Computed tomography features associated with pneumothorax susceptibility in pectus excavatum: a retrospective case-control study of lobar morphometry, attenuation metrics, and machine-learning projection.

BACKGROUND

Primary spontaneous pneumothorax (PSP) can occur without visible blebs or bullae, suggesting a broader structural susceptibility. Pectus excavatum (PE) is associated with a high incidence of PSP. We evaluated chest computed tomography (CT)-based lobar signatures of PSP and tested whether PE exhibits a PSP-like phenotype.

METHODS

Young adults aged 20-30 years were retrospectively grouped as first-episode PSP [patients with spontaneous pneumothorax (PT)], PE without prior pneumothorax, or healthy controls (HC). Using 3D Slicer®, we extracted lobar morphometric indices [volume, surface area (SA), surface area-to-volume ratio (SA/V), and shape descriptors] and Hounsfield unit (HU)-derived attenuation metrics from CT datasets. Group differences were assessed per lobe and by within-subject upper-lower asymmetry (Δ analysis). Five side-specific machine learning algorithms were trained to discriminate PT from HC using cross-validated predictions. Youden-optimal receiver operating characteristic (ROC) thresholds were applied to the PE cohort without retraining to quantify pneumothorax-like structural susceptibility.

RESULTS

A total of 561 (right 282 and left 279) side-specific lobes were analyzed. PT showed higher SA/V and less compact lobar geometry than HC and broader high-attenuation tails. In Δ analyses, attenuation-based deltas consistently separated groups, whereas PE showed more geometry-driven asymmetry, including reduced Δ-flatness. support vector machine (SVM) discrimination was the most excellent [area under the curve (AUC): right 0.937; left 0.953]. At Youden thresholds (right 0.811; left 0.841), high-risk/PT-like classifications were enriched in PE versus HC (right 30/67 vs. 1/158; left 38/67 vs. 1/158; both P<0.001).

CONCLUSIONS

Quantitative CT identifies distinct morphometric-attenuation phenotypes in PT and reveals a substantial PT-like signature in PE, warranting prospective validation with longitudinal pneumothorax outcomes.