MRI Equipment and Instrumentation Flashcards
Which magnetic susceptibility is slightly repels the main B0?
diamagnetic
Which magnetic susceptibility has a small positive magnetic susceptibility?
paramagnetic
Which magnetic susceptibility has a large positive magnetic susceptibility?
ferromagnetic
Which magnetic susceptibility has intermediate positive magnetic susceptibility?
superparamagnetic
What is another name for the main magnetic field?
primary magnetic field
What is the term for evenness or uniformity?
homogeneity
What is the homogeneity of B0 measured in?
parts per million (PPM)
Which type of shimming adds a secondary electromagnetic field over B0?
active shimming
Which type of shimming uses pieces of metal?
passive shimming
What is the main magnetic field extends beyond the imaging bore in all directions?
fringe field
Which type of shielding uses metal to contain and concentrate B0?
passive shielding
Which type of shielding is done with a secondary B0 created by an electromagnet?
active shielding
What type of current do primary magnet coils, active shim coils, and active shielding coils use?
direct current
Which electromagnet produces heat?
resistive magnets
Which electromagnet produces little to no resistance?
superconducting magnets
What is the operating temperature for MRI?
4 degree kelvin (-452F)
What does x represent in horizontal bore?
right to left
What does y represent in a horizontal bore?
anterior to posterior (top to bottom)
What does z represent in a horizontal bore?
superior to inferior (front to back)
What is the center of the gradient coil?
isocenter (always B0)
What happens when there’s more current?
it creates more gradient
What’s the term for the strength of gradient?
amplitude
What is the gradient amplitude measured in?
milliTesla/meter
What is the time it takes to get to a particular amplitude?
rise time (ms)
What is the rate that combines amplitude and rise time?
slew rate (mT/m/s)
What type of current is used for RF transmission?
alternating current
What is the orientation of RF coils?
always parallel to B0
What is the orientation of signal being transmitted and received?
perpendicular to B0
What is the RF shielding with copper in all walls, windows, and doorways?
Faraday cage
