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Assessing the accuracy of using oscillating gradient spin echo sequences with AxCaliber to infer micron-sized axon
Morgan Mercredi1, Trevor J Vincent2,3, Christopher P Bidinosti4,2
1Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada. mercreme@myumanitoba.ca.
Magma (New York, N.Y.)
|July 15, 2016
Summary
This study demonstrates that magnetic resonance imaging (MRI) using oscillating gradient spin-echo (OGSE) sequences can accurately measure small axon diameters in brain tissue. The findings show feasibility for preclinical scanners to infer these critical microstructural features.
Area of Science:
- Neuroimaging
- Biophysics
- Diffusion MRI
Background:
- Current MRI methods using pulsed gradient spin-echo sequences are limited in measuring small axon diameters due to insufficient diffusion times.
- Accurate measurement of axon diameter is crucial for understanding white matter integrity and neurological disorders.
Purpose of the Study:
- To determine the feasibility of using MRI with oscillating gradient spin-echo (OGSE) sequences combined with the AxCaliber method to infer small axon diameters.
- To assess the capability of this novel approach for measuring micron-sized axon diameters in brain tissue.
Main Methods:
- Monte Carlo simulations were used to generate data from idealized tissue geometries (cylinders of varying diameters).
- Oscillating gradient spin-echo (OGSE) sequences with a range of gradient frequencies were simulated.
- The AxCaliber method was adapted and applied to the simulated data to fit axon diameters, analyzing intra- and extra-axonal water separately and combined.
Main Results:
- Simulations showed that restricting gradient frequencies to maintain a constant apparent diffusion coefficient improved diameter fitting accuracy.
- This approach allowed for the inference of axon diameters as small as 0.5 μm.
- Accuracy was dependent on signal-to-noise ratio (SNR), with smaller diameters being more susceptible to noise, yet distributions remained distinguishable.
Conclusions:
- The study indicates that MRI utilizing OGSE sequences on preclinical scanners is feasible for inferring small axon diameters.
- This technique offers a promising avenue for non-invasive microstructural analysis of brain tissue.
