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Gray Scale (Contrast) Flashcards

1
Q

Radiographic Contrast

Name and describe 2 photographic factors.

Contrast allows what to be seen but doesn’t change what?

What range is used in digital radiography? What 2 things are they?

A

Radiographic Contrast

Name and describe 2 photographic factors. Density (overall darkening) & Contrast (visible differences in density)

Contrast allows what to be seen but doesn’t change what? Contrast allows visibility of detail to be seen but doesn’t change structural lines

What range is used in digital radiography? Dynamic range

  • What 2 things are they? Window width and gray scale
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2
Q

What is contrast?

A

Visible differences in shades of density

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3
Q

High vs Low Contrast

A

High vs Low Contrast

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4
Q

Density Changes

A

Density Changes

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5
Q

Contrast Changes

A

Contrast Changes

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6
Q

Contrast and Density

A

Contrast and Density

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7
Q

What can measure contrast?

A

A penetrometer or step wedge

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8
Q

High contrast or short gray scale is described as densities with what?

What increases contrast?

A

High contrast or short gray scale is described as densities with what? Densities with abrupt changes

What increases contrast? Black to white shades

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9
Q

What is low contrast or long gray scale described as?

More shades of grays is what kind of scale?

A long gray scale increases or decreases contrast?

A

What is low contrast or long gray scale described as? Densities with gradual changes

More shades of grays is what kind of scale? Long scale

A long gray scale increases or decreases contrast? Decreases contrast

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10
Q

Comparison of Gray Scales

A

Comparison of Gray Scales

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11
Q

Short vs Long Gray Scale

A

Short vs Long Gray Scale

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12
Q

Contrast Problem

A

Contrast Problem

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13
Q

Describing Contrast

A

Describing Contrast

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14
Q

What are the 3 categories of contrast?

A
  1. Radiographic Contrast (kVp, air gap grid, etc)
  2. Subject/Patient Contrast (Pt brings own body tissue, pathology)
  3. Film/Film Processing Contrast (Type of film and how it was developed)
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15
Q

Radiographic Factors

What is the major controlling radiographic factor?

What does it control?

What effect is created because of this radiographic factor?

What does it do?

This effect will increase as you increase what?

What occurs during the photoelectric effect?

A

Radiographic Factors

What is the major controlling radiographic factor? kVp

What does it control? Penetration power, energy, and wavelength of primary beam

What effect is created because of this radiographic factor? Compton Effect

What does it do? Creates scatter radiation

This effect will increase as you increase what? Compton effects increases as you increase kVp

What occurs during the photoelectric effect? Absorption of primary beam occurs as you lower kVp

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16
Q

In order to get rid of Compton scatter (fog), what must you do?

A

Increase kVp

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17
Q

What does a grid do?

What kind of problem do you have if your film is “ugly”?

A

What does a grid do? Eliminates scatter from reaching IR

What kind of problem do you have if your film is “ugly”? Contrast Problem

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18
Q

What does having an optimal kVp level mean?

What does optimal kVp allow for?

A

What does having an optimal kVp level mean? Having an appropriate kVp for every body part which will save the patient a radiation dose and for good contrast film

What does optimal kVp allow for? Allows for good penetration for the digital system to have a good signal-ratio signal

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19
Q

What is signal-ratio?

When a film is noisy, it is…

Low noise =

High noise =

Low, grainy film = ___ signal

A

What is signal-ratio? Radiation converted to a numerical value

When a film is noisy, it is grainy

Low noise = good image

High noise = bad image

Low, grainy film = bad signal

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20
Q

Penetrometer and kVp

A

Penetrometer and kVp

21
Q

What 2 things contribute to the overall darkening of an image?

A

What 2 things contribute to the overall darkening of an image? kVp and density

22
Q

What is critical for proper density?

If the image is too dark or too light, you cannot judge what on the radiographic image?

What is compromised if the film is overexposed or underexposed?

When talking about contrast problems, what is adjusted so we do not have density problems?

A

What is critical for proper density? Proper mAs

If the image is too dark or too light, you cannot judge what on the radiographic image? Contrast

What is compromised if the film is overexposed or underexposed? Contrast

When talking about contrast problems, what is adjusted so we do not have density problems? mAs

23
Q

Why were grids invented?

What do grids improve?

  • Higher the grid ratio =
  • Lower the grid ratio =
  • Higher the grid frequency =
  • Lower the grid frequency =

What do you do if you want the patient to absorb more of the beam (ex, kVp too low for a body part)?

A

Why were grids invented? To stop scatter radiation from reaching the film

What do grids improve? Image contrast

  • Higher the grid ratio = increase contrast
  • Lower the grid ratio = decrease contrast
  • Higher the grid frequency = increase contrast
  • Lower the grid frequency = decrease contrast

What do you do if you want the patient to absorb more of the beam (ex, kVp too low for a body part)? Go down in kVp

24
Q

Nongrid vs Grid

A

Nongrid vs Grid

25
What does collimating do? Collimating does what to the contrast? The faster the screen speed, the ___ the contrast. Note: Remember, you can decrease the amount of radiation you use on the fast screen speed. Faster screen speed = ___ radiation needed = ___ scatter created in patient
What does collimating do? **W****ill help to eliminate scatter radiation from being created plus less scattered reaching the film** Collimating does what to the contrast? **Increases contrast** The faster the screen speed, the **higher** the contrast. Note: Remember, you can decrease the amount of radiation you use on the fast screen speed. Faster screen speed = **less** radiation needed = **less** scatter created in patient
26
What does the window level do? What does the window width do?
What does the window level do? **Make image lighter or darker** What does the window width do? **L****ets shades of gray in**
27
What is needed to reduce the patient's radiation skin dose and to produce good images?
Filtration
28
Increased filtration (\_\_\_ wavelengths) = ___ contrast Decrease filtration (\_\_\_ wavelengths) = ___ contrast Abrupt changes = What is harder to penetrate? What will you need to do to penetrate it?
Increased filtration (**shorter** wavelengths) = **decreased** contrast Decrease filtration (**longer** wavelengths) = **increase** contrast Abrupt changes = **lower kVp** What is harder to penetrate? **Barium** What will you need to do to penetrate it? **Go up in kVp**
29
OID = air gap grid Increase OID = ___ contrast Decrease OID = ___ contrast
OID = air gap grid Increase OID = **Increase** contrast Decrease OID = **Decrease** contrast
30
If a film is "too contrasty" the film is too... Too contrast = too much in the differences in the ___ of \_\_\_ What do you do to correct the contrast? What rule to increase kVp? Whats the rule of thumb?
If a film is "too contrasty" the film is too **black and white** Too contrast = too much in the differences in the **shades** of **density** What do you do to correct the contrast? **Raise the kVp and lower the mAs** What rule to increase kVp? **15% rule** Whats the rule of thumb? **Add 10 kVp or half the mAs**
31
What does it mean if the image is "too flat"? What do you do to correct the contrast? What is the % rule? What is the rule of thumb?
What does it mean if the image is "too flat"? **Film is too even in the shades of density/film is too gray in appearance** What do you do to correct the contrast? **Lower the kVp and raise the mAs** What is the % rule? **15% rule to lower kVp and double mAs** What is the rule of thumb? **Subtract 10 kVp, double mAs**
32
What is inherent in the radiographic film and is influenced by the conditions of the film processors? What must be followed or you will decrease contrast on the film? Film speed = ___ vs \_\_\_ Slower the speed = ___ contrast Faster the speed = ___ contrast What is film latitude? Slower the film speed = ___ contrast films Faster the film speed = ___ contrast films
What is inherent in the radiographic film and is influenced by the conditions of the film processors? **Film contrast** What must be followed or you will decrease contrast on the film? **Film processing** Film speed = **slow** vs **faster** Slower the speed = **decrease** contrast Faster the speed = **increase** contrast What is film latitude? **The ability to record the different shades of density** Slower the film speed = **low** contrast films Faster the film speed = **higher** contrast films
33
What does H&D curve stands for? H&D Curve = ___ the ___ contrast H&D curve is a radiographic relationship between what on the film? What are other names for H&D?
What does H&D curve stands for? **Hurter and Driffield Curve** H&D Curve = **plot** the **film** contrast H&D curve is a radiographic relationship between what on the film? **Amount of exposure and the resultant density on the film** What are other names for H&D? **Characteristic curve, Sensitometric Curve, or D log E Curve**
34
Name and describe the 3 parts of the curve
``` **TOE = located in the white area (of x-ray) D min (sensitive minimum)** ``` **• SLOPE = middle of shades of density (how many grays on film) Average gradient** **• SHOULDER = located in the darkest or blackest area (max out at certain darkness) D max**
35
What is base fog? Why is the film tinted? What is base plus fog?
What is base fog? **Density already manufactured on film** Why is the film tinted? **To reduce eye strain** What is base plus fog? **Density that was added to film (becomes part of image)**
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39
Name 6 types of patient contrast
* Tissue thickness * Type of tissue * Condition of tissue * Development of tissue * Tissue densities * Age of tissue
40
Name the 10 things x-ray can penetrate from easiest to hardest.
1. Gas/Air 2. Fat 3. Cartilage 4. Hollow organs 5. Muscle 6. Solid organs 7. Fluid 8. Bone 9. Teeth 10. Barium
41
What body habitus is considered to be the norm? Asthenic habitus is... ___ attenuation of the primary beam so ___ radiation is needed. ___ tissue to interact with ___ compton scatter Hypersthenic habitus is... ___ attenuation of the primary beam so ___ radiation is needed. ___ tissue to interact with ___ compton scatter
What body habitus is considered to be the norm? **Sthenic** Asthenic habitus is **extremely thin.** **Less** attenuation of the primary beam so **less** radiation is needed. **Less** tissue to interact with **less** compton scatter Hypersthenic habitus is **massive body build. More** attenuation of the primary beam so **more** radiation is needed. **More** tissue to interact with **more** compton scatter
42
More radiation = ___ compton scatter = ___ grays If patient absorbs beam, not many shades making it to film
More radiation = **more** compton scatter = **more** grays If patient absorbs beam, not many shades making it to film
43
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45
Methods to reduce scatter to improve radiographic contrast: 1. Removal of scatter radiation through... 2. Reduce the amount of tissue being irradiated through... 3. Reduce the amount of primary beam needed through...
Methods to reduce scatter to improve radiographic contrast: 1. Removal of scatter radiation through **use of a grid (\>60 kVp or \>10cm part) and air gap grid (but will increase magnification)** 2. Reduce the amount of tissue being irradiated through **beam restriction (collimation), proper filtration, and lead blockers (lead glove)** 3. Reduce the amount of primary beam needed through **increasing** **film/screen speeds (fast the system --\> less radiation --\> less compton)**
46
What is contrast? What does is mean when an image has high contrast or short scale? Name 3 characteristics. What does is mean when an image has low contrast or long scale? Name 3 characteristics.
What is contrast? **Differences in shades of density** What does is mean when an image has high contrast or short scale? **Abrupt changes in the shades of densitity.** Name 3 characteristics. **Black to white, low kVp (long wavelenghts), photoelectric effect** What does is mean when an image has low contrast or long scale? **Gradual changes in shades of densitiy.** Name 3 characteristics. **Gray tones added, higher kVp (short wavelengths), compton scatter**
47
Computed radiography is what type of range?
Dynamic range
48
Density is controlled by window... (brightness) Contrast is controlled by window... (gray tones)
Density is controlled by window **level** (brightness) Contrast is controlled by window **width** (gray tones)

Principles of Radiographic Exposure (18 decks)

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