| Background:Rheumatoid arthritis-associated interstitial lung disease（RA-ILD）is the most common respiratory complication in patients with rheumatoid arthritis,which is associated with disease activity and poor prognosis.Studies have shown that the prognosis of patients with RA-ILD is related to the extent and severity of disease involvement,so quantitative evaluation of diffuse lung changes in patients with RA-ILD is of great value.CT quantitative analysis technology can realize automatic extraction,analysis and display of quantitative data by computer based on HRCT images,which is gradually widely used in other lung diseases.Therefore,it is feasible and clinical value to study the application of CT quantitative technology in RA-ILD.Objective:The purpose of the first part of this study was to explore the feasibility of CT quantitative analysis in detecting lung structural changes in patients with rheumatoid arthritis-associated interstitial lung disease,and to screen quantitative indicators.The second part mainly explore the value of CT quantitative techniques for assessing disease progression in the follow-up of RA-ILD by analyzing changes in CT quantitative indices in patients with RA-ILD.Methods:In the first part of the study,HRCT images of 116 RA-ILD patients and 116 controls with no smoking history matched by age and gender range were retrospectively reviewed.Imaging signs and number of injury lobes were recorded through physician discretion.A CT software is applied to analyze CT obtained from both groups.The quantitative indices of emphysema are expressed as the percentage of lung area with attenuation<-950HU to the total lung volume(LAA-950%),and pulmonary fibrosis was expressed as the percentage of lung area with a attenuation of-200 to-700HU to the total lung volume(LAA-200～-700%),quantitative indicators of pulmonary vascular include aortic diameter（AD）,pulmonary artery diameter（PAD）,the ratio of PAD to AD（PAD/AD ratio）,the number of blood vessels（TNV）,and the cross area of blood vessels（TAV）.To explore lung structural alterations in RA-ILD by comparing the differences in quantitative CT indices between the two groups,the area under the curve（AUC）of receiver operating characteristic（ROC）was used to evaluate the ability of different quantitative indices to discover lung structural alterations in RA-ILD.In the second part of the study,HRCT images from 180 cases of 90 patients in the follow-up queue with RA-ILD were analyzed.The imaging diagnostic physicians used the criteria of whether new imaging features appeared or the range of the original features progressed by more than 20%to determine the presence or absence of disease progression and divided the patients into the progression and non-progression groups.Employing the digital lung data analysis platform to analyze CT images of patients for obtaining quantitative indices.Quantitative measures included total lung volume（TLV）,total lung density,density histogram,fibrosis indicators(LAA-200～-700%),and peripheral vascular evaluation indicators TNV and TAV at first and follow-up.Based on the subjective evaluation of diagnostic physicians,the changes of quantitative parameters during baseline scanning and follow-up were compared,and the relationship between the results of quantitative data and the results of subjective evaluation was analyzed.Results:In the first part,the radiographic signs present in the RA-ILD group included honeycomb sign in 30 patients,subpleural ground glass opacity in 67 patients,gridded shadow in 55 patients,traction bronchiectasis in 29 patients,and emphysema in 18 patients,while none of the above signs were found in the control group.The number of lung lobe injuries in RA-ILD:76 patients with 1-2 lobes,27 with lobes 3-4,and 13 with lesions in all lobes.Compared with the control group,the RA-ILD group showed significantly lower TLV,larger LAA-200～-700%and PAD in quantitative indexes,and lower TNV and TAV in vascular indexes.Among them,TAV,an indicator of peripheral blood vessels,has a good discriminating efficacy（AUC=0.894）,TNV（AUC=0.780）and LAA-200～-700%（AUC=0.705）have a certain discriminating efficacy.Combining the above quantitative indexes to establish the diagnostic model had the best diagnostic efficacy（AUC=0.938）.In seconds part,comparison of change values of quantitative data of CT between progression and non-progression group revealed that the change values of TLV,LAA-200～-700%,TNV and TAV in quantitative data of progression group were greater than non-progression group.TLV decreased,LAA-200～-700%increased,TNV and TAV decreased in the progressive group during follow-up,and there were significant statistical differences（P<0.0001）.The quantitative indicators TNV and TAV of patients in the non-progressive group also showed changes,showing that both TNV and TAV decreased（P<0.0001）,Peri-pulmonary vascular indicators may be more sensitive than subjective assessment.Conclusions:Quantitative CT can identify the characteristics of lung lesions and provide a quantitative assessment of lesion extent in patients with RA-ILD.The pulmonary vascular indexes had good evaluation ability,and the combine model of quantitative indexes was able to improve the evaluation efficacy.CT quantitative analysis index can detect and quantify the disease progression in RA-ILD during follow-up,which is consistent with the subjective evaluation results.But quantitative analysis can detect the changes of lung fine structure in RA-ILD,which is a supplement to the subjective evaluation results. |
