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. Author manuscript; available in PMC: 2016 Oct 17.
Published in final edited form as: Adv Radiol. 2015;2015:206405. doi: 10.1155/2015/206405

Figure 14.

Figure 14

Endogenous CEST MRI of tumor pHi. (a) The asymmetry of the magnetization transfer ratio (MTRasym), a measure of CEST, decreases after ischemia is induced in a rat model (black: ischemic region; green: nonischemic contralateral region; data represents the average and standard deviation of results with 7 rats). (b) This decrease in CEST, also represented as a change in the amide proton transfer ration (ΔAPTR), has been correlated with intracellular pH (pHi) as measured with 31P MR spectroscopy. (c) The MTRasym can be mapped in a rat model of ischemia, (d) which can be converted into a pH map. Reproduced with permission from [59, 83, 84].