Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Select and interpret thoracic CT, CT pulmonary angiography and lung ultrasound according to a precise clinical question, recognising each modality's urgent uses, limitations, harms and follow-up responsibilities.
CT excels when cross-sectional anatomy or tissue pattern will change a decision. Standard contrast-enhanced thoracic CT evaluates masses, nodes, mediastinum, pleura and many complications; non-contrast imaging may suit selected nodule, calcification or follow-up questions; thin-section volumetric techniques characterise diffuse parenchymal disease and may include expiratory or prone acquisitions; CTPA times iodinated contrast to the pulmonary arteries. Writing only 'CT chest' transfers the clinical decision to radiology without supplying the information needed to optimise it. A useful request states the suspected condition, tempo, relevant previous imaging, important risk factors, renal or contrast information and the decision the result will determine.
For suspected pulmonary embolism, imaging follows probability rather than preceding it. Apply the current NICE diagnostic pathway, using clinical assessment, the two-level PE Wells score and D-dimer where indicated, while recognising circumstances in which immediate imaging or interim therapeutic anticoagulation is advised. Pregnancy has a separate multidisciplinary pathway because maternal risk, fetal and breast radiation, alternative imaging and local expertise must be weighed. CTPA quality depends on contrast timing, breath-hold, motion and cardiac output; inadequate arterial opacification can make a scan non-diagnostic. A negative result is most reassuring when the study is technically adequate and the pre-test pathway was appropriate.
A contrast filling defect within an adequately opacified pulmonary artery supports acute embolism; chronic embolic disease may show eccentric organised material, webs, vessel narrowing and mosaic perfusion. Right-heart strain features alter urgency but must be integrated with haemodynamics and formal reporting.
Poor pulmonary-artery enhancement, respiratory motion, streak artefact or suboptimal coverage can prevent reliable exclusion of embolism. The report should state the limitation; subsequent imaging or management depends on clinical probability, bleeding risk and available alternatives.
Reticulation, traction bronchiectasis, honeycombing, ground-glass change, nodules and air trapping have meaning through their distribution and combination. A pattern can narrow a multidisciplinary differential but should not be translated into idiopathic pulmonary fibrosis without clinical exclusion of exposures, drugs and connective-tissue disease.
A fluid space bounded by chest wall, diaphragm and collapsed or floating lung confirms effusion and permits depth assessment. Echogenic debris or septation suggests complexity, while solid tissue, liver or spleen must be identified before any needle path is chosen.
Loss of pleural sliding and B-lines with a barcode pattern on M-mode can support pneumothorax, and a lung point is more specific when present. Apnoea, pleurodesis, severe emphysema, mainstem intubation and adhesions can also abolish sliding, so physiology and expertise matter.
Subpleural tissue-like echotexture with dynamic air bronchograms supports peripheral air-space consolidation. Small infarcts, atelectasis and tumour can appear tissue-like; central disease hidden behind aerated lung may be invisible to ultrasound.
A beautifully acquired wrong-phase scan may not answer the clinical question. Contrast timing, slice reconstruction, inspiration and expiratory manoeuvres are diagnostic choices, which is why concise radiologist discussion can prevent both delay and repeat radiation.
Vertical ring-down artefacts arise when subpleural aeration is reduced. Their number and distribution can support an interstitial syndrome, but oedema, fibrosis, contusion and inflammation can all generate them.
Pleural adhesion, apnoea, very shallow ventilation and mainstem intubation can remove visible sliding without pleural air. A lung point strengthens pneumothorax diagnosis, while haemodynamic instability determines urgency.
The evidential value of a negative CTPA depends on suitable pre-test selection and sufficient arterial opacification without prohibitive motion. The technical-quality statement is therefore part of the result, not an optional footnote.
Current RCR and Society of Radiographers advice does not require routine interruption of breastfeeding after iodinated CT or gadolinium MRI contrast. Address individual concern through radiology policy instead of withholding necessary imaging.
Requesting generic CT chest without stating whether the question is embolism, malignancy, pleural disease or diffuse parenchymal disease.
Ordering CTPA because D-dimer is raised without first using the intended clinical-probability pathway.
Treating a technically limited CTPA as confidently negative despite persistent high clinical concern.
Diagnosing cardiogenic oedema from B-lines alone or pneumothorax from absent sliding alone.
Attempting pleural aspiration from an old skin mark after the patient has moved instead of repeating ultrasound at the procedure.
Focusing only on the acute CT indication and losing an incidental nodule or formal follow-up recommendation.
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A stable patient presents with pleuritic pain and tachycardia, and pulmonary embolism is possible. Before requesting CTPA, which approach best aligns the imaging with a safe UK diagnostic pathway?
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. ·
Lung ultrasound answers focused bedside questions dynamically and without ionising radiation. Pleural fluid appears as an anechoic or complex space above the diaphragm; septations may indicate complexity but do not alone determine aetiology. Pleural sliding, B-lines, consolidation with air bronchograms and the lung point can support particular diagnoses, yet each sign has mimics. Ultrasound cannot survey the whole lung through aerated tissue and cannot rule out pulmonary embolism, central tumour or deep parenchymal disease. Operators need training, saved images and governance. As with CT, a result is only safe when its limitation, reporting status, downstream action and incidental findings are made explicit.