week 4: image quality

Question 1

Difference in image brightness between areas of the image

Answer 1

image contrast

Question 2

Image contrast is affected by

Answer 2

Subject contrast, displayed contrast, detector contrast

Question 3

Wide WW = ____ contrast image
Narrow WW = ___ contrast image

Answer 3

low, high

Question 4

visibility of detail affected by

Answer 4

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

Question 5

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

Answer 5

visibility of detail

Question 6

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

Answer 6

contrast resolution

Question 7

contrast resolution is affected by

Answer 7

the contrast sensitivity of the image receptor system, signal contrast, bit depth and the amount of noise present

Question 8

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

Answer 8

electronic noise

Question 9

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 9

structured noise

Question 10

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

Answer 10

anatomical noise

Question 11

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

Answer 11

quantum noise

Question 12

One of the fundamental physical variables related to image quality and refers to the efficiency of a detector in converting incident x-ray energy into an image signal

Answer 12

detector quantum efficiency

Question 13

_____________ measures the cleanliness or lack of noise in the image

Answer 13

detector quantum efficiency

Question 14

DQE is affected by

Answer 14

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

Question 15

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

Answer 15

lower

Question 16

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

Answer 16

spatial resolution

Question 17

True Positive (TP) = _____________________

Answer 17

follow up test; image diagnosis was correct

Question 18

False Positive (FP) = ____________________

Answer 18

follow up test; image diagnosis was incorrect

Question 19

True Negative (TN) = __________________

Answer 19

image diagnosis is negative and confirmed by follow up testing

Question 20

False Negative = _______________________

Answer 20

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

Question 21

percentage or fraction of cases that are diagnosed correctly

Answer 21

accuracy

Question 22

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

Answer 22

sensitivity

Question 23

Indicates the likelihood of a patient obtaining a negative diagnosis when no disease is present

Answer 23

specificity

Question 24

Quality control _________ are available to test accuracy, sensitivity, specificity, positive predictive value and negative predictive value