Changes in cerebral blood flow before and after blood transfusions and haplo-BMT with thiotepa and PTCy in a patient with SCD. Quantitative cerebral blood flow (CBF) maps show that CBF increases to maintain sufficient oxygen and glucose supply in people with anemia. The healthy image depicts the brain of an African American woman (aged 32 years, HbAA) with a hemoglobin concentration of 12.6  g/dL and a cortical CBF (assessed by arterial spin labeling magnetic resonance imaging) of 40 to 60  mL per 100  g per min. The SCD images are from an African American man with SCD (aged 34 years, hemoglobin SS); pretransfusion, his CBF was elevated to offset reduced oxygen content. Following blood transfusion, which increased the total hemoglobin and reduced the proportion of hemoglobin S, the CBF decreased but remained elevated relative to that in nonanemic individuals. After haploidentical BMT (haplo-BMT) with thiotepa and PTCy, both anemia and HbS were eliminated, and CBF approached that of a healthy control (HbAA). CBF heterogeneity was still present in this patient due to underlying moyamoya vasculopathy. Hb, hemoglobin concentration. (From Lancet Neurol. 2021 May;20(5):398-408.)