Figure 2.

Process showing the quantification of the k_ex in the brain. (A) Typical Z-spectra from an ischemic lesion for 3 different B₁: 1.5, 2.5, and 3.5 µT. (B) Water DS was removed by Lorentzian fitting at a B₁ of 1.5 µT. The omega plot was established on the basis of residual signals after the subtraction of DS. (C) Representative DS-removed omega plots of an ischemic lesion (red line) and contralateral tissue (blue line). The x-axis intercept of this plot provides a readout of k_ex. k_ex, proton exchange rate; B₁, saturation power; DS, direct saturation.