Quantum Dipole Interactions Within Transient Hydrogen Bonds (THB) Define T1 Signal and Anisotropy in Neuronal Tissue. Theory and Validation.

Motivation: MRI relaxometry is a powerful tool in research and clinical applications. However, despite more than 50-year history of applications, biophysical mechanisms of relaxation processes are not well understood. Goal(s): To refine and validate recently proposed Transient Hydrogen Bond (THB) theory of T1 signal relaxation and anisotropy in neuronal tissue. Approach: Inversion recovery (IR) experimental data from excised porcine spinal cord with multiple cord orientations with respect to magnetic field B0 were analyzed using THB theory. Results: THB model produced an excellent fit to all IR experimental data, quantitatively explaining T1 anisotropy and experimental IR curves with a single set of THB model parameters. Impact: The proposed and validated Transient Hydrogen Bond (THB) model provides a novel framework linking experimental T1 relaxation measurements to the underlying structure of cellular and myelin membranes. This approach offers a new avenue for investigating the microstructure of biological tissues.