FINAL STUDYGUIDES Flashcards
Which pulse sequence timing parameter combination will result in T1 weighted images when performing a spin echo pulse sequence?
short TR/short TE
Which pulse sequence timing parameter combination will result in Spin Density weighted images when performing a spin echo pulse sequence?
long TR/short TE
Which pulse sequence timing parameter combination will result in T2 weighted images when performing a spin echo pulse sequence?
long TR/long TE
When is a tissue vector considered to be partially saturated?
when it flips >90 degrees but <180
When is a tissue vector considered to be fully saturated?
when it reaches 180 degrees from equilibrium, it is positioned along the –z axis
A technologist sets up a pulse sequence as follows: type of pulse sequence: fast spin echo, TR = 3500 ms, TE = 20ms, matrix 256x192, NSA 3. What is the resulting image weighting?
Proton density
Explain the term homogeneity, as it applies to MRI.
Homogeneity is the even-ness or uniformity of the static field
State the source of T2’ decay.
T2’ decay is caused by inhomogeneities (uneven-ness) of the static field
Which imaging parameter(s) control(s) the amount of T1 weighting present in images obtained by performing a gradient echo pulse sequence?
Flip angle and TR
Which imaging parameter(s) control(s) the amount of T2 weighting present in images obtained by performing a gradient echo pulse sequence?
TE
Name the component of the MR system that induces parallel or anti-parallel alignment of the magnetic moments in a sample of tissue
the static magnetic field
Which gradient is simultaneously activated each time that RF is transmitted?
slice select
Which gradient is applied, as the slice select gradient, when obtaining coronal images of the brain?
the Y gradient
When the MR system applies a greater current amplitude to the activated gradient coils, what is the impact on the slope of the gradient?
the slope becomes steeper
What is the impact on the speed of precession along a gradient?
spins in the area where the magnetic field becomes stronger precess faster, spins in the area where the magnetic field becomes weaker precess slower
What is the impact on the phase position of the spins along the gradient?
The slope of the PE gradient determines the amount of phase shift present in the image; steep gradient has large phase shift and shallow gradient has small phase shift
What is the impact on the direction of the gradient when the polarity of the current in the gradient coils is changed by the MR system?
when the polarity of the current applied to the gradient coil switches, the direction of the magnetic field gradient also switches
Name the 3 processes that make up spatial encoding.
Slice selection, phase encoding, frequency encoding
What two things does the MR system adjust when the technologist selects a slice thickness value?
the transmitted bandwidth and the slope of the slice select gradient
If a technologist makes an adjustment to the bandwidth parameter, which is being adjusted:
receive bandwidth
What is another name for the frequency encoding gradient?
the readout gradient
Along which axis is the phase encoding gradient typically applied?
the short axis of the patient’s anatomy
In what area of k-space is contrast data stored?
the center
In what area of k-space is spatial resolution data stored?
the periphery or the edges
