apparent diffusion coefficient
Quantitative parameter derived from diffusion-weighted imaging that measures the magnitude of water diffusion in tissue, expressed in mm²/s.
Full Definition
The apparent diffusion coefficient (ADC) is a quantitative measure of water molecule mobility within biological tissues, calculated from diffusion-weighted imaging data. ADC values reflect tissue microstructural properties including cell density, membrane integrity, and extracellular space tortuosity. Lower ADC values typically indicate restricted diffusion due to cytotoxic edema, high cellularity, or intact cell membranes. Higher values suggest increased diffusion from cell death, vasogenic edema, or tissue necrosis. ADC mapping is crucial for stroke diagnosis, tumor characterization, and treatment monitoring. Normal brain parenchyma typically shows ADC values between 0.7-1.0 × 10⁻³ mm²/s.
Usage
Usage note: Use ADC after first mention; always include units when reporting quantitative values.
In Context
- "The lesion demonstrated markedly reduced apparent diffusion coefficient values consistent with acute infarction." — Emergency radiology report
- "Quantitative analysis revealed mean apparent diffusion coefficient of 0.45 × 10⁻³ mm²/s in the tumor core." — Research analysis