SNR estimation of a single image

Posted by Winnok H. De Vos on Jul 11, 2007; 12:34pm
URL: http://imagej.273.s1.nabble.com/SNR-estimation-of-a-single-image-tp3698855.html

Dear all

In order to test robustness of an image processing algorithm, I want to
estimate the signal to noise ratio of my images. It concerns a very rough
approximation since I merely want to take Poisson noise into account, hence
making abstraction of detector noise, dark noise etc. (at least for now)
I want to be able to compare with synthetic images (originally without
noise) in which I gradually raise the Poisson noise. When considering the
original noiseless image as O, the current image as C and i the voxel number
I approximate the signal-noise ratio in these synthetic images using
(Manders et al., 1993):

SNR=20log(sqrt(sum(Ci)²/sum(Ci-Oi)²))

Since there is no original image for real images, this formula doesn't
apply. I have found several definitions of defining SNR, but none of them
seem to give values that correspond with what I retrieve after using the
first formula on the synthetic images. The most common way seems to be using
the standard deviation of a region with 'no' signal to estimate noise and
using the dynamic range or maximum of the signal. But this seems rather
arbitrary and dependent on the chosen region. Is there a way of
approximating the noise and SNR of a single image - so not by recording the
image several times - without having to select a signal-free ROI and what
would be the most reliable definition?
Many thanks in advance.

Kind regards,


winnok




______
ir. Winnok De Vos
Research Assistant

dep. Molecular Biotechnology
Faculty of Bioscience Engineering
Ghent University
Coupure links 653
9000 Ghent
Belgium

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www.molecularbiotechnology.ugent.be