| Purpose: To establish a stable and reliable animal model with hypoxic-ischemic encephalopathy in newborn piglets, explore early diffusion weighted imaging charicteristics with HIE, examine dynamic changes of apparent diffusion coefficient and heat shock protein 70 expression observed in the central regions and peripheral regions, and their relationship, so that we could provide the valuable clinical information for early diagnosis, treatment and prognosis jugement of HIE. Materials and methods: Fifty-eight newborn pigs divided into two groups: 1.group model I: normal control group (n=3), sham operation group (n=3), and Shour group (n=4), 6hour group (n=4) and 24hour group (n=4) after cerebral hypoxic-ischemia.2.group model II: normal control group (n=5), sham operation group (n=5), and 3hour group (n=10), 6hour group (n=10) and 24hour group (n=10) after cerebral hypoxic-ischemia. Newborn pigs in the group model I were performed by unbilateral common carotid artery occlusion, then inspirated 8% oxygen about 120 minutes. Newborn pigs in the group model II were performed by bilateral common carotid arteries occlusion, then inspirated 3% oxygen about 30 minutes. With 1.5T Magnet scanner, all pigs were examined with T2-weighted images and echo-planar diffusion-weighted images at varying time point, diffusion in the x-, y-, and z-planes were generated, b values of 0 and 1000 sec/mm2 were used. Meantime ADC maps were obtained and ADC values were measured in the central regions and peripheral ones of lesions on ADC maps obtained,respectively. The expression of heat shock protein 70 was examined by means of SP immunoreactivity technique in all regions corresponding to the DWI lesions and the reduction of ADC values. The statistical analysis of ADC values reduction andHSP70 induction were applied t-test and analysis of variance, their relationship was analysed by Pearson's correlation.Results: (1) There were no abnomal findings on the neurological signs and HE staining pathology in all groups in the group model I. HIE imaging models were obtained by observing the behaviors and their neurological system signs in newborn pigs, examining the HE staining pathology in the group model II. (2) Diffiising-weighted images and ADCmaps showed no abnormal findings in the normal control group and sham operation group and hypoxic-ischemia groups in the group model I. In the group model II Diffusing-weighted images and ADCmaps showed no abnormal findings in the normal control group and sham operation group, their ADC values were (1.058±0.044) X10-3mm/sec; (1.051±0.073) X 10"3mm / sec respectively. Abnormal signal intensity was more easily detected on all diffusion-weighted images and ADC maps in three groups at varying time point after hypoxic-ischmia, compared with conventional T2-weighted images detected obvious hyperintensity at the sixth hour. ADC values in the central regions and peripheral regions of lesions on ADC maps were measured at three varying time points. ADC values in the central regions are (0.556 ± 0.065) X10"3mm/sec; (0.466 ± 0.059) X10-3rnm/sec; (0.371 ± 0.023) X 10-3mm / sec; Those in the peripheral ones are (0.817±0.069) X 10'3mm / sec; (0.793 ± 0. 062) X 10-3mm / sec; (0.534±0. 039) X 10-3mm / sec, respectively, There were marked statistical significances (P<0.01)between ADC values of the central regions and those of the peripheral regions. (3) In the group model I there was no expression of HSP70 in the all groups. There was expression of HSP70 at a lower level at the third hour after HIE in the group model II, Induction of HSP70 was raised at the highest peak at the sixth hour, then rapidly decreased. The HSP70 positive cells at three time points in the central regions are (7.36±0.91), (8.64±2.23), (2.64±1.04); those in the peripheral regions are (14.08 ± 1.96), (33.88±2.76), (8.56 ± 1.67), respectively. There was an obvious statistical significance between HSP70 expression in thecentral regions and those in peripheral ones in all groups (P<0.01). (4) There was no statistical co...
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