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CT Image Production > Image Quality (CTBC 8) > Flashcards

Image Quality (CTBC 8) Flashcards

1
Q

Spatial Resolution

A

(Sharpness)
Clarity level of small parts, spaces b/w small parts, edges of parts

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2
Q

Spatial Resolution & Pitch

A

Decreased pitch requires less interpolation and increases potential spatial resolution in z-axis (reformations)

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3
Q

Spatial Resolution & Matrix Size

A

Larger matrix = more pixels
More pixels allow for greater detail

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4
Q

Decreased acquisition slice thickness produces _______ spatial resolution in z-axis (reformations)

A

Higher

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5
Q

Reconstructing with thin slices –> _______ spatial resolution in z-axis (reformations)

A

highest

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6
Q

Edge-enhancing algorithms (bone/lung) _______ sharpness & spatial resolution

A

increase

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7
Q

Spatial Resolution & DFOV

A

Smaller DFOV creates smaller pixel dimensions w/ability to resolve smaller parts

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8
Q

Increasing spatial resolution can have the effect of increasing the appearance of _______ _______

A

Image Noise

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9
Q

Eventually the appearance of image noise will disguise any increase in _______ ________

A

Spatial Resolution

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10
Q

Smoothing algorithms are utilized instead of edge-enhancing algorithms when…

A

Decrease in apparent image noise is needed

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11
Q

Unit for measuring spatial resolution: visualization of more line pairs indicates higher spatial resolution

A

Line-pairs per mm (lp/mm) [or line-pairs per cm (lp/cm)]

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12
Q

Contrast Resolution (2)

A

Ability of CT machine to create visible difference in brightness levels (aka “contrast”)
Ability of the scanner to visually discriminate between objects with similar physical density

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13
Q

Sensitivity of the System

A

Ability to create visible contrast b/w objects with very similar LAC

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14
Q

Increasing kVp causes more uniform penetration of patient and _______ contrast

A

Decreases

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15
Q

Measurable difference in photon intensity striking detector array

A

Differential Attenuation

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16
Q

Factors influencing display contrast (3+)

A

kVp
Filtration (applied?)
Patient Morphology
Etc.

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17
Q

Decreasing kVp results in (3) _______ Scatter, _______ Differential Attenuation, _______ Contrast Resolution

A

Less Scatter
More Differential Attenuation
Increased Contrast Resolution

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18
Q

Smaller patients result in _______ Scatter, _______ Differential Attenuation, _______ Contrast Resolution

A

Less Scatter
More Differential Attenuation
Increased Contrast Resolution

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19
Q

Window Width controls the range of displayed tissues thereby changing

A

Displayed Contrast

20
Q

Image Noise typically results from

A

Inadequate exposure to detectors

21
Q

Higher Standard Deviation (within ROI) indicates _______ variance and, therefore, _______ image noise

A

Higher Variance–> Higher Image Noise

22
Q

2 methods for quatifying noise

A

Contrast Resolution Test

Measure Standard Deviation using a Simple ROI

23
Q

Decreased Image Noise usually results in _______ patient dose, _______ spatial resolution

A

Increased Patient Dose
Decreased Spatial Resolution

24
Q

Increasing kVp increases detector exposure and _______ image noise

A

Reduces Image Noise

25
Q

Increasing mA increases detector exposure and _______ image noise

A

Reduces Image Noise

26
Q

Increasing Rotation Time _______ detector exposure and _______ image noise

A

Increases Detector Exposure
Reduces Image Noise

27
Q

Increasing (acquisition or reconstruction) Slice Thickness _______ image noise

A

Reduces Image Noise

28
Q

Smoothing Algorithms (e.g., standard) _______ image noise

A

Reduce Image Noise

29
Q

Temporal Resolution

A

Ability to produce still images of moving parts (similar to shutter speed of film camera: faster avoids blurring)

30
Q

Decreasing Rotation Time _______ temporal resolution

A

Increases Temporal Resolution

31
Q

Increasing Acquisition Thickness _______ total scan time, thus _______ temporal resolution

A

Decreases total scan time, Increasing temporal resolution

32
Q

Increasing Pitch _______ total scan time, thus _______ temporal resolution

A

Decreases total scan time, Increasing temporal resolution

33
Q

Half-scan algorithms

A

Use only 180 deg of scan info to reconstruct complete data (thus doubling scan speed), enhancing temporal resolution

34
Q

Certain algorithms improve _______ _______ by reducing motion artifacts

A

Temporal Resolution

35
Q

Gating technology diminishes _______ _______, _______ temporal resolution

A

cardiac motion
increasing temporal resolution

36
Q

CT number Accuracy

A

Assurance that specific materials (and, in turn, specific tissues) generate specific CT numbers

37
Q

HU Water

A

0

38
Q

HU Air

A

-1000

39
Q

Air Calibration typically corrects problems with:

A

HU accuracy

40
Q

Linearity

A

Relationship b/w attenuation properties of material and resulting CT number

41
Q

As attenuation (tissue density) increases, CT numbers increase at a _______ rate

A

Linear rate

42
Q

A linearity test phantom includes several cylinders with varying materials of differing _______

A

Density

43
Q

For a Linearity Test Phantom, the resulting graph (of LAC for the respective cylinders) should be _______.

A

Linear

44
Q

Uniformity

A

Ability of scanner to yield same CT number for same substance regardless of ROI-position

45
Q

Factors impacting Uniformity (3)

A

Beam Hardening
Scatter Radiation
Limited Stability of Scanner

46
Q

Capping Artifact

A

Higher CT numbers in center (of uniform phantom)

47
Q

Cupping Artifact

A

Lower CT numbers in center (of uniform phantom)

CT Image Production (9 decks)

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