Image display apparatus, method and program

[0065]Further, as illustrated in FIG. 3B, the candidate region determination means 14 extracts an overlapped region between the set region and the observation target (S05). When an overlapped region is present (S06 is Y), the candidate region determination means 14 determines, as a rotation center candidate region, at least a part of the overlapped region (S07). In the present invention, a segment that is an overlapped region between straight line S1 and the human body 5 is determined as rotation center candidate region CR1. When an overlapped region between the set region and the observation target is not present (S06 is N), parallel movement of the display position is waited for (S09).

[0066]The rotation center determination means 15 determines a center of rotation in the determined rotation center candidate region CR1 or in the vicinity thereof, as illustrated in FIG. 3B. In the first embodiment of the present invention, the rotation center determination means 15 determines, as ce...

[0086]Further, when an overlapped region is present (S23 is Y), and there are plural overlapped regions (S24 is Y), the candidate region determination means 14 calculates sizes of the overlapped regions OR2A, OR2B with respect to the overlapped regions OR2A, OR2B, respectively (S25). In the present invention, the candidate region determination means 14 calculates the maximum length in the projection direction, as the size of an overlapped region. The maximum length in the projection direction of the overlapped region OR2A is calculated by calculating a distance of the overlapped region in the projection direction from each voxel constituting boundary surface OR2Aa of the observation target on the viewpoint side of the projection image, and by calculating the maximum one of the calculated distances in the projection direction from the respective voxels.

[0087]Next, the candidate region determination means 14 compares the calculated maximum length in the projection direction of the ove...