Review Article

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

Figure 7

EPR imaging of pH. The nitroxide radical TEMPO shows strong EPR signals in solution, which are quenched when TEMPO is encapsulated in a nanoparticle. (a) Degradation of the nanoparticle at low pH dequenches the EPR signals from TEMPO. (b) No change in the nanoparticle at neutral pH retains the EPR-quenched state. (c) Phantom images demonstrate that the difference in pH can be spatially localized. Reproduced with permission from [33].
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