In "Denoising MRI Using Spectral Subtraction"
Erturk, Mehmet Ali, Paul A. Bottomley, and A-MM El-Sharkawy. "Denoising MRI using spectral subtraction." Biomedical Engineering, IEEE Transactions on 60.6 (2013): 1556-1562.
The autour said that "the PSD of the AGN is constant", Really?
I want to simulate this issue by Matlab, Firstly, I generate a 2-D matrix, then I take the first row for example, compute the 1-D FFT of the first row, finally compute the PSD of first row, and plot the orignal and PSD of the first row.
- x = 20.*randn(256,256);
figure, plot(x(1,1:256))
title('Guass Noisy signal');
x1 = x(1,1:256);
F = fft(x1,256);
psd = F.*conj(F)/256;
freq = 1/256*(1:256);
figure,plot(freq,psd)
hold on, title('Power spectral density'),xlabel('Frequency(Hz)')
But I don't find the PSD is a constant, Why, I am very confused.
I also want to konw how to compute the PSD of noise in a image
Dear Duan Caohui, Because the PSD of the AGN is constant, we can subtract the root-mean-square noise power from the PSD of the acquired signal to get an estimate of |Sr (f)|2. This reduces the noise bias on the acquired signal
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