Evaluating pH in the Extracellular Tumor Microenvironment Using CEST MRI and Other Imaging Methods

Figure 19

Tumor pHe measured with acidoCEST MRI using iopromide. (a) The CEST spectra of the agent show that the two CEST effects at 4.2 and 5.6 ppm are dependent on pH. (b) A log₁₀ ratio of the two CEST effects is linearly correlated with pH as measured with a microelectrode. (c, d) The pixelwise pHe map of a mouse bearing a Raji xenograft tumor before and after treatment with MIBG, a midrocondrial poison that causes acidification. Colored pixels have acidic pHe values ≤ 7.0 that correspond to the color-bar. White pixels represent tumor regions with only a single CEST effect at 4.2 ppm, which were considered to have neutral pHe values > 7.0. Reproduced with permission from [68].

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