Towards Highly-Accelerated Hyperpolarized 13C MRSI In Vivo: Advancing Radial EPSI as a Versatile Imaging Tool

Hyperpolarized Carbon-13 magnetic resonance spectroscopic imaging (13C MRSI) is a powerful technique for the in vivo investigation of metabolic processes in real-time. The greatest challenge for tailored MRSI sequences is to acquire all three spatial dimensions together with full spectral information and in multiple timesteps, while being restricted in available acquisition time through rapid decay of the hyperpolarized state (<1 minute). In this work, advancements for radial echo-planar spectroscopic imaging (rEPSI) were implemented and optimized for various applications within the context of hyperpolarized 13C experiments in vivo on a clinical 3 T scanner. Metabolic processes of hyperpolarized 1-13Cpyruvate were monitored in vivo with high spatio-spectral resolution in just 6 seconds. A novel readout scheme with maximal k-space homogeneity successfully suppressed blurring due to the polarization decay and boosted the temporal resolution to the subsecond regime. Further methodological advancements enabled the acquisition of spatially-resolved 3D in vivo spectra of hyperpolarized 1,2-13Cpyruvate for the first time. Moreover, a novel MR fingerprinting approach was developed using rEPSI for estimation of B1+ fields, enabling a pre-scan calibration for hyperpolarized 13C MRSI. In conclusion, this thesis presents the developed advanced rEPSI as an effective and versatile imaging tool for hyperpolarized 13C MRSI, with enormous potential for substrates of high spectral complexity like 1,2-13Cpyruvate.