Fig 1.

Pretreatment MR imaging study.

A, Trace image of DWI₁₀₀₀ shows a lesion in the left MCP, which is hyperintense anteriorly and posteriorly and of intermediate signal intensity centrally. The rounded ring-shaped markings indicate where the regions of interest have been placed on the corresponding ADC maps.

B, Trace image of DWI₃₀₀₀ shows a hypointense lesion center and a peripheral high-signal-intensity rim, which is much more clearly defined than on the trace images of DWI₁₀₀₀ (Fig 1A).

C, Anisotropic image DWI₃₀₀₀, sensitive to water movement in the section (supero-inferior) direction, shows high signal intensity in the right MCP, which is a normal finding because the MCP represents a barrier to free water movement in this direction. The PML lesion in the mid and posterior portions of the left MCP appears no longer hyperintense, implying a loss of structural integrity. Note also that water diffusion is not impeded by the superior cerebellar peduncles, which run in a craniocaudal direction.