Effects of perfusion on diffusion changes in human brain tumors

Area of Science:

• Neuroimaging
• Medical Physics
• Radiology

Background:

• Diffusion MRI measures water molecule movement, providing insights into tissue microstructure.
• Functional diffusion maps (FDMs) track changes in apparent diffusion coefficient (ADC) over time.
• Perfusion, the blood flow to tissues, can influence diffusion measurements.

Purpose of the Study:

• To investigate how perfusion affects diffusion change measurements using standard two-point methods.
• To compare traditional FDMs (tFDMs) with flow-compensated FDMs (fcFDMs) in the context of perfusion.

Main Methods:

• FDMs were generated using both traditional (b=0,1000 s/mm²) and flow-compensated (b=500,1000 s/mm²) sequences.
• Changes in relative cerebral blood volume (ΔrCBV) were analyzed in voxels with differing ADC change classifications between tFDMs and fcFDMs.
• Patients with brain tumors were included in the study.

Main Results:

• Significant differences in ΔrCBV were observed in voxels where ADC changes were classified differently by tFDMs and fcFDMs.
• The mean ΔrCBV was significantly greater (less) than zero in voxels transitioning from iADC to ncADC.
• Mean ΔrCBV was significantly higher (lower) in iADC/dADC voxels on tFDMs compared to fcFDMs.

Conclusions:

• Standard two-point diffusion measurements are confounded by perfusion in areas with co-localized changes.
• Flow-compensated FDMs, utilizing only non-zero b-values, provide a more reliable method for assessing diffusion changes.
• This suggests fcFDMs should be the standard for diffusion analysis in neuroimaging.