Mitigating Head Position Bias in Perivascular Fluid Imaging: LD-ALPS, a Novel Method for DTI-ALPS Calculation

Area of Science:

• Neuroimaging
• Neuroscience
• Biomedical Engineering

Background:

• The glymphatic system clears brain waste via perivascular spaces.
• Diffusion Tensor Imaging Analysis along the Perivascular Space (DTI-ALPS) estimates this flow non-invasively.
• Head position during MRI acquisition can compromise DTI-ALPS validity.

Purpose of the Study:

• Assess current DTI-ALPS practices regarding head orientation.
• Evaluate the impact of head orientation on ALPS index calculation.
• Propose a novel computational approach to enhance measurement validity.

Main Methods:

• Literature review on DTI-ALPS head-orientation correction strategies.
• Analysis of diffusion MRI data from 172 Alzheimer's Disease Neuroimaging Initiative (ADNI) participants.
• Comparison of Unrotated-ALPS, vecrec-corrected ALPS, and the novel LD-ALPS method.

Main Results:

• Most studies use Unrotated-ALPS, lacking head-orientation correction.
• Unrotated-ALPS showed significant bias related to head pitch (r = -0.513, p < 0.001).
• LD-ALPS and vecrec methods eliminated this bias; LD-ALPS also showed greater sensitivity to cognitive status.

Conclusions:

• Head orientation correction is crucial for DTI-ALPS studies.
• The LD-ALPS method enhances reliability and sensitivity of perivascular fluid estimates.
• LD-ALPS is recommended for future research on aging and neurodegeneration.