Unit 2 Flashcards
Static Magnetic Field
magnetic field from that is always present (strength of the machine)
Fringe Magnetic field
edge of the static magnetic field
Gradient magnetic field
adjustable magnetic field for imaging
Magnetic field homogeneity
uniformity of the magnetic field
Active magnetic shielding
coils w/ reverse current to minimize fringe field
Passive magnet shielding
metal shielding to minimize fringe field
Active magnet shimming
coils within the machine to increase the homogeneity
Passive Magnet Shimming
metal platting in the machine to increase the homogeneity
Body coil
RF coil in the machine
RF coil
transmit and/or receive signal for imaging
Tranceiver
RF coil that transmits and receives
Cryogen
coolant used to maintain superconductivity
Array Processor
computer program used to reconstruct the image
Slew Rate
ramping up rate of gradient coils
Faraday Cage
copper cage to block out stray RF signal
Eddy Currents
induced currents in non-magnetic metals
Gradient speed
time in which the gradient ramps up
Maximum magnetic field allowed by FDA for patients >1mo
8T
What metal is used for superconducting coil
nobium titanium
What unit of measure is used for magnetic field homogeneity
ppm
Name the conductive bands that create a gradient magnetic field
physical gradient
Which direction do each of the gradients go?
z - w/ B0
x - left/right
y - up/down
Name the properties used to compare gradient coil
gradient strength
gradient speed
Slew rate
What is the unit of measure of the slope/peak amp?
G/cm
mT/m
Types of RF coils
Volume - typically tranceivers
surface - typically receivers
Phased array - multiple coils used to combine the image
Pros and cons of small RF coils
better SNR and penetration
small area of view
What is the only part of the MR machine that uses AC?
RF transmitter coils
