Ch 9: Digital Imaging Characteristic

Question 1

CR

Answer 1

Film
cassette
computed radiography
“old school”

Question 2

DR

Answer 2

direct digital radiography

Question 3

dynamic range

Answer 3

range of intensities the IR can detect

Question 4

Why is dynamic range good?

Answer 4

can adapt the image and change brightness and window level to make the image quality better

Question 5

Why is dynamic range bad?

Answer 5

can easily overexpose your patient if you aren’t watching your technique or EI

Question 6

matrix

Answer 6

size is how many pixels are in your image/field

Question 7

define matrix

Answer 7

how digital image is recorded

Question 8

pixel density

Answer 8

number of pixels per unit area

Question 9

pixel pitch

Answer 9

distance between pixels (center to center)

Question 10

Can you change your bit depth?

Answer 10

No - specific to each xray unit/system

Question 11

bit depth

Answer 11

determines how many shades of gray the system can create
affects contrast
won’t use every shade of gray for each image
higher bit system allows for longer contrast scale (more shades of gray available)

Question 12

quantum mottle

Answer 12

“dotty” static-y appearance on computer
too low of EI/technique

Question 13

saturation

Answer 13

dark portion of image
too high of EI/technique
too much info that computer cannot fix

Question 14

Why might the window level be adjusted during postprocessing of an image?

Answer 14

to manipulate brightness levels

Question 15

What determines the contrast resolution (shades of gray) of a digital imaging system?

Answer 15

bit depth

Question 16

The sensor chamber for the AEC are located:

Answer 16

between the grid and image receptor

Question 17

In the image intensifier the function of the input phosphor is to:

Answer 17

absorbs the remnant photons exiting the patient to visible light

Question 18

The range of exposures a digital system can retain and use to create the image is:

Answer 18

dynamic range

Question 19

The electric timer must be set to what back-up time in case the automatic exposure control (AEC) fails to terminate?

Answer 19

1.5 times the exposure time

Question 20

What term is defined as the distance from the center of one pixel to the center of an adjacent pixel?

Answer 20

pixel pitch

Question 21

The automatic exposure control (AEC) is a device that measures the quantity of radiation that will reach the ___________ before terminating the exposure?

Answer 21

IR

Question 22

Grayscale on a digital system is:

Answer 22

scale of contrast

Question 23

What are some patient factors that would affect image quality when using AEC?

Answer 23

patient size
pathology
orthopedic hardware

Question 24

A radiographic image displays with obvious quantum noise (mottle). What does this say about EI and the exposure amount? How would you fix it on the repeat image?

Answer 24

EI would be low
IR would be underexposed

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