Diffusion-weighted MR of the brain: methodology and clinical application

Area of Science:

• Neuroimaging
• Radiology
• Medical Physics

Background:

• Diffusion magnetic resonance (MR) imaging visualizes white matter tracts in the brain.
• Two primary approaches exist: isotropic/diffusion-weighted images and apparent diffusion coefficient (ADC) maps.
• Advanced processing computes diffusion tensor, mean diffusivity (D), and fractional anisotropy (FA) for detailed analysis.

Purpose of the Study:

• To explore the capabilities and applications of diffusion MR imaging in clinical settings.
• To highlight its role in diagnosing and managing various neurological conditions.
• To emphasize its utility in quantitative assessment and understanding pathophysiological mechanisms.

Main Methods:

• Utilizing echo planar imaging sequences with diffusion-sensitizing gradients.
• Reconstructing isotropic or diffusion-weighted images for subjective evaluation.
• Generating ADC maps for objective, quantitative assessment.
• Computing diffusion tensor, D, and FA from multi-directional diffusion-weighted images.

Main Results:

• Diffusion-weighted imaging complements conventional MR for acute ischemic stroke evaluation.
• Quantitative diffusion MR (tensor-based) is crucial for assessing brain maturation and white matter diseases in children.
• It enhances characterization of lesions in conditions like hypoxic-ischemic encephalopathy, infections, and inherited metabolic diseases.
• Diffusion MR aids in differentiating brain abscess from cystic tumors and epidermoid from arachnoid cysts.
• It improves understanding of multiple sclerosis (MS) by characterizing lesions and detecting damage in normal-appearing white and grey matter.
• Diffusion changes correlate with cognitive deficits in MS patients and clinical disability.
• Ageing shows a mild increase in brain ADC/D, primarily in white matter.
• In neurodegenerative diseases, diffusion MR reveals grey and white matter damage, correlating with clinical deficits and aiding early diagnosis.

Conclusions:

• Diffusion MR imaging, particularly quantitative analysis, is fundamental for diagnosing and monitoring a wide range of neurological disorders.
• It offers superior characterization of white matter integrity and pathological changes compared to conventional MR imaging.
• Its application extends from acute stroke to chronic neurodegenerative diseases, providing valuable prognostic and diagnostic information.