Diffusion MRI with free gradient waveforms on a high-performance gradient system: Probing restriction and exchange in...

Area of Science:

• Neuroimaging
• Biophysics

Background:

• Diffusion MRI signal dependence on diffusion time reveals restricted diffusion and exchange.
• Understanding these time-dependent signatures is crucial for in vivo human brain studies.

Approach:

• Utilized free gradient waveforms with varying sensitivities to restricted diffusion and exchange.
• Conducted experiments on six healthy volunteers using strong and ultra-strong gradients (80-300 mT/m).
• Analyzed 150 gradient waveform samples to identify unique signatures in grey and white matter.

Key Points:

• Grey matter exhibits both restricted diffusion and exchange, while white matter predominantly shows restricted diffusion.
• Gradient waveforms can independently map restricted diffusion and exchange.
• Brain tissue exchange is consistently at least twice as fast in grey matter compared to white matter.
• Shortest observed exchange times were in the cerebellar cortex (115 ms).

Conclusions:

• Free gradient waveforms effectively detect time-dependent signatures of restricted diffusion and exchange in vivo.
• The developed method shows potential for clinical applications, with contrast preserved in shorter protocols.
• This technique could serve as a valuable tool for studying diseased brain tissue.