week 3: image quality

Question 1

image contrast is affected by

Answer 1

subject contrast, displayed contrast, detector contrast

Question 2

contrast created by the computer hardware/software and then displayed on the viewing monitor

Answer 2

displayed contrast

Question 3

contrast from the distribution of tissue densities and/or physiologic changes that are present in the anatomic part

Answer 3

subject contrast

Question 4

Window width is the measure of the ___________________

Answer 4

range of gray shades that an image contains

Question 5

Wide WW = (high/low) contrast image

Answer 5

low

Question 6

Marrow WW = (high/low) contrast image

Answer 6

high

Question 7

visibility of detail is affected by

Answer 7

Contrast resolution
Pixel brightness
Image contrast
Measured in digital imaging by DQE

Question 8

visibility of detail is how well ___________________________-

Answer 8

the structures in the image can be seen in the displayed image

Question 9

Ability of an imaging system to distinguish structures with similar tissue densities as separate entities

Answer 9

contrast resolution

Question 10

how can contrast resolution be measured?

Answer 10

either signal-to-noise or contrast-to-noise ratio

Question 11

Noise has a ____________ impact (increases/decreases) contrast resolution

Answer 11

negative, decreases

Question 12

signal fluctuations that can randomly occur or be caused by internal electronics

Answer 12

electronic noise

Question 13

noise that occurs in DR systems, also known as tiling; each tile may have slightly more or less amplification than surrounding chips, causing a tile-like appearance in the image

Answer 13

structured noise

Question 14

patterns on the image generated by patient anatomy that is always present but not important for diagnosis

Answer 14

anatomical noise

Question 15

caused by quantum mottle, uneven distribution of photons that is seen when not enough photons reach the image receptor; results in speckled appearance

Answer 15

quantum noise

Question 16

DQE stands for

Answer 16

detector quantum efficiancy

Question 17

DQE is one of the fundamental physical variables related to image quality and refers to the efficiency of a detector in ______________ into __________

Answer 17

converting incident x-ray energy, an image signal

Question 18

DQE measures the __________________-

Answer 18

cleanliness or lack of noise in the image

Question 19

DQE is affected by _____________________

Answer 19

the x-ray beam energy
x-ray photon quantity in detector area detector material
spatial frequency

Question 20

the higher the DQE, the (higher/lower) the patient exposure dose

Answer 20

lower

Question 21

The ability of an imaging system to create separate images of closely spaced objects and determines the edge definition capability

Answer 21

spatial resolution

Question 22

what is spatial resolution affected by?

Answer 22

geometric factors
object factors
motion factors
image receptor factors

Question 23

diagnostic performance measurement meanings

True Positive (TP)

Answer 23

True Positive (TP) – follow up test; image diagnosis was correct

Question 24

diagnostic performance measurement meanings

False Positive (FP)

Answer 24

follow up test; image diagnosis was incorrect

Question 25

diagnostic performance measurement meanings

True Negative (TN)

Answer 25

image diagnosis is negative and confirmed by follow up testing

Question 26

diagnostic performance measurement meanings

Positive Negative (FN)

Answer 26

image diagnosis is negative but follow up testing shows presence of disease

Question 27

Percentage or fraction of cases that are diagnosed correctly

Answer 27

diagnostic performance measurement accuracy

Question 28

Indicates likelihood of obtaining a positive diagnosis in a patient with the disease

Answer 28

diagnostic performance measurement sensitivity

Answer 29

diagnostic performance measurement specificity