What is the primary purpose of a spoiler gradient pulse in MRI?

The primary purpose of a spoiler gradient pulse in MRI is to de-phase unwanted signals. This function is crucial for improving the quality of the images obtained during an MRI scan. When tissues have differing magnetic susceptibilities or when there is residual transverse magnetization from previously excited spins, these signals can lead to artifacts and degrade image quality.

Spoiler gradients are applied after a radiofrequency (RF) pulse to disrupt the coherence of spins that are out of phase. By rapidly changing the magnetic field across the imaging volume, these gradients effectively "spoiler" the unwanted signals that stem from spins that should not contribute to the final image, allowing for a cleaner, more precise representation of the area being imaged.

In contrast, enhancing the signal or improving spatial resolution involves different mechanisms, such as adjusting RF pulse sequences or using specific coil designs and sequences optimized for high-resolution imaging. Reducing motion artifacts typically involves other approaches, such as implementing motion-tracking techniques or acquiring images at time points where patient movement is less likely to affect the results.