Thoracic Imaging
Core concepts
Build a systematic approach to the chest radiograph (ABCDE: airway, breathing/lungs, circulation/cardiac, diaphragm, everything else). Know focal vs diffuse opacity patterns: consolidation (air bronchograms), ground-glass, reticulation, honeycombing, and the UIP pattern. Understand mediastinal compartments (anterior, middle, posterior) and their masses. Know pulmonary nodule assessment: size, spiculation, calcification pattern (benign central/laminated/popcorn), and follow-up versus PET. Learn the PE protocol (CTPA timing, filling defects) and basic ILD classification. Recognise pneumothorax, pleural effusion, and the signs of lobar collapse (volume loss, fissure shift).
Traps
- A ground-glass nodule can be transient (infection) or a precursor of adenocarcinoma-size and persistence matter.
- Popcorn calcification suggests hamartoma, not malignancy.
- Silhouette sign localises opacity to an adjacent structure-do not overcall.
- In CTPA, look for indirect signs: right heart strain, septal bowing.
- Miliary pattern is a differential (TB, metastasis, sarcoid), not a diagnosis.
Worked example / rule of thumb
A solid nodule of 8 mm in a low-risk patient: follow-up CT at 3 months, not immediate biopsy. Rule of thumb for nodules: <6 mm low-risk-no routine follow-up; 6–8 mm-interval CT; >8 mm-PET/CT or biopsy (adapt to local guidelines). For a suspected PE with a normal CTPA, consider alternative diagnoses and the value of lower-limb ultrasound.
Key points
- Use a systematic chest radiograph approach; localise with the silhouette sign.
- Know mediastinal compartments and typical masses.
- Assess nodules by size, margin, and calcification.
- CTPA: filling defects plus right heart strain signs.
- Miliary and ground-glass patterns have broad differentials.