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Abstract #0298

Measuring extracellular pH in 3D using an iterative least squares frequency decomposition and hyperpolarized 13C-labelled Z-OMPD

Jakob Gaubatz1, Andre Wendlinger1, Nadine Setzer1, Florian Gaksch1, Martin Grashei1, and Franz Schilling1,2,3
1Technical University of Munich, TUM School of Medicine and Health, Department of Nuclear Medicine, TUM University Hospital, Munich, Germany, 2Technical University of Munich, Munich Institute of Biomedical Engineering, Garching, Germany, 3German Cancer Consortium (DKTK), Partner Site Munich and German Cancer Research Center (DKFZ), Heidelberg, Germany

Synopsis

Keywords: Hyperpolarized MR (Non-Gas), Hyperpolarized MR (Non-Gas), 3D pH-acquisition, Z-OMPD, Kidney, Frequency determination, UMPIRE, pH imaging, Hyperpolarization, 13C MRI

Motivation: Hyperpolarized [1,5-13C2]Z-OMPD exhibits a pH-dependent chemical shift and serves as a pH-sensitive probe. However, multiple pH compartments in vivo lead to multiple closely located resonances, which currently limits acquisition to slow 2D spectroscopic sequences.

Goal(s): To develop a method to decompose an unknown number of frequencies from multiple echo images, thereby enabling faster 3D multi-compartment pH mapping.

Approach: An IDEAL-like iterative least squares method was developed for a voxel-wise signal approximation and frequency decomposition.

Results: 3D pH maps acquired in vitro and in vivo showed good agreement with pH-electrode measurements and results of other studies.

Impact: The proposed iterative least squares frequency decomposition method enables fast 3D pH measurement using hyperpolarized [1,5-13C2]Z-OMPD, providing an alternative to the previously used 2D spectroscopic sequences. The acquisition of 3D pH maps enhances the ability to investigate tumor acidification.

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