High b-value diffusion-weighted imaging in progressive multifocal leukoencephalopathy in HIV patients

Area of Science:

• Neuroimaging
• Radiology
• Diffusion-Weighted Imaging

Background:

• Progressive multifocal leukoencephalopathy (PML) diagnosis relies on characteristic diffusion-weighted imaging (DWI) findings.
• The typical DWI pattern includes an ill-defined hyperintense rim and hypointense core.
• Optimizing DWI parameters can enhance lesion visualization and characterization.

Purpose of the Study:

• To evaluate if a higher b-value (b3000) improves the visualization of PML lesions compared to a standard b-value (b1000).
• To determine if b3000 provides different structural information about PML lesions.
• To assess the impact of b3000 on the apparent diffusion coefficient (ADC) values and lesion component volumes.

Main Methods:

• Retrospective analysis of HIV-positive patients with confirmed PML.
• Inclusion of both b1000 and b3000 DWI sequences in the study protocol.
• Measurement and comparison of signal intensities, ADC values, and volumes of lesion rims, cores, and normal-appearing white matter (NAWM) between b1000 and b3000.

Main Results:

• The b3000 DWI sequence enhanced the visualization of the PML lesion rim and core.
• Higher signal intensity was observed in the rim and lower signal intensity in the core at b3000 compared to NAWM.
• While total lesion volumes were similar, b3000 revealed significantly larger core volumes and smaller rim volumes than b1000.
• The hyperintense rim showed non-restricted ADCs but contained foci of restricted diffusion on both b-values.

Conclusions:

• The b3000 DWI sequence improves contrast resolution and visualization of the characteristic rim-and-core pattern in PML.
• b3000 reclassifies some rim tissue into the core, potentially offering more precise biomarkers for PML activity and prognosis.
• This higher b-value DWI may lead to more accurate assessments of disease activity and tissue damage in PML.