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Flashcards in Safety Deck (38)
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1

What items can become projectiles?

Ferromagnetic items

A paper clip can travel at 40 mph in 1.5T scanner

2

MRI safety issues name 6

Static MF bio and mech
Gradient MF auditory and electrical (time varying)
RF MF bio and thermal
Contrast agents
Physiological such as anxiety

3

Guidelines for safe MR

Education
Proper screening
Warning signs
Emergency prep
Routine maintence

4

ASTM

American Standard for testing and materials
F2504

5

ASTM labeling

Safe - been tested
Unsafe - not tested
Conditional - such as pacemaker and clips on some conditions

6

MRI safety zones

1- entrance to facility
2- reception and dressing area
3- control room
4- magnet

7

Screening and tools

Patient
Ancillary equipment
Personnel

Metal detector
Bar magnet
Patient contact

8

Assessment and monitoring 3

Conscious sedation with medication
Capnometer to measure carbon dioxide levels
Pulse oximetry

9

Contrast media for MRI and what are 4 agents

Gadolinium

Magnevist
Multihance
Omniscan
OptiMark

10

Gasolinium similarities and distinctions

No difference except prices

Physic helical characteristics such osmolarity which is concentration and viscosity which is resistance of agent

11

Contraindications for GAD

None

Only associated effects
Overall reactions is less than 3%
9.8 ha
4.1 nausea
2 vomit

12

Gad precautions

Pregnancy- can leak to baby
Lactation- pump and dump
Renal failure- can't process
Respiratory- asthma

13

NSF

Nephrogenic systemic fibrosis
Causes fibrosis of skin and connective tissue, hardening of tissue

14

Renal GFR

Normal routine if greater than 60
Half dose if 59-30
Don't inject if less than 29

Creative levels under 1.5

15

ACR say about contract media

Frequency of reactions to gad are 2.3-3.7 time higher in pts with history to iodine agents

8 times higher if precious reaction to gad

16

Biological concerns for MRI

Static MF
Time varying MF
RF
Sound pressure

17

Bio effects on 2T and above

Fatigue
Ha
Hypotension
Irritability
Cell dehydration

18

FDA limits MF for adults and babies

8 T
New born a to 1 month 4T

19

Bio effects below 2T

Magnetic hydrodynamic effect which blood or conductive fluid moves across a MF
Increase T wave in pts EKG

20

Mechanical concern

Ferromagnetic torque forces
Surgical stainless steel
Pacemakers, implants, etc

21

Magnetic shielding 2

Passive- walls
Active- coils in gantry

22

RF shielding

Line walls with copper

23

Safety concerns(5)

Cryogen
Physiological
Contrast agents- less than 3%
Environment- temp.. 65-72 to prevent static artifacts and humidity 45-65
Safety line- pacemaker line

24

Fringe fields and pacemaker line

Stray magnetic fields outside of bore

Pacemaker line is at 5G line

25

TVMF what it can do and the effects

Induce a current thru any conductive medium
Threat is vessels nerves and muscles

Effects:
Involuntary muscle contractions
Cardiac arrhythmia
Stimulation of retinal phosphenes
Mild cutaneous sensations

26

FDA limits with gradient field strength

The change in gradient MF strength to any time rate of change sufficient to produce severe discomfort or painful nerve stimulation

27

Gradient auditory concerns- FDA

Regulation at 149 decibels

So use earbuds and headphone.
60-103 is norm

Hearing ranges from 20-20000 hertz

43% pts scanned without protection will experience temporary hearing loss

28

TF focal power deposition guidelines and theory

Remove unnecessary electrical conductors from bore
Pts tissues and electrical don't form loops
Use only MR safe items
Add thermal insulation btwn conductors and pts.

Pts tissue acts as conductor causing a thermal injury

29

SAR and how measured

Bio effect of heating tissue
Specific Absorption Rate
Amt of energy deposited into tissue
Measured as watts/kg
Bigger means more sweat

30

RF absorption according to FDA whole body, head, torso, extremities

What if pregnant?

Whole body is 4 watts
Head is 3 watts
Torso 8 watts
Extremities 12 watts

Wait til third trimester but can do earlier if needed