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Flashcards in Data Acquisition and Processing Deck (77)
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1

What are the 5 basic steps to a pulse sequence

alignment
excitation slice selection
phase encoding
rephasing slice selection
frequency encoding

2

What hardware performs alignment in a pulse sequence

main magnet

3

What hardware performs excitation slice selection in a pulse sequence

RF coil and gradients

4

What hardware performs phase encoding in a pulse sequence

phase encoding gradient

5

What hardware performs rephasing slice selection in a pulse sequence

RF coil (for SE)
gradients (for GE)

6

What hardware performs frequency encoding in a pulse sequence

frequency encoding gradient

7

What are the 2 types of pulse sequences

spin echo and gradient echo

8

Which pulse sequence uses a 90° excitation pulse followed by one or more 180° rephasing pulses in order to generate one or more spin echos

spin echo

9

What are the 3 types of spin echos

conventional spin echo (CSE)
fast spin echo (FSE)
inversion recovery (IR)

10

This type of spin echo uses a 90 alpha pulse and a singe 180 rephasing pulse per TR

conventional spin echo

11

How many lines of K space are filled per TR during a conventional spin echo

one (resulting in longer scan times, so CSEs are usually only T1 weighted)

12

What are the advantages of a conventional spin echo

excellent image quality
"true" image weighting (since there is no signal averageing of multiple echos)

13

What are the disadvantages of a conventional spin echo

long scan times (only 1 line of K space is filled per TR)

14

What are the TR and TE parameters for a T1 weighted CSE

TR = 300-700 ms
TE = 10-30ms

15

What are the TR and TE parameters for a T2 weighted CSE

TR = 2000ms+
TE = 80ms+

16

What are the TR and TE parameters for a PD weighted CSE

TR = 2000ms+
TE = 20ms

17

Fast spin echoes (FSE) are also referred to as what

Turbo spin echoes (TSE)

18

Which pulse sequences use a 90゚ alpha pulse and multiple 180゚ rephrasing pulses per TR

Fast spin echoes (FSE) aka Turbo spin echoes (TSE)

19

What parameter is averaged during a fast spin echo

TE is averaged and creates an "effective TE"

20

Is it possible to acquire true image weighting during FSE sequences

no because the TEs for each echo are averaged

21

What are the advantages of an FSE sequence

Shorter scan times (multiple lines of K space are filled per TR)

decreased magnetic susceptibility artifacts

22

What are the 4 disadvantages of an FSE sequence

Increased motion artifact (sinse signal during motion is acquired multiple times)

increased image blurring (from signal averaging of long echo trains)

decreased SNR

decrease of ability to detect small hemorrhages (because of the reduction in magnetic susceptibility artifacts)

23

Which spin echo sequence combines FSE with a Partial Fourier technique in order to fill all lines of K space during a single TR period

Single shot fast spin echo (SS-FSE)

24

What are the advantages of a single shot fast spin echo (SS-FSE) sequence

Dramatic reduction in scan time

25

What are the disadvantages of single shot fast spin echo (SS-FSE) techniques

Increased tissue heating

increased SAR (due to the extra RF rephasing pulses)

26

What does the acronym DRIVE stand for

Driven Equilibrium Fourier Transform

27

Which pulse sequence uses a reverse flip angle excitation pulse after the echo train (90-180-180-90), thus driving any residual transverse magnetization into the longitude plane so that it cannot be further excited at the beginning of the next TR cycle

Driven Equilibrium Fourier Transform (DRIVE)

28

Which pulse sequence yields a hyper intense fluid signal when compared to standard FSE pulse sequences

Driven Equilibrium Fourier Transform (DRIVE)

29

What are the TR and TE parameters for a T1 weighted FSE

TR = 300-700 ms
effective TE = minimum

30

What are the TR and TE parameters for a T2 weighted FSE

TR = 3000-10000 ms
effective TE = 80-140ms