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Review Of Radiologic Physics > 6 Image Quality > Flashcards

6 Image Quality Flashcards

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1
Q

What is the definition of subject contrast?

A

Depiction of lesions results from differential attenuation of the x-ray beam between the lesion and background tissues.
Subject contrast is the difference in x-ray intensity that is transmitted through a lesion in comparison to the adjacent tissues.

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2
Q

What is the definition of subject contrast?

A

Depiction of lesions results from differential attenuation of the x-ray beam between the lesion and background tissues.
Subject contrast is the difference in x-ray intensity that is transmitted through a lesion in comparison to the adjacent tissues.

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3
Q

What is the definition of positive contrast?

A

Subject contrast can be positive if the lesion absorbs fewer x-rays compared to the surrounding tissues.
Positive contrast will result in darker lesions in conventional radiographs.

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4
Q

What is the definition of image contrast?

A

The difference in the film density of a lesion in comparison to the film density of the adjacent tissues.

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5
Q

What is the definition of image contrast?

A

The difference in the film density of a lesion in comparison to the film density of the adjacent tissues.

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6
Q

What is the definition of film latitude?

A

The range of air kerma values that results in a satisfactory image contrast. Latitude is known as dynamic range in engineering.

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7
Q

What are the benefits of breast compression?

A

Reduces variation of air kerma in mammography, and permits the use of high-contrast film.

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8
Q

What is the definition of image contrast in digital imaging?

A

The difference in the monitor brightness of a lesion in comparison to the monitor brightness of the adjacent tissues.

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9
Q

What is the definition of Resolution (spatial resolution, high-contrast resolution, sharpness, or blur)?

A

Resolution is the ability of an imaging system to display two adjacent objects as discrete entities.

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10
Q

What is the penumbra?

A

The result of x-rays arriving from slightly different locations in the focal spot.

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11
Q

What is the definition of focal spot blur or geometric unsharpness?

A

The resultant loss of sharpness.

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12
Q

What is the definition of noise?

A

Noise describes the content of an image that limits the ability to visualize lesions or pathology.

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13
Q

What is the definition of Standard deviation?

A

Used to describe the spread or distribution of a data set and is the square root of the average of the square of all the sample deviations.

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14
Q

What is the definition of Bias?

A

The presence of systematic error.

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15
Q

What is the definition of Precision?

A

The reproducibility of a result but does not imply accuracy.

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16
Q

What is the definition of Accuracy?

A

Refers to how close a measured value is to the true value.

17
Q

What is the definition of True positives (TPs)?

A

Are positive test results in patients who have the disease.

18
Q

What is the definition of True negatives (TNs)?

A

Are negative test results in patients who do not have the disease.

19
Q

What is the definition of False positives (FPs)?

A

Are positive test results in patients who do not have the disease.

20
Q

What is the definition of False negatives (FNs)?

A

Are negative test results in patients who have the disease.

21
Q

What is the definition of Sensitivity?

A

The ability to detect disease and is TP/(TP + FN), also known as the true-positive fraction.
A sensitive test has a low false-negative rate.

22
Q

What is the definition of Specificity?

A

The ability to identify the absence of disease and is TN/(TN + FP), also known as the true-negative fraction.
A specific test has a low false-positive rate.

23
Q

What is the definition of Accuracy?

A

The fraction of correct diagnosis and is (TP + TN)/(TP + FP + TN + FN).

24
Q

What is the definition of Positive predictive value?

A

The probability of having the disease given a positive test and is TP/(TP + FP).

25
Q

What is the definition of Negative predictive value?

A

The probability of not having the disease given a negative test and is TN/(TN + FN).

26
Q

What is the definition of Prevalence of the disease?

A

(TP + FN)/(TP + FP + TN + FN).

27
Q

The achievable number of lp/mm is normally taken to be

A

∼1/(2 ×FWHM).

28
Q

The limiting spatial resolution (lp/mm) of a (dedicated) chest screen–film unit is likely

A

5.

29
Q

The detector air kerma in digital photospot imaging is

A

1 μGy.

30
Q

The air kerma that produces a single digital fluoroscopy frame is

A

0.01 μGy.

Review Of Radiologic Physics (11 decks)

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