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Updated: Dec 28, 2025
Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging
Published on: November 8, 2012
MRI profiling of focal cortical dysplasia using multi-compartment diffusion models
Sara Lorio1,2, Sophie Adler1, Roxana Gunny3
1Developmental Neurosciences, Great Ormond Street Institute of Child Health, University College London, London, UK.
Objective:
Focal cortical dysplasia (FCD) lesion detection and subtyping remain challenging on conventional MRI. New diffusion models such as the spherical mean technique (SMT) and neurite orientation dispersion and density imaging (NODDI) provide measurements that potentially produce more specific maps of abnormal tissue microstructure. This study aims to assess the SMT and NODDI maps for computational and radiological lesion characterization compared to standard fractional anisotropy (FA) and mean diffusivity (MD).
Methods:
SMT, NODDI, FA, and MD maps were calculated for 33 pediatric patients with suspected FCD (18 histologically confirmed). Two neuroradiologists scored lesion visibility on clinical images and diffusion maps. Signal profile changes within lesions and homologous regions were quantified using a surface-based approach. Diffusion parameter changes at multiple cortical depths were statistically compared between FCD type IIa and type IIb.
Results:
Compared to fluid-attenuated inversion recovery (FLAIR) or T1-weighted imaging, lesions conspicuity on NODDI intracellular volume fraction (ICVF) maps was better/equal/worse in 5/14/14 patients, respectively, while on SMT intra-neurite volume fraction (INVF) in 3/3/27. Compared to FA or MD, lesion conspicuity on the ICVF was better/equal/worse in 27/4/2, while on the INVF in 20/7/6. Quantitative signal profiling demonstrated significant ICVF and INVF reductions in the lesions, whereas SMT microscopic mean, radial, and axial diffusivities were significantly increased. FCD type IIb exhibited greater changes than FCD type IIa. No changes were detected on FA or MD profiles.
Significance:
FCD lesion-specific signal changes were found in ICVF and INVF but not in FA and MD maps. ICVF and INVF showed greater contrast than FLAIR in some cases and had consistent signal changes specific to FCD, suggesting that they could improve current presurgical pediatric epilepsy imaging protocols and can provide features useful for automated lesion detection.
Insights
New diffusion imaging techniques, spherical mean technique (SMT) and neurite orientation dispersion and density imaging (NODDI), show promise for focal cortical dysplasia (FCD) lesion detection. Intracellular volume fraction (ICVF) and intra-neurite volume fraction (INVF) maps offer better lesion characterization than standard MRI.
Area of Science:
- Neuroimaging
- Radiology
- Medical Physics
Background:
- Focal cortical dysplasia (FCD) diagnosis and subtyping are challenging with conventional MRI.
- Advanced diffusion MRI models like SMT and NODDI may offer more specific microstructural tissue characterization.
Purpose of the Study:
- To evaluate SMT and NODDI diffusion maps for FCD lesion characterization.
- To compare these advanced diffusion metrics against standard FA and MD for radiological and computational analysis.
Main Methods:
- Calculated SMT, NODDI, FA, and MD maps for 33 pediatric patients with suspected FCD.
- Assessed lesion visibility and quantified signal profile changes using a surface-based approach.
- Statistically compared diffusion parameter changes between FCD types IIa and IIb.
Main Results:
- NODDI's intracellular volume fraction (ICVF) and SMT's intra-neurite volume fraction (INVF) showed improved lesion conspicuity compared to FA and MD.
- Significant reductions in ICVF and INVF were observed in FCD lesions, with greater changes in FCD type IIb.
- No significant changes were detected on FA or MD maps.
Conclusions:
- ICVF and INVF maps reveal FCD-specific signal changes not apparent on FA or MD.
- These advanced diffusion metrics can enhance pediatric epilepsy imaging protocols and aid automated lesion detection.
