| Part one Application of spectral CT in the differentiation of T3 andT4a staged gastric carcinoma Objective:To investigate the value of spectral CT in the differentiation of T3 and T4 a staged gastric carcinoma. Materials and methods:After obtaining the approval from the institutional ethics committee of the first affiliated hospital of zhengzhou university with waiver of informer consent, sixty-two cases(38 men, 24 women, age range:33~77 years, mean age:58.63years±10.38) with gastric carcinoma confirmed by the pathology before operation underwent abdominal double-phase enhanced scanning with GE Discovery 750 HDCT from December 2013 to December 2014, all imaging were performed in gemstone spectral imaging mode. The features of the serosa and adjacent perigastric fat plane of all cases were blindly observed by two professors in our department.Contents observed are as follows:whether the local serous coat was smooth, and the changes of adjacent perigastric fat spaces.Iodine concentration(IC) and water concentration(WC) of perigastric fat tissue adjacent to the lesion were measured during arterial phase(AP) and venous phase(VP), and normalized iodine concentration(n IC) was calculated respectively. Two-sample t tests were used to compare the three parameters between T3 cases and T4 a cases during AP and VP. Receiver operating characteristic(ROC) was used to determine the threshold of n IC for differentiating T3 and T4 a staged gastric carcinoma.Combing the features of the serosa and the adjacent parigastric fat spaces with the threshold of n IC respectively to differentiate the T3 and T4 a staged gastric carcinoma and the corresponding accuracy, specificity and sensitivity were calculated. Results:Among 62 patients with gastric cancer, 20 T3 cancers and 42 T4 a cancers were confirmed by the pathology examination, and 45 cases were confirmed as poor differentiation, 17 cases as well differentiation.The sensitivity, specificity and accuracy of serosal change to differentiate T3 and T4 a staged carcinoma were 85.71%、80%、83.87% respectively. The sensitivity, specificity and accuracy of perigastric fat plane to differentiate T3 and T4 a staged carcinoma were 80.95%、65.5%、75.81% respectively. There was no significant difference of the overall accuracy in two kinds of CT features for differentiation.Significantly higher IC values(100μg/ml) and n IC values were obtained in T4 a cases than that of T3 cases(-5.185±0.81 vs.-3.435±1.54;-0.046±0.01 vs.-0.028±0.01)(P<0.01) during arterial phase. IC and n IC were also higher in T4 a cases compared to T3 cases(-3.776±0.94 vs.-1.624±1.43;-0.043±0.01 vs.-0.017±0.02)(P<0.01) during venous phase. There were no significant difference of WC in two groups during arterial and venous phase. According to the ROC, area under the curve of IC and n IC in venous phase was 0.873 and 0.905 respectively. Taking-0.031 as the threshold of n IC during venous phase, the corresponding sensitivity and specificity were 81% and 85%.Combining the serosal features and threshold of n IC, the diagnostic accuracy was 91.94%(57/62), however, it was not significantly improved compared with the diagnostic performance of just basing on the serosal change, P=0.169. Combining with the fat plane features, the diagnostic accuracy was significantly improved from75.81%(47/62) to 90.32%(56/62), P<0.05.Conclusion:1. Features of serosa and perigastric fat plane have certain value in differentiating T3 and T4 a staged gastric carcinoma.2. The iodine concentration of perigastric fat tissue adjacent to the tumor is significantly higher in cases of T4 a staged gastric carcinoma to that of T3 staged gastric carcinoma, and the difference in venous phase are obvious than that in arterial phase.3. Combining with the n IC of perigastric fat tissue can increase the diagnostic accuracy.Part two Preliminary study of Spectral CT single energy imagingin early gastric carcinoma Objective:To investigate the application of spectral CT generated monochromatic images at different energy levels compared to the conventional CT in T1 staged gastric carcinoma. Materials and methods:Eighteen cases(11 men, 7 women, age range:41~72 years, mean age:56.33years±9.76) with gastric carcinoma confirmed by the pathology before operation underwent abdominal double-phase enhanced scanning in gemstone spectral imaging mode with GE Discovery 750 HDCT. Three sets of images were generated during the arterial phase(AP) and venous phase, conventional 140-k Vp polychromatic images, monochromatic images at 70 ke V energy level and optimal ke V images with highest CNR(using the optimal CNR technique in the GSI Viewer). The tumor to gastric wall contrast to noise ratio(CNR) and mean image noise were calculated and compared using paired t test for each group. The scores of lesion conspicuity and overall image quality were recorded and compared using Wilcoxon test. Results:Among 18 patients with T1 gastric cancer, 4 intramucosal cancers and 14 submucosal cancers were confirmed by the pathology examination. The range of optimal ke V in this group was 51~62 ke V.Compared to 140 k Vp images,images at 70 ke V had significantly lower mean noise(11.22±1.14 vs. 12.49±1.35 in AP; 11.13±1.09 vs.12.27±1.28 in VP)(P<0.05) and significantly higher CNR value(1.51±0.56 vs.2.08±0.52; 1.37±0.48 vs.1.58±0.54)(P<0.05) during arterial phase(AP) and venous phase(VP).The score of both lesion conspicuity and overall image quality of 70 ke V images compared to that of 140 k Vp images were also significantly higher during two phases(P<0.05). Optimal ke V images had significantly higher CNR value and lesion conspicuity score(P<0.05) compared with 140 k Vp images during AP. There were no significant difference of overall image quality score during two phases. Conclusion:The overall image quality of monochromatic images are higher than polychromatic images. The CNR of early gastric carcinoma can be improved in the monochromatic images and can be used in the detection of the early gastric carcinoma. |
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