Figure 8: Results of segmentation of the arterial lumen and plaque surface in the presence of artificially added Gaussian noise of varying strengths. Each row gives the probability map (right) and segmentation result (middle) for given noise and threshold settings (left). sqrt(Noise level) × 255 gives the approximate standard deviation of the Gaussian noise added in grey levels (e.g., noise level = 0.02 corresponds to a standard deviation of approximately 36.1 grey levels, cf., maximum range of 255 grey levels).