Safety

Question 1

What items can become projectiles?

Answer 1

Ferromagnetic items

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

Question 2

MRI safety issues name 6

Answer 2

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

Question 3

Guidelines for safe MR

Answer 3

Education
Proper screening
Warning signs
Emergency prep
Routine maintence

Question 4

ASTM

Answer 4

American Standard for testing and materials

F2504

Question 5

ASTM labeling

Answer 5

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

Question 6

MRI safety zones

Answer 6

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

Question 7

Screening and tools

Answer 7

Patient
Ancillary equipment
Personnel

Metal detector
Bar magnet
Patient contact

Question 8

Assessment and monitoring 3

Answer 8

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

Question 9

Contrast media for MRI and what are 4 agents

Answer 9

Gadolinium

Magnevist
Multihance
Omniscan
OptiMark

Question 10

Gasolinium similarities and distinctions

Answer 10

No difference except prices

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

Question 11

Contraindications for GAD

Answer 11

None

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

Question 12

Gad precautions

Answer 12

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

Question 13

NSF

Answer 13

Nephrogenic systemic fibrosis

Causes fibrosis of skin and connective tissue, hardening of tissue

Question 14

Renal GFR

Answer 14

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

Creative levels under 1.5

Question 15

ACR say about contract media

Answer 15

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

Question 16

Biological concerns for MRI

Answer 16

Static MF
Time varying MF
RF
Sound pressure

Question 17

Bio effects on 2T and above

Answer 17

Fatigue
Ha
Hypotension
Irritability
Cell dehydration

Question 18

FDA limits MF for adults and babies

Answer 18

8 T

New born a to 1 month 4T

Question 19

Bio effects below 2T

Answer 19

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

Question 20

Mechanical concern

Answer 20

Ferromagnetic torque forces
Surgical stainless steel
Pacemakers, implants, etc

Question 21

Magnetic shielding 2

Answer 21

Passive- walls

Active- coils in gantry

Question 22

RF shielding

Answer 22

Line walls with copper

Question 23

Safety concerns(5)

Answer 23

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

Question 24

Fringe fields and pacemaker line

Answer 24

Stray magnetic fields outside of bore

Pacemaker line is at 5G line

Question 25

TVMF what it can do and the effects

Answer 25

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 ```

Question 26

FDA limits with gradient field strength

Answer 26

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

Question 27

Gradient auditory concerns- FDA

Answer 27

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

Question 28

TF focal power deposition guidelines and theory

Answer 28

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

Question 29

SAR and how measured

Answer 29

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

Question 30

RF absorption according to FDA whole body, head, torso, extremities What if pregnant?

Answer 30

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

Question 31

Pregnant technologist

Answer 31

Avoid tvmf and RF fields during scanning

Question 32

Absolute contraindications that are conditional (3)

Answer 32

Pacemakers Aneurysm clips Cochlear implants Intra occular bodies

Question 33

Aneurysm clips considered safe

Answer 33

Titanium | Sugita, yasargil, Vari-angel

Question 34

Intravascular filters safe??

Answer 34

Allow to be in place for 4-6 wks to grow into tissue

Question 35

Apparently safe devices

Answer 35

``` Hip prosthesis Dental fillings Braces Sternal wire sutures IUD Abdominal clips post 1 wk ```

Question 36

Quench

Answer 36

Rapid loss of super conductivity Hypothermia Asphyxia Frostbite

Question 37

Helium liquified at what temp? Nitrogen?

Answer 37

4K or -269C expands to 760:1 77K expanding to 695:1

Question 38

Quenching safety

Answer 38

Evacuate all personnel Oxygen near by Ventilation system check