Boundary-based registration improves sensitivity for detecting hypoperfusion in sporadic frontotemporal lobar...

Area of Science:

• Neuroimaging
• Neurology
• Radiology

Background:

• Frontotemporal lobar degeneration (FTLD) is characterized by tau (FTLD-tau) or TDP (FTLD-TDP) inclusions.
• Arterial Spin Labeling (ASL) MRI detects regional cerebral blood flow (CBF) changes, often acquired with T1-weighted (T1w) images.
• Accurate registration of ASL and T1w images is crucial for detecting subtle hypoperfusion.

Purpose of the Study:

• To evaluate if boundary-based registration (BBR) with more degrees of freedom enhances ASL-T1w image alignment compared to manual registration.
• To assess if improved registration increases sensitivity to regional hypoperfusion differences in FTLD patients.
• To investigate the association between hypoperfusion and FTLD-clinical dementia rating scale sum-of-boxes (FTLD-CDR) scores.

Main Methods:

• Recruited patients with sporadic FTLD-tau (sFTLD-tau; N=21), sFTLD-TDP (N=14), and controls (N=50).
• Compared three ASL-T1w registration methods: manual, manual+BBR, and FLIRT+BBR, assessing alignment via Pearson's Correlation Coefficients (CC).
• Analyzed mean CBF in regions of interest (ROIs) and used linear regression to correlate CBF with FTLD-CDR.

Main Results:

• All registration methods showed significant hypoperfusion in frontal and temporal regions in both FTLD groups compared to controls.
• Hypoperfusion in the left insular cortex, middle temporal gyrus, and temporal pole was detected in sFTLD-TDP relative to sFTLD-tau.
• FTLD-CDR inversely correlated with CBF in right temporal and orbitofrontal ROIs in sFTLD-TDP; manual+BBR and FLIRT+BBR performed similarly.

Conclusions:

• ASL MRI, particularly with BBR registration, is sensitive to distinct hypoperfusion patterns in FTLD subtypes.
• Decreased cerebral blood flow is associated with increased disease severity in sFTLD-TDP.
• BBR provides adequate registration of ASL-T1w images for both controls and FTLD patients.