EXAM #10 — PHYSICS UNIT 03 Flashcards
define the following term:
specific absorption rate (SAR).
a measure of energy (RF) dissipation in the body
define the following term:
time varying magnetic fields.
magnetic fields whose strength varies over time
define the following term:
exclusion zone.
the area around the MRI magnet where the field strength is 5 Gauss or stronger
identify the 3 types of electromagnetic fields that are used in MRI.
static field, gradient fields, RF
identify the maximum static magnetic field strength allowed by the FDA for clinical imaging of patients over 1 month old.
8 Tesla
discuss the risk of irreversible biological effects of static magnetic field strengths less than 2T.
no known risk of irreversible biological effects
identify the primary safety hazard associated with static magnetic fields.
interaction with metallic objects
identify the primary safety hazard associated with gradient magnetic fields.
induced electrical currents in conductors
identify 3 reversible, temporary biological effects associated with very rapidly
switching gradient magnetic fields.
visual flashes, skin sensation, and muscle contractions
identify the unit of measure of specific absorption rate (SAR).
Watts/kilogram (Wlkg)
identify the maximum SAR values for:
a. whole-body imaging in the US. ___ W/kg
b. head imaging in the US. ___ W/kg
identify the maximum SAR values for:
a. whole-body imaging in the US. 4.0 W/kg
b. head imaging in the US. 3.0 W/kg
discuss the primary potential biological response to RF in the MRI environment.
tissue heating
discuss the primary hazard associated with RF in the MRI environment.
burns or fires caused by the induction of electrical currents in conductors
state the patient information that directly affects SAR calculation.
weight and age
state 4 ways in which an implanted cardiac pacemaker is dangerous in the MRI environment.
deflection of pacemaker generator, reed switch malfunction, pacemaker reprogramming, induction of electrical current in pacemaker leads
identify 2 objects that are often present in an MRI site and have wires that can form conductive loops.
surface coils, patient monitoring equipment (EKG)
discuss 3 hazards associated with metallic implants and MR imaging.
deflection, heating, artifacts that can cause misdiagnosis
safe / unsafe / conditionally
cardiac pacemaker.
Unsafe
safe / unsafe / conditionally
intracranial aneurysm clip.
Conditionally safe (depends on specific model)
safe / unsafe / conditionally
intravascular filter or stent.
Conditionally safe (depends on time since implantation)
safe / unsafe / conditionally
vascular access port.
Conditionally safe (depends on specific model)
safe / unsafe / conditionally
prosthetic heart valve.
Safe
safe / unsafe / conditionally
otologic implant.
Conditionally safe (depends on specific model)
safe / unsafe / conditionally
ocular implant.
Conditionally safe (depends on specific model)
