Diffusion restriction: Meaning in a Radiology Report

Diffusion restriction means water molecules cannot move as freely as usual in part of the tissue, a pattern seen on diffusion MRI images.

What it means

Water molecules in the body are always drifting slightly. Diffusion MRI images measure how freely they move. Where cells are swollen or tightly packed, or where fluid is thick like pus, the water cannot move as freely. That area looks bright on the diffusion images (DWI) and dark on a matching map called ADC. Seeing both together confirms true restriction.

When it matters

In the brain, new diffusion restriction is the classic sign of a recent stroke, often seen earlier than on CT. It can also come from an abscess (a pocket of infection), some tumors with tightly packed cells, or a recent seizure. In other organs, such as the prostate, it is one clue among several. A report of no diffusion restriction usually means no recent stroke was seen. Doctors read it alongside your symptoms and the other images.

Questions to ask your doctor

Does the diffusion restriction fit a recent stroke or something else?
Is the area also dark on the ADC map?
What usually comes next after a finding like this?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.