Chest X-Ray Interpretation

Film Placement (F)

• Look for the letter "L" in the upper left-hand corner of the film for correct placement.
• Ensure the larger part of the heart is on the left side (left ventricle).

Inspiratory Effort (I)

• Count posterior ribs above the diaphragm on a PA film.
• At least 8 ribs indicate good inspiratory effort.

Rotation (R)

• A centered film shows uniform exposure of both lung fields.
• Assess rotation by examining the spinal processes, tracheal air shadow, and interclavicular space.

Exposure (E)

• Observe vertebral bodies - they should be visible through the cardiac shadow.
• Overexposed: Vertebral bodies are easily seen, and lung fields appear black/hyperlucid.
• Underexposed: Vertebral bodies are difficult to identify, and lung fields appear white/radiopaque.
• Proper exposure avoids misinterpretation of pulmonary abnormalities.

Heart (C)

• Identify the Superior Vena Cava, Right Atrium, Inferior Vena Cava, Aortic Knob, Left Pulmonary Trunk, Left Pulmonary Artery, Left Atrium, Left Ventricle, and the Left Cardiophrenic angle.
• A normal-sized heart occupies 1/3 of the right side and 2/3 of the left side of the chest.

Hilar Point and Shadow of Hilum (H)

• This refers to the area where the main bronchi, pulmonary arteries, and veins enter the lungs.

Heart Size

• The Cardiac Thoracic Ratio (CTR) should be no greater than 50% of the width of the thorax.
• An enlarged heart can indicate Congestive Heart Failure (CHF).

Effect of Age on the Heart

• The heart naturally enlarges with age, this is a normal change and not indicative of disease.

Silhouette Sign

• Helps determine the location of pulmonary infiltrates (consolidation or fluid buildup).
• Infiltrates in contact with the cardiac border blur or obliterate this border.
• If a boundary line is visible between a lung opacity and the heart, the opacity is located posterior in the lower lobe.
• If no boundary line is visible, the opacity is likely anterior in the middle lobe.

Air Bronchogram

• Intrapulmonary bronchial tree appears radiolucent due to surrounding air-filled alveoli and bronchi.
• When alveoli are consolidated, the bronchi appear linear and branching.
• Often seen in pneumonia and pulmonary edema.

Atelectasis

• Collapsed lung tissue.
• Compressive Atelectasis: Caused by external pressure (e.g., pleural effusion, pneumothorax, hemothorax, space-occupying lesion).
• Obstructive Atelectasis: Occurs when ventilation to the area is blocked (e.g., tumor, aspiration, mucus plugging, obstruction, fibrosis).
• Radiographic findings include radiopacity, tracheal shift, hilar shift, fissure shift, volume loss, and hemidiaphragm elevation.

Lateral Decubitus Position

• Helps identify small pleural effusions (<25-50 ml) and pneumothorax.

Evaluation of Lines and Tubes

• Oral and Nasal Tracheal Tubes: Inferior tip should be 3-5 cm above the carina (between the clavicles).
• CVP and Swan-Ganz Placement: Should be placed through subclavian or jugular vein, resting in the SVC, right atrium, or pulmonary artery.
• NG tubes - should be positioned in the stomach.
• Chest tubes: Confirm placement, tube position should be in the pleural space.

Nasogastric Tube

• Proper position: In the stomach.
• Improper position: If the tube is too high, it is not in the stomach.

Rib Fractures

• Look for breaks in the rib bones.

Right Main Stem Intubation

• When endotracheal tube (ETT) is placed too low, it enters the right main stem bronchus, collapsing the left lung.

ETT Placement

• Good Position: Medial ends of the clavicles (T5-T7) or 3-5 cm above the carina.
• Too High: The tube is above the clavicles.
• Too Low: The tube is below the clavicles.

ETT and Rotation

• Patient rotation can affect tube positioning.
• If the patient is rotated, the ribs will be longer on the side of rotation.

Newborn Right Main Stem Intubation

• The ETT can easily be inserted into the right main stem bronchus in newborns.

Tracheostomy

• Look for the tracheostomy tube in the trachea.

Evaluation of Lines - CVP

• Confirm placement of the central venous pressure (CVP) line in the superior vena cava (SVC) or right atrium.

Pulmonary Artery Catheter

• Should be placed in the pulmonary artery.

Pacemaker

• A pacemaker is typically implanted in a subcutaneous pocket over the pectoralis muscle.
• Electrodes are placed in the right ventricle or atria.

Central Venous Catheter (CVC)

• Should be placed in the superior vena cava (SVC) or right atrium.

Central Venous Pressure (CVP) Catheter

• Should be placed in the internal jugular or left subclavian veins.

Tomography

• A special x-ray examination where the x-ray tube rotates, focusing rays into a central point.
• Produces "cuts" 1 cm wide.
• Useful for pinpointing chest lesions and their size and shape.

Indications for Chest Radiograph

• Detect abnormal pulmonary conditions
• Determine appropriate therapy
• Evaluate effectiveness of treatment
• Determine position of invasive devices
• Observe progression of lung disease

Radiopaque vs.Radiolucent Appearance

• Dense objects absorb more x-rays = opacity
• Bone/tissue = less penetration = radiopaque = less darkening/white shadows
• Air-filled objects absorb less x-rays = lucencies
• Lung tissue = more penetration = radiolucent = more darkening/black

PA View

• Patient takes a deep breath before exposure
• Patient stands upright
• Back to the x-ray source
• Anterior chest against metal cassette containing the film
• Arms out of the way
• This helps to move scapulae out of the way

Lateral Chest X-Ray

• Preferred view to avoid cardiac magnification

Compartments/Main Structures of the Lateral Chest X-Ray

• Anterior Compartment: Fat, lymph nodes, thymus, heart, ascending aorta
• Middle Compartment: Trachea, bronchi, lymph nodes, esophagus, descending aorta
• Posterior Compartment: Vertebral column and soft tissue

Portable CXR (AP view)

• Typically obtained in critically ill patients
• X-ray source is placed in front of the patient and film behind patient’s back
• Interpretation of the film:
  • AP film usually not centered
  • Overexposed or underexposed
  • Full vs partial inspiration
  • Extrathoracic shadows: bedding, gowns, ECG leads, tubing.
• Evaluate placement of tubes and lines

Heart Size: PA vs. AP

• PA view is preferred because it avoids cardiac magnification
• AP view magnifies the heart

Anterior Ribs and Posterior Ribs

• Anterior ribs are more horizontal
• Posterior ribs are more oblique
• These are helpful in distinguishing between the two on chest x-rays

Lung Fissures

• Major fissures separate lobes of the lungs
• Minor fissures separate the superior lobe from the inferior lobe
• Should be seen on chest x-rays

Lobe Opacity

• Opacities can be caused by fluid buildup

Lobe Anatomy

• Right lung: upper, middle, lower
• Left lung: upper, lower
• Lobe locations on chest x-ray are important to identify when diagnosing

Special Radiographic Views

• Lateral Decubitus:
  • Patient lays down on one of the sides to see free fluid in the chest.
  • Film placement is important to check. Look for the letter L in the upper left-hand corner to ensure proper placement.

Inspiratory Effort (I)

• Count posterior ribs above the diaphragm
• ≥ 8 ribs on a PA film indicate good effort

Lung Anatomy

• Right lung: upper, middle, lower
• Left lung: upper, lower
• Hilum is visible on the medial side of each lung on chest x-ray

Inspiratory Film

• If patient takes a shallow breath, the heart can appear enlarged.
• Take a second film with deep inspiration to assess the heart size accurately

Rotation (R)

• Centered film = uniform exposure of both lung fields
• Assessed by identifying spinal processes, tracheal air shadow, interclavicular space on midline

Exposure (E)

• Examine vertebral bodies
• They should be visualized through the cardiac shadow
• Overexposed = vertebrae are easily seen, lung fields are black/hyperlucid
• Underexposed = vertebrae are difficult to identify, lung fields are white/radiopaque

Airways/Lungs and Bones

• Airways/Lungs:
  • Trachea
  • Costophrenic angles
  • Diaphragm
• Bones:
  • Clavicles
  • Ribs
  • Spine

Rib Fractures

• Can be seen on a chest x-ray
• May appear as a sharp, linear break in the rib

Skin

• Can sometimes be seen on a chest x-ray

Heart (C):

• 1 = superior vena cava
• 2 = right atrium
• 3 = location of inferior vena cava
• 4 = aortic knob/arch of aorta
• 5 = left pulmonary trunk
• 6 = left pulmonary artery
• 7 = left atrium
• 8 = left ventricle
• 9 = left cardiophrenic angle
• Normal size heart: right side 1/3, left side 2/3

Hilar Point and Shadow of Hilum

• The hilum is the area where the bronchi, blood vessels, and nerves enter the lung.
• It appears as a dense shadow on the chest x-ray.

Heart Size

• The Cardiac Thoracic Ratio (CTR) should be no greater than 50% of the width of the thorax.
• CTR greater than 50% = enlarged heart = CHF

Effect of Age on the Heart

• The size of the heart increases with age
• This is a normal change and does not necessarily indicate disease

Radiographic Findings in Lung Disease

• Silhouette Sign:
  • Useful in determining where the pulmonary infiltrate is located.
  • Presence of infiltrates in contact with cardiac border cause this border to be blurred or obliterated.
  • Rule of Thumb:
    • If a boundary line can be seen between the lung opacity and the heart, the opacity is located posterior in the lower lobe.
    • If a boundary line cannot be identified, the opacity must have a more anterior location in the middle lobe.
• Air Bronchogram:
  • Intrapulmonary bronchial tree is radiolucid on the chest film because surrounding alveoli and bronchi are air-filled structures.
  • If surrounded by consolidated alveoli they will be appear as linear branching air shadows.
  • Often seen in pneumonia and pulmonary edema.

Atelectasis:

• Collapse of lung tissue.
• **Types: **
  • Compressive:
    • Pleural effusion
    • Pneumothorax
    • Hemothorax
    • Any space-occupying lesion
  • Obstructive:
    • Ventilation to the area is absent leading to collapse.
    • Usually entire lobes or segments are involved.
    • Causes: Tumor, aspiration, mucus plugging, mechanical obstruction, fibrosis.
    • Complete vs partial obstruction, one-way valve mechanism.
• Radiological Findings:
  • Radiopacity of entire segments or lobes
  • Shift of the trachea, heart, and great vessels
  • Shift of the fissure lines toward the collapsed area
  • Movement of hilar structures toward the area of collapse
  • Loss of volume in lung affected
  • Hemidiaphragm elevation
  • Microatelectasis, or plate-like atelectasis when the lesion causing the compression is not large enough to cause obstruction.
  • Appear as diffuse linear radiopaque densities

Pneumothorax

• Extreme form of atelectasis.
• Air in pleural space from a hole in the chest wall or from a hole in the lung.
• Causes loss of negative pleural pressure.
• Tension Pneumothorax:
  • Causes: Stab wounds, rib fractures, central lines placement, positive pressure ventilation, etc.
  • One-way valve mechanism allows air into pleural space resulting in positive pressure
  • Shifts structures away from affected side
  • Affects ability of contralateral lung to expand, affects venous return, and cardiac contractility

Subcutaneous Emphysema and Spontaneous Pneumothorax

• Emphysema is the presence of air in the subcutaneous tissue.
• A spontaneous pneumothorax is a pneumothorax that occurs without any obvious cause, such as injury.

Hyperinflation

• Most common cause: COPD
• Radiological changes:
  • Large lung volumes
  • Increased retrosternal and retrocardiac spaces
  • Depressed diaphragms
  • Small narrow heart
  • Enlarged intercostal spaces

Pleural Fluid

• Free fluid in the intrapleural space.
• If PA/AP film questionable = lateral decubitus.
• Radiological changes depend on the volume of fluid in the pleural space:
  • Blunting of the costophrenic angle
  • Small meniscus sign on side of the chest wall
  • Partially obscured diaphragm with elevation from its normal position
  • Complete “whiteout” of involved side when large volume is present

Consolidation

• Fluid-filled lung parenchyma
• Pneumonia.
• Radiographic signs:
  • Minimal loss of volume
  • Usually lobar distribution
  • Homogeneous density
  • Air bronchogram if airway leading to consolidated area is open

Congestive Heart Failure

• Pulmonary edema:
  • Redistribution of pulmonary vasculature to the upper lobes.
  • Lower lobes congested.
  • Upper lobes are relatively fluid-free areas.
• C/T ratio is increased > 0.50
  • Normal: ≤ 0.5
• Kerley B lines (interstitial edema):
  • Typically seen in R base.
  • 1mm thick and 1-2 cm long.
  • Start at the periphery and follow the line toward the heart.
• Butterfly or batwing outline:
  • Represents edema in the central portion of the lungs

Case Reports

• Case 1
• The patient has a well-developed right pectoral muscle. This can cause a difference in the density of the lungs on the chest x-ray, making one lung appear darker than the other.
• Case 2
• The patient has had a right-sided pneumonectomy. This means that the right lung has been removed. This explains why the right lung appears completely white out on the chest x-ray.

This quiz covers essential techniques for interpreting chest X-rays, including film placement, inspiratory effort, rotation, exposure, and heart identification. Master these skills to improve your diagnostic accuracy and understanding of pulmonary abnormalities.