Figure 18

Black blood contrast from spin echo pulse sequences. Black blood appearance using spin echo pulse sequences is caused by the motion of blood through the image slice between the 90° and 180° pulses. The 90° pulse causes resonance in all the tissue within the slice, however a spin echo signal is only produced when the same tissue and blood also receive the 180° refocusing pulse. Blood that moves out of the slice during the time between the 90° and 180° pulses doe not produce a spin echo, resulting in a signal void as seen in the major vessels of the black blood spin echo image example.