Oops...OK, I tried 3dhistog and it also seems to identify 18 ROIS....?
[juliefrostb:SCOP_BLOCK/CONTROLS_scop.blk/RESULTS] Julie% 3dhistog NEW_ROI_MASK_July3107+tlrc.HEAD
#Magnitude Freq Cum_Freq
0.000000 4484157 4484157
1.000000 1149 4485306
2.000000 1147 4486453
3.000000 6424 4492877
4.000000 6701 4499578
5.000000 14698 4514276
6.000000 14866 4529142
7.000000 1112 4530254
8.000000 986 4531240
9.000000 30273 4561513
10.000000 30592 4592105
11.000000 2174 4594279
12.000000 2197 4596476
13.000000 4773 4601249
14.000000 4274 4605523
15.000000 16731 4622254
16.000000 16611 4638865
17.000000 2268 4641133
18.000000 2268 4643401