Noise filtering
X-ray medical imaging. 2D image processing
Article REF: MED203 V1
Noise filtering
X-ray medical imaging. 2D image processing

Author : Thierry LEMOINE

Publication date: June 10, 2015 | Lire en français

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6. Noise filtering

All the above applies to both the useful signal and the noise, but it is the search for improved signal perception that has been the main motivation. Noise is also filtered, but its perception can nonetheless be enhanced, as mentioned above.

6.1 Anscombe transform

Let's focus on the case of an image whose noise is of quantum origin (electronic noise is neglected, which is legitimate most of the time): if N represents the signal per pixel (in number of primary quanta absorbed), the average signal, then √ represents the noise level and (consequently) the signal-to-noise ratio. The Anscombe transform involves substituting its square root (N → 2√(N + 3/8)) for the signal. Francis Anscombe showed in 1948

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