Simultaneous mapping of B0, B1 and T1 for the correction of CEST-MRI contrast

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Chemical exchange saturation transfer (CEST) MRI is a relative new and versatile MR method. In CEST MRI, exogenous or endogenous compounds with exchangeable protons are selectively saturated. After the transfer of magnetization from the compound to surrounding water molecules, the compound can be detected indirectly as a reduction of the bulk water signal with increased sensitivity compared to a direct detection. Besides physiological parameters like metabolite concentrations and pH value, the detected CEST effect further depends on the T1 relaxation time of the examined object as well as on possible inhomogeneities of the static magnetic (B0) and/or RF excitation field (B1) of the MR system. Thus, quantitative mapping of these parameters is necessary for a subsequent pixel-wise correction of the acquired CEST data. Usually these three parameter maps are acquired using three separate MR pulse sequences, which comes along with a lot of effort for the implementation as well as essentially prolonged acquisition times. Therefore, the idea of this project is to develop a method for the simultaneous acquisition of all three parameter maps. The proposed method is based on a previously developed approach for the quantification of B0 and B1 that will be extended and combined with the utilization of a neuronal network to enable the additional mapping of T1. The method is compatible with conventional CEST pulse sequences, will provide 3D parameter maps of B0, B1 and T1 in less than two minutes and therefore contribute to the dissemination of unbiased CEST MRI in the clinical routine.