Week 2 Lecture 2

Question 1

+ numbers on the Hounsfield scale

Answer 1

tissues MORE dense than water

Question 2

• numbers on the Hounsfield scale

Answer 2

tissues LESS dense than water

Question 3

naturally occurring anatomic structures have HU values ranging from?

Answer 3

-1000 to +1000

Question 4

what does windowing control?

Answer 4

brightness and contrast of a displayed image by manipulating gray scale

Question 5

windowing is a (pre/post)-processing technique.

Answer 5

post-processing

Question 6

what are the two parameters of windowing?

Answer 6

1. window level
2. window width

Question 7

window level affects?

Answer 7

affects image brightness

Question 8

window level

Answer 8

acts as a reference point that should be the average of the tissue of interest’s attenuation value

Question 9

↑ WL = (↑/↓) image brightness, why?

Answer 9

↑ WL = ↓ image brightness
more HUs will display as black (WL moving towards positive side of the scale)

Question 10

↓ WL = (↑/↓) image brightness, why?

Answer 10

↓ WL = ↑ image brightness
more HUs will display as white (WL moving towards the negative side of the scale)

Question 11

window width affects?

Answer 11

affects image contrast

Question 12

window level vs. window width in terms of CT numbers

Answer 12

window level selects which ct numbers will be displayed as shades of grey

window width controls how many ct numbers are included as shades of gray; max. number of gray shades to be displayed)

Question 13

any HU value that falls outside the specified window width will appear?

Answer 13

black or white

Question 14

why would we need to play with the window width?

Answer 14

it can improve assessment of anatomy

Question 15

↓ WW = (↑/↓) image contrast = (more/less) shades of gray

Answer 15

↓ WW = ↑ image contrast = less shades of gray

Question 16

↓ WW = (↑/↓) image contrast = (more/less) shades of gray

Answer 16

↑ WW = ↓ image contrast = more shades of gray

Question 17

more shades of gray helps with reducing the appearance of artifacts and image noise. t/f

Answer 17

true

Question 18

tissues with similar densities should be displayed on what size ww?

Answer 18

smaller ww

Question 19

smaller ww = fewer shades of grey = ?

Answer 19

easier to visualize “colour” differences in soft-tissue structures

Question 20

scan field of view (SFOV) aka?

Answer 20

calibration field of view
scan diameter

Question 21

SFOV

Answer 21

determines the size of the area within the gantry where raw data will be collected

Question 22

SFOV and the relationship to detectors

Answer 22

SFOV identifies the number of detector cells used during data acquisition

Question 23

out-of-field artifact

Answer 23

when any anatomy falls outside the SFOV

Question 24

display field of view aka?

Answer 24

display field of zoom, display field of target

Question 25

DFOV

Answer 25

selects how much and which section of raw data is used in image display

Question 26

smaller DFOV = ?

Answer 26

zoomed image

Question 27

DFOV improves:

Answer 27

visualization of ROI and pixel size

Question 28

↑ DFOV = (↑/↓) pixel size = (↑/↓) spatial resolution

Answer 28

↑ DFOV = ↑ pixel size = ↓ spatial resolution

Question 29

↑ DFOV = (↑/↓) spatial resolution

Answer 29

↑ DFOV = ↓ spatial resolution

Question 30

↓ DFOV = (↑/↓) spatial resolution

Answer 30

↓ DFOV = ↑ spatial resolution

Question 31

DFOV can only be (≥/≤) the SFOV.

Answer 31

DFOV can only be ≤ the SFOV

Question 32

DFOV changes are applied to (raw/image) data

Answer 32

DFOV changes done to RAW data

Question 33

*raw data = ? image data = ?

Answer 33

raw data = reconstruction image data = reformatting/post-processing

Question 34

single detector ct = slice thickness is controlled by?

Answer 34

collimation