Artificial intelligence-based analysis of the spatial distribution of abnormal computed tomography patterns in SARS-CoV-2 pneumonia: association with disease severity

Abstract

Background: The substantial heterogeneity of clinical presentations in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia still requires robust chest computed tomography analysis to identify high-risk patients. While extension of ground-glass opacity and consolidation from peripheral to central lung fields on chest computed tomography (CT) might be associated with severely ill conditions, quantification of the central-peripheral distribution of ground glass opacity and consolidation in assessments of SARS-CoV-2 pneumonia remains unestablished. This study aimed to examine whether the central-peripheral distributions of ground glass opacity and consolidation were associated with severe outcomes in patients with SARS-CoV-2 pneumonia independent of the whole-lung extents of these abnormal shadows.

Methods: This multicenter retrospective cohort included hospitalized patients with SARS-CoV-2 pneumonia between January 2020 and August 2021. An artificial intelligence-based image analysis technology was used to segment abnormal shadows, including ground glass opacity and consolidation. The area ratio of ground glass opacity and consolidation to the whole lung (GGO%, CON%) and the ratio of ground glass opacity and consolidation areas in the central lungs to those in the peripheral lungs (GGO(C/P)) and (CON(C/P)) were automatically calculated. Severe outcome was defined as in-hospital death or requirement for endotracheal intubation.

Results: Of 512 enrolled patients, the severe outcome was observed in 77 patients. GGO% and CON% were higher in patients with severe outcomes than in those without. Multivariable logistic models showed that GGO(C/P), but not CON(C/P), was associated with the severe outcome independent of age, sex, comorbidities, GGO%, and CON%.

Conclusion: In addition to GGO% and CON% in the whole lung, the higher the ratio of ground glass opacity in the central regions to that in the peripheral regions was, the more severe the outcomes in patients with SARS-CoV-2 pneumonia were. The proposed method might be useful to reproducibly quantify the extension of ground glass opacity from peripheral to central lungs and to estimate prognosis.

Keywords: COVID-19; Central area; Ground glass opacity; Peripheral area; Pneumonia; Quantitative analysis.

Fig. 1

Representative images of SARS-CoV-2 pneumonia. A and B indicate two representative CT images of the nonsevere and severe cases, respectively. C and D are corresponding images after segmentation of lungs, ground-glass opacification/opacity (GGO) and consolidation (CON). The blue and pink colored areas indicate the area of GGO and CON respectively. In the nonsevere case (A, C), the percentages of whole, peripheral, and central lungs occupied by GGO (GGO%, GGO%(P), GGO%(C)) were 5.61%, 11.0%, and 2.22%, respectively. The percentage of whole, peripheral, and central lungs occupied by CON (CON%, CON%(P), CON%(C)) were 5.37%, 3.54%, and 6.52%, respectively. In the severe case (B, D), GGO%, GGO%(P), GGO%(C) were 9.68%, 10.8%, 8.31%, and CON%, CON%(P), CON%(C) were 12.1%, 15.0%, 8.70%

Fig. 2

Patient flow chart. DICOM  digital imaging and communications in medicine. AIQCT  novel artificial intelligence-based quantitative CT image analysis software

Fig. 3

The distribution of parenchymal lesions in the whole lung area. The percentages of lungs occupied by each CT pattern was compared between nonsevere and severe cases. Normal  normal parenchymal, GGO  ground-glass opacification/opacity, CON  consolidation, RET  reticulation, HON  honeycomb lung, GRA  granular opacities, LUC  hyperlucent lung. P values were calculated by the Wilcoxon rank-sum test and Pearson correlation test [P < 0.05 (*); P < 0.01 (**); P < 0.001 (***)]

Fig. 4

The distribution of the ratio of GGOs and CON in the peripheral or central lung region. A and B The percentage of lungs occupied by ground-glass opacification/opacity and consolidation were calculated in the peripheral and central regions (GGO%(P), GGO%(C), CON%(P), and CON%(C), respectively). C The central to peripheral ratio for GGO% and CON% were calculated (GGO(C/P) and CON(C/P)). D A correlation between GGO% and GGO(C/P). The boundary between the central and peripheral regions was set as 5 mm from the pleura. These variables were compared between patients with severe outcomes and those with nonsevere outcomes. P values were calculated by the Wilcoxon rank-sum test [P < 0.05 (*); P < 0.01 (**); P < 0.001 (***)]