MRI Flashcards
What is the Larmor Equation
precession frequency = gyromagnetic ratio x field strength
precession frequency is directly proportional to:
magnetic field strength
What two things does the RF pulse do?
- decreases the longitudinal magnetization and 2. it causes the protons to sync up and precess in-phase (which establishes a transverse magnetization)
Who is allowed entry into level III space
level 1 and level 2 personnel (level 2 are people in the radiology department)
what is the most commonly reported adverse event associated with MRI?
thermal injuries
long TR, long TE
T1
short TR, short TE
T2
long TR, short TE
PD
what type of image when combined with DWI, would generate contrast in a diffusion weighted image?
T2
type of curve for recovery of longitudinal magnetization
exponential curve approaching 100% over time
T1 definition
time at which the longitudinal magnetization is 63% of its final value
time at which the longitudinal magnetization is 63% of its final value
T1
Duration of an MRI scan
Tr x Npy x Nex
MRI slice thickness equation
thickness = transmit RF/ (SS gradient x k)
less gradient does what to slice thickness?
thicker slice
More gradient does what to slice gradient?
thinner slice
parameters that improve MRI spatial resolution
big matrix, small FOV, thinner slices
parameters that improve MRI SNR
small matrix, large FOV, thicker slicer, stronger field strength, smaller surface coils, more excitations (longer TR, shorter TE), narrow receiver bandwidth
What is special about HASTE?
a turbo spin echo techinique that is used for sequential acquisition of high resolution T2 weighted images.
HASTE uses a shingle-shot technique to acquire sufficient data for an entire image from a single TR.
It collects fewer data points per repetition time (TR) interval. Only about half of k-space is acquired per TR and symmetry is used to fill the remaining half.
