Project Details
Projekt
Rapid mapping of tissue ion concentrations
Applicants
Dr. Lena Gast; Professor Armin Nagel, Ph.D.
Subject Area
Medical Physics, Biomedical Technology
Nuclear Medicine, Radiotherapy, Radiobiology
Nuclear Medicine, Radiotherapy, Radiobiology
Term
since 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 500888779
Sodium (23Na) and potassium (39K) magnetic resonance imaging (MRI) represent valuable tools for non-invasively assessing tissue ion concentrations. In addition, 23Na and 39K MRI offer the possibility to gain information on the molecular environment based on quadrupolar interactions of these spin-3/2 nuclei. However, the MR sensitivity of 23Na – and especially 39K nuclei – and their concentration in the human body is strongly reduced when compared to protons (1H). The achievable signal-to-noise ratios (SNRs) of 23Na and 39K MRI are several orders of magnitude lower than that of 1H MRI. Thus, 23Na and 39K MRI can only usually be performed with low spatial resolutions (~3 mm for 23Na, ~10 mm for 39K) and require relatively long acquisition times (~10 min per 3D data set). On the other hand, 23Na and 39K MRI greatly benefit from ultra-high field strengths such as 7 T due to the approximately linear increase in SNR with main magnetic field strength. This project is part of the research unit (RU) “Fast Mapping of Quantitative MR biosignatures at Ultra-high Magnetic Field”. Its overall aim is to accelerate the acquisition of 23Na and 39K MRI at 7 T to achieve a clinically feasible total scan time of below 15 min while retaining high repeatability of the applied techniques. Therefore, rapid acquisition and corresponding reconstruction techniques will be developed for quantitative 23Na/39K MRI of the brain, skeletal muscle and breast, as well as for the selective detection of Na+ and K+ ions within specific molecular environments. To achieve these goals, the full potential for acceleration, from optimizing the acquisition schemes to applying advanced reconstruction and post-processing approaches will be exploited. For example, interleaved (i.e. quasi simultaneous) acquisition schemes will be implemented for 23Na and 39K MRI, enabling a time-efficient examination of both nuclei within a single sequence, and therefore reducing the acquisition time by approximately 50%. Furthermore, instead of working on a voxel-wise basis, we will focus on determining tissue- or organ-averaged ion concentrations, which is sufficient for most of the intended clinical applications. 1H MRI techniques will be used to take the presence of fat tissue into account and provide a proper normalisation for the glandular tissue or muscle volume. First, a reliable protocol for quantitative 23Na and 39K MRI in < 15 min will be set up. This protocol will then be included into the MR biosignature scan of the RU, containing also chemical exchange saturation transfer, quantitative susceptibility mapping as well as diffusion weighted MRI acquisitions. In the second step, the quantitative X-nuclei protocol will be further accelerated, so that environment-selective techniques can be included into the 15 min protocol.
DFG Programme
Research Units
