MRSO - RADIO FREQUENCY - MODULE 4 Exam Questions With Complete Solutions.

Purpose of RF (B1) field - excite hydrogen protons RF energy is absorbed by tissues - within the volume of the RF transmit coil. This is a thermogenic process. Thermogenic process - Results in production of heat. Ex: RF energy absorption MRI local and whole-body tissue heating is due to - magnetic induction Types of RF coil designs --linearly polarized -circularly polarized (quadrature) Function of coils - -transmit only -receive only -transmit/receive Most common type of coil used - receive only Integrated body coils are capable of functioning - -as transmit/receive coil -as transmit only coil When receive only coil is used, RF energy is transmitted by - the integrated body coil Modern integrated body coils are - circularly polarizedQuadrature mode - -some 3T systems have option -Advantage: dielectric shading reduction -safety considerations with implants/devices RF Power Distribution Maps - -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 - 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.