Which of the following imaging sequences is considered most sensitive for detecting diffuse axonal injury?

• A. Diffusion weighted imaging
• B. T2-weighted
• C. Susceptibility-weighted imaging
• D. Proton density

Answer: (C)

Diffuse axonal injury often produces tiny microhemorrhages in white matter tracts, including areas like the corpus callosum and brainstem. Detecting these microbleeds is key to identifying DAI, and that’s where susceptibility differences from blood breakdown products become crucial. Susceptibility-weighted imaging enhances sensitivity to those magnetic differences, using phase information to make iron-containing debris and deoxyhemoglobin stand out as dark foci. This makes even very small microhemorrhages visible, which standard sequences can miss.

Diffusion-weighted imaging looks for restricted water movement and is excellent for acute ischemia or widespread axonal injury signals, but it isn’t as reliable for picking up tiny microbleeds. T2-weighted and proton density sequences show edema or gross lesions well, but small hemorrhages can be invisible or faint on them. So, for the goal of identifying the subtle microhemorrhages that define diffuse axonal injury, susceptibility-weighted imaging provides the best sensitivity.