Radiology: Chest Imaging

Chest Imaging

Densities

• Four densities on XR• Black – air/gas• Dark grey – fat• Light grey – fluid/solid organ• White – bone/calcium

Increasing opacification

CXR

• Rule No 1! – always check name of patient and date

• Check orientation (L & R labeled correctly)• Projection (PA or AP, lateral, decubitus,

supine)• Accurate assessment of heart size and

mediastinum on PA views• All supine/portable - AP

CXR - systematic• ABCDE for both frontal & lateral projection• A – airways

– Trachea/central bronchi midline or just to right, no narrowing, carinal angle <90°

• B – breathing/lungs– Parenchyma – too white or too black?

• Look at the fissures

– Bones – ribs, vertebrae, humeri clavicles, scapulae – for fractures, lytic(black), sclerotic (white) lesions, vertebral body heights

• C – cardiac/vessels– Cardiac silhouette & Mediastinum contours & width– Hilum – normal hilar shadow made up of vessels, Lt is higher than right by 0-2.5

cm. Must have concave shape– Pulmonary vessels – upper zone vessels vessels smaller than lower

CXR - systematic

• D – look under the diaphragm– free gas – perforated viscus– Costophrenic angle for pleural effusion

• E – extremities– The corners of the film

• Line position• Hidden areas: lung apices, behind the heart,

breast shadows, paravertebral, thyroid

Normal CXRTrachea

Rt Mainstem bronchus

Aortic Arch

Pulm artery

Pulm artery

LV

Diaphragm

stomach

RA

Atrial appendage

Normal CXR

Trachea

Pulmonary artery

RVLV

Aortic arch

Costophrenic angle

LA

Anatomy

RUL

ML

RLL

LUL

LLL

Heart

• Cardiothoracic ratio (CTR)– <50% adults– PA film – AP magnifies heart– Causes of increased CTR

• Obesity, pectus, portable film, cardiomegaly, pericardial effusion

• Shape• Valve calcification

Lungs• Too black• Too white

– Opacity, density, infiltrate, mass/nodule• Alveolar air cells

– Normally contain air (black)– Cells eg infection/inflam pus, tumour, eosinophils– Fluid eg aspiration, drowning, oedema, haemorrhage

• Interstitial• Collapse V consolidation

– Volume loss: mediastinal shift, fissures, diaphragm, hilum, rib crowding

– Air bronchograms

Silhouette sign

• When air in alveoli replaced with fluid/cells contrast between the lung and the neighbouring structure (heart, diaphragm) is lost and borders become indistinct.

• Use the silhouette sign to determine which lobe of the lung consolidation is in.

14 y M

Hx: 61 y M SOB

10 y F bilateral crackles. No response to ventolin

Hx 60 y M, chronic cough, haemoptysis

Hx 12 Y F fever & cough

Hx: 5Y M reduced air sounds left chest, decrease O2 sat

Hx 23 F confusion

66 Y F SOB

FHx: 54 y M SOB

Hx 41 Y F

Hx 16 Y M known malignancy

Hx: 88 Y M fever weight loss

Hx 78 Y F previous rectal cancer

The Black Lung

• First consider Rotation: – (look at the clavicles)– The lung closer to the film plate will absorb

more of the x-rays and so be whiter, whilst the lung further away allows distance for scattered rays to get through, and so will be blacker

9 y M Wheeze

23 y M

21 y M chest pain

20 Y M

87 y M SOB

pseudopneumothorax

Pulmonary embolism

• Abnormalities seen on CXR in PE– MORE OFTEN NORMAL – never forget this!!– Segments/subsegments of linear atelectasis– Raised hemidiaphragm– Focal region of hyperlucency (oligaemia) “Westermark’s sign” – black area of lung seen in only 2%

– Peripheral foci of consolidation (infarction) e.g. Hampton’s Hump. <10% show infarction.

– Dilated central arteries due to arterial hypertension.– Abrupt cut-off of a vessel – only if in the central

arteries– Pleural effusion

38 y M

Pleural Plaques

• Associated with asbestos exposure• Thickening of the parietal pleura which

calcifies, especially seen over the diaphragmatic surface as dense linear bands.

• Does NOT equal asbestosis, which is pulmonary parenchymal disease related to asbestos exposure – can occur together.

77 y M

• Hilar Enlargement – unilateral or bilateral – Look for the convex contour

• Neoplasm: – central bronchogenic tumour itself, or lymphadenopathy. e.g. Ca

Bronchus, lymphoma, Lymphangitis carcinomatosis• Infective e.g. TB (usually unilateral), Mycoplasma, Viral in children• Sarcoidosis rarely unilateral, very symmetrical• Post-stenotic dilatation of pulmonary artery• Pulmonary artery aneurysm (very rare)• All causes of pulmonary arterial hypertension: primary (idiopathic) or

secondary e.g. COAD, long- term PE, chronic left to right cardiac shunt.

Mediastinum• When reviewing CXR, don’t forget this

region, which contains the oesophagus, the trachea, the aorta, the thymus

• Differential Diagnosis of an anterior Mediastinal mass: “The 4 Ts”

• Thymoma• Thyroid goitre• Teratoma• Terrible Lymphoma• Assessing the mediastinal width after

severe road trauma is important to assess for

– aortic rupture. However, these films are always supine (so AP) so very variable!!

• In practice, if the widest part of the upper mediastinum is >30% of the total thorax diameter at that level, suspect aortic injury if clinically possible. However, NEVER ignore high clinical suspicion even if the xray seems normal.

14 y M