Multiquantum filters and order in tissues

Area of Science:

• Biophysics
• Magnetic Resonance Imaging (MRI)
• Spectroscopy

Background:

• Anisotropic molecular motion in ordered systems leads to non-averaged quadrupolar and dipolar interactions.
• These interactions enable the formation of double quantum (DQ) coherences, particularly in biological tissues.

Purpose of the Study:

• To review the effects of anisotropic motion of water and sodium ions in biological tissues on NMR spectroscopy and MRI.
• To explore the application of double quantum filtered (DQF) techniques for analyzing ordered biological structures.

Main Methods:

• Utilized double quantum (DQ) coherences and double quantum filtered (DQF) Nuclear Magnetic Resonance (NMR) spectroscopy.
• Applied DQF spectroscopy and imaging to (2)H, (1)H, and (23)Na nuclei in various biological tissues.
• Manipulated pulse sequences and creation times to selectively detect DQ coherences from anisotropic motion.

Main Results:

• DQF spectra of water and sodium ions were detected in ordered tissues like ligaments, tendons, cartilage, and blood vessels.
• The technique differentiated tissues based on their unique DQF signal dependence on creation time, enabling compartment-specific analysis (e.g., sciatic nerve).
• Demonstrated the ability to deduce axon diameter, study blood vessel wall strain, map collagen fiber orientation, and monitor tendon healing.

Conclusions:

• DQF NMR spectroscopy and imaging are powerful tools for characterizing molecular order and dynamics in biological tissues.
• The method provides sensitive insights into tissue microstructure and function, surpassing conventional imaging in some applications.
• The successful implementation on a whole-body MRI spectrometer highlights its significant potential for clinical diagnostic imaging.