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