How does the presaturation pulse influence signal in TOF MRA?

The presaturation pulse in Time-of-Flight (TOF) Magnetic Resonance Angiography (MRA) is utilized to specifically target and manipulate the signals from certain spins, particularly to suppress signals from stationary tissues. By applying a presaturation pulse, the signal from these stationary spins—such as those in surrounding structures or tissues—is effectively eliminated as they enter the imaging area. This is crucial because it allows the vascular structures of interest to be visualized more clearly against a less cluttered background, improving the overall quality and contrast of the MRA images.

This technique leverages the fact that the presaturation pulse selectively excites the spins of static tissues within the pre-saturated volume, thereby reducing their contribution to the signal detected during image acquisition. Therefore, the presaturation pulse enhances the visibility of moving spins, like blood flow, which is essential for accurate vascular imaging in TOF MRA.