Figure 4. Interactive segmentation of the prostate central gland (PCG) in 3D with a spherical template.

The leftmost images show the original scan in axial (top), coronal (middle) and sagittal (bottom) views. The second image from the left presents the segmentation outcome (red) for a user-defined seed point (blue) that has been placed inside the prostate (note: the seed point has been placed in the axial view, but it is also displayed in the coronal and sagittal views). For comparison, the green masks display the outcome of a manual slice-by-slice segmentation from an expert. However, as the initial seed point is placed close to the right border of the prostate, the algorithm missed the contours of the PCG on the left (axial and coronal views). Though, the interactive real-time behavior of the approach makes a repositioning easy, and thus it is also easy finding a good segmentation outcome for the axial, coronal and sagittal views (third image from the left). In the rightmost image, the segmentation result has been further refined with an additional seed that has been placed in the lower right within the sagittal view.