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Abstract #4456

Towards Temperature-Corrected pH Mapping using CEST Imaging: Quantification of the Underlying Calibration as a Function of Temperature

Philip S Boyd1, Jana C Lechner1,2, Jannis B Wirtz1,2, Mark E Ladd1,2,3, Peter Bachert1,2, and Andreas Korzowski1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, 3Faculty of Medicine, University of Heidelberg, Heidelberg, Germany

Synopsis

Keywords: CEST / APT / NOE, CEST & MT

Motivation: CEST-based pH mapping relies on a strongly temperature-dependent calibration, yielding the parameter kc characterizing the exchange rate. Previously, this calibration has only been performed at T=37°C, thus impeding quantitative pH mapping at different temperatures.

Goal(s): Enabling more reliable, i.e. temperature-corrected, quantitative CEST-based pH mapping.

Approach: We quantified the temperature dependency of kc(T) for amide, amine and guanidino protons at B0=9.4T using creatine and protamine model solutions at various pH and temperatures.

Results: For all proton species, the measured kc(T) showed exponential temperature dependencies with doubling of kc(T) for distinct temperature increases (ΔT=Tdouble) of around 4−11°C. Interestingly, each proton species exhibited a characteristic Tdouble.

Impact: These findings enable CEST-based pH mapping at any desired temperature, which, previously, has only been possible at T=37°C. Prospectively, quantitative pH mapping will now also be possible in anatomical regions, e.g. human lower leg, where temperatures may deviate from T=37°C.

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