CEST-MR images of 30 mM iobitridol solution titrated at different
pH values (5.5, 6.0, 6.3, 6.7, 7.0, 7.4, 7.9). ST images obtained
upon irradiation with RF saturation levels of 1.5 μT (a) and
of 6 μT (b). (c) Ratiometric RPM map calculated by using eq 1 from the ratio of the corresponding ST images (a
and b). (d) The pH map calculated from the ratiometric map and the
calibration curve of Figure 2b; and (e) pH
calculated vs pH titrated for 30 mM iobitridol phantoms, R2 = 0.98 (Bo = 7 T, 310 K).