Safety Flashcards
What items can become projectiles?
Ferromagnetic items
A paper clip can travel at 40 mph in 1.5T scanner
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
Guidelines for safe MR
Education Proper screening Warning signs Emergency prep Routine maintence
ASTM
American Standard for testing and materials
F2504
ASTM labeling
Safe - been tested
Unsafe - not tested
Conditional - such as pacemaker and clips on some conditions
MRI safety zones
1- entrance to facility
2- reception and dressing area
3- control room
4- magnet
Screening and tools
Patient
Ancillary equipment
Personnel
Metal detector
Bar magnet
Patient contact
Assessment and monitoring 3
Conscious sedation with medication
Capnometer to measure carbon dioxide levels
Pulse oximetry
Contrast media for MRI and what are 4 agents
Gadolinium
Magnevist
Multihance
Omniscan
OptiMark
Gasolinium similarities and distinctions
No difference except prices
Physic helical characteristics such osmolarity which is concentration and viscosity which is resistance of agent
Contraindications for GAD
None
Only associated effects Overall reactions is less than 3% 9.8 ha 4.1 nausea 2 vomit
Gad precautions
Pregnancy- can leak to baby
Lactation- pump and dump
Renal failure- can’t process
Respiratory- asthma
NSF
Nephrogenic systemic fibrosis
Causes fibrosis of skin and connective tissue, hardening of tissue
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
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
Biological concerns for MRI
Static MF
Time varying MF
RF
Sound pressure
Bio effects on 2T and above
Fatigue Ha Hypotension Irritability Cell dehydration
FDA limits MF for adults and babies
8 T
New born a to 1 month 4T
Bio effects below 2T
Magnetic hydrodynamic effect which blood or conductive fluid moves across a MF
Increase T wave in pts EKG
Mechanical concern
Ferromagnetic torque forces
Surgical stainless steel
Pacemakers, implants, etc
Magnetic shielding 2
Passive- walls
Active- coils in gantry
RF shielding
Line walls with copper
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
Fringe fields and pacemaker line
Stray magnetic fields outside of bore
Pacemaker line is at 5G line
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
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
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
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
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
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
Pregnant technologist
Avoid tvmf and RF fields during scanning
Absolute contraindications that are conditional (3)
Pacemakers
Aneurysm clips
Cochlear implants
Intra occular bodies
Aneurysm clips considered safe
Titanium
Sugita, yasargil, Vari-angel
Intravascular filters safe??
Allow to be in place for 4-6 wks to grow into tissue
Apparently safe devices
Hip prosthesis Dental fillings Braces Sternal wire sutures IUD Abdominal clips post 1 wk
Quench
Rapid loss of super conductivity
Hypothermia
Asphyxia
Frostbite
Helium liquified at what temp?
Nitrogen?
4K or -269C expands to 760:1
77K expanding to 695:1
Quenching safety
Evacuate all personnel
Oxygen near by
Ventilation system check
