CBF and OEF maps from a child with SCA. This 7-year-old boy underwent an MRI scan before CTT initiation and again before and after an exchange transfusion (only CTT values included in cohort-level analyses). The whole-brain CBF was highest at his first scan (138 mL/100 g per minute). After 17 months of CTT, his pretransfusion CBF was lower than his initial scan (118 mL/100 g per minute; 14% drop) and further decreased after transfusion to 100 mL/100 g per minute (15% drop). The whole-brain OEF was highest at the first scan (46.1%), with dramatic reduction in OEF measured pretransfusion (29.4%; 38% drop) and only modest reduction posttransfusion (28.6%; 3% drop). His OEF maps were also notable for regionally elevated OEF in the deep white matter (blue arrows), which was most prominent before CTT initiation. This peak OEF was still detectable on the pretransfusion scan, although less prominent. After transfusion, the peak OEF region was absent, with restoration of homogeneous OEF across the brain.