Gradient Echo

FLASH (Fast Low Angle SHot) is used for T1-weighted rapid MR imaging with short repetition time TR (TR<<T1). After a number of repetitions of gradient echoes with low angle RF-excitations, a steady state is achieved. If we say "steady state" in this context, we relate it to the net-magnetization. Strictly speaking "steady state" means exactly identical state after each TR (which is used in case of SSFP). The FLASH sequence is also known as spoiled GRASS (Gradient Refocused Acquisition in the Steady-State). At this juncture the word "spoiling" refers to the elimination or "spoiling" of the steady-state transverse magnetization. There are various ways for accomplishing this task:

1. gradient-spoiling
2. RF-spoiling
3. (lengthening TR)

We are interested in the first two.

After applying the generating echo and dephasing, there is still some residual transverse magnetization remaining.
What to do with Mxy?

• or lose it a spoiling (RF and gradient).

-> Apply a spoiling, in order to destroy the transverse magnetization!