Figure 3.

Example of a TRUS image (a) without and (e) with attenuation correction; the corresponding median feature (b), (f); the corresponding probability models (c), (g), where blue corresponds to those pixels most unlikely to belong to the prostate, red corresponds to those pixels most likely to belong to the prostate; and the final registration results (d), (h). Blue arrows in (d) and (h) show boundary regions which are well aligned on MRI and TRUS, while red arrows show boundary regions which are misaligned. The region highlighted by the red circle in (b) and (f) show regions where attenuation correction improved the feature contrast between the prostate and background pixels. The corresponding region on the probability models is highlighted by the black circle (c), (g). Note the image with attenuation correction (g) is better able to distinguish between pixels belonging to the prostate from the background, resulting in a more accurate registration.