| Part one:feasibility study of material suppressed iodine images of energy spectrum CT for solitary pulmonary nodules assessmentPURPOSE to evaluate the feasibility of material suppressed iodine images for solitary sulmonary nodules assessment. MATERIALS AND METHODS Energy spectrum CT data of 44 patients with solitary pulmonary nodules were analysed retrospectively, CT and SD value differences in true non-enhanced image and in double phase energy spectrum enhanced images on 70keV were analysed, pairwise comparison of CT and SD value differences were anlaysed with the paired t test. To evaluate the material suppressed iodine images for presenting number of the calcifications in pulmonary nodules and in mediastinal lymph nodes on the basis of true non-enhanced image. Pairwise comparison of DLP differences in three phase scan were performed with the paired t test and the drop rate of radiation dose was calculated when only one phase enhanced scan was performed. RESULTS [1]the CT value differences of pulmonary nodules between true non-enhanced and arterial material suppressed iodine image was not statistically significant[(29.58±12.94)HU vs (31.86±11.71)HU,t=-1.807,P=0.078]; the CT value differences of pulmonary nodules between true non-enhanced and venous material suppressed iodine image was not statistically significant[(29.58±12.94)HU vs (31.16±11.79)HU,t=-1.234, P=0.224]; the CT value differences of pulmonary nodules between arterial and venous material suppressed iodine image was not statistically significant[(31.86±11.71)HU vs (31.16±11.79)HU, t=1.041, P=0.304]; [2] SD value of pulmonary nodules was higher in true non-enhanced image than in arterial material suppressed iodine image[(13.91±2.96) vs (11.87±2.81),t=4.254, P=0.000]; SD value of pulmonary nodules was higher in true non-enhanced image than in venous material suppressed iodine image[(13.91±2.96) vs (12.06±2.80), t=3.617, P=0.001]; SD value of pulmonary nodules was similar in arterial and venous material suppressed iodine image[(11.87±2.81) vs (12.06±2.80), t=-1.054,.P=0.298]; [3]13 calcifications were detected in the pulmonary nodules of 9 patients and 96 calcifications were detected in the lymph nodes of 30 patients on true non-enhanced images, on both arterial and venous phase material suppressed iodine images 92.30%(12/13)) of calcifications in pulmonary nodules and 97.92%(94/96) of calcifications in the lymph nodes were presented. [4]The DLP in true non-enhanced scan was lower than in arterial phase[(391.42±331.36) mGy·cm vs (618.36±253.25) mGycm, t=-5.028, P=0.000]; The DLP in true non-enhanced scan was lower than in venous phase[(391.42±331.36) mGycm vs (618.36±253.25) mGycm, t=-5.028, P=0.000]; the DLP in arterial phase was equal to venous phase. CONCLUSIONS [1]CT value on 70keV material suppressed iodine images derived from enhanced 70keV monochromatic level is similar with that measured on true non-enhanced images; [2]SD value is lower on material suppressed iodine images than on true non-enhanced images; [3]material suppressed iodine images can successfully detect calcifications in solitary pulmonary nodules and mediastinal lymph nodes. [4]material suppressed iodine images derived from enhanced 70keV monochromatic level can replace the true non-enhanced images for solitary pulmonary nodules evaluation and effectively reduce the patient radiation dose.Part two:energy spectrum CT imaging multiparameter quantitative determination differentiate benign and malignant solitary pulmonary nodulesPURPOSE [l]to evaluate correlation between iodine concentration and CT value on 40-140 keV monochromatic level of solitary pulmonary nodules; [2]to evaluate the diagnostic efficiency of CT value on 40～140 keV monochromatic level, basic material concentration(iodine and water) and enhancement degree based on material suppressed iodine images for the differential diagnosis of solitary pulmonary nodules. MATERIALS AND METHODS Energy spectrum CT data of 44 patients with solitary pulmonary nodules were analysed retrospectively,24 patients with malignant nodules serve as the malignant group and 20 patients with benign nodules as the benign group. Correlation between iodine concentration and CT values on monochromatic images from 40～140 keV in both arterial and venous phase was analysed with the bivariate pearson correlation and the correlation coefficient was calculated.11 CT value on 40～140 keV monochromatic level(interval 10 keV), basic material concentration(iodine and water) and enhancement degree differences in double phase enhanced scan were compared between two groups with the independent sample t test, ROC was adopted to evaluate the diagnostic efficiency for indicators that is statistically significant and threshold, sensitivity and specificity were calculated when the Youden’s index is maximum, pathological results as the gold standard. RESULTS [1]There is a linear positive correlation between iodine concentration and CT values on monochromatic images from 40～140 keV in both arterial and venous phase(r=0.396～0.937, P=0.001～0.008) and (r=0.335～0.981, P=0.001～0.026) respectively. [2]the CT value on 40～ 90 keV monochromatic level of malignant group pulmonary nodules is higher than benign group pulmonary nodules in arterial phase (all P<0.05), there was no statistically significant difference between two groups in terms of CT value on 100-140 keV monochromatic level in arterial phase (all P>0.05), there was no statistically significant difference between two groups in terms of CT value on 40～140 keV monochromatic level and in venous phase (all P>0.05), the diagnostic efficiency is best at monochromatic energy level of 40 keV in arterial phase and the diagnostic sensitivity and specificity were 91.67% and 70% when the CT value threshold of 40 keV monochromatic images was set at 112.66HU, AUC is 0.798, there is also a certain diagnostic value at the monochromatic level of 50～90 keV in arterial phase, AUC is 0.719-0.796; [3] the iodine concentration of malignant group pulmonary nodules is higher than benign group pulmonary nodules in arterial phase (P<0.05), there was no statistically significant difference between two groups in terms of iodine concentration in venous phase (P>0.05), the diagnostic sensitivity, specificity of iodine concentration is 91.67%,65% when the threshold was set at 11.50(100 μg/cm3) in arterial phase, AUC is 0.781; there was no statistically significant difference between two groups in terms of water concentration in double enhanced phase (all P>0.05). [4]The enhancement degree of malignant group pulmonary nodules is higher than benign group pulmonary nodules in arterial phase [(36.36±33.18) HU vs (16.93±24.17) HU, t=2.243, P=0.030], however, the enhancement degree of two groups is similar in venous phase[(21.99±15.87) HU vs (17.62±24.15) HU, t=0.694, P=0.493], the diagnostic sensitivity, specificity of enhancement degree is 91.67%,65%when the threshold was set at 14.74HU in arterial phase, AUC of enhancement degree in arterial phase is 0.792. CONCLUSIONS [1]There is a linear positive correlation between iodine concentration and CT values on monochromatic images from 40-140 keV of solitary pulmonary nodules, the correlation level is decreased with the increase of monochromatic energy level, correlation coefficient is maximum at 40 keV and minimum at 140 keV. [2] the diagnostic efficiency of CT values on 40 keV monochromatic images, iodine concentration and enhancement degree in arterial phase is similar. |
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