Pulse sequences-L's Flashcards
In an SE, What is the term for the time between the 90 degree RF pulse and the 180 degree RF pulse?
- Tau
- TE/2
Which of the following pulse sequences is the most “flow sensitive” ?
- SE
- IR
- GRE
- STIR
GRE
In a GRE sequence, if the FA is lowered while holding the TR constant, which of the following would be reduced?
- chemical shift artifact
- saturation
- magnetic susceptibility
- scan time
saturation
which of these statements is true regarding spoiled GRE sequences?
- spoils the transverse signal
- only longitudinal signals contribute to next RF pulse
- increases T2* dependence
a
b
what type of pulse sequence begins with a 90 degree RF pulse and is immediately followed by the collection of the echo?
partial saturation
the peak signal strength of a spin echo is less than the initial strength of the FID because of___
T2 relaxation
what is the term for an echo formed by the application of two successive 90 degree RF pulses?
Hahn echo
Which of the following statements are true regarding GRE pulse sequences?
- rephased GRE sequences preserve transverse signal
- both longitudinal and transverse signals contribute to the next RF pulse
- rephased GRE sequences increase T1 dependence
A and B
Which of these statements is not true regarding steady state?
- The TR must be shorter than the T1 and T2 of the tissues.
- the TR must equal the tau of the spin echo
- during the acquisition, the FA and the TR maintain the steady state.
- All of the above are true
D
What is the term for the distance traveled between the positive and negative lobe of the velocity encoding gradient?
velocity
Using Flip angles of 10 degrees or less in a GRE pulse sequence will result in what effect on the image?
less SNR
coherent, incoherent, and steady state free precession (SSFP) pulse sequences can be differentiated according to whether or not they use the FID or spin echo signals. Which statement is correct?
- coherent pulse sequences use a gradient reversal to rephase both the FID and the dephasing portion of the spin echo
- incoherent pulse sequences use a gradient reversal to rephase both the FID and rephasing portion of the spin echo
- SSFP uses an RF pulse to initiate the rephasing process and a rewinder to move the spin echo to occur before the RF pulse.
A and C
which of the following pulse sequences allow tissues to relax over twice the dynamic range possible with SE pulse sequence?
- 45 degree GRE
- 3DFT
- EPI
- IR
IR
In a CSE pulse sequence, a 90 degree RF pulse is followed by a 180 degree RF pulse. How much more power does it take to deliver a 180 degree RF pulse compared with the 90 degree RF pulse?
- twice
- half
- quadruple
- eight times
quadruple
