%0 Generic
%A Reichert, Simon
%C Heidelberg
%D 2024
%F heidok:34464
%R 10.11588/heidok.00034464
%T Advancing Sodium Triple Quantum (TQ) Nuclear Magnetic Resonance (NMR) Spectroscopy and Imaging
%U https://archiv.ub.uni-heidelberg.de/volltextserver/34464/
%X Slow interactions of sodium ions with macromolecules result in a sodium triple quantum (TQ) signal. This TQ signal is intracellularly sensitive and promises to be a valuable biomarker for cell viability. However, a deeper understanding of the sodium molecular environment and the detected TQ signal as well as substantial reduction in measurment time are necessary to leverage the full potential of the sodium TQ signal in clinical applications. As a first step of this thesis, a simulation framework for sodium nuclear magnetic resonance (NMR) dynamics was implemented, including a refined motion model for simultaneous compatibility with T1 and T2 relaxation times. For both the TQ time proportional phase intrement (TQTPPI) and the inversion recovery TQTPPI (IRTQTPPI) sequences, the simulation showed good agreement with the experimental data. In a second step, the sodium molecular environment was further investigated by using globular proteins of different sizes with different sodium binding affinities. TQ signal increased with protein size. However, a strong sodium binding affinity and the structure of the protein hydration shell had a stronger influence than the protein size. In a third step, a novel IRTQTPPI sequence was proposed to investigate the TQ signal and thus the sodium molecular environment on a different time scale. This sequence allows for a reliable and simultaneous quantification of T1 relaxation times and TQ signal. Measurements at 9.4 T and 21.1 T showed a separation of T1 relaxation times of at least 15 ms and a strong T1-TQ signal for agar samples. The separation in T1 relaxation time and T1-TQ signals were smaller than their T2 counterparts, indicating a unique sensitivity of the T1-TQ signal to a molecular environment on a different time scale. In the last part of this thesis, a novel and fast TQ acquisition method using only a single pulse sequence was proposed. The TQ signal of this method was in close agreement with the TQTPPI sequence and the theoretical prediction. Furthermore, the method reproduced the expected TQ signal behavior even for multi-compartment systems and in the presence of noise. This approach, combined with multi-echo ultra-short echo time (UTE) imaging, provides an efficient method to extract the sodium TQ signal in vivo without increasing acquisition time compared to SQ sequences and a dramatically reducing scan time compared to conventional phase cycling sequences. The proposed NMR techniques are a promising research tool to obtain a deeper understanding of the sodium molecular environment and thus leverage the full potential of the sodium TQ signal in vivo.