MRSO - RADIO FREQUENCY - MODULE 4 Test Review |Question and Answers| 100% Correct

MRSO - RADIO FREQUENCY - MODULE 4 Test Review |Question and Answers| 100% Correct Purpose of RF (B1) field *Ans* excite hydrogen protons RF energy is absorbed by tissues *Ans* within the volume of the RF transmit coil. This is a thermogenic process. Thermogenic process *Ans* Results in production of heat. Ex: RF energy absorption MRI local and whole-body tissue heating is due to *Ans* magnetic 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 *Ans* receive 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 *Ans* the integrated body coil Modern integrated body coils are *Ans* circularly 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 *Ans* determine 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 *Ans* less Radiofrequency definition *Ans* electromagnetic 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 *Ans* 43 mHz at 1T to 298 mHz at 7T Radio frequency is applied in *Ans* short bursts (pulses) Only the _________ rotating component of the magnetic (B) field is used to excite the protons *Ans* positive When determining RF energy, strength of magnetic field is measured in *Ans* mT Main biological effect of exposing tissue to electromagnetic radiation in that frequency range *Ans* tissue heating Cause of tissue heating *Ans* Magnetic induction results in eddy currents of conductive tissu