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MRSO - RADIO FREQUENCY - MODULE 4 EXAM QUESTIONS AND ANSWERS () LATEST UPDATED
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MRSO - RADIO FREQUENCY - MODULE 4 EXAMQUESTIONS AND ANSWERS (2024-2025) LATEST
UPDATED
The purpose of the RF (B1) field is to excite hydrogen protons
Tissues absorb RF energy inside the volume of the transmit coil. This is a
thermogenic process.
ANSWER: Thermogenic processes produce heat. For example, the absorption of
radio frequency energy
MRI local and whole-body tissue heating is caused by magnetic induction.
Types of RF coil designs - ANSWER: linearly polarized
Circularly polarized (quadrature)
Function of coils: ANSWER - send only
Receive only.
-transmit/receive
The most frequent form of coil used is ANSWER receive only.
Integrated body coils are capable of working as a transmit/receive coil.
-As transmit only coil
,When a receive-only coil is utilized, RF energy is conveyed by the integrated body
coil.
Modern integrated body coils are circularly polarized.
Quadrature mode - ANSWER: Some 3T systems have an option.
-Advantage: Reduced dielectric shadowing.
-Safety considerations for implants/devices
RF Power Distribution Maps: ANSWER-specific to vendor and transmit coil
-Graph: The horizontal axis denotes z.
-100% power is at the isocenter (distance from the isocenter should be equal on
both sides).
Measured in centimetres.
-used just for vendor-integrated transmit coil, not transmit/receive head or knee
coil.
The purpose of the RF Power Distribution Map is to identify the percentage of RF
frequency power at a specific place inside the volume of the radiofrequency
transmitting coil.
-If the metal item cannot be removed, this map will be handy.
The RF power exposure decreases as the distance from the isocenter increases.
Radiofrequency definition: electromagnetic radiation with oscillating electric and
magnetic fields ranging from 3 kHz to 300 gHz.
, Clinically validated MRI systems imaging hydrogen use radio frequencies that
range from around - ANSWER 43 mHz at 1T to 298 mHz at 7T.
Radio frequency is used in brief bursts (pulses).
Only the rotating component of the magnetic (B) field is used to excite the protons.
- ANSWER: positive
When determining RF energy, the strength of the magnetic field is measured in mT.
The primary biological impact of exposing tissue to electromagnetic radiation in
that frequency range is tissue heating.
Causes of tissue heating - ANSWER Magnetic induction produces eddy currents in
conductive tissue.
Tissue heating is largely ______________ with very little ______________ -
ANSWER: peripheral, deep body heating
How does the patient disperse RF power? ANSWER cooling.
If the input exceeds the output, heating ensues.
SAR (specific absorption rate): RF power absorbed per unit mass of tissue.
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