Objective  To investigate the features of MR diffusion imaging for a rabbit model of severe burn with brain edema at primary stage and its diagnostic value.   Methods  Thirty-five healthy New Zealand white rabbits were equally randomized into 7 groups

control group and burn groups (post-burn at 1

2

3

4

5 and 6 h respectively). Severe burn injury was inflicted by 50% total burn surface model with stage III burn. Routine MRI T

1

WI

T

2

WI

DWI and DTI with cerebral dynamic observation of apparent diffusion coefficient (ADC)

fractional a

nisotropy (FA) and exponential apparent diffusion coefficient (eADC) values were performed. Changes of cerebral water content were calculated by wet and dry weight method.   Results  No significant change was observed in T

1

WI and T

2

WI images within 6 h. Compared with control group

apparent decrease in ADC value (P0.01) was observed along with significant increase in eADC value (P0.01)

while no significant alteration was seen in FA value（r=0.1）. The water content of brain was found to increase with the elapse of time

which reached peak in 3 to 6 h post burn. Significant correlations were found between brain water content with ADC value (r=0.898

P0.01) and eADC value(r=0.871

P0.01)

however

no correlation was seen with FA value (r=0.135

P=0.438).    Conclusion  MR diffusion image well reflects the change of brain water content post severe burn

and is of significant value in diagnosis of brain edema in primary stage of burn.