Figure 3.

GRE signal phase (A) increases monotonically with increasing T₂ for small RF phase increments (ΔΦ), e.g. 1-4°. Using a small RF phase increment (e.g. 2°), the signal phase is sensitive to T₂ over a wide range of T₂ values, a property that is favorable for encoding T₂ information. Note also that the signal phase is relatively insensitive to varying T₁ (B) and flip angle (for midrange flip angles such as 18°) for phase increments of 1° and 2°. The phase and magnitude of the GRE signal over the low range of RF phase increments were generated using Bloch equation simulations with physiological T₁ and T₂ values and TR=10ms.