Assessment And Control Of Radiographic Image Quality Flashcards
Unsharpness
Lack of fine detail on a processed radiograph
Causes of radiographic unsharpness
- Geometric factors
- Photographic factors
- Movement factors
Geometric unsharpness
Arises due to:
1. Focal spot size
2. Object film distance
3. Source to object distance minimizes penumbra
Photographic unsharpness
Arises due to limitations in the film screen system
* Poor film screen contact
Motion unsharpness
Arises due to relative movement during the exposure
Amount of motion unsharpness depends on
- Speed of movement
- Direction of movement
- Duration of exposure
- Film movement
- Machine movement
Total unsharpness
Combined effect of geometric, photographic and motion factors
Over and under penetrated radiographs are caused by
- grid cut off
- Equipment failure
- Processing errors
- Use of non standard FFD
- Poor choice of exposures
Image fogging can be caused by
- scattered radiation
- Poor safelighting
- White light leakage into the cassette exposing the film
- Chemical fog resulting from developer
Image artifacts caused by
- screen marks
- Pressure marks
- Static marks
- Finger marks
- Surface damage
- Radiographic artefacts
The distorted image caused by
- foreshortening ( object plane not perpendicular to x-ray beam)
- Elongation ( film not perpendicular to x-ray beam)
- Differential magnification
Double images
Radiograph produced with 2 images superimposed on each other
Factors leading to double images
- Using a previously used cassette
- Producing double images during the time of exposure
Graininess
- Intrusive grain appearance in radiographs
Caused by - Structure mottle- excessive processing temp making silve grains clamp together to form particles
- Quantum mottle- use of high speed rare earth intensifying screens with low mas
Causes of quantum mottle
- Random x-ray exposure
- Statistical fractuations in number of quanta
