Abstract #4451

Determining the conditions for robust acidoCEST MRI to measure extracellular pH in tumors in vivo

Rohan S. Virgincar¹, Kai H. Barck¹, Mary Ann Go², Geoffrey Del Rosario², Shang-Fan Yu², ManKin Choy¹, Alvin Gogineni¹, Justin Elstrott¹, Herman S. Gill¹, Jan Marik¹, Genee Lee², Mark D. Pagel³, Alex de Crespigny⁴, Teemu T. Junttila⁵, Christoph Spiess⁶, Robby M. Weimer¹, and Luke Xie¹

¹Biomedical Imaging, Genentech, South San Francisco, CA, United States, ²Translational Oncology, Genentech, South San Francisco, CA, United States, ³Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, TX, United States, ⁴Early Clinical Development, Genentech, South San Francisco, CA, United States, ⁵In Vivo Pharmacology, Genentech, South San Francisco, CA, United States, ⁶Antibody Engineering, Genentech, South San Francisco, CA, United States

Synopsis

AcidoCEST MRI is a promising technique to directly measure extracellular pH in vivo and is well-suited to imaging tumors, which can exhibit acidosis. However, few studies have demonstrated the conditions and the minimum contrast agent concentrations needed for robust acidoCEST MRI. In this study, we employed micro-CT to determine the uptake of iopamidol in tumors with intratumoral and intravenous delivery of isovue-370, estimated the accuracy of pH measured by MRI vs. a pH meter, demonstrated the minimum iopamidol concentration required for acidoCEST MRI, and reported pH measurements in different tumor xenograft models.

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