Week 6 - Window Settings

Question 1

What is displayed on the monitor?

Answer 1

-cross sectional images (grayscale)
-patient info, scan parameters can be displayed in colour

Question 2

What factors contribute to the image being viewed differently?

Answer 2

WW and WL
(Bone, soft tissue, lung)

Question 3

T/F
Window sheeting’s are subjective, and have a personal preference component

Answer 3

True

Question 4

T/F
Each hounsfield unit can have many shades of gray

Answer 4

True

Question 5

How many HUs exist?

Answer 5

> 2000 HU values exist (more than)

Question 6

How many different shades of gray can the monitor display?

Answer 6

256

Question 7

How many shade of gray can the human eye differentiate?

Answer 7

40

Question 8

T/F
The human eye cannot appreciate contrast differences of <10% (less than)

Answer 8

True

Question 9

T/F
CT can show differences in contrast <1% (less than)

Answer 9

True

Question 10

Assigns a certain number of housfield unit to each level of grey to overcome the limitation of the human eye not being able to differentiate contrast as much as what can be displayed

Answer 10

Display processor
Determined by window width ( grayscale)

Question 11

What shade of gray is assigned to a higher HU?

Answer 11

Lighter shade of gray (bone)

Question 12

What shade of gray is assigned to a lower HU?

Answer 12

Assigned a darker shade of gray (lungs)

Question 13

What is the most common image processing technique used in CT?

Answer 13

Windowing

Question 14

Refers to a method by which the CT image grayscale can be manipulated with the CT numbers of the image

Answer 14

Windowing

Question 15

T/F
When manipulating CT numbers of various tissues using windowing, the data is not changing but the view of it is changing

Answer 15

True

Question 16

-range of CT numbers in the image
-determines the maximum number of shades of gray that can be displayed on the CT monitor

Answer 16

Window width

Question 17

The Center or midpoint of the range of CT numbers

Answer 17

Window level

Question 18

What determines how many HUs will be displayed?

Answer 18

Window width
*software assigns the shades of gray
-values higher than the range will appear WHITE
-values lower than the range will appear BLACK

Question 19

-indicates that there is a relatively long grayscale or a large block of CT numbers that will be assigned some value of gray
-the transition between black (low CT number) and white (high CT number) will be large

Answer 19

Wide window width

Question 20

The transition between black and white will take place over a relatively few CT numbers

Answer 20

Narrow window width

Question 21

What are some examples of anatomy that a wide window width is used for?

Answer 21

*greatly differing attenuations
-350-600HU body scan
-1000-2000HU lung and bone

Question 22

What are some examples of anatomy that a narrow window width would be used for?

Answer 22

*similar densities
-50-250HU
-80-150HU brain
-100-250HU liver

Question 23

Determines the HU values to be displayed on the screen - not the quantity

Answer 23

Window level

Question 24

Brightens darker tones

Answer 24

Low window level

Question 25

Darkens lighter tones

Answer 25

High window level

Question 26

Brain window setting

Answer 26

WW 100 WL 30

Question 27

Temporal bone window setting

Answer 27

WW 2800 WL 600

Question 28

Neck window setting

Answer 28

WW 250 WL 30

Question 29

Mediastinum window setting

Answer 29

WW 350 WL 50

Question 30

Lung window setting

Answer 30

WW 1500 WL -600

Question 31

Soft tissue abdomen window setting

Answer 31

WW 350 WL 50

Question 32

Liver window setting

Answer 32

WW 150 WL 30 *high contrast

Question 33

Pelvis soft tissue window setting

Answer 33

WW 400 WL 50

Question 34

Pelvis bone window setting

Answer 34

WW 1800 WL 400

Question 35

Spine soft tissue window setting

Answer 35

WW 250 WL 50

Question 36

Spine bone window setting

Answer 36

WW 1800 WL 400

Question 37

T/F Increased WW allows for more HUs to be included in the grayscale

Answer 37

True Ex. More HUs will be included in each shade of gray

Question 38

T/F WL selection should be similar to the HU of the tissue of interest

Answer 38

True

Question 39

WW varies, but is usually:

Answer 39

500-2000

Question 40

T/F Increased WW shows more anatomy but decreased image contrast

Answer 40

True

Question 41

Increased WW can suppress noise; what is this good for?

Answer 41

Good for metal artifacts and obese patients

Question 42

T/F Tissues with a similar density should have a narrow WW

Answer 42

True WW 50-500 Ex. Brain is composed of gray (HU 25) and white matter (HU 40) *not much difference in tissue density

Question 43

T/F As window width decreases, contrast increases

Answer 43

True

Question 44

What windowing algorithms are available to suppress noise and improve detail?

Answer 44

-standard algorithm -smoothing algorithm -edge enhancement algorithm

Question 45

Usually used before previous algorithms, especially when a balance is needed between image noise and image detail

Answer 45

Standard window algorithm

Question 46

-reduces image noise -shows good soft tissue anatomy -used where soft tissue discrimination is important to visualize very low contrast resolution

Answer 46

Smooth window algorithm

Question 47

-emphasizes edges of structures and improves detail -creates image noise

Answer 47

Edge enhancement window algorithm

Question 48

Edge enhancement is used in exams where fine detail is needed. What are some examples of these exams?

Answer 48

-inner ear bones -bone structures -thin slices -fine pulmonary structures

Question 49

Differing WW settings Fixed WL setting

Answer 49

As WW decreases, contrast increases

Question 50

Differing WL settings Fixed WW setting

Answer 50

As WL decreases, the picture changes from black to white (Higher CT numbers are displayed) Opposite is true also