Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

APPH 226 > Density > Flashcards

Density Flashcards

1
Q

For selection of an optimal radiographic technique, three groups of factors must be considered

A
  • image quality factors ex density, contrast
  • exposure technique factors ex kvp, mAs, SID
  • patient factors ex pathology
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Visibility is achieved with the balance of

A
  • radiographic density

- radiographic contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Radiographic density

A
  • the amount of overall BLACKNESS produced on the image after processing
  • must achieve balance
  • must have sufficient density (allows us to visualize the structures, excess or insufficient density results in poor visualization of anatomy)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the factors that alter radiographic density of images (aka prime exposure factors)

A
  • kVp
  • exposure time
  • mA
  • SID
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does it mean when an image is said to be too dark?

A
  • has a high OD
  • caused by overexposure
  • more information
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does it mean when an image is said to be too light?

A
  • has a low OD
  • caused by underexposure
  • less information
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

OD can be controlled by two major factors

A
  • mAs
  • SID
  • direct relationship between mAs and OID
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

MAs and exposure

A
  • mAs is primary factor used for density
  • determines the number of x-rays produced (quantity)
  • direct relationship
  • double the mAs=double the exposure
    • provided nothing else changes
    • also generally doubles the density
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Reciprocity law

A
  • the density produced on a radiograph remains the same for any combination of mA and exposure times as long as the value of the mAs is the same
    • as long as the resultant mAs is the same, regardless of the mA and time combination used, the OD produced on the image will be the same
  • failure of law occurs with: extremely short exposures and extremely long exposures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When do we use the reciprocity law?

A
  • motion
  • focal spot size
  • breathing technique
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

MAs and density

A
  • for us to notice a visible change in radiographic density
    • mAs needs to be changed by at least 25-30%
  • what if the mAs is changed by 10%?
    • the change will not be visible to us
  • the general rule of thumb for mAs changes is to make adjustments in doubles or halves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when mAs is decreased?

A

Radiographic density is decreased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens when mAs is increased?

A

Radiographic density is increased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

True or false: mAs controls density; directly proportional

A

TRUE!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What role does kVp play in optical density?

A
  • affects the intensity of the beam
  • controls energy (strength) with which the electrons hit the target (anode)
  • major player in quality (some effect on x-ray quantity)
  • primary controller of x-ray beam quality and controls RADIOGRAPHIC CONTRAST
  • what is contrast? Shades of grey on the image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Contrast

A
  • function: to make anatomy more visible
  • the difference in OD between the adjacent structures, or the variation of OD on an image
  • without it, would not be able to discern structural borders
  • is a result of the x-ray beam being attenuated differently as it passes through the tissues of the body
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Kvp and density

A
  • has an effect on density because it ALTERS PENETRABILITY OF THE BEAM (this also affects the amount of radiation that reaches the IR)
  • if the kVp is decreased, less radiation reaches the IR, resulting in: decreased OD (image will be lighter)
  • if the kVp is increased, more radiation reaches the IR, resulting in: increased OD
18
Q

15% rule

A
  • increasing the kVp by 15% will have the equivalent effect on radiographic density, as doubling the mAs
  • this rule can be applied for maintaining or adjusting density
19
Q

KVp vs mAs

A
  • so if both affect radiographic density, how do I decide what to adjust?
  • mAs THE SIMPLEST ADJUSTMENT TO MAKE, as it has a direct relationship with density
  • when do we adjust kVp?
  • when we want to change the contrast of the image
  • when we want to control motion (as kVp is increased, mAs is decreased, meaning shorter exposure times can be achieved)
20
Q

The density of a radiographic image can be defined as?

A

-the amount of overall blackness produced on the image after processing

21
Q

What type of property is density?

A
  • geometric

- photographic

22
Q

What range of OD can be detected by human vision?

A

-0.25-2.50 OD

23
Q

What are prime factors?

A
  • kVp
  • exposure time
  • mA
  • SID
24
Q

If you had to choose between an image with too much or too little density you would choose?

A
  • an image with too much density
25
Q

How is visibility achieved?

A

-with the balance of radiographic density and radiographic contrast

26
Q

What type of relationship does mA and time have with radiographic density?

A

-directly proportional

27
Q

If all other factors were left unchanged, and the exposure time was decreased from 0.1 sec to 0.05s, how will the radiographic density on the image be affected?

A

-the density has been halved

28
Q

KVp primarily controls

A

Contrast

29
Q

True or false: The number of electrons in the thermionic emission cloud is controlled by kVp

A

FALSE

30
Q

X-rays with more penetrating power have a ____ wavelength than weaker x-rays

A

Shorter!

31
Q

When kVp is increased

A
  • the # of x-rays transmitted is increased

- compton scattering is increased

32
Q

What is the relationship between dose and distance?

A
  • if we increase one we have to decrease the other

- inversely proportional

33
Q

Does focal spot size influence the density of an image?

A

No!

34
Q

What is another name for the density maintenance formula?

A

Direct square law

35
Q

What is the relationship between distance and density maintenance?

A

⬆️ distance, ⬇️ density

⬇️ SID (distance), ⬆️ density

36
Q

How can OID affect radiographic density?

A

⬆️ OID,results in ⬇️radiograophic density

37
Q

A ______pathology will increase the radiopacity of tissue

A

Constructive!

38
Q

A _____ pathology will increase the radiolucency of tissue

A

Destructive

39
Q

When you ____ the kVp, you ____ the number of interactions

A

-increase, decrease

40
Q

Why is there a difference in intensity of the x-ray beam when the SID is changed? How does this affect radiographic density?

A

-with increased SID, get a change in intensity. Same # of photons cover a larger area, so they become less intense

APPH 226 (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions