7. Qualities of the radiographic image Flashcards
What is the controlling factor for spatial resolution?
Acquisition pixel size (small pixels that are inside of the IR)
What is spatial resolution?
The geometrical sharpness/structural sharpness
What are the four things that spatial resolution is affected by?
- Focal spot size
- Movement
- OID
- SID
With a decrease in focal spot size, will there be an increase or a decrease in sharpness?
Increase sharpness
With an increase in focal spot size, will there be an increase or a decrease in sharpness?
Decrease sharpness
There is less sharpness with a larger focal spot size because of the increase in focal spot blur. The more focal spot blur, the less sharp or lower spatial resolution that an image has.
What is another word for focal spot blurriness?
Penumbra
With an increase in SID, will there be an increase or decrease in sharpness?
Increase sharpness
Why do we not always use a longer SID?
More wear on the machine due to higher mAs, and its not always practical
With a decrease in OID, will there be an increase or decrease in sharpness?
An increase in sharpness
What 3 things are size distortion caused by?
Increase in OID, decrease in SID, post processing
What has a more dramatic affect on size distortion/magnification? OID or SID?
OID
What is shape distortion? What are the 2 types?
“Misrepresentation” of an objects true shape
1. Foreshortening
2. Elongation
How does foreshortening happen?
When object is angled, CR remains perpendicular to the IR
How does elongation happen?
- Object is parallel to the IR, CR is angled
- CR is perp. to the object, IR is angled
How do you measure detail/spatial resolution?
Measure the detail with a lp (line pair)/mm test tool
In a lpmm test, how do you know that there is an increase in detail?
The greater the amount of line pairs that are visible in a given space, the better the detail
What will cause less anode heel effect, an increase or a decrease in SID?
An increase in SID causes LESS anode heel effect
Which side should you image thicker anatomy on, the cathode or the anode?
Cathode
