
Q

the accepted standard of care for the detection of intraocular ferrous foreign bodies is

A

plain film

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11
Q

a method that is more accurate in the detection of small inraocular ferrous foreign bodies is

A

CT

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12
Q

before a patient enters the MRI environment they should be screened for

A

prior injuries

prior surgical implants

pregnancy

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13
Q

of the following implants which would be considered acceptable to scan my MRI

A

heart valves

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14
Q

if monitoring is to be achieved by electrical and or mechanical devices it is important that compatibility with the MR system be demonstrated by

A

manufacturer declaration

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15
Q

the following items are usually allowed to enter the scan room in high magnetic field systems

A

copper tools

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16
Q

when used for MRI cables from RF coils and ECG leads should be

A

braided and placed straight though the imager

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17
Q

surface soil cables can potentially cause damage to the patient when

A

they are slightly touching the patient and frayed

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18
Q

a quench can be used to

A

rapidly remove superconductivity and the magnetic field

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19
Q

during a quench patients and operators should be evacuatied from the room to avoid

A

asphyxiation and frostbite

ruptured tympanic membranes

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20
Q

what is regulated by the FDA

A

accoustic noise

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21
Q

for optimum operation of MRI systems the ambient temperature and relative humidity should remain between

A

65-75 F and 70%

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22
Q

the acceptable safe level for exposure to magnetic fringe fields with respect to patients with cardiac pacemakers has been reported to be

A

below 5g

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23
Q

magnetic field shielding can be achieved wither actively or passively passive shielding can be achieved by lining the MRI room with

A

steel

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24
Q

RF shielding can be achieved by lining the MRI room with

A

copper

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25
Q

it is acceptable for the general population to be exposed to a field strength of

A

5.0 guass

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26
Q

the unit of measure of RF absorption is

A

watts per kilogram

27
Q

MR imagers are magnetic field shielded such that

A

the fringe field is confined to/within the scan room

28
Q

firnge fields are less of a concern for

A

low field

vertical field permanent magnet imagers

29
Q

in July of 2003 the FDA center for devices and radiologic health (CDRH) modified the limit on RF absorption (dose) to ______for the HEAD

A

4.0W/kg absorption for 15 min

30
Q

the FDA limits the allowable RF absorption to

A

4.0 W/kg averaged over the body

31
Q

the term used to describe RF absorption is

A

specific absorption rate (SAR)

32
Q

the predominant biologic effect of RF fields is

A

tissue heating

33
Q

RF antenna effects can cause

A

RF interference artifacts

thermal injury and flames

34
Q

the FDA limits the effect of RF absorption to an increase in core body temperature of

A

1 C

35
Q

the increse in body temperature as the result of RF absorption is

A

greatest on the outside becoming less at the center

36
Q

RF energy used in MRI is classified as

A

low energy, nonionizing radiation

37
Q

as the flip angle is double RF deposition increases by a factor of

A

four

38
Q

RF hearing is more of a concern in imaging sequences usch as

A

fast spin echo

39
Q

areas of the body that are most sensitive to the heat from SAR are

A

globes of the eyes and testicles

40
Q

for adult imaging in MRI the FDA guidellines limit the field strength of clinical imagers to

A

8.0 T

41
Q

a magnetic field strength of 1 T is equal to

A

10,000 g

42
Q

all of the following are regulated by the FDA

A

field strangth of the main magnet for clinical imaging

RF absorption (SAR)

acoustic noise

43
Q

no biologic effects have been reported in humans as the result of exposure for

A

static magnetic fields below 2 T

44
Q

the field strength at isocenter is measured in units of

A

tesla

45
Q

magnetic field strength outside the imager is usually measured in

A

gauss

46
Q

the attractive force that an object will experience at a distance of 6 feet from isocenter is dependent on

A

ferromagnetic properties of the opbject

mass of the object

field strength of the system

47
Q

as a conductive medium (blood) moves across a magnetic field, an effect knows as the magnetic hemodynamic effec occurs resulting in

A

elevated T-wave

48
Q

it is _____for all patients to be provided with hearing protection in the form of________

A

recommened

headphones or earplugs

49
Q

the gradient magnetic fields

A

produce heat in the gradient coils during the scan

can produce noise to cause temporary hearing loss

change rapidly during the scanning process

50
Q

when a patien is placed within the bore of a magnetic resonance imager an effect can be noted on the ECG whereby there is an elevated T wave. This effect is known as

A

magnetohydrodynamic effect

magnet-hydrodynamic effect

magnet hemodynamic effect

51
Q

the effect whereby the patient experiences a visual impression of seeing stars in their eyes is known as

A

magnetophosphenes

52
Q

the FDA lmit on time varying magnetic fields is

A

until a patient experiences peripheral nerve stimulation

53
Q

time carying magnetic field (TVMF) effects include all of the followoing

A

acoustic damage and hearing loss

peripheral nerve stimulation and tingling

magnetophosphenes and stars in the eyes

54
Q

TVMF effects are of greater concern for which type of scanner

A

EPI

55
Q

the strength of gradient magnetic fields is measured in

A

Milli Tesla per meter

Gauss per centimeter

56
Q

gradient magnetic fields are a safety concern because they

A

induce current in conductors

57
Q

time varying magnetic fields have been reported to have caused

A

mild cutaneous sensations and images of flashing lights in patients

involuntary muscle contractions and cardiac arrhythmias in patients

58
Q

the FDA limit for the static magnetic field for clinial imaging for patients over 1 month of age is

A

4.0 T

59
Q

the FDA limit for the static magnetic field for clinical imaging for ALL patients is

A

4.0 T

60
Q

the imaging sequence that is of the most concern for time varying magnetic field effects is

A

echo planar

61
Q

gradient rise time is

A

the time it takes for a gradient to get full amplitude

62
Q

the duty cycle is

A

the time gradients are on during a TR period

63
Q

to avoid auditory damage during MRI all patients should be offered

A

headphones

earplugs

antinoise devices

MRI Review Part A (5 decks)

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