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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 9.

Figure 9

31P MR spectroscopy of tumor pHe. (a) The 31P spectrum from mouse leg muscle injected with 3-APP can measure extracellular pH (pHe) from the 3-APP chemical shift and can measure intracellular pH (pHi) from the chemical shift of inorganic phosphate (Pi). (b) The 31P chemical shift of 3-APP is correlated with pH as shown by an in vitro titration. (c) The pHe and pHi measured with 3-APP and Pi in a tumor before (bottom) and after (middle) injection of 3-APP, and after euthanasia (top). Reproduced with permission from [41].