問題一覧
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contribute to overall radiographic quality
Geometric Qualities
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2 Geometric Qualities ______ - distinct representation of objects true borders, edges ______ - misinterpretation of true size or shape of an object
- Recorded detail - Distortion
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degree of difference or ratio between
Radiographic Contrast
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no differences in density
Homogenous Object
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object with different absorption characteristics produces an image with varying densities
Differential Absorption
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Evaluating radiographic quality in contrast is ______
Subjective
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- controlling factor of contrast - difference in potential applied to x-ray tube - directly proportional to average x-ray spectrum or x-ray quality - plays role in adjusting amount of penetration in an acquisition - energy of x-rays (higher penetrability)
kVp
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examples of: low subject contrast > high kVp > long scale contrast
Air/Fluid
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examples of: high subject contrast > low kVp > short scale contrast >
Bone
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properties that comprise visibility of detail. Appear Gray
Contrast
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visible to human eye
Visibility of detail
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difference between adjacent densities
Image Contrast
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number of useful visible densities or shades of gray
Scale of Contrast
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described by scale of contrast
Radiographic Images
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conversion factor between exposure to ionizing radiation
Technique Conversion Factors
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what to do To maintain exposure when increasing kVp:
- increase kVp by 15% - reduce mAs to half
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what to do To maintain exposure when decreasing kVp:
- decrease kVp 15% - multiply mAs by 2
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tissues that makeup the human body that attenuate the beam of radiation
Patient Factors
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- device used to improve contrast of radiographic image - absorbs scattered radiation before it reaches image receptor - employed when body part thickness is greater than 10cm or kVp is 60 - used for obese patients
Grid
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3 X-ray Interaction through the body PBI
- Pass through the body - Be absorbed by body - Interact & change direction
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interaction that produces scatter radiation
Compton Interaction
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3 Amount of Scatter Radiation increase with: ILD
- Increased patient thickness - Larger field sizes - Decrease in atomic number of tissue
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account for lead content of grid
Grid Conversion Factor aka Bucky Grid
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- placed in cassette close contact with film, function is to reinforce the action of x-rays - amplify the incoming x-ray beam - introduced by Thomas Edison in 1896
Intensifying Screens
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2 TYPES OF INTENSIFYING SCREENS
- Calcium Tungstate: blue light - Rare Earth: green light
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percent of x-rays that reach cassette
33%
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invisible product of x-ray film
Latent Image
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4 PARTS OF INTENSIFYING SCREEN BRPP
- Base Layer - Reflective Layer - Phosphor Layer - Protective Coat
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layer of IS that is polyester or cardboard or metal
Base Layer
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layer of IS that is made up of magnesium oxide or titanium dioxide
Reflective Layer
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active layer of IS , absorbs energy
Phosphor Layer
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protects phosphor layer from abrasions
Protective Coat
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3 Types of Beam Restrictors ACC
- Aperture Diaphragms - Cones/Cylinder - Collimators
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beam restrictor that is a flat sheet of metal
Aperture diaphragms
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circular aperture diaphragms
Cones/Cylinder
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commonly employed beam restriction
Collimators
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purpose is to deposit enough metallic silver at latent image sites
Film Processing
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4 Processing Steps
> Developing - silver is deposited at latent image > Fixing - clearing agent > Washing - water to remove developer solutions > Drying - hot air
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critical part of archiving process
Storage
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radiograph time or expiry
5-7 years
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- visibility of anatomy and sign of pathology - affected by photographic and geometric quality
Image Quality