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Radiology Principles Class > Unit 2 Quality Factors I: IR Exposure > Flashcards

Unit 2 Quality Factors I: IR Exposure Flashcards

1
Q

Radiographic Quality Factors

A
  1. Exposure to the Image Receptor
  2. Subject/Image Contrast
  3. Details
  4. Distortion
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2
Q

Density

A

The degree of blackening on an x-ray film

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3
Q

IR Exposure

A

Total signal received by the IR

S number VS EI number
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4
Q

Brightness

A

-A monitor control function that determines the overall appearance of an image.

-NOT related to exposure to IR

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5
Q

Window Level

A

post-processing function that produces changes in overall brightness/gray level

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6
Q

Sensitivity Number (S#) is ____________ proportional to exposure

A

Inversely

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7
Q

Exposure Index (EI) is ____________ proportional to exposure

A

Directly

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8
Q

Log Median Exposure (LgM) is ____________ proportional to exposure

A

Directly

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9
Q

Deviation Index

A

Indicator that compares the actual exposure received with the target exposure

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10
Q

Controlling factor for IR Exposure

A

-mAs
• mAs controls current to Tube filament
• Number of electrons boiled off filament
• Number of x-ray photons in beam (Beam Intensity)

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11
Q

Influencing Factors for IR Exposure

A

kVp, SID, OID, Grid use, Patient factors, Beam restriction, Screen speed

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12
Q

How does kVp affect the x-ray beam?

A
  1. Influences the number of X-ray Photons in the beam (Intensity)
  2. Controls the energy of the x-ray beam (Quality)
  3. Alters the ratio of Photoelectric to Compton interactions
    -Increase in kVp = Reduction in PE = Proportional Increase in Scatter
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13
Q

Low kVp means

A

• More absorption
• Less transmission
• Less scatter

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14
Q

High kVp means

A

• Less absorption
• More transmission
• More scatter

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15
Q

Kilovoltage Peak (kVp): 15% Rule

A

A 15% increase in kVp will double the exposure to the IR.
A 15% decrease in kVp will cut the exposure in half.

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16
Q

When might a technologist use the 15% Rule in clinical practice?

A
  1. Pregnancy (15% increase)
  2. Reduce Exposure Time
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17
Q

What is the Exposure Maintenance Formula used for?

A

To maintain IR exposure when the mAs is changed

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18
Q

Increase in SID is a ___________ in mAs

A

Decrease

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19
Q

Directs Square Law Formula (Exposure Maintenance)

A

mAs 1 D1 (squared)
——— = ——————
mAs 2 D2 (squared)

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20
Q

mAs and exposure have a ________ equation

A

Linear

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21
Q

How does OID affect IR exposure?

A

-Increased OID decreases the amount of scatter/secondary radiation that reaches the IR
-Increased OID decreases the exposure to the IR

22
Q

Small OID = __________ exposure to IR

A

Increased

23
Q

Large OID = __________ exposure to IR

A

Decreased

24
Q

Beam Restriction (Collimation)

A

• Decrease in overall Number of Photons interacting with the IR
• Decrease in Exposure to the IR

25
Q

Screen Speed

A

• CR vs. DR: DR is more sensitive than CR
• Same mAs produces higher exposure on DR compared to CR

26
Q

Grid Use

A

• Grids absorb scatter and secondary radiation before it reaches the IR
• Grids reduce overall exposure to the IR

27
Q

Define Focal Spot Blooming
What effect does it have on IR exposure?

A

-On target, but not on the focal track
-Negligible(small/unimportant) effect on IR Exposure

28
Q

Anode Heel Effect

A

-IR Exposure is greater at the cathode side of the tube
-More pronounced at LARGE field size (wide Collimation) and SHORT SID

29
Q

Histogram

A

A graphic representation of the grayscale of an image. The X axis is the different shades of gray, and the Y axis represents the number of pixels of that particular color.

30
Q

Define Rescaling

A

Computers way to correct brightness for under/over exposure (computer attempt to bring a radiographic image into the expected level of brightness)

31
Q

How does Rescaling affect total IR exposure?

A

No affect

32
Q

Does Window Level brightness change the IR exposure?

A

No

33
Q

Insufficient Exposure causes

A

-Quantum Noise
-Quantum Mottle

34
Q

What are Quantum Noise and Quantum Mottle

A

-Quantum Noise: Lack of sufficient incoming data for processing
-Quantum Mottle: Blotchy/grainy image artifact

35
Q

Excessive Exposure

A

Excessive mAs will result in Overexposure to the patient and the IR

36
Q

How should a Radiographer ensure there is no quantum noise on the image?

A

increase the mAs of the x-ray beam so that the number of incoming signals/x-ray photons is also increased

37
Q

Increase in SID means a __________ in IR exposure

A

Decrease

38
Q

The difference between adjacent IR exposure levels.

A

Image contrast

39
Q

Amount of x-ray signal received by the Image receptor

A

Image receptor exposure

40
Q

A graphic representation of the grayscale of an image. The X axis is the different shades of gray, and the Y axis represents the number of pixels of that particular color.

A

Histogram

41
Q

The digital processing that produces changes in the range of brightness.

A

Window width

42
Q

A monitor control function that can change the lightness and darkness of the image on a display monitor, but is not related to IR exposure.

A

Brightness

43
Q

Image manipulation parameter that changes image brightness on the display monitor, usually through the use of a mouse

A

Window level

44
Q

The ability of a system to differentiate on the image objects with similar densities

A

Low contrast resolution

45
Q

Technique by which diagrams of the body on the console guide the technologist in selection of a desired kVp and mAs.

A

Anatomically Programmed Radiography (APR)

46
Q

Alternative to using a radiographic grid in which the anatomical area of interest is placed away from the IR so that scatter and secondary radiation might be deflected away from the IR and/or absorbed in the air gap.

A

Air gap technique

47
Q

The intensity of radiation is inversely proportional to the square of the distance from the source

A

Inverse Square Law (ISL)

48
Q

Measures the accuracy of an image compared to the original object on a scale of 0-1. It measures the percentage of the object contrast that is recorded.

A

Modulation Transfer Function (MTF)

49
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

50
Q

Describes the total amount of signal recieved by the IR

A

Exposure

51
Q

A numeric representation of the quantity of exposure received by a digital image receptor. It is used by Carestream and is directly proportional to IR exposure.

A

Exposure Index (EI)

52
Q

Controlling factor for subject contrast

A

kVp

Radiology Principles Class (10 decks)

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