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PRE 1 Chapter 29
Distortion
Question | Answer |
---|---|
What is distortion? | The second of two geometric properties affecting radiograph image quality |
What is the only possible size distortion in radiography? | Magnification |
What are the two classifications of distortion? | Size or shape distortions |
True or false can distortion exist even if it can't be seen due to poor visibility? | True |
Factors that Control distortion with size or what | OID and SID |
Factors that control distortion with shape or what? | Alignment and angulation |
What are the reasons distortion would be a factor with alignment? | Central ray part and image receptor |
What are the reasons distortion would be a factor with angulation | Direction and degree |
The greater the SID ______ the magnification | greater smaller |
Distortion is directly related to what? | positioning |
True or false X-ray photons can be reflected for refracted by ordinary methods? | False, they can only diverge from their point of source |
SID | Source to image receptor distance |
OID | Object to image receptor distance |
Does reduced Magnification size distortion increase or decrease the resolution of recorded detail? | increases |
What is the magnification factor formula | M= SID ------ SOD |
what is Fidelity? | – true representation (the sharpness) of the image of the radiographed object |
Property of geometric factors: | OID SID FSS (focal spot size) Distortion |
Geometric factors: | Magnification Distortion Focal spot blur |
A longer SID __________________magnification A shorter SID_________________ magnification | decrease increases |
OID has significant impact at both | magnification and resolution (detail) |
what is MF ? | Magnification factor |
what is the formula for MF? | MF=. Image size ____________ object size |
will the image size be bigger or smaller than the object? | bigger |
What is the formula for calculating object size? | OS = image size --------------- MF |
what are the two factors that affect image magnification? | SID and SOD |
To minimize magnification Large (long) ________: use as large SID as possible | SID |
Small (short) OID: place an object as ___________as possible to the IR | close |
Define Elongation | Projects the object so it appears longer than its actual size. |
Define Foreshortening | Projects the object so that it appears shorter than its actual size. |
when does elongation occur ? | This will occur when the CR and image receptor is improperly aligned. Occurs when IR is improperly aligned |
When does foreshortening occur? | This occurs only when the part is improperly aligned (not parallel to the IR). |
What happens If object plane and IR plane is not parallel | distortion occurs |
True or false Thicker objects are less distorted than thinner object | False, they are more distorted |