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28 Cards in this Set
- Front
- Back
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What is subject contrast dependent on?
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1. The amount of irradiated part (thickness, mass of body part)
2. The type of irradiated part. (Bone, muscle, fat, etc.) |
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High Contrast, short scale images are mainly produced by what?
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A low kVp
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What does window width on post-processing control?
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The range of contrast
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What does window level on post-processing control?
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The level of density
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What is the visible differences between any two selected areas of density levels within the radiographic film called?
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Contrast
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What two factors allow detail to be visualized on an image?
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Density and contrast
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When grids absorb scatter, what type of contrast does the image result in?
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High contrast image.
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What does greater tube filtration do?
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Absorbs low energy photons.
*This leaves the high energy photons to leave the tuber as the incident ray. |
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How do each act in regards to contrast?
1. Scatter 2. Grid 3. Collimation 4. Increased OID 5. Film |
1. Scatter decreases contrast (resulting in a low contrast, long scale image)
2. Grids increase contrast (resulting in a high contrast, short scale image) 3. If collimating down it will increase contrast (since collimating down reduces the amount of scatter that will be produced after hitting an object) 4. Increased OID will increase the contrast on an image. (This is due to the scatter not hitting the IR) 5. If the developer time is too long or the temperature is too high, the image will be of low contrast. |
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To maintain density when using a grid, what must be increased?
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mAs
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What tissue type has the lowest water content and atomic number?
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Fat tissue
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True or False
Water is an efficient producer of scatter. |
True
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What is the effective atomic number for bone?
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13.8
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What is the effective atomic number for muscle?
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7.4
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What is the effective atomic number for water/fluid?
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7.4
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What is the effective atomic number for fat tissue?
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6.3
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What is the primary x-ray absorber in bone tissue?
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Calcium
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What tissue type has the highest water content?
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Muscle
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Scale of contrast
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The number of densities or number of shades of gray
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What produces the total image contrast?
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Subject contrast and film
*Both the anatomical structures and the IR |
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How can you manipulate contrast?
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Adjusting the kvp (for film)
or Adjusting window width (digital imaging) |
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What type of image does a high kvp produce?
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A low contrast, long scale image.
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What is the range of kvp for typical contrast?
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60-90 kvp
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X-rays of thicker body parts require what technique adjustment?
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Increase kvp
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What do thicker body parts create?
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Create more interactions, thus creating more scatter. (More comptens)
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Subject Contrast
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The range of differences in intensity of x-ray beam after attenuation by subject/body part.
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Film Contrast
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The inherent ability of a radiographic film to record a range of densities.
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What three things need to be considered when dealing with subject contrast?
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1. Tissue thickness
2. Tissue density 3. Atomic number of tissue |
