MRSO - RADIO FREQUENCY - MODULE 4 Questions & Correct Revised Verified Answers
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Course
MRSO
Institution
MRSO
When determining RF energy, strength of magnetic field is measured in - Answer mT
Main biological effect of exposing tissue to electromagnetic radiation in that frequency
range - Answer tissue heating
Cause of tissue heating - Answer Magnetic induction results in eddy currents of
conductive tis...
MRSO - RADIO FREQUENCY - MODULE 4
Questions & Correct Revised Verified Answers
When determining RF energy, strength of magnetic field is measured in - Answer mT
Main biological effect of exposing tissue to electromagnetic radiation in that frequency
range - Answer tissue heating
Cause of tissue heating - Answer Magnetic induction results in eddy currents of
conductive tissue
Tissue heating is mostly ______________ with very little _______________ - Answer
peripheral , deep body heating
How patient dissipates RF power - Answer cooling.
If the input is greater than the output, heating occurs.
SAR (specific absorption rate) - Answer RF power absorbed per unit mass of tissue
SAR is SPECIFIC to: - Answer body part and tissue
SAR represents - Answer ABSORPTION of RF into the body/tissues
SAR is the - Answer RATE of RF exposure and absorption
SAR is measured in - Answer watts/kg
, SAR is proportional to: - Answer -the power of 2 for system's resonant frequency (factor
of 4)
-the power of 2 for B1 amplitude of RF field (doubling flip angle with increase SAR by
factor of 4)
-the power of 5 for the pt's circumference
-patient's average conductivity
Is muscle or fat more conductive? - Answer muscle
SAR is not measured, it is: - Answer estimated via algorithms that differ with MR
manufacturer
There is no standard for SAR estimations - Answer each vendor uses different algorithm
Estimations of SAR are based on: - Answer -field strength
-RF frequency / coil
-scan parameters: type, # RF pulses, TR, # of slices per TR
-pt characteristics: weight, height, body part
-assumed tissue conductivity
It is widely accepted that most if not all vendors are very
___________________________ in their SAR estimates - Answer conservative
SAR is believed to serve as a - Answer crude measure of heating potential
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