FIG. 5.

(a) Experimental (star) and simulated (solid line) CEST contrasts for a creatine/agar sample vs. θ. The simulation parameters were from the fitting results from a CW-CEST experiment on the same sample. (b) Experimental CEST contrast ratios for creatine/agar samples with benchmark, a, b, and c on the x-axis representing three samples with approximately the same k_sw (57± 5, 55 ± 4, 59 ± 6, and 56 ± 4 1/s, respectively), but high f_s = 0.0019 ± 0.0002 for sample ‘a’(vs. 0.0009 for ‘benchmark’, ‘b’ and ‘c’), short T_1w = 1.42 ± 0.06 s for sample ‘b’(vs. 2.80 s for ‘benchmark’, ‘a’ and ‘c’), and low f_m = 0.005 ± 0.001 for sample ‘c’ (vs. 0.016 for ‘benchmark’, ‘a’ and ‘b’). (c) Experimental CEST contrast ratio vs. the titrated pH. The fitted k_sw are 32 1/s, 57 1/s, and 84 1/s for pH of 5.6, 6.0, and 6.4, respectively. Note that the ratio changes with k_sw in figure 5c, but not other parameters in figure 5b. Also note that the experimental results (star) are close to our simulation results (dot) with fitted parameters.