Postoperative CBF decreased areas displayed in transverse sections.

Decreased ratio (%) at the area of significantly decreased CBF on postoperative SPECT compared with preoperative SPECT was shown in contralateral hemisphere to the STA-MCA bypass site by SPM8 with DARTEL (a). Since global mean normalization to the value of 100 was conducted for all SPECT data, ipsilateral CBF increase in wide area is likely to cause pseudo CBF decrease in the contralateral site. The conventional analysis showed significant decreased CBF areas on the surface of the ipsilateral hemisphere of bypass site (b). No decreased CBF areas were detected in the contralateral hemisphere, which suggests that decreased CBF areas in the operated hemisphere compensate CBF increase from the viewpoint of global mean normalization method.