Week 9 - Radiographic Sharpness Flashcards
The accuracy of the recorded anatomical structures on a radiographic image
Radiographic sharpness
How is radiographic sharpness achieved?
Maximizing spatial resolution and minimizing distortion
Refers to the smallest object that can be detected on an image
Measured in line pairs per millimeter (lp/mm)
Spatial resolution
What factors affect spatial resolution?
SID
OID
focal spot size
Motion
What order should spatial resolution problems be approached in?
- Eliminate motion
- Reduce OID
- Reduce focal spot size
- Increase SID
Motion under direct control of the patient
Voluntary motion
Motion that is not under the conscious control of the patient
Involuntary motion
What is the best method to reduce motion seen on an image?
Reduce exposure time
What distance factors improve resolution?
Increased SID
decreased OID
What effect does focal spot size have on sharpness and resolution?
Increased focal spot size increases unsharpness and decreases resolution
How does SID affect sharpness and resolution?
Increased SID decreases unsharpness and increases resolution
P = focal spot size x OID / SOD
Penumbra (Ug) calculation
*SID = SOD + OID
Results from the radiographic misrepresentation of either the size (magnification) or shape of the anatomical part
Distortion
T/F
As SID decreases, size distortion (magnification) decreases
True
T/F
As OID increases, size distortion (magnification) increases
True
