End of chapter 11 (Fosbinder)
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| What is recorded detail? | Distinctness or unsharpness
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| What is umbra? | Pure, true, complete shadow.
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| An increase in detail causes a ________ in unsharpness (blur) | Decrease
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| What is blur? | Also referred to as penumbra, edge gradient and geometric unsharpness, partial shadow of the edge of an object.
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| What is the controlling factor for recorded detail? | Focal spot size
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| What are the influencing factors of recorded detail. | SID
OID
Film Screen Speed
Patient Motion
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| How does focal spot size effect recorded detail? | Inversely.
Increased focal spot size = decreased recorded detail
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| How is focal spot size and blue related? | Directly.
Increase focal spot size, decrease in recorded detail = increase of blur
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| What is the size range of a small focal spot? | .5mm-.6mm
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| What is the size range of a large focal spot? | 1.0mm-1.2mm
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| How does SID influence recorded detail? | Increased SID, decrease in blur = increased recorded detail
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| How does OID influence recorded detail? | Increased OID, increased blur = decrease in recorded detail
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| Blur Formula? | Focal Spot Size x OID = _____mm
SOD
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| How do you fine SOD? | SID-OID=SOD
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| When there is an excessive amount of OID the amount of blur can be decreased by? | Increasing SID
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| What is image receptor blur? | Variations in construction and composition of film screen systems affect photographic properties and geometric properties
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| How does film screen speed effect recorded detail? | High speed screens required less X-rays, decrease patient dose, increase blur = decrease in recorded detail.
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| What is quantum mottle? | Blotchy appearance of a radiograph that has been exposed by means of a fast intensifying screen.
Looks like salt and pepper
****faster screen = more artificial light***
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| What tool do you use to test film screen contact? | Wire mesh
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| What is resolution? | Ability of the image system to resolve or distinguish between two adjacent structures.
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| What is spatial resolution? | Minimum distance between two objects at which they can be recognized as two separate objects. (Physical distance)
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| What is contrast resolution? | The ability of the imaging system to distinguish between small objects having similar subject contrast. (Depends on your system)
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| What is a line pair? | A line and a space
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| How many line pairs can the human eye discern? | 5Lp/mm
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| 2 types of blur | 1. Voluntary (within patient control)
2. Involuntary (outside patient control)
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| What 3 things can you do to limit patient movement? | 1. Communication
2. Immobilization
3. Short exposure time
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| What is distortion? | Radiographic misrepresentation of size or shale compared to the actual size and shape of the structure.
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| What factors influence distortion? | SID
OID
Central ray angle
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| What is spatial distortion? | The intentional distortion used to avoid superimposition
Ex: inlet/outlet pelvis, lateral knee, sacrum/coccyx
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| Define magnification | The equal enlargement (both length and width) of the recorded image as compared to the actual size to the structure
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| How is magnification and OID related? | Directly.
Increase OID = increase magnification
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| How is magnification and SID related? | Inversely.
Decrease magnification = increase SID
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| Formula to calculate image and object size. | Image size = SID
Object size SOD
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| What is magnification factor? | Indicates how much he size distortion is demonstrated on the image
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| What is the magnification factor formula? | SID Or Image
SOD Object
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| Formula to calculate object size using magnification factor. | Object = Image
Magnification factor
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| Formula to calculate percent of magnification | Image - object x 100
Object
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| 2 types of shape distortion | 1. Elongation
2. Foreshortening
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| Elongation happens when... | The tube is angled
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| Foreshortening happens when... | When the part is angled
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| When angling the tube you must decrease your SID by... | 1inch for every 5 degrees
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