Contrast, Detail, Distortion
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| An image with few densities but many differences between them has ___ Contrast? | High Contrast (Short Scale)
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| An image with many Blacks and Whites, with few grays? | High Contrast
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| An image with many densities but little difference between them has ___ Contrast? | Low Contrast (Long Scale)
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| An image with many shades of Gray? | Low Contrast
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| #1 Controlling Factor of Contrast? | kVp
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| How is Digital Contrast controlled? | kVp, but altered by Computer
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| ↑ kVp = __ Transmission | ↑ Transmission
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| ↑ kVp = __ Compton Interactions | ↑ Scatter
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| ↑ kVp = __ Photoelectric Effect | ↓ Absorption
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| ↑ kVp = __ Fog | ↑ Fog
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| ↑ kVp = __ Contrast | ↑ kvp = ↓ Contrast
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| Low kVp has more of what type of Interactions? | Low kVp = ↑ Photoelectric Absorption
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| Contrast Influencing Factors | Grids, Collimation, OID, Anatomic Part, Filtration
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| ↑ kVp = __ Scatter | ↑ kVp = ↑ Scatter
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| ↑ Grid Ratio = __ Scatter = __ Contrast | ↑ Grid = ↓ Scatter = ↑ Contrast
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| ↑ Collimation = __ Tissue Exposure = __ Contrast | ↑ Collimation = ↓ Tissue Exposure = ↑ Contrast
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| ↑ OID = __ Scatter = __ Contrast | ↑ OID = ↓ Scatter = ↑ Contrast
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| Do we adjust OID for contrast? Why or why not? | No, ↑ Contrast but also ↑ Distortion
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| How does increasing OID increase Contrast? | "air gap" of OID allows Scatter to Miss the IR (↓ Scatter = ↑ Contrast)
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| ↑ Tissue Thickness = __ Scatter = __ Contrast | ↑ Tissue = ↑ Scatter = ↓ Contrast
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| ↑ Tube Filtration = __ Scatter = __ Contrast | ↑ Filtration = ↑ Scatter = ↓ Contrast
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| How does Tube Filtration decrease Contrast? | Filtration absorbs low energy photons that increase beam intensity and in turn Scatter (↑ Scatter = ↓ Contrast)
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| Result of kvp and absorption characteristics of anatomic tissue? | Subject Contrast
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| Result of manufacturing properties and processing conditions? | Film Contrast
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| _____ changes Absorption Characteristics of tissue by ↑ or ↓ Beam ____ ? | Contrast Medium, Attenuation
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| (-/+) Contrast Agents increase beam attenuation and produce less film density? | + Contrast Agent = More Absorption/Increased Brightness
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| (-/+) Contrast Agents increase transmission? | Negative Contrast Agents (Air)
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| (+/-) Contrast Agents require increase in exposure factors? | Positive Contrast Agents (Barium)
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| Film Processing temperatures outside Normal will ↑ or ↓ Contrast? | ↓ Contrast
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| kVp changes for ages below 6? | -15% kVp
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| Minimum kVp for Premies | 50 kVp
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| Minimum kVp for Infants | 55 kVp
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| Minimum kVp for Child | 60 kVp
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| mAs adjustment for ages 0-5? | 25% (75% less)
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| mAs adjustment for ages 6-12? | 50% mAs of adult
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| What types of casts do not require technique changes? | Fiberglass
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| Dry vs Wet theory for technique adjustment with Plaster Cast? | Dry = 2x mAs
Wet = 3x mAs
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| Alternate theory for technique adjustment with Plaster Cast? | Treat cast as increase in Part Thickness
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| ____ Diseases increase absorption characteristics of part, making it more difficult to penetrate? | Additive Diseases
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| Examples of Additive Diseases | Ascites, Cirrhosis, CHF, Pleural Effusion
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| ____ Diseases decrease absorption characteristics of part, making penetration easier? | Subtractive Diseases
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| Examples of Subtractive Diseases | Bowel Obstruction, Free Air, Emphysema
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| Which type of diseases may need an increase in kVp? | Additive Diseases
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| When would you visualize soft tissue on an image? | Foreign body, Croup, Obstruction
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| Which exposure factor do you change when soft tissue needs less Density to visualize the area of interest? | ↓ mAs = ↓ Density
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| Which exposure factor do you change when soft tissue needs a change in Contrast to visualize the area of interest? | ↑ or ↓ kVp
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| Geometric Properties control ____ ? | Sharpness
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| ____ is the distinctness or sharpness of the structural lines that make up the recorded image? | Recorded Detail
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| 3 Factors of Geometric Unsharpness | OID, SID, Focal Spot Size
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| Another term for Geometric Unsharpness | Penumbra
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| Penumbra | Area of unsharpness or blurred margin
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| Focal Spot Size only affects ____ ? | Recorded Detail
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| Small focal spot size | .5-.6 mm
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| Large focal spot size | 1-1.2 mm
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| ↑ SID = __ Unsharpness = __ Recorded Detail | ↑ SID = ↓ Unsharpness = ↑ Recorded Detail
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| How does increasing SID increase Recorded Detail? | Xray photons more perpendicular to IR/Object with greater SID
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| ↑ OID = __ Unsharpness = __ Recorded Detail | ↑ OID = ↑ Unsharpness = ↓ Recorded Detail
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| Factor with #1 impact on Unsharpness? | OID
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| Optimal recorded detail when OID is ___ ? | zero
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| How do you compensate for unavoidable OID? | ↑ SID sligthly
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| Calculating Distance Formula | SID = OID + SOD
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| Geometric Unsharpness Formula | Geometric Unsharpness = (Focal Spot Size x OID)/SOD
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| Better recorded detail with (High/Low) Unsharpness value? | Lowest # is Better Detail
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| ↑ Film Speed = __ Recorded Detail = __ Unsharpness | ↑ Film Speed = ↓ Recorded Detail = ↑ Unsharpnes
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| High film speed reduces radiation required but at the expense of __ ? | Less dose but Lower Recorded Detail
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| Unsharpness caused by patient motion? | Motion Unsharpness (Blur)
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| Ways to control motion... | 1. Short exposure
2. Clear Communication
3. Immobilize
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| ____ is the imaging system's ability to distinguish btwn two adjacent structures? | Resolution
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| ____ is the smallest detail detected on the image? | Spatial Resolution
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| ____ is the imaging system's ability to distinguish btwn small objects with similar subject contrast? | Contrast Resolution
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| Resolution is expressed in what unit of measure? | Line pairs per millimeter (Lp/mm)
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| Define Line Pair | One metal line + space = Line Pair
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| ___ is the misrepresentation of size or shape? | Distortion
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| Shape Distortion where the part is misaligned? | Foreshortening
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| Shape Distortion where the CR or IR is misaligned? | Elongation
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| Another term for Size Distortion? | Magnification
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| ___ has the greatest effect on Size Distortion? | OID
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| ↑ OID = __ Size Distortion | ↑ OID = ↑ Magnification
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| Parts Closest to the IR will have more size distortion (T/F)? | False - Further Away more Distortion
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| ↑ SID = __ Size Distortion | ↑SID = ↓ Mag/Size Distortion
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| ___ indicates how much Size Distortion is on an image? | Magnification Factor
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| Magnification Factor Formula (Size) | MF = Image Size / Object Size
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| Magnification Factor Formula (Distance) | MF = SID / SOD
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| % of Magnification Formula | % Mag = {(Image Size-Object Size)/Object Size} x100
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| To calculate Image/Object Size, 1st Calculate ___ ? | Magnification Factor (MF)
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| Image/Object Size Formula | Object Size = Image Size/MF
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