Fig. 5.
Comparison of the derived labile proton ratio and exchange rate. a) For the pH CEST phantom, the labile proton fraction ratio shows little change with pH (R2=0.603, P>0.12). b) The exchange rate increases exponentially with pH (R2=0.996, P<0.03). c) For the concentration phantom, the derived labile proton fraction ratio increases linearly with creatine concentration (R2=0.994, P<0.01). d) The chemical exchange rate shows very little change with the creatine concentration (R2=0.0903, P>0.60).