Effects Of Reconstruction Algorithm On Quantitative CT Measure In Chronic Obstructive Pulmonary Disease

Purpose:To compare the influence of different reconstruction algorithms on quantitative computed tomography (CT) measurement of pulmonary function, for the purpose of the most precise CT scanning solutions.Material and Methods:35patients (6females and29males) who suffered chronic obstructive pulmonary disease (COPD) were included with an average age of56.0±4.0years. The whole lung of each patient was scanned on a64slices spiral CT scanner (SOMATOM, SIEMENS, German) at the end of deep inspiration (tube voltage120kV, tube current120mAs, collimator64×0.6mm2, gantry rotation time0.5s/cycle, pitch1.0, slice thickness1mm). The raw data were reconstructed using3different CT algorithms: smooth (kernel B30), sharp (kernel B50) and very sharp (kernel B70). By use of the automatic post-processing software, the CT parameters of emphysema, including emphysema index (EI) at the end of deep inspiration, mean lung density (MLD) and lung volume (LV). In the statistical analysis, the correlations between the CT and routine parameters of pulmonary function tests were examined at first. Meanwhile, we tested the correlations of the CT parameters of lung volume with other CT arguments of pulmonary function. According to the data distribution, the strength of correlations was evaluated with Spearman's (non-normal) or Pearson's (normal) coefficient with P<0.05as statistically significant.Results:The comparisons among the groups of kernel B30, B50and B70showed no significant differences in LV (F=48.80; P=1.000), but marked divergences in MLD and El (F=39.79and22.43, respectively; P<0.001). Further, the pairwise comparisons revealed that there were significant differences in MLD (kernel B50vs. B30, P=0.001; kernel B70vs. B30, P<0.001) and El (kernel B50vs.B30, P=0.034; kernel B70vs.B30, P=0.001) between the groups of kernel B30and kernel B50or B70. The linear correlation analyses demonstrated that the associations between the CT results based on the3algorithms and the parameters of routine PFTs:LV of kernel B30, B50and B70were positively correlated with TLC (all the Spearman's coefficients=0.70; P<0.01). By contrast, El of kernel B30, B50and B70had negative correlations with FEV1(Spearman's coefficients=-0.61to-0.47; P<0.01), whereas MLD of kernel B30, B50and B70positively correlated with FEV1(Spearman's coefficients=0.38to0.49; P< 0.05).Conclusion:The CT reconstruction algorithm could affect MLD and EI.Thus, for follow-up examinations the same reconstruction algorithm has to be used. Purpose:The aim of this study was to use three-dimensional quantitative CT scan data in inspiration and expiration for the quantitative evaluation of the correlations of CT parameters of lung volume with the ones of pulmonary function based on routine tests and CT scans.Materials and Methods:Eighty-four patients (19females and65males; age40to75years, mean[±SD],62.2±5.0years) with COPD were included. Among them,62were current smokers with a history of20±5years (1to2packet per day), the others were all past smokers who had quitted it for1to10years. In the84patients,18were from the group of grade A which were categorized based on the GOLD scale,20in the group of grade B,24in grade C and22in grade D. The CT images were analyzed with a full-automatic post-processing software (syngo InSpace lung Parenchyma Analysis). Three-dimension analysis was performed to obtain the following CT parameters of pulmonary function during both the inspiratory and expiratory phases:emphysema index (El), mean lung density (MLD) and lung volume (LV), and the ratios and differences of MLD and LV between the inspiratory and expiratory phases were calculated. The steps of statistical analyses were as follows:first, the linear correlations between the CT parameters of pulmonary functions and the ones of routine pulmonary function tests (PFTs) were examed. Also, the correlations of lung volume parameters with the other CT parameters were tested. Spearman's (normality) or Pearson's (non-normality) coefficients were calculated according to the data distribution with P<0.05as significant. Multivariant step wise regression was done between MLD (dependent) and El, LV (independent), and R square values were calculated to determine degree of correlations. Results:The CT parameters of pulmonary function (MLDin, MLDex, and△LV) were positively correlated with logFEV1and FEV1/FVC (Spearman's coefficients0.31to0.70; P<0.001) and negatively with RV/TLC (Spearman's coefficients-0.34to-0.60; P<0.001). On the other hand, the other parameters of pulmonary function (EIin, EIex, MLDex/in,△MLD, LVex and LVex/in) had negative correlations with logFEV1and FEV1/FVC (Spearman coefficients-0.48to-0.73; P<0.001) whereas positive correlations with RV/TLC (Spearman coefficients0.41to0.66; P<0.001). Unfortunately, the linear relationships between LVin and logFEV1,RV/TLC showed no statistical significance of linear correlations (Spearman's coefficients=0.10and0.17, respectively; P>0.05). As to the relationships between the parameters of lung volume and pulmonary function, the correlations of LVin and LVex with MLDin and MLDex were negative (Spearman's coefficients-0.89to-0.54; P<0.001), whereas their correlations with△MLD, MLDex/in, Elin and EIex were positive (Spearman's coefficients0.30-0.82; P<0.001). Likewise,△LV had negative correlations with MLDex,△MLD, MLDex/in, EIex (Spearman's coefficients;-0.72to-0.41; P<0.001), and positive correlations with MLDex (Spearman's coefficient=0.50; P<0.001). In addition, LVex/inwas negatively correlated with MLDex (Spearman's coefficient=-0.75; P<0.001) and positively correlated with△MLD, MLDex/in, EIin, and EIex (Spearman's coefficient0.39-0.89; P <0.001. The correlations between other parameters also reveal no statistical significance (P>0.05). The further multivariate step wise regression demonstrated that El, LV (independent) and MLD (dependent) could introduce a regression equation with R square values of0.77and0.73, respectively (P<0.05). In the model, the relative contribution of LV of either expiratory or inspiratory CT were higher (standardized coefficients:-0.61vs.-0.66for expiratory phase and-0.33vs.-0.29for inspiratory phase; P<0.001).Conclusion:There was an ideal association between LVex/in and the parameters of routine PFTs, which was able to reflect the collapsibility of lung. Moreover, LVex/in can be considered to be equivalent to MLDex/in.Taking into account the impact of scanning parameters on MLDex/in, LVex/in may play a complementary role (that is, lower LVex/in suggests higher collapsibility and less severe conditions in COPD), which demonstrated the feasibility and application value of this parameters in the assessment of pulmonary function. Object:With the use of64slices spiral computed tomography (CT), this study was aimed to investigate the correlations between the parameters of quantitative CT scans (on paired inspiratory and expiratory examinations) and the results of pulmonary function tests (PFTs). Furthermore, to determine the values of quantitative CT for the severity assessment of pulmonary function impairment of patients who suffered chronic obstructive pulmonary disease (COPD).Methods:a total of84patients (male65, female19) with COPD were enrolled. Their average ages were62.2±5.0years. Among those84patients,18were categorized into the group of grade A based on GOLD scale,20and24in the groups of grade B, C, respectively, while22were classed into grade D. For each patient, CT scanning was done during deep inspiratory and expiratory breath-hold on a64slices spiral CT scanner (SOMATOM, SIEMENS, German). By means of the automatic post-processing software, we employed a three-dimension quantitative measurement of the CT parameters of emphysema (i.e., emphysema index [EI], and the lth and15th percentiles at the end of the deep inspiration) and air trapping (i.e., the expiration to inspiration ratio of mean lung density, the change in relative lung volume with attenuation values from-860Hu to-950Hu and the expiration to inspiration ratio of lung volume). In statistical analyses, the differences of the above parameters among the4groups and the results of PFTs were tested by One-Way ANOVA at first, with P<0.05considered as significant. Subsequently, the correlations of the above CT parameters of emphysema and air trapping with the ones of PFTs were evaluated, and the level of significance was also set to a P<0.05. Finally, those correlated parameters with statistical significance acted as independent parameters, and the data from PFTs were considered as dependent parameters when univariate linear regressions were done. In addition, the CT parameters of emphysema and air trapping were combined pairwise as a CT model, and multivariate linear regressions were undertaken to investigate their relationships with the parameters of PFTs.Results:Against the means of group D, significantly less values were found in the group A and B (P<0.05), whereas only a slight difference appeared in group C (P>0.05). The linear correlation analysis showed that Perc1and Perc15from the CT parameters of emphysema was positively correlated with logFEVl, FEV1/FVC, whereas negatively correlated with RV/TLC, which were all statistically significant (P<0.001). On the contrary, the other CT parameter of emphysema El and the parameters of air trapping, RVC-860to-950, MLDex/in, LVex/in had negative correlations with logFEV1, FEV1/FVC (P<0.001) and positive correlations with RV/TLC (P<0.001). The further univariate linear regressions between EI,Percl,Perc15, RVC-860to-950,MLDex/in,LVex/in and the parameters of PFTs introduced the R square values of the regression equation, ranged from0.27to0.66(P<0.001). After the pairwise combinations of the parameters of emphysema and air trapping, multivariate linear regressions were done with the PFTs parameters as the dependent agents. As a result, much better R square values from0.66to0.85were obtained.Conclusions:Compared with the Two-dimension quantitative CT scanning, more comprehensive results on pulmonary functions of patients with COPD can be acquired from Three-dimension quantitative CT scans with much faster and simpler automatic post-processing software. In patients who suffered COPD, the CT parameters of emphysema and air trapping (El, Perc1, Perc15, RVC-860to-950, MLDex/in and LVex/in) were correlated with PFTs parameters. Those CT parameters were able to reflect the progressions of patients'pulmonary functions. Moreover, the combinations of the two types of CT parameters correlated better with the PFTs parameters and revealed more precisely the impairment of pulmonary functions in COPD.