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ChestImage Interpretation
Simon Clarke
Senior Radiographer
PAM3006
University of Exeter
Learning OutcomesBy the end of this lecture you should be able to:
• Identify bony and soft tissue anatomy
• Use a systematic approach to reading a CXR
• Identify lines and tubes
• Recognise common chest abnormalities
• Be aware of normal variants
Anatomy of the Thorax
Basic Anatomy
Trachea
Basic Anatomy
Trachea
Positioned centrally, but may angle to the right.
The trachea gradually shifts to the right with age.
Bifurcation
Carina
Basic Anatomy
Trachea
Positioned centrally, but may angle to the right.
The trachea gradually shifts to the right with age.
Don’t use the Trachea to judge how rotated the image may be!
Bifurcation
Carina
Basic Anatomy
Aortic arch
Basic Anatomy
Aortic arch
Also referred to (inaccurately) as the Aortic knuckle.
The arch tends to unfold, and become more prominent, with age.
Basic Anatomy
Heart
Basic Anatomy
Heart
Size and position is vital
Basic Anatomy
Heart
Size and position is vital
Cardio-Thoracic Ratio (CTR) should be <50% on a PA image
Basic Anatomy
Lung FieldsRight Upper Lobe
Right Middle Lobe
Right Lower Lobe
Left Upper Lobe
LeftLower Lobe
Basic Anatomy
Hilar
• Made up of the major bronchi, pulmonary arteries and veins on the medial aspect of each lung
• Anchors the lungs to the heart, trachea, and surrounding structures
Basic Anatomy
Hilar
• The left hilum is commonly higher than the right
• Changes in density, size or positioning of the hilar is highly indicative of abnormality
Basic Anatomy
Hilar enlargement
• Lymphadenopathy and tumours
• Pulmonary venous hypertension (LVF, mitral stenosis or mitral reflux)
• Pulmonary arterial hypertension (primary pulmonary hypertension and lung diseases such as COPD)
• Increased pulmonary blood flow
Basic Anatomy
Pleural surfaces
• Visceral Pleura (outer)
• Parietal Pleura (inner)
• Lung markings should reach the thoracic wall
Basic Anatomy
Pleural surfaces
Only visible when there is an abnormality present
• Pleural thickening
• Fluid in the pleural spaces
• Air in the pleural spaces
Basic Anatomy
Diaphragm
• The hemidiaphragms are not at the same level.
• The left hemidiaphragm is commonly higher than the right by one intercostal rib space height (~2 cm)
Basic Anatomy
Diaphragm
• When one hemidiaphragm is significantly higher than the other (>3cm) an abnormality is likely
The importance of image quality
The importance of image quality
RotationSide lifted from detector appears lighter. Hila can look distorted
The importance of image quality
RotationSide lifted from detector appears lighter. Hila can look distorted
InspirationLess than 6 anterior/8 posterior ribs causes crowding of diaphragm and hila
The importance of image quality
RotationSide lifted from detector appears lighter. Hila can look distorted
InspirationLess than 6 anterior/8 posterior ribs causes crowding of diaphragm and hila
PenetrationUnder-exposed = can cause false positives for pulmonary fibrosis or oedema
The importance of image quality
RotationSide lifted from detector appears lighter. Hila can look distorted
InspirationLess than 6 anterior/8 posterior ribs causes crowding of diaphragm and hila
PenetrationUnder-exposed = can cause false positives for pulmonary fibrosis or oedema
AngulationClavicles projected over apexes
Systematic review of the CXR
1. Trachea2. Lung Fields3. Silhouette Sign4. Mediastinum & Heart5. Fissures6. Hila7. Diaphragm and below diaphragm8. Bones9. Soft tissue10. Abnormal densities
Don’t forget satisfaction of search!
Silhouette Sign
Silhouette Sign
On a normal CXR, the outline (silhouette) of the heart borders; aortic arch; ascending and descending aorta and hemidiaphragms should be clearly visible where they are in contact with a specific portion of the lung due to the natural subject contrast.
Silhouette Sign
The silhouette sign is a loss of this clearly defined border.
Identify exactly which silhouette is obliterated - this will indicate where the lung pathology is located.
Pushed or Pulled?
When lung anatomy has shifted, it’s important to decide if it has been pulled to one side, or pushed away from the other.
Pushed or Pulled?
Pushed• Massive pleural effusion• Structures displaced to
other side• Diaphragm depressed• Ribs widened
Pulled• Lobular collapse• Structures displaced to
the same side• Diaphragm pulled up• Ribs crowded
Lines and Tubes
Nasogastric Tube
NG tube is used for short or medium term nutritional support, and also for aspiration of stomach contents
Nasogastric Tube
Check correct position:
• tube bisects the carina
• tube crosses the diaphragm in the midline
• the tip sits below the diaphragm
Nasogastric Tube
It shouldn’t divert down the bronchi and into the lung!
Nasogastric Tube
It shouldn’t divert down the bronchi and into the lung!
Or be curled in the oesophagus!
Endotracheal Tube
Inserted into the trachea to establish and maintain a patent airway
The tip of the ET tube should be approximately 5 cm above the carina
Carina
Tip of ET tube
PICC Line
Peripherally Inserted Central Catheter
Intravenous access for a prolonged period (e.g., chemotherapy, extended antibiotic therapy, or total parenteral nutrition)
PICC Line
• Inserted under Interventional Radiology or Theatre C-arm
• Inserted into peripheral vein in the arm (cephalic, basilic or brachial)
• Tip rests in the distal superior vena cava or cavoatrial junction.
CVC Line
Central Venous Catheter
• inserted into the superior vena cava or right atrium
• Inserted without X-ray guidance, so check CXR required
White arrow:PICC Line
Black arrow: CVC Line
Common abnormalities
Pneumothorax
Air trapped in the pleural space
Causes include:• Penetrating injury to the lung• Rib fractures• Air blisters breaking open under
pressure changes (diving or high altitude flight)
• Medical interventions (biopsies, pacemaker insertions, etc.)
Pneumothorax
In some cases, intra-pleural air volume will increase, exerting pressure on the mediastinal and intra-thoracic structures.
This is known as a
Tension Pneumothorax
Positive pressure
Pneumothorax
In some cases, intra-pleural air volume will increase, exerting pressure on the mediastinal and intra-thoracic structures.
This is known as a
Tension Pneumothorax
This is a medical emergency!
Positive pressure
TensionPneumothorax
Additional possible signs:
• Ipsilateral increased intercostal spaces
• Shift of the mediastinum to the contralateral side
• Depression of the hemidiaphragm
(Ipsilateral = same side / Contralateral = opposite side)
Increased space
Flattened
Shift
Consolidation
• Alveoli and small airways fill with fluid, giving dense white appearance
• Consolidation does not necessarily imply an infection
Area of consolidation(Upper Right Lobe)
Horizontal fissure
Consolidation
Larger, fluid-free airways may appear darker against the white-out lung area.
This is called an air bronchogram
Pleural effusion
• Pleural effusion is excess fluid that accumulates in the pleural cavity
• Impairs breathing by restricting the expansion of the lungs
Curved meniscus with blunting of costaphrenic and cardiophrenic angles
Pleural effusion
• Need at least 175ml of pleural fluid before it becomes visible on a PA image
• On a lateral image effusion of >75ml can be visible
• At least 500ml must be present to be seen on a supine CXR
Pericardial effusion
Pulmonary Oedema
• Fluid accumulation in the air spaces and parenchyma (functional parts) of the lungs
• Impairs gas exchange can lead to fatal respiratory distress or cardiac arrest
• Due to either left ventricular failure (LVF) or injury to the lung
Lung Mass
• Lung cancer is the most common fatal malignancy worldwide in both men and women
• Lesions are smaller than 3cm
• Masses are larger than 3cm
Solitary Pulmonary Nodule
Widespread pulmonary metastases
Lung Mass
• Cavitation or calcification - highly associated with malignancy
• Lobulated or scalloped margins - intermediate probability
• Smooth margins - more likely benign (unless metastatic in origin)
Malignant cancerous mass
Tuberculosis Pneumonia (RML)
Surgical Emphysema Perforated Bowel
Rib fracture Rib lesion (osteomyelitis)
Normal variants
Dextrocardia situs inversus totalisDextrocardiaComplete transposition (right to left reversal) of all of the abdominal organs
Heart points toward the right side of the chest
Any questions?
Thank you for your attention
Simon Clarke
Senior Radiographer
PAM3006
University of Exeter