# Single-inspiratory quantitative CT nomogram for enhanced PRISm and COPD differentiation: a cross-sectional study with interpretable diagnostic boundaries

## TL;DR

A new CT-based method helps distinguish between two lung conditions using a single scan, reducing radiation exposure and improving accuracy.

## Contribution

A single-inspiratory CT nomogram with interpretable metrics for differentiating PRISm from COPD is developed.

## Key findings

- Reduced superficial vessel diameter is a key biomarker for PRISm differentiation.
- The diagnostic model achieved an AUC of 0.984 for distinguishing PRISm from severe COPD.
- Age, gender, and CT markers like Pi10 and AVD9 show significant differences between groups.

## Abstract

Differentiating preserved ratio impaired spirometry (PRISm) from chronic obstructive pulmonary disease (COPD) is challenging. Traditional biphasic CT scans are limited by radiation exposure, while single-inspiratory CT-based deep learning lacks interpretability. This study aimed to develop a single-inspiratory quantitative computed tomography (QCT) nomogram integrating parenchymal, airway, and vascular parameters to redefine imaging definition boundaries.

This retrospective study (approved by Ethics Committee YJ-NBEY-KY-2023-107-01) screened 1,265 patients from Ningbo No. 2 Hospital (January 2021–December 2023), yielding 658 eligible participants (Normal: 135, PRISm: 328, COPD: 195) based on predefined inclusion/exclusion criteria. Single-inspiratory CT metrics (parenchymal, airway, vascular) were quantified using the Aview® system. Four logistic regression models distinguished PRISm from normal and COPD group receiver operating characteristic-area under the curve (ROC-AUC) evaluated performance.

Progressive deterioration in age (COPD: 73.3 vs. PRISm: 69.1 vs. Normal: 64.1 years), male predominance (84.6% COPD vs. 57.9% PRISm), pulmonary function (FEV1%, FEV1/FVC), and CT markers (Pi10: PRISm 3.65 vs. Normal 3.26, P < 0.001) were observed. PRISm showed reduced superficial vessel diameter (AVD9: 2.64 mm vs. Normal 2.95 mm, P < 0.001). Diagnostic models achieved AUCs up to 0.984 (PRISm vs. severe COPD) and 0.853 (PRISm vs. all COPD).

The QCT nomogram robustly differentiates PRISm from COPD, highlighting reduced superficial vessel diameter as a key biomarker. This radiation-efficient approach enables early COPD stratification via interpretable structural-functional metrics.