Which MRI sequence is most useful for differentiating an acute cerebral infarct from a low-grade brain tumor, and what is the characteristic finding for an acute infarct on this sequence?

Diffusion-weighted imaging (DWI) is most useful for this differentiation. Acute infarcts typically show restricted diffusion, appearing hyperintense on DWI and hypointense on the corresponding ADC map. In contrast, low-grade neoplasms generally do not exhibit restricted diffusion. Be cautious of mimickers such as abscesses or certain high-grade tumors, which can also show restricted diffusion.