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PRE 1 Chapter 29

Distortion

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
Created by: knt5411