High-resolution CT (HRCT) plays an important role in diagnosing and monitoring interstitial lung diseases (ILDs). Despite advances, predicting disease progression and treatment response remains challenging. HRCT enables noninvasive visualization and classification of patterns of lung injury and assessment of disease extent. Visual estimation of CT extent of fibrotic lung disease is an independent predictor of mortality and progression, but is subjective, with only modest interobserver agreement for radiologic interpretation of ILD. Machine learning-based textural analysis of fibrosis extent on baseline and serial HRCT scans shows robust correlations with physiologic measures and strong association with risk of disease progression or mortality across various fibrosing ILDs. In idiopathic pulmonary fibrosis, quantitative CT (QCT) assessment is associated with physiologic impairment and risk of progression and death, and increasing severity of fibrosis on longitudinal evaluation is associated with increased risk of progression and death. Similar results have been noted for fibrotic hypersensitivity pneumonitis and connective tissue disease. This review focuses on QCT techniques for ILDs. We describe the clinical need for quantification of lung disease and illustrate the role of conventional visual evaluation and of QCT approaches in defining disease severity, prognosis, and longitudinal progression, both in established disease and in preclinical interstitial abnormality.

LI-RADS Treatment Response Algorithm (TRA) version 2024 (v2024) introduced separate algorithms for detecting hepatocellular carcinoma (HCC) viability after radiation and nonradiation locoregional therapies (LRT). The nonradiation algorithm incorporated MRI-based ancillary features to optionally upgrade lesions from LR-TR Equivocal to LR-TR Viable. To compare the diagnostic performance of LI-RADS Nonradiation TRA v2024 with LI-RADS TRA version 2017 (v2017) and modified RECIST (mRECIST) for evaluating HCC response to LRT on MRI, with attention to the impact of ancillary features. This retrospective study included 231 patients (198 male, 33 female; median age, 56 years) who underwent LRT for HCC followed by liver resection or transplant between January 2017 and December 2022. Two radiologists (R1, R2) independently evaluated treated lesions (n=306) using LI-RADS Nonradiation TRA v2024, LI-RADS TRA v2017, and mRECIST. Lesions were classified as showing pathologic viability (n=249) or complete pathologic necrosis (n=57) based on curative surgery pathology. Diagnostic performance for pathologic viability was compared using Bonferroni-adjusted McNemar tests, classifying LR-TR Equivocal assessments as test negative. Sensitivity, specificity, and accuracy for LI-RADS Nonradiation TRA v2024 with ancillary features were 85.5%, 75.4%, and 83.7% (R1), and 87.2%, 63.2%, and 82.7% (R2); for LI-RADS Nonradiation TRA v2024 without ancillary features were 81.1%, 78.9%, and 80.7% (R1), and 80.3%, 78.9%, and 80.1% (R2); for LI-RADS TRA v2017 were 79.9%, 82.5%, and 80.4% (R1), and 79.1%, 79.0%, and 79.1% (R2); and for mRECIST, were 83.9%, 54.4%, and 78.4% (R1), and 78.2%, 40.4%, and 78.4% (R2). LI-RADS Nonradiation TRA v2024 with ancillary features showed higher sensitivity and accuracy than LI-RADS Nonradiation v2024 without ancillary features (both readers); higher sensitivity than LI-RADS TRA v2017 (both readers); higher specificity than mRECIST (both readers); and higher accuracy than LI-RADS TRA v2017 (R2) (p<.008); remaining comparisons between LI-RADS Nonradiation TRA v2024 with ancillary features and other systems were not significant (p>.008). LI-RADS Nonradiation TRA v2024 showed good diagnostic performance in detecting pathologic viability. Ancillary features yielded improved sensitivity and accuracy without significant change in specificity. Use of LI-RADS Nonradiation TRA v2024 with ancillary features is recommended for guiding prognostic assessments and treatment decisions after LRT.