What type of signal does stationary blood produce in a SE MRA?

In a Spin Echo Magnetic Resonance Angiography (SE MRA) sequence, stationary blood produces a strong echo signal primarily due to the principles of T1 and T2 relaxation times, and the mechanisms of flow and saturation effects. When blood is stationary, it remains within the same magnetic environment during the time it takes for the pulse sequence to complete. This allows the spins of the protons within the blood to remain in phase, resulting in the production of a strong echo upon signal acquisition.

In MRA, it is particularly important to highlight that stationary fluids generally experience less signal loss due to movement-related phenomena, such as through-flow related dephasing. This results in clear and pronounced echo signals for stationary structures—such as blood that is not in motion—contrasting other types of echo signals that can be generated under different circumstances, including flowing blood where complex flow phenomena may reduce signal strength or result in different imaging characteristics.