Usual Interstitial Pneumonia Spectrum: UIP, Probable UIP, and Indeterminate UIP

The usual interstitial pneumonia (UIP) pattern remains central to the diagnosis and management of fibrotic interstitial lung diseases (ILDs), particularly idiopathic pulmonary fibrosis (IPF). Thin-section computed tomography enables noninvasive characterization across the UIP spectrum, with structured pattern classification demonstrating strong correlation with histopathology and survival outcomes. In appropriate clinical settings, thin-section CT can obviate the need for surgical lung biopsy. Multidisciplinary discussion remains essential to integrate imaging, clinical, and pathologic findings for optimal therapeutic decision-making, including timely antifibrotic initiation and transplant referral. This review synthesizes current knowledge on the UIP imaging spectrum, emphasizing its diagnostic, prognostic, and clinical implications. We further outline recent advances in quantitative imaging, deep learning models, and molecular biomarkers that improve diagnostic precision and risk stratification. We also highlight emerging frontiers, including AI-driven spatiotemporal modeling and molecular imaging, that promise earlier detection, individualized prognostication, and precision-guided therapy.