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Physics > Test Validation/QA > Flashcards

Test Validation/QA Flashcards

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1
Q

Parameters commonly used to judge efficacy of a diagnostic test:

A

Sensitivity
Specificity
Accuracy

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2
Q

The gold standard test for carotid artery stenosis

A

Digital subtraction angiography

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3
Q

Gold standard for deep vein thrombosis

A

Venography

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4
Q

If no gold standard test, then only autopsy can be used.

T/F

A

False, sometimes clinical info or findings at surgery can be used

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5
Q

What does true positive mean?

A

Testing procedure demonstrates disease and disease is really present

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6
Q

What does true negative mean?

A

Test and gold standard both said there was no pathology

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7
Q

What does false positive mean?

A

Test said pathology is present, gold standard said no pathology present

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8
Q

False negative is when:

A

Test - normal

Gold standard - abnormal

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9
Q

How do you find the sensitivity of a test?

A

True Pos divided by true pos plus false neg

TP/TP+FN

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10
Q

Sensitivity is the ability of a test to:

A

Detect disease

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11
Q

Sensitivity measures how often a test will:

A

Miss real disease

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12
Q

Minimizing false negatives decreases sensitivity.

T/F

A

False, increases

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13
Q

How would you find specificity?

A

True neg divided by true neg plus false pos

TN/TN+FP

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14
Q

Specificity is the ability of a test to:

A

Identify normality or rule out pathology

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15
Q

Specificity is a measurement of:

A

How real a disease finding by that exam is

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16
Q

Decreasing false positives will:

A

Increase specificity

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17
Q

How do you find overall accuracy?

A

True pos plus true neg divided by total # of tests

TP + TN/total #

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18
Q

Accuracy quantifies the tests ability to:

A

Give correct answer

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19
Q

Accuracy should be left as

A

A fraction

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20
Q

What does PPV stand for?

A

Positive predictive value

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21
Q

What figures are required for PPV?

A

Only positive figures

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22
Q

How would you find PPV?

A

True pos divided by true pos plus false pos

TP/TP+FP

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23
Q

PPV tells you how meaningful a

A

Positive result really is

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24
Q

A test with a low positive predictive value cannot be used as an initial screening tool.
T/F

A

false, it may be useful but further testing may be recommended

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25
Q

PPV and NPV are represented as:

A

Fractions

26
Q

NPV is:

A

Negative predictive value

27
Q

How do you find NPV and what does it tell us?

A

True neg divided by true neg + false neg
TN/TN+FN
How meaningful a negative result really is

28
Q

A test with a low negative predictive value is likely to miss disease and puts the patient in danger.
T/F

A

True

29
Q

How would you find prevalence?

A

True pos plus false neg divided by total # of tests

TP+FN/Total #

30
Q

Prevalence validates the test.

T/F

A

False, only shows the proportion of sample population that have pathology being tested for

31
Q

Important qualities of an initial screening test:

A

High sensitivity
Low false neg rate
Low risk, low cost
Low specificity is acceptable

32
Q

Qualities of a diagnostic test to determine treatment:

A

High specificity
Low false positive rate
Low sensitivity is acceptable if known

33
Q

Example of initial screening test

A

ABI for arterial disease of LE, high sensitivity with little info on area/extent of disease
Duplex US or angiography can test that

34
Q

Example of diagnostic test

A

US for gallstones, ectopic pregnancies, appendix

Tests may not detect all of pathology but surgery can be reliably planned based on pos finding

35
Q

What is quality assurance?

A

Routine, periodic evaluation of sonography equipment and transducers

36
Q

QA detects image quality problems and assures proper operation of equipment before it effects the:

A

Images or causes equipment to fail

37
Q

Preventative maintenance is usually performed once a year by
appropriate service personnel.
T/F

A

False, 2-3 times

38
Q

Results of QA are compared to:

A

Past results to identify if change is necessary to unit

39
Q

Everyday maintenance of unit:

A

Cleaning transducers
Inspecting cables
Keeping unit dust and dirt free

40
Q

File of QA documents includes:

A 
Original equipment purchase order
Equipment specs
Warranty
Results of QA performed
Documentation of problems
Follow up service report 
Preventative maintenance reports
41
Q

Reports are needed to document the need to replace equipment but not necessary for accreditation.
T/F

A

False

42
Q

AIUM 100 mm test object is composed of:

A

Series of .75 mm diameter stainless steel rods arranged in groups in transparent plastic tank filled with mixture of alcohol and water that is equal to 1.54 mm/us at room temp

43
Q

The AIUM 100 mm test object is used more commonly with current technology.
T/F

A

False

44
Q

The AIUM 100 mm test object cannot evaluate:

A

Gray scale or contrast resolution

45
Q

Embedded in the gel of the tissue phantom are several groups of fibers which can be used to evaluate:

A 
Axial res
Lateral res
Depth calibration
Image uniformity
Distance accuracy
46
Q

Inner material of the phantom is gelatin based so in extreme temperatures the base will change its consistency but it’s still okay to use.
T/F

A

False

47
Q

What is the dead zone ?

A

Distance between transducer face to area in near field that cannot be used due to reverb or transducer design

48
Q

Axial res is tested by scanning rod group located:

A

In the middle

Placed in oblique plane

49
Q

The largest separation of two closest rods seen represents axial res.
T/F

A

False, smallest

50
Q

Lateral resolution is found by scanning the:

A

Same rod group as with axial res

51
Q

How is system sensitivity measured?

A

Of the weakest echo sign visualized determined by gain setting with no TGC using the bottom rod of the group is six vertical equidistant rods

52
Q

Face A of test object is used to test:

A

Dead zone and axial res

53
Q

Face b is used to test:

A

Lateral res

54
Q

Elevational res can be documented using:

A

Tissue phantom or inclined plane phantom

55
Q

Limitation of using tissue phantom for slice thickness testing:

A

Cystic objects suspended in phantom at certain depths that cannot be changed. Elevational focus must coincide with this depth or can’t be evaluated

56
Q

Inclined plane phantom uses an interface oriented at:

A

45 degree angle

57
Q

A horizontal band is formed when testing for slice thickness. How is it measured?

A

The axial height equals slice thickness

58
Q

Some phantoms have a series of gray scale targets that range in contrast from:

A

+15dB to -15dB

59
Q

Doppler phantoms may contain:

A

A tube embedded in tissue mimicking medium connected to pump that pushes fluid through at adjustable velocities
OR
A string that moves immersed in water bath using echoes from vibrating string to imitate reflections from blood cells

60
Q

Using Doppler phantoms, what can be evaluated?

A

Sensitivity
Sample volume accuracy
Doppler angle accuracy
Max depth of detectable Doppler signal

Physics (4 decks)

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