| Part 1 Experimental Study on Spectra CT of Silicon Dioxide,Calcium Carbonate and Calcium Dihydrogen PhosphateObjective: To explore the identification points between SiO2 and the two kinds of calcium salt,such as Ca?H2PO4?2.H2 O,Ca CO3,and the impaction of different ROI situation,and then to lay the foundation for the analysis of silicosis nodules.Three samples of SiO2,Ca?H2PO4?2.H2 O and Ca CO3 were underwent Gemstone Spectral CT?GSI?scanning.Using different positions and sizes of ROI,then analysised the different indicators of ROI energy spectrum by using a variety of energy spectrum analysis tools.Materials and Methods: The samples of SiO2,Ca?H2PO4?2.H2 O and Ca CO3 were scanned on American GE Gemstone Spectral CT with conventional CT and Gemstone Spectral CT Imaging?GSI?.The tube voltage of conventional CT was 120 k Vp,and GSI was high-and low-energy?typically at 140 and 80 k Vp,respectively?instantaneous?< 0.5 ms?switched.And the other parameters were consistent as the following: tube rotation time,0.6 seconds;helical pitch,0.984;speed of bed,39.37mm/r;tube current,360 m A;slice thickness and interval for axial images,5mm/5mm;field of view,Medium Body;and collimation,64×0.625 mm.The images were reconstructed with standard mode,and the other parameters as following: reconstruction thickness,0.625 mm,reconstruction interval,0.5 mm;ASIR 30%.GSI images were created to 70 ke V monochromatic energy images and then set to GE ADW4.6 workstation.In the workstation measuremented the mean CT value and SD according to different ROIs?maximum,big,middle,small?of SiO2,Ca?H2PO4?2.H2 O and Ca CO3 on conventional CT;obtained GSI.csv data file?CT value change from 40 ke V to 140 ke V every interval of 10 ke V?HU?,Effective atomic number?Effective-Z?and the concentration of each pair of base material concentration?mg/cm3??.All the.csv data was analyzed by IBM SPSS21 software.The skewness data was expressed as median ± four quartile spacing?M ± P25 P75?.Non-parametric Kruskal-Wallis H?K?test,and the non-parametric Mann-Whitney U test was used to examine the difference between the two groups.The receiver operating characteristic curve?ROC?analysis was used to identify the parameters of Ca?H2PO4?2.H2 O and Ca CO3 from SiO2.The ROC curve could calculate the cut point value?Cut off vule?and specificity and sensitivity.P <0.05 for the difference was statistically significant.Results: 1.There were no significant differences in the monochromatic energy images CT values,the Effective atomic number and the base material concentrationof of Silicon Calcium by GSI scan from 40-140 ke V?P value was greater than or close to 0.05?.The box diagram also showed that the box was overlapped more.There was no significant difference in the CT values between the four different ROIs of Ca?H2PO4?2.H2 O,Ca CO3 and SiO2?P = 0.132?,and box diagram also shows the box overlap by conventional CT scan.But the CT standard deviation?SD value?was statistically significant?P <0.001?,and the dispersion was large.2.The CT values from 40 ke V to 140 ke V,the Effective atomic number and the base material concentrationof the three substances were statistically significant?P <0.001?.The parameter was significant difference between the two groups?P <0.001?,such as Ca?H2PO4?2.H2 O and SiO2,Ca CO3 and SiO2.Even more the area under the ROC curve of the CT values from 40 ke V to 140 ke V,the Effective atomic number and the base material concentrationof of the three substances was 1,and the diagnostic sensitivity and specificity were 100%.Compared with conventional CT scan,Ca?H2PO4?2.H2 O,Ca CO3 and SiO2 were statistically significant?P <0.05?,but the box and extension was overlapped more.3.Compared with GSI CT,the difference of the powder and the crystal block was statistically significant?P <0.001?,and the extension line overlapped less in the box diagram.The Calcium?SiO2?and SiO2?Calcium?were statistically significant?P <0.05?.In Calcium-Silicon diagram,the box and the extension of the powder and the crystal block more overlapped,but in Silicon – Calcium diagram,the box and the extension overlapped less.The results showed that there was no significant difference between the two groups?P = 0.492?about the Effective atomic number of Ca?H2PO4?2.H2 O powder and crystal block.The median position of the box in the box diagram was not much different,and the box and the extension line overlapped more.Compared with conventional CT value of Ca?H2PO4?2.H2 O powder and crystal block,the difference was statistically significant?P <0.001?.There was no overlap between the powder and the crystal block in the box diagram.Conclusions: 1.Conventional CT scan could not completely distinguish the three substances of Ca?H2PO4?2.H2 O,Ca CO3 and SiO2,and the CT value was impacted more by the material form.Conventional CT could not determine the powder and crystal block of Ca?H2PO4?2.H2 O was the same substance.2.SiO2 and Ca?H2PO4?2.H2 O,SiO2 and Ca CO3 could not be effectively distinguished from 40 to 60 ke V,but could distinguished from 70 to 140 ke V,and the greater degree of distinction with the increase of energy level.3.The Effective atomic number,Calcium?SiO2?and SiO2?Calcium?materials of GSI CT could effectively distinguish SiO2 from Ca CO3 and Ca?H2PO4?2.H2 O.And there was no significant difference in the Effective atomic number between the powder and the crystal of Ca?H2PO4?2.H2 O.4.There was no significant difference in the measured values of Ca?H2PO4?2.H2 O,Ca CO3 and SiO2 by different methods.Part 2 The Application of Spectral CT Imaging in the Diagnosis of SilicosisObjective: To explore preliminaryly the value of spectral CT in the diagnosis of silicosis using the observation indexes of the first part study?from 70 ke V to 140 ke V monochromatic energy images,the Effective atomic number and the concentration of pair of base material concentration?.Materials and Methods: 27 patients with silicosis were underwent Gemstone Spectral CT Imaging?GSI?in the study?as silicosis group?.There were 9 cases of stage I,12 cases of stage?,and 6 cases of stage ?,dust duration ranging from 4 to 40 years,an average of 18.44 ± 8.65 years,dust exposure categories respectively quarrying in 7 cases,10 cases of mining,glass blowing in 6 cases,pottery making in 3 cases,marble cutting in 1 case.A total of 20 cases having no dust exposure with multiple nodules or masses of lung were included in the study as control group,who were underwent GSI CT from Mar.2016 to Mar.2017,of which 14 cases of malignant tumor metastasis,pulmonary tuberculosis in 2 cases,physical examination accidentally found nodules in 4 cases.All the object of study were examined on the United States GE Discovery CT750 HD and scanning parameters were consistent as the following: tube rotation time,0.6 seconds;helical pitch,0.984;speed of bed 39.37mm/r;tube current,360 m A;slice thickness and interval for axial images,5mm/5mm;field of view,Medium Body;and collimation,64×0.625 mm.GSI was high-and low-energy?typically at 140 and 80 k Vp,respectively?instantaneous?< 0.5 ms?switched,the scanning range for both sides of the lung field.The images were reconstructed with standard mode,and the other parameters as following: reconstruction thickness,0.625 mm,reconstruction interval,0.5 mm;ASIR 30%.Spectral CT images were created to 70 ke V monochromatic energy images of GSI and then set to GE ADW4.6 workstation.In the workstation choosing suitable size of round or oval ROI,and the ROI should include 1/2 1/3 of the lesion area,small lesions enlarge maximum before measurement.The GSI.csv data file(?CT value change from 40 ke V to 140 ke V every interval of 10 ke V?HU?,Effective atomic number?Effective-Z?and the concentration of each pair of base material concentration?mg/cm3??.Part of.csv datas from 70 ke V to 140 ke V monochromatic energy images,the Effective atomic number and concentration of each pair of base material concentration were took into the statistical analysis.The application of skewed data was represented by the median ± four quartile spacing?M ± P25 P75?,Non-parametric Kruskal-Wallis H?K?test,Non-parametric Mann-Whitney U Test for differences in concentration trends between two groups.The two groups were measured and identified by operator.The operator's characteristic curve?ROC?was used to calculate the cut off vule and the specificity and sensitivity of the silicosis group and the control group.P <0.05 for the difference was statistically significant.Results: 1.Compared the silicosis group with the control group in the monochromatic energy images from 70 ke V to 140 ke V,the difference was statistically significant?P <0.001?.The box and the extension line overlapped,the extreme value was more.But with the energy level,the box gap was getting bigger and bigger.Compared the silicosis group with the control group in the pair of base material concentration the difference was statistically significant?P <0.001?.In the box diagram,SiO2?Water?and Calcium?Water?box and extension line overlapped more,the silicosis group had more extreme values.The remaining groups of the box overlapped less,and extension lines overlapped.The area under the ROC curve of the Effective atomic number was 0.923,and the corresponding sensitivity and specificity index were 93.58% and 81.67%,respectively.Conclusions: The results showed that the difference of the monochromatic energy images from 70 ke V to 140 ke V,the Effective atomic number,the pair of base material concentration between the silicosis group and the control group was statistically significant.The area under the ROC curve of the monochromatic energy images from 100 ke V to 140 ke V,the Effective atomic number,the silicon-water-based material map,the water-silicon-based material map,the silicon-calcium-based material map,the calcium-silicon-based material map,the calcium-water-based material map and the water-calcium matrix material were all greater than 0.85.Among them the area of the Effective atomic number was 0.923,the corresponding threshold was more than 10.52,the diagnostic sensitivity was 93.58% and the specificity was 81.67%,which was the valuable index for the diagnosis of silicosis. |
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