quantum mottle

mottle caused by the statistical fluctuation of the number of photons absorbed by the intensifying screens to form the light image on the film; faster screens produce more quantum mottle.

Any critique of radio graphic image quality must include an evaluation of quantum mottle, a fundamental limitation of the imaging process. 


Effect on Quantum Mottle:

1. Increases Quantum mottle / mottel:
1. Decrease scan time, 
2. Increase Matrix size
3. Increase Patient Thickness
2. Decrease Quantum Mottle / mottel
1. Increase pixel size
2. Increase slice thickness
3. Increase MA
3. No effect on Mottel / Mottle
1. Changing technique from 50 MA in 2sec to 100MA in 1s

Radiographic image quality characterizes the ability of an imaging system to accurately depict structures in a radiographed object. Six components affect image quality -- spatial resolution (or sharpness), contrast, density, radiographic mottle (or noise), distortion and artifacts. Of these six parameters, radiographic mottle is the most difficult to understand and relate to the imaging process. Radiographic mottle creates a grainy, blotchy, textured or snowy appearance in a radiographic image.

The final image on film is a composite of these sampling events. Increased photon absorption by the screen (a higher number of information carriers in the imaging chain) reduces quantum mottle and improves visualization of the structure.

 The component in the imaging chain with the lowest number of information carriers establishes the level of quantum mottle in the final image. This component is called the quantum sink.

Because the recording step limits the information content of the final image, this step becomes the quantum sink. The quantum sink denotes the operation in which quantum mottle has the major influence upon image resolution. The initial process of detection establishes the maximum information content that cannot be enhanced by -- and often is not preserved by -- other components in the imaging chain.