CT Chest High-Resolution (HRCT) for Interstitial Lung Disease

Indications

• Suspected or known interstitial lung disease (e.g. usual interstitial pneumonia/IPF, NSIP, hypersensitivity pneumonitis, sarcoidosis)
• Characterization of diffuse parenchymal lung disease, air trapping, small airways disease
• Bronchiectasis evaluation
• Follow-up of fibrotic lung disease

Patient prep

• No contrast required for standard HRCT (contrast not used to characterize ILD)
• Coach the patient on inspiratory and expiratory breath-holds; practice prone positioning if used
• Arms above head

Contrast

Technique

• Volumetric thin-section helical acquisition (modern standard) covering apices to bases at full inspiration; supine
• Add end-EXPIRATORY series (detects air trapping/mosaic) — volumetric or sequential
• Add PRONE inspiratory series to distinguish dependent atelectasis from early posterior fibrosis
• 120 kV; mAs per scanner with AEC; iterative reconstruction; reconstruct contiguous thin (0.625-1 mm) high-spatial-frequency (sharp/lung) kernel
• Reformat coronal/sagittal lung images; supine inspiratory volumetric set is reference

Series / Sequences

Key points

• Three acquisitions are classic: supine inspiratory + expiratory + prone inspiratory; expiratory series is essential for air trapping/HP
• Report distribution (upper vs lower, central vs peripheral) and pattern; apply Fleischner/ATS UIP criteria (honeycombing, traction bronchiectasis, reticulation)
• Generally non-contrast; thin sharp-kernel images are mandatory
• Volumetric acquisition now preferred over spaced axial sequential to allow MIP/minIP and reformats

References