Selective filters of translational molecular diffusion dynamics in human brain microstructures

Motivation: Our primary aim is to enhance non-invasive tissue-microstructure characterization as a diagnostic paradigm through advanced MRI methods. Goal(s): We explore microscopic tortuosity in human white-matter using the Non-uniform Oscillating-Gradient Spin-Echo (NOGSE) contrast in a clinical 3T MRI-scanner. Approach: The NOGSE contrast was obtained by subtracting distinct OGSE acquisitions, allowing the discrimination of signals from molecules within specific brain compartments. Results: We found restriction-sizes consistent with human histological findings, and evidence that the dominant signals originate from extra-axonal spaces, supporting microscopic tortuosity effects. This compartment-size specific contrast opens a path for diagnosis based on quantitative imaging. Impact: We characterize microscopic-tortuosity mechanisms in human-brain white-matter through the Non-uniform Oscillating-Gradient Spin-Echo contrast, which targets the signal of confined molecules in specific microscopic-sizes. This novel contrast, demonstrated at 3T-MRI, promises a quantitative tissue-microstructure paradigm for medical diagnosis of diseases.