chap 5 & 6

Question 1

used when a patient can’t hold still, filled as a block & rotated about the central axis of k space, decreasing scan time, increasing the SNR & decreasing motion

Answer 1

propeller

Question 2

sensitivity encoding, fills multiple lines of k-space per TR by assigning to coils. reduction or acceleration factor

Answer 2

parallel

Question 3

T/F: data in K space is/are symmetrical

Answer 3

true

Question 4

T/F: phase encoding gradient positive fills the bottom half of K space

Answer 4

false

Question 5

scan time in 2D imaging =

Answer 5

Tr x M(p) x NSA

Question 6

scan time in FSE =

Answer 6

TR x M(p) x NSA / ETL

Question 7

scan time in 3D imaging =

Answer 7

TR x M(p) x NSA x Ns

Question 8

scan time in EPI =

Answer 8

TR x #shots x NSA

Question 9

positive frequency encoding gradient

Answer 9

left to right

Question 10

negative frequency encoding gradient

Answer 10

right to left

Question 11

positive phase encoding gradient

Answer 11

top half

Question 12

negative phase encoding gradient

Answer 12

bottom half

Question 13

how fast do we sample frequencies according to the Nyquist theorem

Answer 13

2x/cycle

Question 14

T/F: K space is not the image

Answer 14

true

Question 15

data acquisition; all data from 1 slice then all data from 2nd slice etc

Answer 15

sequential

Question 16

data acquisition; 1 line of k-space for slice 1 then the same for slice 2 etc

Answer 16

2D

Question 17

data acquisition; no slices, aquires and entire volume

Answer 17

3D

Question 18

partial fourier + FSE, half the lines are acquired and half are transposed. reduces SAR but has SNR penalty

Answer 18

single shot fast spin echo

Question 19

k space filling where we fill high signal amplitudes starting in the center of our K space and filling outward to the periphery

Answer 19

Centric filling

Question 20

simplest form, k space filled in a linear manner from top to bottom or bottom to top

Answer 20

Cartesian

Question 21

T/F: the scan time is the time to fill k space

Answer 21

true

Question 22

encodes along the short axis of anatomy

Answer 22

phase

Question 23

encodes along the long axis of anatomy, FOV

Answer 23

frequency

Question 24

T/F: the top half of data in k space is identical to the bottom half

Answer 24

true

Question 25

concerning k space, data in the central lines contribute

Answer 25

to signal & contrast

Question 26

concerning k space, data in the outer line contribute to

Answer 26

resolution

Question 27

locates a slice in the scan plane selected

Answer 27

slice select

Question 28

locate a signal along the long axis of the image

Answer 28

frequency encoding

Question 29

locate a signal along the short axis of the image

Answer 29

phase encoding

Question 30

when is the slice select gradient switched on during a spin echo pulse sequence

Answer 30

during the 90 & 180 degree pulses

Question 31

what does the slope of the frequency encoding gradient determine?

Answer 31

- the size of the anatomy covered along the frequency encoding axis - the FOV

Question 32

a shallow or weaker gradient selects a ________ bandwidth

Answer 32

broader

Question 33

a steeper or stronger gradient will select a __________ bandwidth

Answer 33

narrow

Question 34

which gradient performs phase encoding for coronal slices

Answer 34

X gradient

Question 35

which gradient locates signal along the long axis of the anatomy

Answer 35

frequency encoding gradient

Question 36

amplitude of the frequency encoding gradient

Answer 36

frequency FOV

Question 37

number of different phase encoding steps

Answer 37

phase matrix

Question 38

amplitude of the steepest phase encoding gradient positively & negatively

Answer 38

phase resolution (pixel size)

Question 39

amplitude of the slice select gradient & transmit BW

Answer 39

slice thickness & slice gap

Question 40

steep sloping TBW

Answer 40

thin slices

Question 41

gradual sloping TBW

Answer 41

thick slices

Question 42

when does the slice select gradient turn on

Answer 42

at the same time as the RF excitation pulse (and the rephasing pulse in SE)

Question 43

when does the frequency encoding gradient turn on

Answer 43

switched on during the echo

Question 44

when does the phase encoding gradient turn on

Answer 44

switched on any time, usually after the RF

Question 45

slice selection for sagittal image

Answer 45

X

Question 46

phase axis on sagittal image

Answer 46

Y

Question 47

frequency axis on sagittal image

Answer 47

Z

Question 48

which gradient is the readout gradient

Answer 48

frequency

Question 49

the slice select for a coronal image

Answer 49

Y

Question 50

phase encoding for coronal image

Answer 50

X

Question 51

frequency encoding on coronal image

Answer 51

Z

Question 52

slice select for an axial brain image

Answer 52

Z

Question 53

phase encoding gradient on axial brain

Answer 53

X

Question 54

frequency encoding gradient for axial brain

Answer 54

Y

Question 55

steepness of the slope of the frequency encoding gradient determines the size of the anatomy

Answer 55

FOV

Question 56

duration of the readout gradient (acquisition window)

Answer 56

sampling time

Question 57

mathematical process that converts time into a frequency domain

Answer 57

FFT

Question 58

artifact caused by sampling too infrequently (less than 2)

Answer 58

aliasing

Question 59

the mathematical process that converts time into a frequency domain

Answer 59

Fast Fourier Transform