Contrast Flashcards by Jill Feehan

Arrt f/s

scale of contrast

Refers to the number of densities visible (or the number of shades of gray).

How well did you know this?

Not at all

Perfectly

Arrt f/s

long scale

Term used when slight differences between densities are present (low contrast) but the total number of densities is increased.

How well did you know this?

Not at all

Perfectly

Arrt Film screen

contrast

Radiographic contrast is defined as the visible differences between any two selected areas of density levels within the radiographic image.

How well did you know this?

Not at all

Perfectly

Arrt f/s

short scale

Term used when considerable or major differences between densities are present (high contrast) but the total number of densities is reduced

How well did you know this?

Not at all

Perfectly

Arrt f/s

film latitude

The inherent ability of film to record a long range of density levels on the radiograph.
Film latitude and film contrast depend upon the sensiometric properties of the film and processing conditions, and are determined directly from the H and D curve.

How well did you know this?

Not at all

Perfectly

ARRT f/s

Film Contrast

The inherent ability of the film emulsion to react to radiation and record a range of densities.

How well did you know this?

Not at all

Perfectly

Arrt f/s

exposure latitude

The range of exposure factors which will produce a diagnostic radiograph.

How well did you know this?

Not at all

Perfectly

Arrt f/s

subject contrast

The difference in the quantity of radiation transmitted by a particular part as a result of the different absorption characteristics of the tissues and structures making up that part.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

contrast

Image contrast of display contrast is determined primarily by the processing algorithm. The default algorithm determines the initial processing codes applied to the image data.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

scale of contrast

Is synonymous to “gray scale” and is linked to the bit depth of the system.
Gray scale is used instead of scale of contrast when referring to digital images.

How well did you know this?

Not at all

Perfectly

Algorithm

Mathematical codes used by the software to provide the desired image appearance.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

dynamic range

The range of exposures that may be captured by a detector. The dynamic range for imaging is much larger than film.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

receptor contrast

The fixed characteristics of the receptor. Most digital receptors have an essentially linear response to exposure. This is impacted by contrast resolution (the smallest exposure change or signal difference that can be detected.)
Ultimately, contrast resolution is limited by the dynamic range and the quantization (number of bits per pixel) of the detector.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

exposure latitude

The range of exposures which produces quality images at appropriate patient dose.

How well did you know this?

Not at all

Perfectly

Arrt digital radiography

subject contrast

The magnitude of the signal difference in the remnant beam.

How well did you know this?

Not at all

Perfectly

Windows level

Identifies the brightness of the type of tissue imaged.

How well did you know this?

Not at all

Perfectly

Window width

The gray scale representation of the tissue.

The wider the window width, the longer the gray scale.

How well did you know this?

Not at all

Perfectly

What factor affect contrast

kVp
Grids
Processing 
IR speed
Subject 
Beam restriction

How well did you know this?

Not at all

Perfectly

Contrast resolution means

The smallest exposure changes and signal differences that can be detected

How well did you know this?

Not at all

Perfectly

Quantization

Number of bits per pixel

How well did you know this?

Not at all

Perfectly

Dynamic range

Range of values over which a system

How well did you know this?

Not at all

Perfectly

Low contrast aka

Long scale
Reduced contrast
Diminished contrast

How well did you know this?

Not at all

Perfectly

High kVp exposure gives — contrast

Low contrast

How well did you know this?

Not at all

Perfectly

If there are lots of shades of gray, the image is —- contrast, and —- scale.

Low contrast

Long scale

How well did you know this?

Not at all

Perfectly

If there are less density differences on an image, it is ---- contrast

Low

Low kVp exposure produces ---- contrast

High

High contrast aka

Short scale contrast | Increasing contrast

If there are fewer shades of gray between black and white the image is ----- scale contrast

Short

If there are big density differences on the image, it is ---contrast

High

What controls the penetrability of the beam

kVp

A thicker object density will produce

Less density on the image

Long scale contrast with have a ---- straight line portion on an HD curve.

Flatter

A steeper straight line portion of the HD curve means

Short scale/ high contrast

A sensiometric strip is created with

Stepwedge | Penetrometer

The thinner end of the stepwedge will create more ---- on the strip.

Density / blackness

The function of contrast

To make detail visible

Fog will --- contrast

Decrease

Contrast aka

Density differences

Factors that do not influence contrast

mA Time SID

Factors that influence contrast in f/s and digital

``` kVp Subject IR Collimating Beam restriction Grid Compression ```

Factors that influence contrast in f/s

Chemical processing Intensifying screen Film speed

Factors that influence contrast in digital

IR Digital processing Bit depth

Increasing kVp from 80 to 95 will effect contrast how?

More long scale | Low contrast

Changing from no grid to 8:1 grid will effect contrast how?

More short scale | High contrast

If chemistry was hot, adding chemical fog to film

More long scale | Low contrast

Change from 200 speed screen to CBH and correct mAs will effect contrast how?

More long scale | Low contrast

As screen speed increases then

Contrast increases Higher contrast Shorter scale

As grid ratio increases then

Contrast increases Shorter scale Higher contrast

As speed screen decreases

Contrast decreases

Going from no cone to extended cone will effect contrast how?

Increase contrast

Why does adding an extension cylinder increase contrast

Less scatter is produced

Why does adding compression increase contrast/more short scale

Less matter less scatter

A patient with osteoporosis will ---contrast. Why?

Increase contrast/more short scale Because the part is less dense; so image is more black and white ( this pathology needs less kVp)

Do a patient with ascites

More long scale | Because more matter, more scatter; it needs more kVp

The more you collimate

Less scatter Less grey Short scale contrast Higher contrast

Bit depth

How many bits you are stacking | Stacking of digital brightness

Define aerial beam/remnant beam

The beam that emerges from the body.

What is subject contrast and what does it contain

The contrast in the remnant beam. Contains wanted information derived from the patient And also unwanted information--scatter.

4 factors that affect subject contrast

Radiation Quality Radiographic Object Scatter Radiation Fog

How does radiation quality affect subject contrast

⬆️ kVp = ⬆️ penetrating ability Thereby producing a longer scale of contrast ⬇️ contrast

Radiographic object means

Body part Thickness Nature of part: tissue density and pathology-additive and destructive

Name 5 radiographic objects ranging from greatest to least radiopacity

1. Tooth enamel 2. Bone 3. Tissues of H2O density such as muscle, glands, liver, spleen, pancreas, kidney 4. Adipose tissue 5. Gas/ air filled structures

Scatter is

A noise factor obscuring information or detail | Impairs contrast by a fogging affect

Scatter radiation can be controlled by

Beam restriction and grid

Fogging

From any other source, contributes to noise. | Imparting an overall grey appearance to the image and reducing contrast

----interferes with our ability to see something

Scatter

Is subject contrast is unaffected by

The type of image receptor used to create image

Image receptor contrast includes 3 components

Film/Screen combinations Development Process Digital Systems

Image receptor contrast F/S combinations; Film emulsions are designed by manufacturers to

Display different scales of contrast | Depends on facility's body parts imaged

Intensifying Screens convert what?

Over 98% of X-ray photons to light

Why does the IS conversion process enhance contrast

Because S/F is designed to respond to the light emitted by the IS

As film-screen system speed ⬆️ then contrast

As film-screen system speed ⬆️ then contrast ⬆️ (shorter scale), and latitude ⬇️ (less steps in the range).

Image Receptor Contrast Development Process What affects contrast

Different chemicals/ingredients within the developer; excess chemical ⬆️ fog and ⬇️ contrast. Excessive temperature or other processor problems; ⬆️ temperature ⬆️ fog ⬇️ contrast

Image Receptor Contrast Development Process How do you ensure optimum quality

Daily sensitometry | Strict adherence to QC

Bushong defines Contrast Resolution as

The ability to distinguish anatomical structures of similar subject contrast

All digital systems have better ------- than F/S systems.

Contrast resolution

Windowing

Changing the image brightness and/or contrast scale

Why doesn't doubling mAs change gray scale?

Because every step gets twice as dark, but the density differences between the steps has not changed.

When is contrast ideal?

When you see what you need to see

When would you want long scale contrast

To see detail; and subtle changes in density

Histograms and LUTS in digital systems

Is the recipe card; processing algorithms

Differential absorption

Different degrees of X-ray absorption based on the body tissue and densities and thickness it determines subject contrast

If you need to produce the same OD at a slightly reduce contrast scale

5% rule

⬆️kVp 15% and ⬇️ mAs 30%

If image has too many gray/ long scale, or too black and white

Apply 15% change while either 1/2 or double mAs

4 factors that RT must judge

Anatomical part Body habitus Suspected pathology X-ray IR characteristics

Pixel represent a

BIT

4 factors that RT must judge

Anatomical part Body habitus Suspected pathology X-ray IR characteristics

Pixel represent a

BIT

Image contrast is a result of which 1. Differential tissue absorption 2. Atomic number of tissue being traversed 3. Proper regulation of mAs

1. Differential tissue absorption | 2. Atomic number of tissue being traversed

In comparison with 60kV, 80 kV will? 1. Permit greater exposure latitude 2. Produce more scatter radiation 3. Produce shorter scale contrast

1. Permit greater exposure latitude | 2. Produce more scattered radiation

Which of the following technical changes would best serve to remedy the effect of very different tissue densities? 1. Use of a small focal spot 2. Use of a high ratio grid 3. High kilovoltage exposure factors 4. High MAS

3. High kVp

A 15% decrease in kilovolt age accompanied by a 50% increase in MAS will result in? 1. Shorter scale of contrast 2. Increase in exposure latitude 3. Increase in radiographic density 4. Decrease in recorded detail

Shorter scale of contrast

Under exposure of a radiograph can be caused by all of the following except insufficient 1. mA 2. Exposure time 3. KVp 4. SID

SID | Insufficient SID will result in increased exposure rate and radiographic overexposure.

All The following have an impact on contrast except? 1. Photon energy 2. Grid ratio 3. OID 4. Focal spot siz

Focal spot size

An increase in kilovoltage will serve to produce --- scale contrast

Long

Brightness and contrast resolution in digital imaging can be influenced by 1. Window level 2. Window width 3. Look up table

All of them

Which of the following are associated with subject contrast? 1 patient thickness 2. Tissue density 3. Kilovoltage

All of them

As kilovoltage increases, beam attenuation is decreased and subject contrast

Decreases

As grid ratio is decreased the scale of contrast becomes

Longer

As window level increases

Brightness increases