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MRSO - RADIO FREQUENCY - MODULE 4 questions and answers rated A+ 2024/2025 $10.49   Add to cart

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MRSO - RADIO FREQUENCY - MODULE 4 questions and answers rated A+ 2024/2025

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MRSO - RADIO FREQUENCY - MODULE 4 questions and answers rated A+ 2024/2025

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  • August 21, 2024
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MRSO - RADIO FREQUENCY - MODULE
4

Purpose of RF (B1) field - ANSexcite hydrogen protons

RF energy is absorbed by tissues - ANSwithin the volume of the RF transmit coil. This is a
thermogenic process.

Thermogenic process - ANSResults in production of heat. Ex: RF energy absorption

MRI local and whole-body tissue heating is due to - ANSmagnetic induction

Types of RF coil designs - ANS-linearly polarized
-circularly polarized (quadrature)

Function of coils - ANS-transmit only
-receive only
-transmit/receive

Most common type of coil used - ANSreceive only

Integrated body coils are capable of functioning - ANS-as transmit/receive coil
-as transmit only coil

When receive only coil is used, RF energy is transmitted by - ANSthe integrated body coil

Modern integrated body coils are - ANScircularly polarized

Quadrature mode - ANS-some 3T systems have option
-Advantage: dielectric shading reduction
-safety considerations with implants/devices

RF Power Distribution Maps - ANS-specific to vendor and transmit coil
-graph: horizontal axis represents z
-100% power is at isocenter (distance from isocenter should be identical on each side)
-measured in cm
-used for vendor integrated transmit coil only, not transmit/receive head or knee coil

Purpose of RF Power Distribution Map - ANSdetermine percentage of RF frequency power at a
given location within the volume of the radiofrequency transmit coil

, -if metal item can not be removed, this map would be useful.

The further from isocenter, the _______ the RF power exposure - ANSless

Radiofrequency definition - ANSelectromagnetic radiation with oscillating electric and magnetic
fields that range from 3 kHz to 300 gHz

Clinically approved MRI systems imaging hydrogen utilize radio frequencies ranging from
approximately - ANS43 mHz at 1T to 298 mHz at 7T

Radio frequency is applied in - ANSshort bursts (pulses)

Only the _________ rotating component of the magnetic (B) field is used to excite the protons -
ANSpositive

When determining RF energy, strength of magnetic field is measured in - ANSmT

Main biological effect of exposing tissue to electromagnetic radiation in that frequency range -
ANStissue heating

Cause of tissue heating - ANSMagnetic induction results in eddy currents of conductive tissue

Tissue heating is mostly ______________ with very little _______________ - ANSperipheral ,
deep body heating

How patient dissipates RF power - ANScooling.

If the input is greater than the output, heating occurs.

SAR (specific absorption rate) - ANSRF power absorbed per unit mass of tissue

SAR is SPECIFIC to: - ANSbody part and tissue

SAR represents - ANSABSORPTION of RF into the body/tissues

SAR is the - ANSRATE of RF exposure and absorption

SAR is measured in - ANSwatts/kg

SAR is proportional to: - ANS-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

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