Black Blood Versus Bright Blood Imaging

Abstract

The spin echo pulse sequence generates images that have intrinsic black blood contrast. This is because it uses two pulses, the 90° and 180° pulses, to produce the spin echo signal (Fig. 12.1). Both of these pulses are slice-selective but are separated by a time equal to half the echo time. The transverse magnetization of blood flowing through the slice that moves out of the slice between the two pulses is not refocused by the 180° pulse and does not contribute to the generation of a spin echo. If the flow is sufficiently rapid for all the blood receiving the 90° pulse to move out of the slice, this results in a signal void, also known as a “Black Blood” or “Dark Blood” appearance. This effect is also known as the spin washout effect, referring to the “washout” of proton spins form the image slice that would otherwise be refocused and contribute to the spin echo signal.