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ChestDemonstration data

CT Chest (High-Resolution)

High-resolution CT of the chest uses thin-section, high-spatial-frequency reconstruction to characterize the pulmonary interstitium and small airways in exquisite detail. It is the reference imaging test for diffuse parenchymal (interstitial) lung disease, bronchiectasis, and emphysema, often allowing a confident pattern-based diagnosis such as usual interstitial pneumonia (UIP). Complementary prone and expiratory images distinguish dependent atelectasis from disease and reveal air trapping.

Indications

  • Suspected interstitial lung disease and characterization of a diffuse parenchymal pattern (e.g., UIP, NSIP, HP)
  • Bronchiectasis assessment and evaluation of chronic productive cough
  • Quantification and distribution of emphysema
  • Suspected hypersensitivity pneumonitis, sarcoidosis, or occupational/connective-tissue lung disease
  • Unexplained dyspnea with restrictive pulmonary function or reduced diffusing capacity
  • Small-airways disease and suspected air trapping (expiratory imaging)

Contraindications & Cautions

  • No absolute contraindication; the standard protocol is non-contrast
  • Pregnancy: justify and use dose reduction; the low-dose HRCT technique limits fetal scatter dose
  • Radiation stewardship in young patients and for serial follow-up; use low-dose protocols and iterative reconstruction
  • Inability to perform breath-holds or follow inspiratory/expiratory commands degrades the study
  • If iodinated contrast is later required for another indication, screen renal function and allergy history

Patient Preparation

  • No fasting or IV access required for a standard non-contrast HRCT
  • Coach breath-hold technique: full suspended inspiration for supine images
  • Position supine, arms above the head; add prone imaging when posterior dependent opacity is present
  • Explain expiratory acquisition and rehearse the maneuver for air-trapping assessment
  • Remove radiopaque garments and monitoring leads from the field where possible
  • Confirm the clinical question and any prior imaging for comparison

Technique & Parameters

  • Volumetric thin-section acquisition, 0.625-1.25 mm collimation, reconstructed with a sharp/high-spatial-frequency kernel
  • Full-inspiration supine helical acquisition covering lung apices to costophrenic angles
  • Prone thin-section images to resolve dependent atelectasis from early fibrosis
  • Expiratory images (end-expiration) to detect mosaic attenuation and air trapping
  • Typically 120 kVp with dose modulation; low-dose protocols for follow-up; no IV contrast
  • Review on lung (W1500/L-600) and mediastinal windows; use MIP for micronodules and minIP for mosaicism/emphysema

Systematic Review

  • Determine the axial distribution: upper vs lower zone, central vs peripheral/subpleural
  • Characterize the dominant pattern: reticular, nodular, ground-glass, cystic, or low-attenuation
  • Assess for honeycombing and traction bronchiectasis indicating established fibrosis
  • Evaluate the airways for bronchial dilatation, wall thickening, and mucous plugging
  • Look for mosaic attenuation and confirm air trapping on expiratory images
  • Review the mediastinum and hila for lymphadenopathy; check for pleural and pericardial disease
  • Inspect for nodules, and correlate distribution (perilymphatic, centrilobular, random)

Key Findings & Significance

  • Honeycombing with basal, subpleural predominance and traction bronchiectasis: UIP pattern (e.g., IPF)
  • Ground-glass opacity with subpleural sparing and reticulation: NSIP pattern
  • Centrilobular ground-glass nodules, mosaic attenuation, and air trapping: hypersensitivity pneumonitis
  • Upper-lobe perilymphatic nodules with symmetric hilar/mediastinal nodes: sarcoidosis
  • Cylindrical/varicose/cystic bronchial dilatation with signet-ring sign: bronchiectasis
  • Low-attenuation areas without walls (centrilobular) or with walls (paraseptal): emphysema subtypes
  • Crazy-paving (ground-glass with superimposed septal thickening): broad differential including infection and alveolar proteinosis

Differential Considerations

  • UIP pattern: idiopathic pulmonary fibrosis vs chronic HP vs connective-tissue disease vs asbestosis
  • Cystic lung disease: LAM vs Langerhans cell histiocytosis vs lymphoid interstitial pneumonia vs Birt-Hogg-Dube
  • Mosaic attenuation: small-airways disease (air trapping) vs vascular (chronic PE) vs ground-glass infiltration
  • Upper-lobe fibrosis: sarcoidosis vs chronic HP vs pneumoconiosis vs prior TB/radiation
  • Ground-glass opacity: infection/edema (acute) vs NSIP, DIP, or alveolar proteinosis (subacute/chronic)
  • Perilymphatic nodules: sarcoidosis vs lymphangitic carcinomatosis vs silicosis

Pearls & Pitfalls

  • Prone imaging is essential to avoid overcalling dependent atelectasis as early fibrosis
  • Expiratory scans confirm air trapping; without them, mosaic attenuation is nonspecific
  • Traction bronchiectasis within ground-glass indicates fibrosis, changing the interpretation
  • Follow current IPF diagnostic guidelines for confident UIP versus probable/indeterminate patterns
  • Micronodule distribution (perilymphatic vs centrilobular vs random) is the key to the differential
  • Correlate with occupational, drug, and connective-tissue history; imaging pattern alone is often insufficient

Structured Report

  • State protocol (inspiratory, prone, expiratory) and comparison studies
  • Describe the dominant pattern, its zonal and axial distribution, and extent
  • Report presence or absence of honeycombing, traction bronchiectasis, and air trapping explicitly
  • Comment on airways, nodules, mediastinal/hilar nodes, and pleura
  • Assign a diagnostic pattern (e.g., typical UIP, probable UIP, indeterminate, alternative) per current criteria
  • Impression: give the most likely diagnosis or narrowed differential and recommend MDT discussion or biopsy where appropriate

References

  • ATS/ERS/JRS/ALAT Clinical Practice Guideline: Diagnosis of Idiopathic Pulmonary Fibrosis (2018/2022 update)
  • Fleischner Society: Glossary of Terms for Thoracic Imaging
  • ACR Appropriateness Criteria: Diffuse Lung Disease
  • Webb, Muller, Naidich: High-Resolution CT of the Lung

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.