Unit 3 Flashcards
What is SAR?
Specific Absorption Rate
measure of energy (RF) dissipation in the body
What are time varying magnetic fields?
magnetic fields caused by the gradient magnetic coils
What is exclusion zone?
area where fringe field is 5G or more;
area should not be allowed to public access
Types of EM fields in MR
static, gradient, RF
Max static magnetic field strength allowed in patients >1mo
8T
Primary safety hazard associated w/ static fields
projectile
Primary safety hazard associated w/ gradient fields
Induced electrical currents in conductors
Reversible biological effects associated w/ rapid switching of gradient field
altered vision, involuntary muscle contractions, skin sensations
Unit of measure of SAR
W/kg
Max SAR for whole body imaging
4 W/kg
Max SAR for head imaging
3.2 W/kg
Primary biological response to RF in MR
absorption => tissue heating
Primary hazard associated w/ RF in MR
burns
Patient info directly affecting SAR calculation
weight, age
Objects that have wires that can form a conductive loop in MR
monitoring equipment, coil cables
