Why is ramped angle excitation used in MRA?

Ramped angle excitation is particularly valuable in Magnetic Resonance Angiography (MRA) because it effectively enhances the signal from slowly flowing blood, which is often critical for visualizing vascular structures.

In MRA, the blood flow characteristics can vary significantly, and higher signal intensity from slowly moving blood enhances the contrasting visibility of vascular details against the surrounding tissues. Traditional excitation methods may not differentiate effectively between static tissue and slowly flowing blood, but ramped angle excitation optimizes the selection of the appropriate flip angle throughout the imaging sequence. This approach minimizes the loss of signal from the slower moving protons within the blood vessels, facilitating clearer and more defined images of the vasculature.

By tailoring the flip angles during excitation, it ensures that the signals from these regions are maintained during image acquisition, ultimately resulting in better visualization of blood vessels, which is essential in clinical evaluations where precise imaging of vascular anatomy is necessary.