Which sequence is particularly useful for measuring slow flow or stagnant blood?

The choice of Phase Contrast Magnetic Resonance Angiography (PC MRA) is particularly advantageous for measuring slow flow or stagnant blood due to its unique ability to quantify blood flow based on the phase shift of moving protons. PC MRA utilizes a specific encoding technique that differentiates between stationary and moving spins, making it especially effective in assessing areas where blood flow may be minimal or absent, such as in vascular malformations, slow-flow venous structures, or regions of stasis.

In PC MRA, the direction and velocity of blood flow can be visualized and quantified, allowing for detailed examination of flows even at sluggish velocities. The sequence incorporates dedicated gradients that are sensitive to the speed of blood flow, facilitating the differentiation between static tissue and flowing blood.

Other sequences mentioned, such as Time-of-Flight Magnetic Resonance Angiography (TOF MRA), while useful for visualizing the lumen of blood vessels, are not specifically designed for quantifying low-velocity flow. Echo Planar Imaging (EPI) and Fast Spin Echo (FSE) sequences also serve different purposes, with EPI typically being used for rapid imaging and FSE providing high-resolution images but not specifically targeting blood flow dynamics like PC MRA does.