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Updated: Sep 9, 2025
Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
Diffusivity anisotropy signature of slowly expanding lesions predicts progression independent of relapse activity in
Alberto Calvi1, Francesc Vivó Pascual2, Elisabeth Solana2
1Neuroimmunology and Multiple Sclerosis Unit and Laboratory of Advanced Imaging in Neuroimmunological Diseases (ImaginEM), Hospital Clinic Barcelona, IDIBAPS, Universitat de Barcelona, Barcelona, Spain acalvi@clinic.cat.
Background:
Slowly expanding lesions (SELs) in multiple sclerosis (MS) are markers of chronic active lesions and seem to trigger disability. This study aimed to analyse spatial features of SELs through diffusion MRI and their clinical impact on progression independent of relapse activity (PIRA).
Methods:
An observational study of MS subjects prospectively followed since 2011; inclusion required at least three longitudinal T1/T2-weighted and diffusion-weighted MRIs. Subjects followed clinical assessments, using Multiple Sclerosis Functional Composite (MSFC) and Expanded Disability Status Scale. At MRI, lesions were categorised using non-linear deformation as definite or possible SELs, and non-SELs. Fractional anisotropy (FA) was extracted from each lesion core and perilesional area. Differences in FA values across core and perilesional areas by SEL category were assessed using the Mann-Whitney test. Associations with PIRA and clinical outcomes were evaluated using mixed-effects, logistic and Cox regression models.
Results:
130 subjects underwent MRI (median 25 months) and clinical assessments (median follow-up 9.2 years), of which 29 (22%) developed PIRA. Of 4811 lesions, 8% were definite SELs. Definite SELs exhibited FA decline over time in core and perilesional areas compared with other lesions. Longitudinal core FA reductions within definite SELs were associated with worse MSFC z-score evolution (β=0.03, 95% CI 0.01 to 0.05, p=0.003), higher odds for PIRA (OR=0.01, 95% CI 0.01 to 0.12, p=0.001) and predicted faster time to reach first PIRA event (HR=0.03, 95% CI 0 to 0.49, p=0.015).
Conclusions:
Definite SELs show distinct greater microstructural damage and are associated with PIRA, making their FA signature a potential predictor of MS progression.
Insights
Slowly expanding lesions (SELs) in multiple sclerosis (MS) show greater microstructural damage. Their diffusion MRI signature, fractional anisotropy (FA), predicts progression independent of relapse activity (PIRA).
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Slowly expanding lesions (SELs) are linked to chronic active lesions in multiple sclerosis (MS).
- SELs are associated with disease progression and disability.
- Understanding SELs' spatial features is crucial for predicting MS outcomes.
Purpose of the Study:
- To analyze the spatial characteristics of SELs using diffusion MRI.
- To investigate the clinical impact of SELs on progression independent of relapse activity (PIRA).
- To correlate microstructural changes in SELs with MS clinical progression.
Main Methods:
- Observational study of MS patients with longitudinal MRI and clinical data.
- Lesion categorization into definite SELs, possible SELs, and non-SELs using non-linear deformation.
- Fractional anisotropy (FA) extraction from lesion cores and perilesional areas.
- Statistical analysis including Mann-Whitney, mixed-effects, logistic, and Cox regression models.
Main Results:
- Definite SELs (8% of lesions) showed significant FA decline over time in core and perilesional areas.
- Longitudinal FA reduction in definite SELs correlated with worse MS Functional Composite (MSFC) scores.
- FA changes in definite SELs were associated with higher odds of PIRA and predicted faster time to PIRA events.
Conclusions:
- Definite SELs exhibit distinct microstructural damage compared to other lesions.
- The FA signature of definite SELs is a potential imaging biomarker for MS progression.
- SELs are significant contributors to PIRA in multiple sclerosis.
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