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RAD 102: Radiographic Technique > Ch 26-29 > Flashcards

Ch 26-29 Flashcards

1
Q

Monitor control function that can change the lightness and darkness of the image on a display monitor but it isn’t related to exposure
Not interchangeable with density; only on digital
The concept of density as it is displayed on a soft-copy monitor for digital images

A

Brightness

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2
Q

Degree of overall blackening that is the result of black metallic silver deposited in the emulsion of film
Viewable result of a film’s response to exposure
When the IR was primarily film, this term could adequately describe the effects of IR exposure
In the digital environment this important image quality factor hasn’t changed but can be expressed simply as IR exposure because film is no longer the primary IR

A

Density

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3
Q

Used when switching distances and mAs and want to maintain density/exposure
A direct square law; mAs must increase when distance increases and vice versa in order to maintain IR exposure
mAs1/mAs2 = D1^2/D2^2

A

Exposure maintenance formula

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4
Q

Along with contrast, one of two photographic properties that allow detail to be seen; in digital imaging it is the critical quality factor to assess and comparable to density in film/screen environment

A

IR exposure

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5
Q

Digital post-processing that produces changes in brightness

A

Window level

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6
Q

Along with contrast, one of two photographic properties that allow detail to be seen

A

Density/IR exposure

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7
Q

What is the controlling factor of density/IR exposure and how is it affected?

A

mAs

Direct relationship between mAs and density/exposure; one goes up the other goes up

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8
Q

How are density/IR exposure adjustments made for changes in kVp?

A

Small changes can have profound impact on density/IR exposure
15% rule

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9
Q

How do variations in the anatomical part affect density/IR exposure?

A

Inverse relationship between tissue thickness/type and density/IR exposure; as tissue thickness, average atomic number of the tissue, and/or tissue density increases, density/IR exposure decreases
Thicker person decreases exposure

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10
Q

What are the relationships to density/IR exposure of grid ratio, frequency, interspace material and grid use?

A

The more efficient the grid, the less will be the density/IR exposure
Grids with high ratios, low frequency and dense interspace material; moving grids; and improperly used grids (incorrect focal distance, etc.) all reduce density/IR exposure

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11
Q

One of the properties that comprise visibility of detail; the difference between adjacent densities

A

Contrast

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12
Q

The result of differences in transmission of the beam as it passes through the patient resulting in signal differences to the digital detector

A

Differential attenuation

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13
Q

The concept of contrast as it is displayed on a soft-sopy monitor for digital images; range of density/brightness of the display monitor light emisson

A

Dynamic range

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14
Q

The number of shades of gray in a radiographic image

A

Grayscale

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15
Q

The number of useful visible densities or shades of gray

A

Scale of contrast

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16
Q

Degree of differential absorption resulting from the differing absorption characteristics of the tissues in the body

A

Subject contrast

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17
Q

The digital processing that produces changes in the range of density/brightness, which can be used to control contrast

A

Window width

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18
Q

Short scale
Short/narrow dynamic range
Portable chest x-rays tend to be more high contrast bc of the tech factors you use (no grid)
Low kVp
Dif in adjacent densities is great
Short/narrow dynamics = white & black

A

High contrast

19
Q

Long scale
Large/wide dynamic range
Radiographers prefer this for chest x-rays bc it shows more info bc there are a lot of dif tissues w/dif Z#’s so they have more attenuation
High kVp gives long-scale/low contrast bc x-ray photons are greater to interact w/dif tissues & able to knock out e-’s & scatter
Similar densities, dif in adjacent densities is minimal
Large/wide dynamic range = range of exposures you can see is v many (many steps)

A

Low contrast

20
Q

Total range of density/IR exposure values recorded by the IR

A

Physical contrast

21
Q

Total range of density/IR exposure values that can be perceived by the human eye in a single image

A

Visible contrast

22
Q

3 factors that affect subject contrast

A

Kilovoltage (can control)
Amount of irradiated material
Type of irradiated material (ex: air, bone, contrast media, etc.)

23
Q

What factors affect image receptor contrast?

A

Histogram and LUT used affect final image

Use of proper kVp still important

24
Q

Concept of contrast as it is displayed on a soft-copy monitor for digital images; range of density/brightness on the display monitor light emission

A

Dynamic range

25
Q

How does density/IR exposure affect image receptor contrast?

A

When the difference in adjacent densities is great there is high contrast
When there are similar densities/difference in adjacent densities is minimal there is low contrast

26
Q

How do variations in the anatomical part affect contrast?

A

Dependent on tissue type, thickness, pathology, etc.

27
Q

What is the effect of a grid on contrast?

A

Directly related: increase grid ratio increases contrast

Grids reduce scatter; reduce scatter = increase contrast

28
Q

How do the histogram and look-up table affect display contrast?

A

Histogram has idea of what image should look like

LUT looks at image that comes in at standard contrast that machine tells it it should have, tries to fix it to this

29
Q

Occurs when Nyquist Criterion not met
Low-frequency image wraps around high-frequency image
Visual appearance of two images slightly out of alignment

A

Aliasing

30
Q

One of the geometric properties of image quality; the degree of geometric sharpness or accuracy of structural lines actually recorded in the image

A

Definition/recorded detail/sharpness/spatial resolution

31
Q

Expression of the boundaries of an image

A

Edge spread function (ESF)

32
Q

Background information that the IR receives

A

Imaging noise

33
Q

Measurement of recorded detail, sharpness and resolution; the ability of a film/screen system to accurately measure the boundaries of an image

A

Line spread function (LSF)

34
Q

Measurement of recorded detail, sharpness and resolution; measures the resolving ability of a film/screen combination

A

Modulation transfer function (MTF)

35
Q

The sampling of the spatial resolution frequency signal twice from each cycle in digital systems

A

Nyquist criterion

36
Q

Expression of the boundaries of an image; determined by a mathematical measurement of an image produced at a single point

A

Point spread function (PSF)

37
Q

A lack of sufficient incoming data to process an image

A

Quantum mottle/noise

38
Q

Lack of sharp definition of fine detail

A

Unsharpness

39
Q

How is resolution measured?

A

Line pair per millimeter (lp/mm)

40
Q

How does the OID affect recorded detail?

A

Resolution is improved when OID decreases and is degraded whenever it increases
Penumbra decreases when the OID decreases

41
Q

How does the SID affect recorded detail?

A

Resolution is improved when SID increases and is degraded whenever it decreases
Penumbra decreases as the SID decreases

42
Q

What is the relationship between focal spot size and recorded detail?

A

Focal spot size is controlled by the line focus principle
The focal spot size is a major controller of image resolution because it controls penumbra
As the focal spot decreases in size, penumbra also decreases thus increasing resolution
Penumbra decreases when the focal spot decreases

43
Q

Imperfect, unsharp shadow surrounding the umbra

With light it is the region of partial illumination that surrounds the complete shadow

A

Penumbra/edge gradient

44
Q

Distinctly sharp area of a shadow or the region of complete shadow

A

Umbra

RAD 102: Radiographic Technique (7 decks)

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