Figure 3.

Simulations of the B₀ field offset-dependence of GABA and MM. Normalization of the signal curves was performed with respect to the maximum total signal of the GABA+ experiment to allow for comparison between both editing schemes. (A) GABA and MM signals, as well as their sum (GABA+), are shown for the MM-unsuppressed experiment with 14 ms editing pulses. The relative amounts of GABA and MM are set to be equal at zero offset. (B) GABA and MM signals for the MM-suppressed acquisition with 20 ms editing pulses. The MM response to the MM-suppressed experiment shows a zero-crossing at zero field offset, as expected. As the field offset increases or decreases, the total observed signal will contain contributions from both GABA and MM, with either positive or negative MM contributions depending on the direction of the offset. The solid dark curve represents a 50:50 MM:GABA ratio; dashed lines indicate 45:55 and 55:45 ratios, respectively. (C) Percentage changes the MM-unsuppressed (from A) and MM-suppressed simulations (from B). It can be seen that the MM-suppressed signal changes much more rapidly (by about an order of magnitude) as a function of field offset.