DWI
Also written as: DWI — Diffusion-Weighted Imaging
Diffusion-weighted imaging; MRI technique that detects acute ischemia by measuring water molecule movement restriction.
Full Definition
Diffusion-weighted imaging is a specialized MRI sequence that detects early ischemic changes by measuring the random motion of water molecules in tissue. In normal brain tissue, water molecules move freely in all directions (unrestricted diffusion). During acute ischemia, cellular energy failure leads to cytotoxic edema and restricted water movement, appearing as bright signal on DWI and dark signal on apparent diffusion coefficient (ADC) maps. DWI can detect acute stroke within minutes of onset, often before changes are visible on conventional MRI sequences. The technique is highly sensitive for acute infarction but can also show restricted diffusion in other conditions such as abscess, tumors, or recent seizure activity. In neurocritical care, DWI is invaluable for diagnosing acute stroke, monitoring infarct evolution, and detecting new ischemic lesions in critically ill patients.
Usage
Usage note: Standard imaging abbreviation; often paired with ADC in reporting.
In Context
- "DWI revealed acute restriction in the left MCA territory consistent with recent infarction." — MRI report
- "Serial DWI showed expansion of the ischemic lesion despite reperfusion therapy." — Follow-up imaging note