Isotropically weighted intravoxel incoherent motion brain imaging at 7T

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Perfusion MRI offers insights into brain microvasculature for diagnosing abnormalities like stroke and tumors.
• Conventional MRI perfusion techniques face limitations including contrast agent issues and lower resolution.
• Intravoxel Incoherent Motion (IVIM) imaging, an extension of diffusion MRI, provides an alternative for estimating brain perfusion parameters.

Purpose of the Study:

• To evaluate the application of a novel isotropic diffusion weighted sequence for IVIM parameter assessment at ultra-high 7T field MRI.
• To compare IVIM metrics derived from the new sequence with those from a conventional pulsed gradient sequence.
• To analyze the influence of blood flow and vessel density on IVIM metrics in the human brain.

Main Methods:

• Development and application of a novel isotropic diffusion weighted sequence for fast and efficient data acquisition at 7T.
• Utilizing a bi-exponential fitting model for signal attenuation analysis to derive IVIM scalar metrics.
• Comparison of IVIM metrics obtained with the new sequence against a conventional pulsed gradient sequence, including analysis with a vessel density atlas.

Main Results:

• The isotropic diffusion weighted sequence demonstrated high immunity to image-degrading factors, enabling efficient data acquisition.
• Voxels containing large and middle brain vessels showed significantly higher diffusion coefficients and perfusion fractions compared to other tissues.
• A strong dependence of IVIM metrics on the vessel density atlas values was not observed.

Conclusions:

• The developed isotropic diffusion weighted sequence is a promising tool for IVIM-based brain perfusion assessment at ultra-high fields.
• The findings highlight the ability of IVIM to differentiate tissue characteristics based on vessel size.
• Further research is needed to fully explore the potential and limitations of this advanced perfusion imaging technique.