Table of Contents
Advances in Radiology
Volume 2015, Article ID 206405, 25 pages
Review Article

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

1Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
2Department of Biomedical Engineering, University of Arizona, Tucson, AZ 85721, USA
3Department of Medical Imaging, University of Arizona, Tucson, AZ 85724, USA
4University of Arizona Cancer Center, University of Arizona, Tucson, AZ 85724, USA

Received 22 October 2014; Revised 8 February 2015; Accepted 8 February 2015

Academic Editor: Orazio Schillaci

Copyright © 2015 Liu Qi Chen and Mark D. Pagel. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Tumor acidosis is a consequence of altered metabolism, which can lead to chemoresistance and can be a target of alkalinizing therapies. Noninvasive measurements of the extracellular pH (pHe) of the tumor microenvironment can improve diagnoses and treatment decisions. A variety of noninvasive imaging methods have been developed for measuring tumor pHe. This review provides a detailed description of the advantages and limitations of each method, providing many examples from previous research reports. A substantial emphasis is placed on methods that use MR spectroscopy and MR imaging, including recently developed methods that use chemical exchange saturation transfer MRI that combines some advantages of MR spectroscopy and imaging. Together, this review provides a comprehensive overview of methods for measuring tumor pHe, which may facilitate additional creative approaches in this research field.