Non-Invasive CEST-MRI Measurement of Ph in the Human Kidneys using an Approved CT Contrast Agent

Jochen Keupp¹, Ivan Dimitrov^2,3, Sander Langereis⁴, Osamu Togao³, Masaya Takahashi³, A. Dean Sherry³

Clinical MR techniques to report on local pH would be of high interest, because several pathologies are associated with pH changes like in renal diseases. Fortuitously, a clinically approved CT agent, Iopamidol, has been shown to have exchangeable protons that generate pH-dependent CEST (chemical exchange saturation transfer)-MRI contrast. It provides two proton pools, which allow a ratiometric pH measure independent from the local agent concentration, as recently demonstrated pre-clinically. In the present study it is shown, that Iopamidol can be used for in vivo human pH measurement in the renal pelvis using breathing triggered CEST-MRI on a clinical 3T scanner.