week 2 review Flashcards
the ______ controls the amount of saturation
flip angle
T1 weighting requires
short TR
T2 weighting requires
long TE
T2 decay graph
starts high, ends low
T1 recovery graph
starts low, ends high
to achieve T1 weighting in gradient echo sequences, the flip angle should be
large
which allows for PD to dominate
long TR & short TE
the 2 results of resonance
- the NMV moves out of alignment and away from B0
- the magnetic moments of hydrogen nuclei move into phase with each other
percent of the transverse magnetization remains in phase after one T2 decay time
37
the decay of the FID following the excitation pulse
T2*
the difference in the SNR between two adjacent areas
contrast to noise ratio
what is the extrinsic parameter that controls the amount of diffusion seen in an image
b-factor
on T1 weighted images of the spine, the CSF appears
hypointense to the spinal cord
PD image has a ____ flip angle
small
T/F: even echo rephasing reduces intra-voxel dephasing
true
what material is used to make superconducting wires
niobium-titanium alloy
RF shielding material
copper
material to make permanent magnets
alnico
passive shielding material
steel
maintains low temperatures
cryostat
the precessional frequency of hydrogen at 3T
127.71 MHz
the precessional frequency of hydrogen at 1.5T
63.86
chemical shift of fat & water at 1.5T
220 Hz
chemical shift of fat water at 3T
440 Hz
fine matrix =
smaller boxes
ferromagnetic plates around the circumference of the bore
passive shielding
additional solenoid magnets, used to optimize each pt exam
active shielding
which spatially encode
gradients
RF coils
to maintain the magnetic field of a resistive magnet, ________ should be applied to the magnet coils
current
