Effect of intravoxel incoherent motion on diffusion parameters in normal brain

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Diffusion MRI is sensitive to intravoxel incoherent motion (IVIM) from microcirculation.
• IVIM's impact on normal brain tissue diffusion MRI signals is not fully understood.
• Previous studies focused on IVIM in tumors and body perfusion.

Purpose of the Study:

• To investigate and quantify the IVIM effect on diffusion MRI signals in normal brain tissue.
• To assess the IVIM signal fraction (f*) in different brain regions.
• To explore the relationship between IVIM and demographic factors like age and gender.

Main Methods:

• Diffusion MRI data acquired from 137 healthy adult patients.
• Comparison of diffusion tensor parameters using mono-exponential fits at different b-values (0/1000 vs. 250/1000 s/mm²).
• Quantitative assessment of IVIM signal fraction (f*) using an asymptotic fitting method.

Main Results:

• Significant IVIM effect observed, with higher impact in cortical gray matter (7.8%) than white matter (4.5%) or thalamus (4.3%).
• Perfusion fraction (f*) estimated as 0.033 in WM, 0.066 in cortical GM, and 0.033 in thalamus.
• f* significantly increased with age in cortical GM and thalamus, but not in WM; no gender effect on f* was found.

Conclusions:

• IVIM is a measurable phenomenon in normal brain tissue, affecting diffusion MRI quantification.
• The perfusion fraction (f*) varies across brain regions and increases with age in GM and thalamus.
• These findings are crucial for accurate diffusion MRI analysis and understanding brain physiology.