DI QUIZ 2 LECTURE 11

Question 1

Indirect Acquisition

Answer 1

Converts x-ray photons to light

Question 2

Direct Acquisition

Answer 2

converts x-ray photons to an electronic signal

Question 3

What does post processing mean?

Answer 3

Anything added or changed after exposure taken

Question 4

What does windowing mean?

Answer 4

changing/reassigning the values of the pixels

Question 5

Explain window level

Answer 5

Brightness (higher the window level = brighter the image)

Question 6

Explain window width

Answer 6

Contrast (higher window width = lower contrast and lower window width = higher contrast)

Question 7

What is more dense: fat, water, or muscle?

Answer 7

Muscle

Question 8

Examples of post processing

Answer 8

windowing (contrast, brightness), adding markers/text, flipping/rotating image, magnification (enlarging photo), image inversion (dark areas to white)

Question 9

Advantages of digital radiography

Answer 9

lowers patient dose, fewer repeats, higher contrast resolution, no darkroom/film cost, able to post process, electronic image storage, can be electronically sent

Question 10

Why are fewer repeats a thing in digital radiography?

Answer 10

Due to automatic rescaling

Question 11

Disadvantages of digital radiography

Answer 11

DDR machines are expensive, lower spatial resolution than film, collimation / centring, dose creep (using higher mAs than actually needed)

Question 12

What is dose creep

Answer 12

System is good at fixing over exposures - so we tend to use higher mAs than needed

Question 13

What is needed for image contrast to occur?

Answer 13

Subject contrast

Question 14

Subject contrast determined by

Answer 14

differential absorption, kvp, thickness, atomic number, physical / mass density

Question 15

Image contrast depends on

Answer 15

algorithm (set values), post processing

Question 16

Can image contrast be altered?

Answer 16

yes

Question 17

Subject contrast is affected by

Answer 17

scatter radiation

Question 18

Acquisitions of direct digital radiography

Answer 18

indirect acquisition and direct acquisition

Question 19

In reality, detector DQE values are

Answer 19

less than 100%

Question 20

ideal detector would have a DQE

Answer 20

1 (100%)

Question 21

Why does DR have lower patient dose?

Answer 21

Due to higher DQE

Question 22

What determines quantum mottle

Answer 22

number of photons hitting IR to create signal (image)

Question 23

Define quantum mottle

Answer 23

number of photons hitting IR to create a signal - every image has this

Question 24

What is it called when an image has a lot of QM? meaning?

Answer 24

pronounced QM - meaning you can see that it’s grainy

Question 25

regarding QM, increasing mAs/kVp =

Answer 25

increasing signal, increasing photons to IR, decreasing noise

Question 26

regarding QM, decreasing mAs/kVp =

Answer 26

decreasing signal, decreasing photons to IR, increasing noise

Question 27

What is the ADC

Answer 27

raw data