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Objective:To investigate the clinical value of multiparametric myocardial imaging using a dual-layer detector spectral CT in the non-invasive preoperative assessment of patients with coronary atherosclerotic heart disease (CHD) undergoing percutaneous coronary intervention (PCI).Methods:The clinical and imaging data of 90 patients who underwent coronary CT angiography (CCTA) with dual-layer spectral detector CT and invasive coronary angiography (ICA) within 30 days at the Affiliated Changshu Hospital of Nantong University from January 2021 to October 2022 were retrospectively analyzed. A total of 189 coronary arteries were included in the study cohort. The patients were divided into PCI ( n=44) and non-PCI groups ( n=46) according to whether they received PCI after evaluation with ICA. The diameter stenosis rate of the coronary arteries, myocardial iodine concentration (IC) and effective atomic number (Z eff) values were obtained from CCTA conventional and spectral images. The IC values and Z eff values of the myocardium in the areas with abnormal perfusion were compared with those in the areas with normal perfusion. The diagnostic performance of these parameters, as well as their combined model, was evaluated and compared using receiver operating characteristic (ROC) curve and area under the curve (AUC) in the pre-PCI assessment of patients with CHD. Results:Baseline patient data did not show statistically significant differences between the PCI and non-PCI groups (all P>0.05). There were statistically significant differences in IC values [(0.42±0.28) and (2.26±0.48) mg/ml] and Z eff values (7.39±0.33 and 8.50±0.25) between the myocardium areas with abnormal perfusion and the myocardium areas with normal perfusion in all patients (all P<0.001). The AUC for assessing whether patients with CHD need PCI treatment using myocardial IC and Z eff values were 0.865 and 0.853, respectively, which were significantly higher than assessment based only on lumen diameter stenosis rate (AUC=0.726, P<0.001). Conclusions:The IC and Z eff derived from myocardial spectral images can be used to diagnose myocardial perfusion abnormalities in patients with CHD. The spectral myocardial multi-parameters imaging shows promising potentials in pre-PCI assessment of patients with CHD, which can improve the efficiency of evaluation and may help to avoid unnecessarily invasive procedures.
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Objective:To evaluate the feasibility of artificial intelligence (AI) diagnosis of pulmonary nodules on virtual non-contrast(VNC) images derived from dual-layer detector spectral CT.Methods:Totally 52 patients who underwent non-contrast and dual-phase enhanced chest CT scan from May 2022 to November 2022 were enrolled in this study. The VNC images of lung were reconstructed based on venous phase data. CT values and image noise of lung parenchyma, signal-to-noise ratio (SNR) were measured. The dose-length product (DLP) of each scan was recorded and the effective dose ( E) was calculated. All of the objective indicators of image quality and radiation dose were compared by Paired t test. Image quality was evaluated subjectively by two radiologists and compared with Wilcoxon non-parametric test. Wilcoxon symbolic rank test was used to compare the sensitivity and false positive detection rate (FPDR) of AI diagnosis between two groups. Results:Compared with TNC, the noise of venous VNC image was decreased by 13.8%, SNR increased by 14.9%, and both of DLP and E decreased by 33.3% ( t=5.82, -5.35, 22.93, 22.92, P <0.05). There were no significant differences in CT values and subjective scores between 2 groups ( P >0.05). For different types of pulmonary nodules, there was no statistical difference in the sensitivity of AI diagnosis between two groups ( P >0.05). For solid nodules with diameter ≤4 mm and all pulmonary nodules in general, FPDR in VNC group was slightly increased with statistical significance ( Z=-2.03, -3.09, P<0.05), while for other types of pulmonary nodules, there was no statistical difference ( P >0.05). Conclusions:The VNC images of thoracic venous phase based on spectral CT can significantly reduce the radiation dose of patients while the image quality and the AI diagnostic sensitivity of pulmonary nodules remain unchanged, and the FPDR without significantly increase. And it could replace TNC for daily routine.
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Objective:To investigate the clinical value of virtual monoenergetic images (VMI) and electron density map (EDM) derived from the dual-layer spectral detector CT (DLCT) in the differential diagnosis of benign and malignant pulmonary ground glass nodules (GGN).Methods:From July 2019 to August 2020, a total of 65 patients with lung GGN (27 benign GGNs and 38 malignant GGNs) confirmed by pathology were retrospectively enrolled in Gulou Clinical Medical College of Nanjing Medical University. All the patients underwent DLCT plain scanning within two weeks before the surgery. The conventional 120 kVp polyenergetic image (PI), EDM and 40-80 keV VMI were reconstructed. The differences of CT and electron density (ED) values between benign and malignant lesions on different images were compared by Mann-Whitney U test. Independent t-test was used to compare the lesion size and χ 2 test was used to analyze the CT features (including lesion location, shape, edge, internal structure, adjacent structure, nodule type) between benign and malignant lesions. Receiver operating characteristic (ROC) curve was used to analyze the efficacy of different energy spectrum quantitative parameters in the differential diagnosis of benign and malignant GGN. The statistically significant CT signs and energy spectrum quantitative parameters were analyzed by logistic regression analysis to find out the independent risk factors of malignant GGN, and then ROC curve analysis was performed for each independent risk factor alone or in combination. Results:There were significant differences in lesion shape, spiculation, lobulation, location and size between benign and malignant groups ( P<0.05). The CT value of pulmonary GGN in PI, 40-80 keV VMI and the ED value in EDM were statistically different between benign and malignant lesions ( P<0.05). The area under ROC curve (AUC) were 0.680, 0.682, 0.683, 0.686, 0.694, 0.676 and 0.722, respectively, among which the ED value had the highest AUC. Binary logistic regression analysis was carried out with GGN shape, spiculation, lobulation, location, size, ED value and CT value in PI, 40-80 keV VMI as independent variables, and malignant GGN as dependent variables. The results showed that ED value (OR=1.045, 95%CI 1.001-1.090, P=0.044), lesion size (OR=1.582, 95%CI 1.159-2.158, P=0.004), spiculation sign (OR=11.352, 95%CI 2.379-54.172, P=0.002) were independent risk factors for malignant GGN. ROC curve analysis showed the AUC of ED value, lesion size, spiculation sign and combination of the three for differential diagnosis of benign and malignant GGN were 0.722, 0.772, 0.698 and 0.885. The AUC for the combined parameters was the largest, with sensitivity of 92.1% and specificity of 74.1%. Conclusion:The diagnostic efficacy of EDM is higher than that of other VMI in the differential diagnosis of pulmonary GGN by DLCT images; The efficacy is further improved when EDM is combined with lesion size and spiculation sign for comprehensive diagnosis.
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Objective:To investigate the feasibility of reducing the radiation dose on coronary artery calcium score (CS) of virtual non-contrast (VNC) scanning in dual-layer spectral coronary CT angiography(CCTA).Methods:One hundred and twenty-two patients were examined on a dual-layer spectral detector CT scanner from March 2019 to August 2020. Volume CT dose index (CTDI vol), dose length product (DLP), effective dose ( E) were all evaluated for each patient. CS was calculated from both true non-contrast (TNC) and VNC images for left anterior descending (LAD), left circumflex (LCx), right coronary artery (RCA), and the total coronary artery (Total) by two radiologists independently. Pearson′s correlation coefficient was calculated for measuring the association between variables. The correction coefficients of each branch (λ LAD, λ LCx, and λ RCA) and the average correction coefficient (λ AVG) of the total coronary artery were obtained. The calibrated calcium score (CCS_VNC) was equal to λ multiplied by CS_VNC. The CS_TNC and CCS_VNC were compared using repeated oneway analysis of variance test. Correlation analyses for CS_TNC and CCS_VNC and agreement evaluation with Bland-Altman-Plots were performed. Results:The average effective doses in TNC, CCTA and total group were 0.69, 6.47 and 7.16 mSv, respectively. The effective dose was reduced by 10.6% and the scan time was reduced by 39% while using VNC images. There were significant differences among the CS_TNC and CS_VNC of LAD, LCx, RCA and Total ( t=6.75, 5.33, 4.99, 6.60, P< 0.05). Excellent correlations were observed between CS_VNC and CS_TNC ( R2 values were 0.929, 0.896, 0.958, and 0.918; λ values were 2.18, 1.18, 2.15, and 2.07, respectively). There were no significant statistically difference among the CS_TNC, CCS_VNC AVG, and CCS_VNC LAD/RCA of the LAD and RCA (all P> 0.05). The difference was statistically significant among the CS_TNC, CCS_VNC AVG, and CCS_VNC LCx of the LCx ( F=10.94, P<0.05). The paired comparison were performed in groups and the differences were statistically significant between the CS_TNC versus CCS_VNC AVGand CCS_VNC AVG versus CCS_VNC LCx ( t=3.31, 3.43, all P<0.05). There was no significant statistically difference between the CCS_VNC LCx and CCS_VNC AVG( P>0.05). Conclusions:It was feasible to accurately evaluate the CS_VNC from spectral data in comparison to TNC imaging, and to reduce the patient radiation dose and acquisition time.
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Objective:To explore the value of dual-layer spectral detector CT in differentiating the diagnosis of lung cancer and inflammatory nodules.Methods:A total of 92 patients undergoing enhanced chest scan from March 2019 to September 2020 at Renji Hospital, School of Medicine, Shanghai Jiaotong University, were retrospectively enrolled in the study. The conventional CT parameters, spectral CT parameters were measured and the nodules′ morphological characteristics were analyzed. Later the factors with statistical significance were identified as independent variables in a logistic regression model to establish models for predicting malignant nodules. ROC curve was used to assess the diagnostic performance for the conventional CT model, spectral CT parameters and combined model, respectively. Differences in the area under the ROC curve (AUC) were analyzed by the DeLong test.Results:Lobulated sign (42 and 8, respectively, χ2=10.779, P=0.001), short burr sign (41 and 7, respectively, χ2=11.911, P=0.001), pleural indentation sign (45 and 9 respectively, χ2=11.705, P=0.001), vascular convergence sign (35 and 8, respectively, χ2=5.337, P=0.021) and the venous phase iodine concentrations (IC) value [(2.1±0.5) mg/ml, (2.3±0.5) mg/ml, t=-2.464, P=0.016], normalized iodine concentrations (NIC) value (0.40±0.06, 0.45±0.08, t=-6.943, P<0.001), and Z-effective (Z eff) values (8.38±0.21, 8.49±0.19, t=-2.122, P=0.037) were significantly different between the lung cancer group and the inflammatory group, while other CT signs and CT indicators were not significantly different between the lung cancer group and the inflammatory group ( P>0.05). The conventional CT model was established with lobulated sign, short burr sign, pleural indentation sign, vascular convergence sign, and the AUC for differential diagnosis of lung cancer and inflammatory nodules was 0.827. The spectral CT parameter model was established with venous phase IC, venous phase NIC, and venous phase Z eff value, and the AUC for differential diagnosis of lung cancer and inflammatory nodules was 0.899. The conventional CT model combined spectral CT parameter model was established with the significant factors in the univariate analysis, and the AUC for differential diagnosis of lung cancer and inflammatory nodules was 0.925. The AUC of the combined model showed no significant difference from that of the spectral CT parameter model ( Z=1.794, P=0.073). However, AUC of the combined model was significantly higher than that of evaluation based on conventional CT alone ( Z=2.156, P=0.031). Conclusion:Spectral CT parameters combined with conventional CT signs can improve the differential diagnosis efficiency between lung cancer and inflammatory nodules.
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Objective:To explore the feasibility of quantitative evaluation of extracellular volume (ECV) fraction in acute ST-segment elevation myocardial infarction (STEMI) by dual-layer spectral detector CT.Methods:The clinical and imaging data of 20 patients with STEMI who underwent cardiac contrast-enhanced CT and MRI from January to October 2019 in Renji Hospital affiliated to Shanghai Jiaotong University School of Medicine were retrospectively analyzed.The dual spectral detector was used in the enhanced CT scan of the coronary artery with retrospectively gate and the late iodine enhancement with prospective gate. Conventional image and holographic spectral image were obtained by iterative and spectral reconstruction. The short axis image of the heart matched with MR image was obtained by multiplanar reconstruction. Based on the data of spectral based image, the IDD map was reconstructed for the calculation of myocardial CT-ECV during the late iodine enhancement. ECV of infarcted myocardium, salvageable myocardium and remote myocardium based on CT and MRI were calculated respectively. Bland-Altman consistency test and intra group correlation coefficient analysis (ICC) were used to compare the consistency of two measurements and different methods. The correlation between CT-ECV and MRI-ECV was compared by Spearman method.Results:The CT-ECV values of infarcted, salvageable, and remote myocardium were 51.21 (49.27, 53)%, 38.64 (36.17, 40)%, and 51.21 (49.27, 53)%, respectively. The difference was statistically significant ( H= 43.17, P<0.01). The CT-ECV value of infarcted myocardium was significantly higher than that of salvageable myocardium and remote myocardium ( Z=-24.60, 35.40, P<0.01), but there was no significant difference between salvageable myocardium and remote myocardium ( Z= 10.80, P=0.15). The T 1 values of infarcted myocardium, salvageable myocardium and remote myocardium were (1 554.85±70.94), (1 443.85±67.28) and (1 307.05±91.73) ms respectively, the difference was statistically significant ( F=51.35, P<0.01). The T 1 value of infarcted myocardium was higher than that of salvageable myocardium and remote myocardium ( t=-5.07, 9.55, P<0.01), and salvageable myocardium was significantly higher than that of remote myocardium ( t=5.38, P<0.01). The MRI-ECV values of infarcted myocardium, salvageable myocardium and remote myocardium were 55.00 (49.27, 57.75)%, 33.50 (29.00, 35.00)%,and 27.00 (26.00, 29.00)%, respectively. The difference was statistically significant ( Z= 47.12, P<0.01). MRI-ECV of infarcted myocardium was significantly higher than that of salvageable myocardium and remote myocardium ( Z=37.45, -20.30, P< 0.01), and salvageable myocardium was significantly higher than that of remote myocardium ( Z = 17.15, P<0.05). The difference between CT-ECV and MRI-ECV measured by two physicians was good. The bias of Bland-Altman analysis was -0.1% (95% CI:-5.5%-5.2%), 0.8% (95% CI:-9.8%-8.2%), and the ICC values were 0.92 and 0.94, respectively. The bias of Bland-Altman analysis in CT-ECV and MRI-ECV consistency test was 4.00% (95% CI:-9.0%-16.9%) and ICC value was 0.88, which had a good correlation ( r=0.75, P=0.001). Conclusions:The iodine density based ECV fromdual-layer spectral detector CT can be used to quantitatively evaluate the changes of extracellular space after acute STEMI, which is helpful to quantitatively evaluate the histological changes after myocardial ischemia.
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Objective:To investigate the clinical value of iodine density map and low keV virtual monoenergetic images (VMI) derived from dual-layer spectral detector CT (DLCT) for the pancreatic neuroendocrine tumors (pNETs) detection.Methods:From January to June 2019, data of 23 pathologically confirmed patients of pNETs were retrospectively analyzed. All of the patients underwent pancreas enhanced DLCT scanning within 1 week before surgery. The conventional polyenergetic images (PI), iodine density map and 40, 50, 60, 70 keV VMI were generated. One resident radiologist with 3 years’ experience and one senior radiologist with over 10 years’ experience interpreted the images for the lesion detection independently using the following image series: PI, VMI (40-70 keV), PI combined with iodine density map. Lesion detection rates were recorded and compared among different image series. The CT value and noise of lesion, normal pancreatic parenchyma, and abdominal subcutaneous fat were measured in PI and VMI in both arterial and portal vein phases. The contrast-to-noise ratio (CNR) of lesion was calculated. The CT value of lesion and normal pancreatic parenchyma, CNR of lesion, and image noise were compared using repeated one-way ANOVA test. Subjective image quality was assessed with a 5-point scale and compared with Friedman test.Results:A total of 26 lesions were confirmed from 23 patients. For resident radiologist and senior radiologist, the detection rates of pNETs lesion using PI were 76.9% (20/26) and 84.6% (22/26) respectively, and both improved to 92.3% (24/26) using image series of 40 and 50 keV VMI. For senior radiologist, the pNETs lesion detection rate was further improved to 96.2% (25/26) using image series of PI with iodine map. The CT value of lesion and normal pancreatic parenchyma, CNR, and image noise had statistical differences among PI and VMI (40-70 keV) in both arterial and portal vein phase ( P<0.001). The mean CT attenuation and CNR of lesion in VMI increased significantly as the energy level decreased.The CNR of lesion in all VMI (40-70 keV) was significantly higher than that in PI. The median of subjective scores of image quality in PI and VMI (40-70 keV) were 3, 3, 4, 4, and 5 respectively, and the difference was statistically significant (χ2=66.393, P<0.001). Conclusions:The low keV VMI derived from DLCT can increase the CT value and CNR of pNETs, and the lesion detection rate can be improved combined with iodine density map. The CNR of pNETs is the highest in 40 keV VMI, and image noise is still lower than that of PI, so 40 keV VMI is recommended for clinical application.
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Objective:To explore the optimal monochromatic level for the observation of coronary in-stent lumen by dual-layer spectral CT (DLCT).Methods:Forty-nine patients with 74 stents after percutaneous coronary intervention (PCI) who underwent coronary CTA (CCTA) examinations by a DLCT between January 2016 and September 2017 were retrospectively enrolled. A total of 12 groups of images including 60-120 keV (kilo electron voltage) images with 10 keV interval, 140-200 keV images with 20 keV interval and conventional images. In-stent lumen diameter of proximal, mid and distal portion was measured. Difference of CT values between in-stent lumen and ascending aorta was used to describe as blooming artifact, and noise of in-stent lumen as image noise. Then Likert 5-point scale was performed to evaluate images noise, enhancement of in-stent lumen, blooming artifact and diagnostic confidence. Differences of objective and subjective parameters among conventional and various monochromatic images were compared by Friedman test.Results:In the diameter measurement of the proximal, middle and distal segments of the stent, the difference between the images of each group was statistically significant (χ 2 = 427.270, 426.375, 400.981, P< 0.001). The diameter of the lumen measured by 120-200 keV single-level image was larger than that measured by 60-100 keV single-level image, and the difference was statistically significant ( P< 0.05). In the comparison of CT difference between the stent lumen and ascending aorta, the difference between the images of each group was statistically significant (χ 2 = 242.193, P< 0.001), and 100-200 keV single-level images were lower than the conventional images, the difference was statistically significant ( P< 0.05). In the comparison of noise values, the difference between the images of each group was statistically significant (χ 2 = 420.161, P< 0.001), and the difference was statistically significant ( P< 0.05). In the subjective scores of noise, enhancement, halo artifact and diagnostic confidence, there were statistically significant differences among the groups (χ2= 333.827, 455.989, 276.824, 399.497, P< 0.001). The noise score of 100-200 keV single-level image was higher than that of conventional image, the difference was statistically significant ( P< 0.05). The enhancement score of 60 keV was significantly higher than that of other images ( P< 0.05). The halo artifact score of 100-200 keV single level image was higher than that of 60-90 keV image, the difference was statistically significant ( P<0.05). The scores of 90-120 keV single-level images were higher than those of other single-level images, and the difference was statistically significant ( P< 0.05). Conclusions:CCTA examinations can be effectively performed by DLCT in patients after PCI in clinical settings, and 120 keV is recommended as the optimal monochromatic image for the observation of in-stent lumen.
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Objective:To explore the image quality of 40 keV virtual monoenergetic images (VMI) derived from dual-layer spectral detector CT （DLCT） pancreas dynamic enhanced scanning and its optimal window setting.Methods:From January to July 2019, 28 patients who underwent pancreas enhanced DLCT scan within one week before surgery and pathologically confirmed of pancreatic neuroendocrine tumors (pNETs) were retrospectively enrolled. Conventional polyenergetic images (PI) and 40 keV virtual monoenergetic images （VMI 40 keV） were generated after scanning.CT value of normal pancreatic parenchyma, lesion, abdominal subcutaneous fat, abdominal aorta and portal vein were measured in PI and VMI 40 keV. The contrast-to-noise ratio (CNR) of the pNETs lesion was calculated. All these objective results were compared between VMI 40 keV and PI using paired ttest. Individual window settings （W-Ind, including window width and window level） of VMI 40 keVwere recorded. Calculated window settings （W-Calc） were mathematically calculated via regression analysis and optimized window settings （W-Opt） were obtained.Subjective image quality was assessed with a 5-point scale and compared among VMI 40 keV with different window settings (W-Std, W-Ind, W-Calc and W-Opt) using Friedman test, and compared PI with standard abdominal window setting (W-Std) and VMI 40keV with W-Opt settings using Wilcoxon test.The maximum diameter of lesion was measured and compared with one-way ANOVA analysis among PI and VMI 40 keV with different windows settings. Results:For VMI 40 keV in both arterial phase and portal vein phase, the CT attenuation [(464.0±136.7), (375.4±79.2) HU] of pNETs lesion were statistically significantly higher than those in PI [（168.8±38.0), (140.5±23.5) HU] （ t=-16.107,-22.225, P<0.001）, CNR （16.5±11.1, 10.9±6.1） were also statistically significantly higher than those in PI （4.5±2.9, 3.0±1.9） （ t=-7.838, -9.781， P<0.001）,while with lower image noise in VMI 40 keV[（11.8±1.5),(11.8±1.4) HU] than PI （13.1±1.5,12.9±1.3 HU）（ t=6.356,3.891， P<0.001）. The subjective score for PI with W-Std and VMI 40 keV with W-Std, W-Ind, W-Calc, W-Opt in arterial phase were 4（1）, 1（0）, 5（0）, 5（0.75）, 5（1）, and which in portal vein phase were 3.5（1）, 1（0）, 5（0）, 5（0）, 5（1）.The subjective score of VMI 40 keV with different window settings had statistical differences （χ 2=76.143,76.000， P<0.001）. Compared to the image quality of PI with W-Std settings, VMI 40 keV with W-Opt settings have higher objective score （ Z=4.685, 4.235， P<0.001）. The maximum diameter of lesion has no statistical difference among PI and VMI 40 keV with different window settings （ F=0.008, 0.004， P>0.999） in both arterial phase and portal vein phase. Conclusions:The VMI 40 keV in pancreas dynamic enhancement scanning derived from dual-layer spectral detector CT have higher image quality than PI. Due to changes of CT value of tissue in VMI 40 keV, it is recommended to optimize window settings （window width/window level， 880/230 HU for arterial phase and 840/260 HU for portal vein phase） to obtain the best image quality.
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Objective To explore the feasibility of the virtual non-contrast images derived from dual-layer spectral detector CT (SDCT) substitute for true non-contrast images.Methods From July 2017 to September 2017,40 patients under-went pre-and arterial-venous dual-phase post-contrast abdominal imagining on a SDCT in Shanghai Jiaotong University School of Medicine Affiliated Ruijin Hospital.The images were retrospectively analyzed.The arterial VNC images (VNC-a) and venous VNC images (VNC-v)were derived from spectral based image (SBI) datasets of arterial and portal venous phase using a dedicated software respectively.Then mean CT attenuation,mean image noise,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared with one-way ANOVA analysis among TNC,VNC-a,VNC-v images in liver,spleen,pancreas,abdominal aorta,inferior vena cava,psoas muscle,L4 vertebra and perirenal fat.And Bland-Altman plots was used to analyze the CT attenuation equivalence between TNC and VNC.Subjective image quality was assessed with a 5-point scale and compared with Friedman H test.The dose length product (DLP) of pre-and post-contrast scans were recorded.Results The CT attenuation of abdominal aorta,perirenal fat,L4.vertebra among three kinds of images had significant differences (P＜0.05)which overestimated the CT attenuation of perirenal fat and underestimated CT attenuation of abdominal aorta and vertebra compared to TNC,VNC.Except for pancreas,the image noise of all other tissues among three kinds of images had significant differences,images noise of VNC images were lower than TNC images (P＜0.05).The SNR of liver,spleen,psoas muscle and inferior vena cava and CNR of pancreas,abdominal aorta,inferior vena cava,L4 vertebra and perirenal fat were statistically significant among the three images (P＜0.05).Except for vertebra and perirenal fat,good equivalence between VNC and TNC images were observed in all relevant tissues with Bland-Altman analysis.Image quality subjective scoring of TNC,VNC-a,and VNC-v were 5.00(1.00),5.00(0.75),5.00(1.00) respectively which had no significant differences (P=0.20).The DLP of TNC,arterial and venous phase scan were (255.2±62.0),(258.9±62.9),(252.0±61.2)mGy·cm,and the total DLP of dual-phase contrast enhanced scan was (766.2± 185.3) mGy· cm.The DLP of TNC accounted for 33.3％(255.2/766.2) of the total DLP,and effective dose of TNC was (3.83±0.90)mSv.Conclusions CT attenuation in VNC image which exhibited lower image noise was identical to TNC images in the majority of abdomen tissues except for vertebra and perirenal fat.and the VNC image.The VNC image which reduces radiation dosage derives from SDCT enhanced image might be used as a substitute for the TNC image.