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Updated: Mar 7, 2026
Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
High b-value diffusion-weighted imaging in progressive multifocal leukoencephalopathy in HIV patients
Claudia Godi1,2,3, Enrico De Vita2,3, Enrico Tombetti4
1Neuroradiology Department, San Raffaele Scientific Institute, Milan, Italy.
Objectives:
An ill-defined hyperintense edge and hypointense core on diffusion-weighted imaging (DWI) is typical of progressive multifocal leukoencephalopathy (PML). We aimed to investigate whether a b-value of 3,000 s/mm2 (b3000) can improve visualisation of PML, or provide different structural information compared to 1,000 s/mm2 (b1000).
Methods:
We retrospectively identified HIV-positive patients with confirmed PML studied under a clinical protocol including both b1000 and b3000 DWI. The rim and core of each PML lesion and normal-appearing white matter (NAWM) were outlined on trace-weighted DWI. Signal intensities, apparent diffusion coefficient (ADC) values and volumes were measured and compared between b1000 and b3000.
Results:
Nine lesions from seven patients were analysed. The rim and core were better visualised on b3000, with higher signal of the rim and lower signal of the core compared to NAWM. The hyperintense rim had non-restricted average ADCs, but included foci of low ADC on both b3000 and b1000. Despite similar total lesion volumes, b3000 displayed significantly larger core and smaller rim volumes than b1000.
Conclusion:
b3000 improves visualisation of this important PML hallmark. Moreover, b3000 partly reclassifies tissue from rim into core, and might provide potentially more accurate biomarkers of PML activity and prognosis.
Key Points:
• B3000 improves contrast resolution between lesion rim, core and normal-appearing white matter. • B3000 improves identification of the typical rim-and-core pattern of PML lesions. • B3000 and b1000 similarly identify lesions, but b3000 results in smaller rims and larger cores. • B3000 excludes some high diffusion components from rim, reclassifying them into core. • B3000 DWI may provide more precise PML biomarkers of disease activity and tissue damage.
Insights
Higher b-value diffusion-weighted imaging (DWI) at 3,000 s/mm² (b3000) improves visualization of progressive multifocal leukoencephalopathy (PML) lesions. This advanced technique may offer more accurate biomarkers for PML activity and prognosis.
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.
