The Application Of New Technology Of Dual Energy CT In The Preoperative Staging Of Gastric Cancer

Part 1 Gastric Cancer: Preoperative staging with individually adjusted Dual-energy Computed Tomography(CT) scanning phasesObjective: To evaluate test bolus scan technology on preoperative diagnostic performance, vascular enhancement and artery visualization for gastric cancer.Methods: The institutional review board approved this study. Fifty-four patients in protocol 1 were resigned to a fixed delay time scan method, and their images were obtained in the late arterial phase(AP) and portal venous phase(PP), with start delays of 40 and 70 seconds, respectively. Fifty-six patients in protocol 2 had undergone the test bolus method first and received the time to peak enhancement of the aorta. Their images were obtained in the AP and PP with start delays in the time to peak enhancement and 20 seconds after the AP, respectively. Two radiologists performed consensus interpretation of the preoperative TNM staging, vascular enhancement, tumor contrast-to noise ratio(CNR) and artery visualization between the two protocols.Results: There is no significant difference in the T, N, and M staging diagnostic accuracy between the protocols(P=0.41, P > 0.99, and P = 0.34, respectively). For serosa negative(T1, T2, and T3) tumors, the diagnostic accuracy obtained with protocol 2 was superior to that obtained with protocol 1(P=0.04). Protocol 2 was superior for perigastric vessel enhancement(left gastric artery, right gastroepiploic artery, and splenic artery; P<0.001, P<0.001 and P=0.001, respectively). The stomach-to-tumor CNR during the PP of protocol 2 was significantly higher than that during either the AP or PP of protocol 1(P=0.004 and P=0.001, respectively). The mean rankings of the artery visualization were significantly higher with protocol 2 than with protocol 1(P<0.001).Conclusions: The dual-phase scan with test bolus technology could improve the tumor CNR and had high staging accuracy for serosa negative tumors as well as high perigastric artery enhancement, yielding satisfactory artery visualization for diagnosis.Part 2 The application of a new reconstruction algorithm using dual-energy CT images in early gastric cancer: apreliminary studyObjective: To evaluate the impact of the advanced image-based techniques used to calculate monoenergetic dualenergy computed tomography(DECT) on image quality, visibility and stage migration in a retrospective dataset of early gastric cancer(EGC).Materials and Methods: Institutional review board approval and informed consent from each patient were obtained. In total, 31 EGC patients(19 men, 12 women; age range, 38-81 years; mean age, 57.2 years) who underwent a three-phasic DECT scan were retrospectively enrolled in this study. The CT findings were compared with surgical and pathological results. Conventionally reconstructed polyenergetic images(PEIs) at 120 k Vp and virtual monoenergetic images(MEIs) and advanced monoenergetic images(AMEIs) at 6 different kiloelectron volt(ke V) levels(from 40 to 90 ke V) were evaluated from the 100 and Sn 140 k V dual energy(DE) image data, respectively. The visibility and stage migration of EGC for all three image datasets were evaluated using multiplanar reconstruction(MPR) and statistically analyzed. The contrast-to-noiseratio(CNR) was also evaluated.Results: AMEIs at 40 ke Vshowed the best visibility(80.7%) and the lowest stage migration(35.5%) for EGC. The stage migration for AMEIs at 40 ke V was significantly lower than that for PEIs(P= 0.026). AMEIs at 40 ke V had statistically higher CNR in both the arterial and portal phases compared with other AMEIs, MEIs and PEIs(all P<.05).Conclusion: Two-dimensional(2D) advanced image-based calculated virtual 40 ke V images with MPR significantly increase the CNR of EGC, leading to significantly lower stage migration of EGC.Part 3 The value of spectral CT features inidentifying serosa invasion of gastric cancerObjective: Clinical and Spectral CT features were explored to estimate serosa invasion of gastric cancer based on Support Vector Machine Recursive Feature Elimination(SVM-RFE) and zero-norm Support Vector Machine(l0-SVM).Methods: 18 patients with gastric cancer(5 patients in pT2, 4 patients in pT3 and 9 patients in p T4 based on the 7th AJCC guidelines) who underwent dual-phasic scans(arterial phase(AP) and portal venous phase(PP)) with GSI mode on high-definition computed tomography were enrolled in our study. 9 patients(p T1, p T2 and p T3 patients) were classified as serosa negative group(group A) and the rest 9 patients(p T4) were classified as serosa positive group(group B). Regions of interest were placed in the lesion of each phase of two groups to collect the spectral information of 11 sets of monochromatic images and different material basis pairs(e.g., calcium-iodine, iodine-water, fat-calcium) which were used as potential features to identify serosa infiltration. SVM-RFE and l0-SVM model were constructed by taking the above spectral features as input index. The output indexes determine whether the tumor invade serosa or not. The clinical features(e.g., sex, age, tumor long axis) were compared by using chi-square or independent sample t tests. The diagnostic performance of the output features were evaluated by receiver operating characteristic(ROC) curves.Results: Among the clinical features, only tumor long axis and tumor short axis had statistically significant difference between the positive and negative groups(all p<0.05). The accuracy, sensitivity and specificity of SVM-RFE model were all 88.9%. The accuracy, sensitivity and specificity of l0-SVM model were 83.3%, 87.5% and 80.0%, respectively. The overlapping output spectral features of two models were fat-calcium(PP), uricacid-calcium(PP), uricacid-calcium(PP), fat-iodine(AP), calcium-iodine(AP), water-iodine(AP) and iodine-water(PP). The area under the ROC curve(AUC) of the features were 0.857 for long axis, 0.781 for short axis, 0.848 for fat-calcium(PP), 0.871 for uricacid-calcium(PP), 0.839 for uricacid-calcium(PP), 0.835 for calcium(AP), 0.830 for fat-iodine(AP), 0.790 for water-iodione(AP) and 0.750 for iodine-water(PP), respectively.Conclusion: Tumor size is closely associated with the depth of tumor invasion. The value of fat-calcium(PP), uricacid-calcium(PP), uricacid-calcium(PP), fat-iodine(AP), calcium-iodine(AP), water-iodine(AP) and iodine-water(PP) were helpful for the diagnosis of GC serosa infilitration.