MRI RF Safety and Electromagnetic Waves

This set of flashcards covers the mechanisms of RF heating, safety protocols, and the physical properties of electromagnetic waves within an MRI environment as described in the lecture notes.

Radiofrequency (RF) Waves Range

Electromagnetic waves typically in the range of $1-100\,MHz$ used in MRI to excite hydrogen nuclei.

Specific Absorption Rate (SAR)

A quantitative measure of the rate at which energy is absorbed per unit mass of the human body from the RF field.

SAR Proportionality

SAR is proportional to the square of the static magnetic field strength and typically increases with the size of the body part exposed.

Antenna Effect

A mechanism of RF burn injury where the length of a conductive wire functions as an antenna for induced RF electric fields, generating heat even without a closed loop.

Standing Waves

Waves formed when RF waves reflect within the body, creating constructive and destructive interference that can lead to hotspots.

Conductive Loop Formation

A primary cause of RF burns involving skin-to-skin contact or contact with conductive objects like cables or implants, allowing eddy currents to concentrate at contact points.

Contact Points Without Loop Formation

RF burns occurring due to strong electric fields near the capacitors of the RF transmit body coil, such as when the human body contacts the bore wall.

RF Heating

The process where electromagnetic energy is absorbed by tissues, leading to an increase in temperature.

Experimental and Numerical Assessments

Methods such as numerical simulations used to understand the distribution of induced RF eddy currents and local heating to develop countermeasures.

Preventive Measures

Strategies to mitigate RF risks including avoiding conductive loops, using proper padding to prevent bore contact, and regular monitoring of SAR levels.