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High-Resolution CT (HRCT) is a specialized CT technique optimized to provide detailed imaging of the lung parenchyma, airways, and interstitium with high spatial resolution.
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It is indispensable in evaluating diffuse lung diseases, interstitial lung disease (ILD), small airways disease, and infectious/inflammatory pulmonary pathology.
| Parameter | HRCT Settings |
|---|---|
| Slice Thickness | ≤1–1.5 mm (thin sections) |
| Reconstruction Kernel | High spatial frequency (bone or detail kernel) |
| Interval | Non-contiguous (e.g., 10 mm) or full volumetric stack |
| Field of View | Limited to thorax (lung windows) |
| Scanning Phase | Primarily non-contrast, supine end-inspiratory |
| Additional Phases | Expiratory, prone, or dynamic if needed |
| Windowing | Lung window: W = 1500 HU; L = –600 HU |
| Category | Conditions |
|---|---|
| Interstitial Lung Diseases (ILDs) | • Usual interstitial pneumonia (UIP) |
| • Non-specific interstitial pneumonia (NSIP) | |
| • Hypersensitivity pneumonitis | |
| • Sarcoidosis | |
| Airway Diseases | • Bronchiectasis |
| • Bronchiolitis | |
| • Asthma | |
| • Cystic fibrosis | |
| Infectious and Inflammatory Lung Disease | TB, PCP, COVID-19, organizing pneumonia |
| Occupational Lung Diseases | Silicosis, coal workers' pneumoconiosis, asbestosis |
| Others | • Connective tissue disease-related lung disease |
| • Lung cancer screening (using low-dose HRCT) | |
| • Pre- and post-lung transplant evaluation |
Key Radiological Patterns on HRCT
| Pattern | Associated Disease |
|---|---|
| Ground-glass opacity (GGO) | NSIP, COVID-19, PJP, edema, alveolar hemorrhage |
| Reticulation | Fibrosing ILD (UIP, NSIP) |
| Honeycombing | UIP, end-stage fibrotic lung disease |
| Traction bronchiectasis | Fibrotic ILD |
| Crazy-paving | Alveolar proteinosis, PJP, ARDS |
| Centrilobular nodules | Hypersensitivity pneumonitis, TB, RB-ILD |
| Tree-in-bud | Endobronchial spread: TB, bacterial infection |
| Mosaic attenuation | Small airway disease, vascular disease |
| Air-trapping (on expiratory) | Bronchiolitis, obliterative bronchiolitis |
| Reverse halo sign | COP, mucormycosis, TB |