Which MRI sequence is most useful for identifying acute infarcts?

• A. Diffusion-weighted imaging
• B. T1-weighted imaging
• C. Proton-density imaging
• D. Functional MRI

Answer: (A)

Diffusion-weighted imaging is the best choice because acute brain infarcts cause cytotoxic edema that rapidly restricts water diffusion. This restriction makes the affected tissue appear bright on diffusion-weighted images within minutes to hours of onset, often before changes are visible on other sequences. The corresponding ADC map confirms true diffusion restriction by showing low values in the infarcted area, helping distinguish acute injury from other T2-related brightness. In contrast, T1-weighted and proton-density images are not sensitive to these early diffusion changes and may look normal in the hyperacute phase, while functional MRI is focused on brain activity and not on identifying acute structural injury.