Abstract #4291

Making the Transfer: Exploiting Hyperpolarized Bicarbonate-CO2 Exchange for Increased Signal-to-Noise pH Imaging

David E Korenchan¹, Jeremy W Gordon¹, Sukumar Subramaniam¹, Renuka Sriram¹, Peder E Z Larson^1,2, Dan B Vigneron^1,2, Robert R Flavell¹, and John Kurhanewicz^1,2

¹Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Bioengineering, University of California, Berkeley and University of California, San Francisco, San Francisco, CA, United States

Hyperpolarized (HP) [¹³C]bicarbonate MR imaging can map pH in vivo, but images generally suffer from low CO₂ signal-to-noise ratio (SNR). However, rapid bicarbonate-CO₂ chemical exchange can increase CO₂ SNR via exchange-mediated polarization transfer. We exploit this phenomenon for HP [¹³C]bicarbonate imaging to boost CO₂ SNR by 2.2-fold at pH 7.6, where CO₂ SNR is lowest in the physiologic range, by acquiring and summing multiple transients. Tip angles and delays are chosen using a priori knowledge of exchange rate to increase SNR while mitigating pH error. This approach can potentially improve imaging SNR in vivo for studying extracellular acidosis in cancer.

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