Purpose:
This study aimed to quantitatively assess thoracic morphometry using thoracic computed tomography (CT) in patients with nonspecific interstitial pneumonia (NSIP), usual interstitial pneumonia (UIP), and healthy controls, and to determine whether morphometric parameters can differentiate between interstitial lung disease (ILD) subtypes.

Material and methods:
A retrospective, cross-sectional study was conducted involving 180 participants (60 NSIP, 60 UIP, and 60 healthy controls). Standardised thoracic CT scans were analysed at 3 thoracic levels (T3, T6, and T9). The ante­roposterior (AP) and transverse (T) thoracic diameters were measured, and their ratios (AP/T) were calculated.

Results:
Significant intergroup differences were observed in thoracic dimensions, mainly at the upper thoracic level (T3). UIP patients showed smaller AP and transverse diameters than NSIP and controls (p = 0.028 and p = 0.003). At T6, the transverse diameter was also reduced in UIP compared with controls (p = 0.029). The AP/T ratio did not differ significantly (p > 0.05), suggesting preserved thoracic geometry despite dimensional reduction. NSIP values were intermediate between UIP and controls.

Conclusions:
Quantitative CT-based thoracic morphometry reveals distinct structural differences among ILD subtypes. Patients with UIP show reduced upper thoracic dimensions consistent with restrictive remodeling, whereas NSIP demonstrates relatively preserved thoracic configuration. CT-derived thoracic diameters represent simple, reproducible, and cost-effective imaging biomarkers that may complement conventional pattern analysis and support objective disease assessment.