| Objective:To determine the efficiency of spectral CT for quantitative detection of fat content in the liver.Methods:35 male Wister rats(weight 200~220g)were randomly divided into control group(10 cases,normal diet)and high-fat group(25 cases,high-cholesterol diet).After the raising for one month,at an interval of two weeks,2 rats were taken from the control group,and 5 rats were taken from the high-fat group.After the intraperitoneal anesthesia with hydrated chlorine,the rats were dissected under the energy spectrum mode,and the liver was dissected by excessive chloral hydrate in the sudden death rats.The left outer lobe of the liver was fixed with formalin for 48 hours and the pathological examination was carried out.(2)image postprocessing and histological analysis: 25mm2 region of interest in the CT image was drawed on the left outer lobe of the liver.The liver tissues taken from the left outer hepatic lobe underwent the pathological examination.(3)statistical analysis: The mean fat-based value,the mean CT value of 70 ke V,and the mean slope of spectral curve underwent the correlation analysis with a fatty degeneration verified by pathological examination.According to the grade of fatty degeneration in non-alcoholic fatty liver disease(NAFLD),the high-fat group was divided into 3 pathological groups: mild,moderate and severe(normal <5%,mild:5%~33%,moderate:33%~66%,severe > 66%).The mean fat-based value,the mean CT value of 70 ke V,and the mean slope of spectral curve underwent the correlation analysis with a fatty degeneration verified by pathological examination.The spectral CT indexs of the control group,mild,moderate and severe groups were examined by Kruskal-Wallis test,and then the any two groups were tested by Mann-Whitney U test.The CT indexs of subgroups of mild,moderate and severe steatosis groups were examined by Kruskal-Wallis test,and then the any two subgroups were tested by Mann-Whitney U test.Result:Histopathological findings in rats: mild steatosis occurred in 1 rat from control group,and the histological quantization was 10%.Mild fatty degeneration group: 5%-15%(3 rats),15%-25%(3 rats)and 25-33%(2rats),moderate fatty degeneration group: 33%-44%(2 rats),44%-55%(2rats),55%~66%(3 rats),serious fatty degeneration group: 66%-77%(2rats),77%-88%(4 rats),> 88%(4 rats).In high-fat group,three indices of spectral CT were correlated to the pathological results:(1)70Kev CT value: Adj.R-Square=0.88734,P < 0.001(2)fat base value: Adj.R-Square=0.93025,P < 0.001(3)spectrum curve slope: Adj.R-Square=0.8075,P < 0.001.The results of the subjective comparison of the energy spectrum curve showed that the control group and the mild fat degeneration group almost coincided,while the other groups of high fat groups and between the high fat groups and the control group had different spectral curve positions or walks.The three indices of spectral CT were significantly different between control group and fatty degeneration groups(P < 0.05);fat-based value(-72.44±20.134 Vs-52.19±30.567 Vs 32.12±19.147 Vs 133.17±33.524),70 Kev CT value(74.14±3.14 Vs 68.17±2.727 Vs 54.12±4.425 Vs43.55±3.347),energy spectrum curve slope(-0.104 ± 0.002 Vs-0.025 ±0.003 Vs 0.047 ± 0.005 Vs 0.175 ± 0.0017).But three indices of spectral CT were not significantly different between control group and mild fatty degeneration group(P > 0.008).The three indices of spectral CT of 3subgroups of mild fatty degeneration : fat-based value(-62.45±30.12 Vs-52.15± 22.97 Vs-39.14 ±14.57),70 Kev CT value(71.45 ±3.21 Vs 68.15± 2.45 Vs 63.11 ±4.77),energy spectrum curve slope(-0.085 ± 0.012Vs-0.035 ±0.004Vs-0.017 ±0.021).The three indices of spectral CT were not statistically significant(P > 0.05).The two indices of spectral CT of 3subgroups of moderate fatty degeneration were significantly different(P< 0.05):fat-based value(-25.17 ± 13.45 Vs 39.15 ± 17.44 Vs 60.44±23.44),energy spectrum curve slope(-0.004 ±0.001Vs0.042 ±0.007Vs0.076 ±0.015).70 Kev CT value(60.17 ±3.22 Vs 56.15 ±2.17 Vs52.17 ± 3.09)was not significantly different(P > 0.05).The three indices of spectral CT of 3 subgroups of severe fatty degeneration were significantly different(P < 0.05).Fat-based value(81.44 ± 33.17 Vs129.47 ±52.15 Vs 167.55 ±64.21),energy spectrum curve slope(0.094±0.011 Vs 0.178 ± 0.017 Vs 0.224 ± 0.023),70 Kev CT value(50.17 ±4.14 Vs 42.15± 3.87 Vs 38.15±3.01).At the same time,The three indices of spectral CT of any two subgroups in severe fatty degeneration group were significantly different(P < 0.017).Conclusion:Spectral CT could rapidly diagnose NAFLD and quantitatively detect moderate fatty and serious fatty degeneration. |
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