Objective: Inflammation is believed to be a major cause of white matter injury in preterm infants. A better understanding of early magnetic resonance imaging (MRI) changes following inflammatory injury would be useful for evaluating these infants. We used an inflammatory model of periventricular leucomalacia in rat pups to characterise changes in diffusion tensor imaging (DTI).

Methods: The images were obtained on a 12 T MRI. One mg/kg of lipopolysaccharide in sterile saline (n  =  8) or sterile saline alone (n  =  6) was administered by stereotaxic injection into the left corpus callosum of 5-day-old rats. The location of the injection was verified through MRI. Both groups had a repeat MRI 4 days after the injection. DTI was acquired with 2 b values (0, 753) and 2 × 6 directions. Rats were then killed, and 50-micron thick sections of the brain were stained for cresyl violet. Regions of interest covering the corpus callosum were placed on three consecutive slices for the calculation of the apparent diffusion coefficient (ADC), relative anisotropy (RA), axial diffusivity and radial diffusivity.

Results: ADC values were increased (lipopolysaccharide 1.03 ± 0.05; control 0.95 ± 0.05 μm²/s, p = 0.02), as was radial diffusivity (lipopolysaccharide 0.77 ± 0.05; control 0.65 ± 0.12 μm²/s, p = 0.013) without any significant difference in RA and axial diffusivity.

Conclusions: The increases in radial diffusivity and ADC were associated with a decrease in cellularity measured on cresyl violet staining (myelin is not yet present at this stage of development).