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Objective:To investigate the feasibility of using spectral CT chest enhancement venous phase images to obtain virtual non-contrast (VNC) images and virtual arterial phase images to achieve one phase scan instead of three phase scans.Methods:Imaging data of 100 patients who underwent spectral CT chest plain and dual-phase enhancement scans at the First Affiliated Hospital of Kunming Medical University from January to May 2022 were analyzed retrospectively. The venous phase images of all patients were post-processed to obtain virtual non contrast (VNC) and 40 keV virtual mono-energy images (VMI) for simulated arterial phase images (Vart). Image quality and lesion detection were compared between true non-contrast (TNC) and VNC images, and conventional arterial phase (CIart) and Vart images by paired t-test, Wilcoxon test and McNemar test. Objective evaluation indexes of image quality included thoracic aorta, all levels of pulmonary artery, T4 vertebral bone cancellous, chest wall fat CT value, background noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR); the subjective score of image quality was assessed by double-blind method on a 5-point scale; the assessment of lesion detection included the detection rate of calcified foci and pulmonary nodules size, density, volume, percentage of solid components and imaging characteristics. Results:Except for chest wall fat and T4 vertebral bone cancellous, the differences in CT values between VNC and TNC images were not statistically significant ( P>0.05); Except for right upper pulmonary artery and right lower pulmonary artery, the differences in background noise values and SNR between TNC images and VNC images were statistically significant ( P<0.05). Compared with CIart images, the CT values of chest wall fat were lower in Vart images ( P<0.05), and the CT values of the remaining sites were significantly higher ( P<0.05); the background noise values of all sites on Vart images were smaller than those on CIart images, and the SNR and CNR values were higher than those on CIart images ( P<0.05).The differences of subjective scores of images quality were not statistically significant between TNC and VNC images, between CIar and Vart images ( P>0.05). Taking TNC as the standard, the overall detection rate of VNC for calcification was 88.53% (301/340). Except for the short diameter of partially solid nodules, the differences of qualitative and quantitative assessment indexes of lung nodules between TNC and VNC images were not statistically significant ( P>0.05). Conclusions:Spectral CT chest venous phase 40 keV VMI can simulate arterial phase images in the diagnosis of vascular lesions, and venous phase VNC basically meets the standard of conventional plain scan, so it is feasible to replace plain scan, arterial phase and venous phase images in a certain range.
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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 investigate the diagnostic value and limitations of dual-energy virtual non-con-trast images of dual-source CT in common benign liver diseases. Methods Dual-source CT was performed on 226 upper abdomen pathogenesis patients. The conventional non-contrast (CNC) scan was performed with single-energy mode, the arterial phase and portal phase scans were performed with dual-energy mode. The virtual non-contrast (VNC) images were derived from the portal data using liver virtual non-contrast software. 117 patients with common benign liver diseases were retrospectively analyzed in CNC and VNC. The lesion detectability, effective radiation doses for single-energy mode and dual-energy mode were compared. Results Among 117 patients, there were 28 (73.6%) hemangiomas, 58 (85.3%) calcifications or stones in VNC, but the hemangiomas, calcifications or stones in CNC were 37 (97.3%) and 68 (100%), respectively. The hemangiomas, calcifications or stones in VNC and CNC were significantly different (P 0.05). The CTDIvol, DLP and ED of dual-energy mode were obviously lower than those of single-energy mode (P < 0.05). Conclusion The detection of hemangiomas, calcifications or stones on VNC images is lower than CNC images. There is no difference in detecting cyst and hepatic steatosis. In addition, radiation dose will be reduced due to adopting VNC.VNC has potential clinical application value.
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Objective To investigate the diagnostic value of dual-energy CT virtual non-contrast (VNC) technology for osteoporosis(OP). Methods Dual-energy CT images of 50 patients with lumbar traumas were collected prospectively.Patients who suffer from vertebral bodies fractures between lumbar 1 to 4, have internal metal fixations or underwent percutaneous vertebroplasty, or presented tumors or compromised bone metabolism induced by diseases or medications were excluded.The scanning range was from the upper edge of the 12th thoracic vertebral body to the lower edge of the first sacral vertebral body. The voltages of tubes A and B were 90 kV and Sn 150 kV,and the reference tubes currents were 220 mAs and 138 mAs. Image reconstruction was performed using Advanced Modeled Iterative Reconstruction (ADMIRE)with iterative strength of 3 and convolution kernel of Qr 40.The default parameters of the virtual non-contrast software were corrected by the standard recommended by the Bone Marrow software of the post-processing platform Syngo.via,and the CT value of calcium(contrast media CM),the CT value of mixed energy images(regular CT value,rCT),the calcium density(CaD)and the fat fraction(Fat)were measured. The bone mineral density (BMD) and T score of each lumbar vertebra from lumbar 1 to lumbar 4 were measured by dual energy X-ray absorptiometry(DXA).With T score less than or equal to the 2.5 standard deviation as the gold standard for the diagnosis of OP,correlations between CT measurements and vertebral BMDs were analyzed using Pearson correlation analysis and linear regression and the diagnostic values of different CT measurements for OP were compared using receiver operating characteristic curve. Results Each of the vertebral bodies was analyzed as a single unit.Fifty of them were osteoporotic and the rest 116 were non-osteoporotic.Except for Fat,the CT measurement parameters of the osteoporotic vertebral bodies were lower than those of the ones without osteoporosis, and the difference was statistically significant (P<0.01).CM,rCT and CaD were significantly correlated with BMD(r were 0.75,0.65,0.71,all P<0.01)and there was a linear relationship(F were 209.91,120.24,167.69,all P<0.01).Meanwhile,CM,rCT,CaD and T score were also significantly correlated (r were 0.74, 0.65, 0.70, all P<0.01) with a linear relationship (F were 195.04,120.29,156.37,all P<0.01).CM,rCT and CaD had relatively high concordance rates against the OP diagnosis gold standard (respectively 81.9%, 62.2% and 81.9%). CM and CaD had higher concordance rates than rCT,the difference being statistically significant(P<0.01),and by the CM less than 239.5 HU or CaD less than 10.9 mg/cm3standard, their sensitivities of diagnosing osteoporosis were respectively 86.0% and 84.0%,while the specificities,80.2% and 81.0%.After superimposing CM and CaD, the results did not improve the diagnosis efficiency of OP (pre-superposition diagnostic performance better than post-superposition (P<0.05). Conclusion The VNC technology on DECT can do both vertebral fractures diagnosis and osteoporosis assessment at the same time, thus optimizing the clinical examination process.
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Purpose To assess the feasibility of applying dual-energy dual-source CT virtual non-contrast (VNC) imaging in the diagnosis of colorectal diseases. Materials and Methods Eighty-ifve patients with clinically suspected colorectal lesions underwent abdominal CT scan as well as arterial and venous phase dual-energy enhanced scan, VCN images of arterial and venous phase were obtained using the dual-energy software, the differences of image quality, radiation dose and diagnostic coincidence rate between the true non-contrast scan and VNC images were compared. Results The radiation dose of two-phase dual-energy scan was 34.8%lower when compared with the conventional three-phase scans. The CT values of the intestinal lesions, metastasis lymph nodes and intestinal fat in VNC were lower than the true unenhanced scan (P0.05), and neither was the diagnostic coincidence rate for intestinal diseases (P>0.05). The noise level of images obtained from VNC was lower than that of the real non-contrast scan (P0.05). Conclusion For colorectal lesions, the virtual non-contrast images from the dual-energy dual-source CT scan can be used to reduce the radiation dose without effecting image quality and diagnosis accuracy.
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Objective To investigate the clinical utility of dual-energy virtual non-contrast CT(VNCT)of dual source CT in the di-agnosis and differential diagnosis of solitary pulmonary nodule(SPN).Methods Thirty-six patients with suspected SPN underwent chest plain single energy CT and dual-phase contrast enhanced CT (DECT)(25 and 90 s).The images of dual energy were sent to a commercial workstation for VNC image generation.CT values of SPN on VNC and true non-contrast(TNC),as well as signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)were compared.The accuracy of calcification detection was compared according to the diameter and density of the calcification.The TNC images were used as the reference.Results CT values,SNR and CNR of VNC had no statistical difference among TNC and VNC at 25 s and 90 s(P >0.05).DECT VNC(5mm slice)could accurate detected calci-fication(diameter>2 mm,CT value>1 50 HU)in SPN.The 2 mm slice performed significantly better than 5 mm slice VNC images. Conclusion The VNC could provide consistent diagnostic information with TNC.The thin slice DECT VNC images can be used in clinical practice to replace TNC without losing small calcification in SPN,which has potential to reduce the patient radiation dose.
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Objective To evaluate the capability of virtual non-contrast (VNC)of the second-generation dual-source CT (DSCT), and to display the adipose tissue of gastric serosa.Methods 48 patients with gastric cancer undergoing preoperative DSCT and sur-gery were enrolled.The true non-contrast (TNC)values and VNC values of perigastric adipose tissue were measured and compared with conventional non-contrast scanning and VNC of arterial phase and venous phase.The VNC values of perigastric adipose tissue were compared between serosal involvement group and non-serosal involvement group.Results There was statistical difference be-tween TNC values and VNC values of perigastric adipose tissue (P <0.05),the absolute differences were under 13 HU.The differ-ence of VNC values between serosal involvement group and non-serosal involvement group was significant (P <0.05).Conclusion VNC of the second-generation DSCT can clearly display the adipose tissue of gastric serosa.It has certain capability in judging sero-sal involvement.VNC has the proficiency to replace conventional non-contrast scanning.
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OBJECTIVE: To evaluate the reliability of virtual non-contrast (VNC) images reconstructed from contrast-enhanced, dual-energy scans compared with true non-contrast (TNC) images in the assessment of high CT attenuation or calcification of mediastinal lymph nodes. MATERIALS AND METHODS: A total of 112 mediastinal nodes from 45 patients who underwent non-contrast and dual-energy contrast-enhanced scans were analyzed. Node attenuation in TNC and VNC images was compared both objectively, using computed tomography (CT) attenuation, and subjectively, via visual scoring (0, attenuation the aorta; 2, calcification). The relationship among attenuation difference between TNC and VNC images, CT attenuation in TNC images, and net contrast enhancement (NCE) was analyzed. RESULTS: CT attenuation in TNC and VNC images showed moderate agreement (intraclass correlation coefficient, 0.612). The mean absolute difference was 7.8 +/- 7.6 Hounsfield unit (HU) (range, 0-36 HU), and the absolute difference was equal to or less than 10 HU in 65.2% of cases (73/112). Visual scores in TNC and VNC images showed fair agreement (kappa value, 0.335). Five of 16 nodes (31.3%) which showed score 1 (n = 15) or 2 (n = 1) in TNC images demonstrated score 1 in VNC images. The TNC-VNC attenuation difference showed a moderate positive correlation with CT attenuation in TNC images (partial correlation coefficient [PCC] adjusted by NCE: 0.455) and a weak negative correlation with NCE (PCC adjusted by CT attenuation in TNC: -0.245). CONCLUSION: VNC images may be useful in the evaluation of mediastinal lymph nodes by providing additional information of high CT attenuation of nodes, although it is underestimated compared with TNC images.
Subject(s)
Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Calcinosis/diagnostic imaging , Contrast Media , Image Processing, Computer-Assisted , Lymph Nodes/diagnostic imaging , Mediastinum/diagnostic imaging , Reproducibility of Results , Sensitivity and Specificity , Tomography, X-Ray Computed/methodsABSTRACT
Purpose To investigate the value of dual-source CT with dual-energy virtual non-contrast imaging in the diagnosis of cervical lymph node disease. Materials and Methods The dual-energy scan data of 126 lymph nodes from 50 patients confirmed pathologically were reviewed. The difference of average CT value, signal to noise ratio, contrast to noise ratio, image subjective assessment and lesion detectability between virtual non-contrast imaging and conventional non-contrast scan were analyzed. The radiation dose of virtual non-contrast imaging and real non-contrast imaging of cervical lymph node were also compared. Results ①The consistency of virtual plain scan combined with dual-energy contrast imaging in the diagnosis of six typical pathological types were all satisfactory (Kappa>0.7, P0.05).③ Compared with conventional enhanced scan, dual-energy phases reduced radiation dose by about 19%. Conclusion Dual-energy virtual non-contrast imaging combined with contrast imaging can provide clear images in the diagnosis of enlarged cervical lymph nodes and reduce radiation dose of subjects, thus can be expected to replace real scan.