Parameters Flashcards
The time limit between excitation pulses is known as the:
A) TI
B) TE
C) TR
D) PR
C) TR
In a spin echo pulse sequence the time between the 90 degree pulse and the 180 degree pulse is:
A) TE
B) TR
C) TI
D) 1/2 TE
D) 1/2 TE
Presaturation pulses are often used to:
A) improve spatial resolution
B) reduce flow artifacts
C) reduce scan time
D) turn flowing blood bright
B) reduce flow artifacts
Gradient echo sequences use flip angles:
A) less than 90 degrees
B) that vary between pulse repetitions
C) to control saturation effects
D) to reduce SAR for larger patients
C) to control saturation effects
“ with gradient echo pulse sequences, increasing the flip angle will increase the saturation effects seen in the image and thus increase T1 weighting”.
Complete saturation is a condition where:
A) not enough time is given to allow the T2 decay to complete
B) the image becomes brighter
C) longitudinal magnetization is not allowed to recover between excitations
D) proton density effects predominate
C) longitudinal magnetization is not allowed to recover between excitations
Increasing the TE:
A) increases the contrast based on T2- relaxation times of the tissues
B) reduces the contrast based on T2-relaxation times of tissues
C) reduces the contrast based on T1-relaxation times of tissues
D) a and c
A) increases the contrast based on T2- relaxation times of the tissues
Reducing the TR down to or below the T1-relaxation time of the tissue:
A) decreases the signal-to-noise ratio (SNR) of the image
B) reduces the contrast based on T2 relaxation times of the tissues
C) increases saturation effects
D) a and c
D) a and c
Reducing the TE:
A) increases the contrast based on T1 relaxation times
B) increases the spin density contrast weighting
C) reduces saturation effects
D) reduces contrast based on T2 relaxation times
D) reduces contrast based on T2 relaxation times
As the TR increases:
A) SNR increases up to a point
B) SNR decreases
C) SNR is not affected by TR
D) TE increases
A) SNR increases up to a point
As the TE increases:
A) SNR increases
B) SNR decreases
C) SNR is not affected by TE
D) TR increases
B) SNR decreases
In a gradient echo sequence, reducing the flip angle while holding the TR constant reduces:
A) T2* contrast weighting
B) Spin density contrast weighting
C) saturation
D) scan time
C) saturation
Another name for TI is:
a Alpha
b Theta
c Sigma
d Tau
d Tau
A short Tl inversion recovery (STIR) sequence can suppress the signal from:
a Fat
b Water
cA gadolinium-enhancing lesion
d a and c
d
A STIR sequence suppresses the signal from tissue, depending on that tissue’s TI
relaxation time and the TI selected. Gadolinium shortens the Tl time of water
molecules to close to the relaxation time of fat. With a short TI, the signal from
both fat and gadolinium “enhancing” tissues can be suppressed.
Decreasing the receiver bandwidth (narrow BW):
a Decreases the SNR
b Inverts the SNR
c Increases the SNR
d Has no effect on the SNR
c Increases the SNR
Decreasing the receiver bandwidth (narrow BW):
a Increases readout time
b Inverts the readout time
c Reduces readout time
d Has no effect on the readout time
a Increases readout time
Decreasing the receiver bandwidth (narrow BW):
a Increases chemical shift artifact
b Inverts chemical shift artifact
c Reduces chemical shift artifact
d Has no effect on chemical shift artifact
a Increases chemical shift artifact
Decreasing the receiver bandwidth (narrow BW):
a Increases readout time
b Inverts the readout time
c Reduces readout time
d Has no effect on the readout time
a Increases readout time
