What type of pulses are used in GRE to eliminate residual transverse magnetization?

The use of spoiler pulses in Gradient Echo (GRE) sequences plays a crucial role in eliminating residual transverse magnetization that can lead to artifacts or unwanted signals in the final image. Spoiler pulses are designed to disrupt or dephase any remaining transverse magnetization after the excitation pulse has been applied and the imaging gradient has been turned off. This is particularly important in GRE sequences since they typically depend on preserving and manipulating the transverse magnetization for image formation.

In practical terms, the spoiler pulses achieve this by applying a magnetic field gradient that varies the phase of the remaining spins in the transverse plane. As these spins become out of phase with one another, they cancel each other out, effectively reducing or eliminating any residual signal that could interfere with the accuracy of the imaging data. This is vital for obtaining high-quality images without contamination from unwanted signals.

In contrast, inversion pulses are typically used for applications like fat suppression or creating specific contrasts rather than directly dealing with residual transverse magnetization. Gradient pulses alone help in causing the motion of spins but do not specifically address residual magnetization. Phase correction pulses are used to adjust for any phase discrepancies that might occur during the imaging sequence but don’t actively eliminate residual transverse magnetization like spoiler pulses do. Thus, spoiler pulses are the