Quantitative study on magnetization transfer imaging in neonatal rabbit models of white matter damage

Objective To explore the value of magnetization transfer ratio (MTR) for quantitative evaluation of white matter damage (WMD) in neonatal rabbit models. Methods Forty 8-day-old neonatal rabbits were randomly divided into the experiment groups (continuous observation group, n=8; parallel observation group, n=24) and control group (n=8). Models of WMD induced by hypoxia- ischemia were established. All the animals underwent MRI studies before and at 4, 24 and 48 h after modeling, and the MTR of WMD was calculated on the workstation. At 0, 4, 12, 24, 36 and 48 h after WMD, 2 to 4 rabbits randomly selected from the parallel observation group were sacrificed and harvested for brain tissues which were studied for pathological changes with transmission electron microscope (TEM) , HE and immunohistochemical staining. Results Neuropathology confirmed the changes in models to be consistent with those in WMD. MTR decreased in both control group and experiment group, and at different time points, significant differences in reduction of MTR at the cortex, midbrain and cerebellum were found between experiment group and control group (all P＜0.01 ), and those were 22.191±0.366 vs 21.393±0.366,20.201±0.388 vs 21.083±0.388, 19.506±0.239 vs 20.151±0.239, 18.488±0.354 vs 20.058±0.354 at the cortex (all P＜0.01). Conclusion MTR may help better quantitative evaluation of WMD in models, and therefore can be promising for early identification of white matter damages and may provide a standard for quantitative outcome evaluation of clinical treatment. Key words: Brain injuries; Hypoxia-ischemia,brain; Magnetization transfer ratio; Models,animal; Magnetization transfer imaging