Baseline TCD measurement of velocity from the MCA before transfusion in a young child with SCD (panel A; TCD velocity = 220 cm/sec). Panel B depicts repeat TCD of the MCA 1 year after regular red-cell transfusions (TCD velocity = 172 cm/sec). Panel C presents a schematic showing the TCD probe and the insonation of stenotic right MCA. Professional illustration by Kenneth Probst.