Basics of Chest X-Ray

AFAMS Residency OrientationApril 16, 2012

Outline

• CXR Basics• Types of CXR– PA vs. AP Films

• Obtaining Images• Systematic method to reading CXR• Common Signs• Examples

Chest X-ray (CXR) Basics• A standard chest X-ray

consists of a – PA Image– Lateral Image– Images read together

• AP for supine patients• Lots of information

available on a CXR• Be systematic with your

reading• Always compare to prior

studies if possible

Basics of X-Rays

• X-Rays are part of the light spectrum

• Unlike visible light, x-rays pass through the human body– Pass through lungs without much interference– Difficult to pass through bones

• Place film cassette on other side of patient and capture the shadow

Basics of X-Ray

• Organs absorb X-rays differently and thus their shadow on the film is different– Bone: high absorption (film appears white)

– Tissue: moderate absorption (film appears grey)

– Air/Lungs: little absorption (film appears black)

Types of CXRs

• PA and Lateral– Patient facing cassette– X-ray 6 feet away

• Supine AP– X-ray 40 inches away– Magnifies anterior

structures and pulmonary vasculature

101 cm

1.83 m

Comparing Chest X-rays Protocols

PA• Preferred method

AP• Note heart enlarged, lung

fields not as clear

PA Image• PA Film– Read as if patient is facing you (Patient’s left side

is on the right of the X-ray)

Lateral Image

• Obtained with patient’s left side against the cassette.

• Minimizes heart silhouette magnification

Assessing Film Technique

• Inspiration• Penetration• Rotation

Inspiration

• Image should be at full inspiration– Diaphragm at level of 8-10 rib– Allows reader to see intrapulmonary structures

Poor Inspiration mimics RML Infiltrate

Same patient with proper inspiration

Penetration• Amount of radiation required for a quality image– PA film: should barely see thoracic spine disc spaces– Lateral: spine should appear darker as move cadually

Examples of adequately penetrated images

Penetration

Overpenetrated Underpenetrated

Rotation• Patient should be flat against the cassette

• Rotation of the patient will alter appearance of mediastinum

• Observe rotation by comparing location of clavicular heads– Should be equal distance from spinous process of

thoracic vertebral bodies

Rotation

Normal Rotated to the Right

Mass vs. Infiltrate

Mass Infiltrate

Lobes and Fissures: PA Film

A: Minor Fissure between RML and RLLB: Upper and lower boundaries of major fissures

Lobes and Fissures: Lateral

B: Major Fissure L Lung A: Minor Fissure R LungB: Major Fissure R Lung

CXR Anatomy

CXR Anatomy

How to Read an X-Ray Part 1• Patient Data (Name, history, age, sex)

• Technique (PA vs. AP, rotation, penetration, etc)

• Trachea: midline or deviated, any masses?

• Lungs: masses, infiltrates?– Costophrenic angles should be sharp (if not = effusions)– Silhouette signs, air-bronchograms, pulmonary edema

• Pulmonary vessels: enlarged?

How to Read an X-Ray Part 2• Hilar Region: masses or lymphadenopathy

• Heart: enlarged, abnormal shape

• Pleura: effusion, thickening, calcification

• Bones: fractures or masses

• ICU Films: looks for line and tube placement

How to Read an X-Ray Part 3

• It is best to focus on a small area of the film and then scan rather than look at the whole film at once

Signs: Silhouette Sign

• Loss of lung/soft tissue interface caused by mass, fluid, or infiltrate in the normally air filled lung

• Commonly applied to heart, aorta, chest wall, and diaphram borders with lung

• Location of silhouette sign helps to localize pathology

Lose Right Heart and Lung border = RML

Signs: Air Bronchogram

• Tubular outline of an airway made visible by filling of the surrounding alveoli by fluid or inflammatory exudates

• Causes– Pulmonary edema– Lung Consolidation– Severe Interstitial Disease– Neoplasm

Signs: Solitary Pulmonary Nodule

• Can be innocuous or potentially fatal lung cancer

• Always compare to prior films for growth

• Nodules with irregular borders are suspicious

Conclusions• Lots of information in a chest x-ray

• Always read the film in the same order– Never skip to the most prominent abnormality, you

will miss a small (but potentially important finding)

• Compare to priors if possible

• We will finish with some examples of common pathology

Examples: Atelectasis

• Collapse or incomplete expansion of alveoli

• Causes:– Endobronchial lesions (mucous plug or tumor)– Extrinsic compression (mass, lymph node)– Peripheral compression (pleural effusion)

• Linear density on CXR

Examples: Pulmonary Edema• Cephalization of pulmonary

vessels (arrow)

• Kerley B Lines

• Peribronchial cuffing

• “Bat Wing” Appearance

• Increased Cardiac Size (arrow)

Examples: Pneumonia

• Airspace disease and consolidation

• CXR Findings– Airspace opacity– Lobar consolidation– Interstitial opacities

Differentiating Atelectasis from Pneumonia

Atelectasis• Volume Loss• Associated ipsilateral shift• Linear, wedge shaped• Apex at hilum• Air bronchograms

Pneumonia• Normal or increased volume• No shift• Consolidation, air space

process • Not centered at hilum• Air bronchograms

Examples: TB• TB can be seen as consolidation, cavitation,

fibrosis, adenopathy, or pleural effusion depending on stage of infection

Examples: Pleural Effusions

Blunting of Costophrenic Angles

Fluid in Costophrenic Angle

Examples: Pneumothorax (PTX)

• Air inside the thoracic cavity but outside the lung

• PTX appears as air without lung markings in least dependent area of chest

Examples: Hemopneumothorax

Lung

Air

Fluid

Examples: Interstitial Lung Disease

• Hazy ground glass opacification

• Volume Loss

• Linear opacities bilaterally

• “Honeycomb lung”

Examples: COPD and Emphysema

• Diffuse hyperinflation

• Flattened diaphragms

• Increased retrosternal space

• Bullae

Examples: Rib Fractures

• Can you find the rib fracture?

Examples: Pericardial Effusion

Examples: Hiatal Hernia

Gastric Bubble

Hilar Enlargement

Enlarged Pulmonary Artery Hilar Adenopathy