Interpretation, Image quality and faults Flashcards
1
Q
What determines the projections required?
A
The area of interest
2
Q
What are the principles of radiographic positioning?
A
- Minimises geometric distortion
- Magnification
- Orthogonal views
- Centering
3
Q
What is geometric distortion?
A
Beam diverges as it leaves the generator
4
Q
What is centering?
A
- Centre to the anatomical area of interest using bony landmarks
- Allows close collimation to avoid scatter
5
Q
What is the purpose of accurate collimation?
A
- Acurate collimation reduces the radiation dose
- Reduces Scatter
- Improves image quality
6
Q
What is quantum mottle?
A
Occurs with under exposure
Creates a grainy appearance
7
Q
What does scatter cause on the image?
A
random blackening of the image
8
Q
How would you reduce scatter?
A
- Using grids
- Appropriate collimation
9
Q
Name three Post-Exposure faults
A
- Partial erasure of image and fading
- White specks and lines
- Moire artefact
10
Q
Name three workstation faults
A
- Incorrect algorithm
- Incorrect cropping
- Uberschwinger artefact
11
Q
What is border effacement?
A
also known as the sillhouette sign
Two structures of the same opacity are in contact
cannot distinguish the margins of the two structures
12
Q
What are the pathological causes of border effacement?
A
- Right middle lobe pneumonia
- Pleural effusion
- Peritoneal effusion
