Dear scientists, I am trying to merge 189 skeleton images resulting from TBSS processes into one 4D file in order to run randomise. Within seconds after typing "fslmerge -t all_skeletons 1_B* 2_B*" I get one of two kinds of error messages: Image Exception : #99 :: Out of memory terminate called after throwing an instance of 'RBD_COMMON::BaseException' Aborted OR terminate called after throwing an instance of 'std::bad_alloc' what(): St9bad_alloc Aborted We are running FSL 4.1.1 on a 64bitOS machine with 8G of RAM, so even though it is a large data set we would be surprised if it was a working memory problem. But if so, does anyone have suggestions on how to reduce the size of the images or run randomise without having to merge images? And if it is not a memory problem, what can it be? Best wishes, Emma