The flowchart of postimaging process of VBA.

In the first place, horizontally flipping was conducted for the SPECT data with left side operation in order to deal with all the SPECT data as that with right STA-MCA bypass surgery. After global mean normalization was performed, pre- and postoperative IMP-SPECT images were co-registered to corresponding 3D T1-weighted images. The 3D T1 images were then segmented into gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF) space using new segmentation tool and DARTEL import files were created for each patient. GM segment of coregistered SPECT (GM-SPECT) was created. Then, DARTEL template was generated with DARTEL import files. In the last place, non-linear warping of all GM images including GM-SPECT to MNI space was conducted with 2 methods as follows, with DARTEL by using flow field, or without DARTEL (a conventional method, which has been used in the previous literatures).