| Part one:diffusion tensor imaging of continuous acute hepatic ischemia in rabbitsAbstract:objective:To evaluate magnetic resonance diffusion tensor imaging (DTI) of continuous acute hepatic ischemia following the first porta deligation in rabbits; thus to disscuss probable causes of rabbits’ quick death through examining changes of the DCavg values and FA values and their laws, and the time of death. Methods:16 healthy rabbits were randomly selected in this study. Continuous acute hepatic ischemia in rabbits was induced by using the Pringle’s method (deligation of the first porta hepatis). In the preoperative and immediately postoperative stages, diffusion tensor imaging was carried out under each preset 6-value (50> 100、200、300、400、500 s/mm2). DCavg value and FA value were measured respectively. The interval between deligation of the first porta hepatis and death was recorded as the time of death (min). One rabbit was chosen at random to undergo a comprehensive anatomy immediately after death. Its brain, right lung, right lobe of liver, the midpiece intestine, right kidney were partly taken to pathological examinations. Pairwise t-test was performed to compare the mean DCavg and FA values measued under the same b-value in the preoperative and immediately postoperative stages.While univariate ANOVA was performed to compare the mean DCavg and FA values between different b-values in the two stages. The area under ROC curve was measured to evaluate the diagnostic efficience of DCavg value under different b-values. The characteristics of pathological change in liver tissue were observed through optical microscope. The relationships between the pathological changes, the image results and the time of death, the cause of death were eventually investigated. Results: Being familiar with the first porta hepatis and surroundings’s anatomy, continuous acute hepatic ischemia was successfully established in each rabbit. There was a general tendency of progressive decrease in DCavg values under each preset b-value in the preoperative and immediately postoperative stages. DCavg values in postoperative group were also significantly lower than those in preoperative group. In the preoperative stage, the differences in FA values were not significant as the b-value increased; in the postoperative stage, there was a significant difference in FA values as b-value changed. While the difference in FA values between the two stages was not statistically significant. According to the area under the ROC curve, the DCavg values had a most high level of diagnostic value when b-value was 50,100,200,300,400 s/mm2. While the DCavg value measured under 500 s/mm2 had a relatively lower level of diagnostic value (the area under the curve,0.90). The DCavg value measured under 200 s/mm2 had the highest level of diagnostic value(the area under the curve,0.94). The time of death ranged from 52 to 98 minutes, the average was 59.5 minutes. An autopsy immediately following death showed a grey liver and congested superficial veins of the gastrointestinal tracts. A pathological biopcy under optical microscope showed intact liver cells with distinct neuclei and nucleole. Conclusion: 1. Continuous acute hepatic ischemia in rabbits could be established by using the Pringle’s method,which had high success rate, and might be more practical,less time-consuming.2. DTI could be capable of evaluating continuous acute hepatic ischemia in rabbits. The DCavg value measured under b-value= 200 s/mm2 had the highest level of diagnostic value, while the FA value seemed useless to evaluate the model.Part two::An animal experimental study based on MSCT technology virtual autopsy to conclude the time of deathAbstract:objective:Discussion on the death of the rabbit multiple organ imaging findings and its evolution over time, rate the value of MSCT virtual autopsy to deduce the time of death.Methods:Died in the first part of the experiment of 16 rabbits all included in this study, only by nine different periods before and after death is divided into nine groups: normal stage, immediately after death, the first day after death, the second day after death, the third day after death, the fourth day after death, the fifth day after death, the sixth day after death, the seventh day after death.Respectively in each time point was carried out on the death of rabbit supine 64 row 128 layer spiral CT of head and neck joint scanning, chest CT scan data to ADW4.4 workstation.Immediately after completed each scan randomly selected an autopsy on rabbit, observe the general situation, and take the middle of the brain, lungs, liver, right, and part of the middle intestine, right kidney pathologic examination.In ADW4.4 post-processing workstation, using the software comes, the features of the cross-section with the shift and the left mouse button outline the largest coronal, sagittal, transverse section of the brain and the right diaphragmatic top level of the chest, liver and liver tissue of continuous three levels above the door, the door right kidney and kidney tissues of continuous three levels above the boundary, the two-dimensional image of CT value for areas of interest-area ratio curve, the curve with CT value as the abscissa, area ratio as the ordinate), according to the experiment to manually set the maximum and minimum CT value (refer to literature and experimental target CT value range), the CT value obtained automatically by the software within the scope of the average CT value and virtual area ratio.Measure the L3 layer vertebral vertebra below (including the vertebral body and attachments) and abdominal area, calculate its area ratio.To observe and compare the death of rabbit brain, chest, abdomen, liver, kidney CT manifestation of each point in time.Draw the rabbit brain, chest, liver, right kidney-CT density curve, with the time-virtual area ratio curve and time-abdominal/vertebrae area ratio curve.SPSS 20 statistical software is used to analyze data, all measurement data use the mean±standard deviation (X±SD), according to multiple sets of the comparison of difference mean using single factor analysis of variance (one-way ANOVA), and the comparison of mean differences between groups using LSD-t method (group variance not neat Welch method, multiple comparison between T2 Tamhane’s method), with P< 0.05 for the difference was statistically significant.Results: 1.The target level of CT value-area ratio curve, on the basis of different organizations interested in area and produce different change after death, and there are corresponding changes in the characteristics:the peak is located in the brain, liver and kidney are unimodal curve between 0-100 Hu, and initial waveform narrower, wave the sharp, with the extension of time after death, increase the gas inside the target tissue, waveform widen, wave can reduce and become flat, are too many gases form the CT value <-800 Hu gas peak;Chest level mostly bimodal curve, the larger wave between-800--800 Hu, smaller wave between 0-100 Hu, also can to unimodal or three peak curve, unimodal lies between-800--800 Hu, three peak at-800--800 hu,-200-0 Hu, between 0-100 Hu, with the increase of the time of death, the chest cavity corruption gas increases, the lung tissue seepage, consolidation, no to corruption, visible<-800 Hu gas peak appears, form more peak or peak only gas.2.The single factor analysis of variance, there are five indicators is not statistically significant(P> 0.05),in addition to the chest cavity the mean value on-800--200Hu,-200～0Hu,0-100Hu CT-value range,and the chest cavity the virtual area ratio on-200～0Hu、0-100Hu CT-value range, the rest of the 10 indicators of the difference had statistical significance.(1) the brain CT average:immediately after the death of stage increases slightly,1 day after the death of the maximum, then slow down, on the sixth day,7 days down to below the normal phase.1-4 days after death compared with normal phase, the difference was statistically significant.Immediately after the death of the mean (2) liver CT:stage significantly reduced,1-2 days back to near normal stage, sexual reduce 3-6 days,7 days and again but still well below normal.Compared with the normal phase 5, and 6 days after death, the difference was statistically significant.Immediately after the death of renal CT (3) the mean:rise,0 to 7 days were higher than normal phase, the highest on day 1, followed by progressive decrease.Immediately after death to 4 days compared with the normal phase, the difference was statistically significant.(4) the chest cavity<-800 hu, the mean CT:0 to 7 days after the death of progressive decrease.Compared with the normal phase 3-7 days after death, the difference was statistically significant.(5) the chest CT-800 hu hu～-200 in average:immediately and 1 day after the death of slightly lower, then the overall rising trend. After the death of all time phase and normal phase comparison, there were no statistically significant difference.(6) the chest CT-200 hu hu-0 in average:no obvious regularity.After the death of all time phase and normal phase comparison, there were no statistically significant difference.(7) the chest of 100 hu hu-0 CT average:immediately after death has no obvious change, slightly increased 1-3 days,4 days down to near normal stage,5-7 days increased again,2 days after the death of the highest.After the death of all time phase and normal phase comparison, there were no statistically significant difference.(8) brain virtual area ratio:it increases slightly, immediately after the death of dying after 2 days up to a maximum,3 days are down a bit, then a progressive decrease.Compared with the normal phase 5-7 days after death, the difference was statistically signi5icant.(9) liver virtual area ratio:immediately after the death of stage increased slightly, slightly reduce 1-2 days but still close to normal phase, 3-6 days progressive reduction,7 days and a back up but still well below normal.Compared with the normal phase 3-7 days after death, the difference was statistically significant(10) kidney empty area ratio: immediately after the death of phase is slightly lower, after the death of 1-2 days is a bit higher, day 1 is highest, followed by progressive decrease gradually.Compared with the normal phase 5 and 7 days after death, the difference was statistically significant.(11) within the chest-800 hu, virtual area ratio:immediately after the death of rise, fall back 1-2 days,3 to 7 days after the death of significantly higher than the normal phase, top 5 days.Compared with the normal phase 5-7 days after death, the difference was statistically significant.Hu-(12) in the chest-800-200 hu, virtual area ratio:overall assumes the progressive decrease.Compared with the normal phase 4 to 7 days after death, the difference was statistically significant.(13) within the chest-200 hu hu-0 virtual area ratio:in addition to the fifth day after the death of close to normal phase, the rest of the time were higher than normal. After the death of all time phase and normal phase comparison, there were no statistically significant difference.(14) intrathoracic 0 hu-100 hu, virtual area ratio: no obvious regularity.After the death of all time phase and normal phase comparison, there were no statistically significant difference.Layer (15) L3 vertebral the abdomen/vertebrae area ratio:the overall a progressive increase, on the sixth day after the death of area than the average maximum,7 days and slightly lower, close to the ratio of 4 days after death.Compared with the normal phase 4 to 7 days after death, the difference was statistically significant.Conclusion:(1) the MSCT virtual autopsy observation of the gas is obviously superior to conventional autopsy.(2) the MSCT virtual autopsy reflects each organ tissue autolysis corruption process has certain commonality:CT average real organs and tissues of virtual area ratio and lower down, gas cavity corruption area ratio increases and the average CT reduces.In CT value area ratio curve at the same time, the density of time-virtual area ratio curve, time-also have their own characteristics.(3)the MSCT virtual autopsy body organs and tissue change dynamic observation, middle to infer the time of death, has certain feasibility. |
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