What type of sequences relies on flow-related enhancement to visualize flowing blood?

The choice that relies on flow-related enhancement to visualize flowing blood is time-of-flight (TOF) magnetic resonance angiography (MRA). TOF MRA is a technique that specifically leverages the phenomenon of flowing blood providing a stronger signal compared to stationary tissues. This is achieved by utilizing repeated saturation of stationary spins, allowing the flowing spins of the blood that enter the imaging volume to produce a clear and enhanced signal.

In TOF sequences, the blood that is flowing into the imaging area is not affected by the saturation pulses that affect the surrounding stationary tissue, thus resulting in a higher signal intensity for the flowing blood. This method is particularly effective in visualizing vessels with fast-flowing blood, as it does not require any contrast agent and is non-invasive.

While other methods also visualize blood flow, such as phase contrast (PC) MRA, which relies on the phase shifts associated with moving spins, TOF is distinct in its reliance on flow-related signal enhancement and is widely used for its effectiveness in assessing vascular structures without the need for intravenous contrast agents.