Diffusion-weighted MRI is particularly useful for detecting which feature in acute stroke?

Diffusion-weighted MRI is particularly useful for detecting which feature in acute stroke?

• A. Early ischemia
• B. Mass effect
• C. Hemorrhage
• D. Normal function

Answer: (A)

Diffusion-weighted MRI detects areas where water movement is restricted, which happens very early in acute ischemia. When neurons lose energy, they fail to regulate their ion balance, causing cytotoxic edema and rapid cell swelling. This restriction of water diffusion makes affected tissue appear bright on diffusion-weighted images and dark on the corresponding ADC map. Because diffusion restriction occurs within minutes of onset, DWI is superb for spotting early ischemic injury, often before other imaging sequences show changes. Hemorrhage is best seen by susceptibility-based sequences because blood products create magnetic susceptibility effects, not diffusion changes. Mass effect or edema from nonvascular causes may be visible elsewhere but isn’t the specific signal DWI is designed to highlight. Normal brain tissue doesn’t display diffusion restriction, so DWI helps distinguish acute ischemia from normal function.

Diffusion-weighted MRI detects areas where water movement is restricted, which happens very early in acute ischemia. When neurons lose energy, they fail to regulate their ion balance, causing cytotoxic edema and rapid cell swelling. This restriction of water diffusion makes affected tissue appear bright on diffusion-weighted images and dark on the corresponding ADC map. Because diffusion restriction occurs within minutes of onset, DWI is superb for spotting early ischemic injury, often before other imaging sequences show changes. Hemorrhage is best seen by susceptibility-based sequences because blood products create magnetic susceptibility effects, not diffusion changes. Mass effect or edema from nonvascular causes may be visible elsewhere but isn’t the specific signal DWI is designed to highlight. Normal brain tissue doesn’t display diffusion restriction, so DWI helps distinguish acute ischemia from normal function.