Figure 13.

Comparison between the combined PCA-Wiener filtering and wavelet denoising for four different noisy projections with SNR = –5dB taken at $\theta =0,\frac{\pi }{4},\frac{\pi }{2}$, and $\frac{3\pi }{4}$. (a) Clean projection (blue) and the PCA denoising of the noisy projection (red); (b) noisy projection (blue) and its filtered version using PCA (red); (c) clean projection (blue) and the wavelet denoising of the noisy projection (red); (d) noisy projection (blue) and its filtered version using wavelets (red). The number of principal components used by the Wiener filter is 6. RMSE: 0.587 for the PCA-Wiener scheme and 0.919 for wavelets.