ABSTRACT
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.
ABSTRACT
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.