Chest X-Ray
Interpretation for the
Internist
Theresa Cuoco, MD
Medical University of South Carolina
February 22, 2012
Disclaimer: I am NOT a radiologist!
Why do we need to know?
 To direct care while awaiting an “official read”
 Low level radiation for the patient
 Easily available and noninvasive
 Relatively inexpensive
Objectives
 Basics of technique
 Type of film and the “tions”
 Identification of structures on a “normal” CXR
 Alveolar vs interstitial, lobar anatomy, silhouette sign,
air bronchograms, and patterns of lung disease
 The mediastinum, pleura, and heart
 Systematic approach to interpretation
 Cases
Technique
 PA and lateral
 AP
 Which is preferred and why?
 Lateral film – left side of chest against x-ray cassette
 Decubitus films
Which is which?
The “tions”
 IdentificaTION
 InspiraTION
 PenetraTION
 RotaTION
Inspiration vs Expiration
Any indications for an expiratory film?
Penetration
A
B
Heavy light exposure causes the film
to be black (A)
Little light exposure causes the film
to be white (B)
Rotation
Normal Anatomy
The Normal Chest X-Ray
Alveolar vs Interstitial
 Alveolar = air sacs
 Radiolucent
 Blood, mucous, tumor, or
edema in alveoli obscure
normal anatomy: “airless
lung”
 Interstitial = vessels,
lymphatics, bronchi, and
connective tissue
 Radiodense
 Interstitial disease:
prominent lung markings
with aerated lungs
Lobar Anatomy
Anterior
Posterior
Lobar Anatomy – Lateral Views
Right
Left
The Silhouette Sign
 There are 4 basic radiographic densities
 Gas, fat, soft tissue (water), and metal (bone)
 Anatomic structures are recognized on x-ray by their
density differences
 Two substances of the same density in direct contact
can’t be differentiated
 Loss of the normal radiologic silhouette (contour) is
called the “silhouette sign”
Localizing Lesions
Where is the silhouette sign?
Localizing Lesions
Localizing Lesions
A
B
Localizing Lesions
A
B
Localizing Lesions
 Obscured L heart border = lingula
 Aortic knob obliterated = left upper lobe
 Right lung base w heart border seen = right lower lobe
 Right lung base w heart obscured = right middle lobe
 Descending aorta obscured = left lower lobe
 EXCEPTIONS:
 Pseudosilhouette of diaphragm in underpenetrated film
 Right heart border my overlap spine
 Heart obscures anterior left diaphragm on lateral
The Air Bronchogram
 When lung is consolidated and bronchi contain air, the
dense lung delineates the air-filled bronchi
 Visualization of air in the intrapulmonary bronchi is
called the “air bronchogram sign”
 Abnormal finding
 Can be seen in:
 PNA, edema, infarction
 Chronic lung lesions
NO Air Bronchograms…
 In pneumonia if bronchi are filled with secretions
 If cancer obstructs a bronchus
 Interstitial fibrosis
 Asthma/emphysema (hyperinflation)
What do you see?
Lung and Lobar Collapse
 When a whole lung collapses, the trachea deviates
TOWARD the side of collapse (due to volume loss)
Fissures
 Formed by 2 visceral pleural layers
 Demarcate the boundaries of the lobes
 Shift of fissures is best sign of lobar collapse
Which lobes have collapsed?
Minor fissure is elevated – RUL
partially collapsed
Heart has moved to right and
silhouette sign of right diaphragm –
indicated RLL collapse
Hilar Displacement
 The left hilum is normally slightly higher than the right
 Hilar depression indicates collapse of lower lobe
 Hilar elevation indicates collapse of upper lobe
Patterns of Lung Disease Pearls
 Pulmonary markings are more visible in interstitial
disease
 Generalized interstitial markings = linear (reticular)
 Discrete/focal thickening = nodular
 Homogeneous or patchy consolidation = alveolar
 Focal consolidation < 3cm = nodule
 Focal consolidation > 3cm = mass
 Heavy calcification generally = benign
What is the pattern?
A: Focal/linear
B: Diffuse/nodular
C: Alveolar
The Mediastinum
The Mediastinum
 I: Anterior Mediastinum
 Heart
 Retrosternal clear space
 5 T’s
 II: Middle Mediastinum
 Esophagus
 Arch and descending aorta
 Trachea
 III: Posterior Mediastinum
 Paravertebral area
 Lymph nodes in all 3!
The Pleura
 The posterior costophrenic angle is the deepest and only
seen on the lateral film
 The lateral film is more sensitive for detection of small
pleural effusions
 How much fluid can be seen on a radiograph?




Erect PA: 175 mL
Erect lateral: 75 mL
Decubitus: >5 mL
Supine: Several hundred mL
What do you see?
The Heart
 The horizontal
width of the heart
should be less than
½ the widest
internal diameter
of the thorax
Left and Right Ventricular Enlargement
 Left ventricular
enlargement
 Frontal: LHB moves
laterally and cardiac apex
inferolaterally
 Lateral: LHB moves
inferoposteriorly
 Right ventricular
enlargement
 Frontal: RHB further right
 Lateral: Contacts lower half
of sternum (instead of
lower 3rd)
Cephalization
 Enlargement of the upper lobe vessels
 “Vascular redistribution”
 “Kerley B” lines: interstitial edema
thickening the interlobular septa
causing short lines perpendicular
to the pleural surface
Systematic approach
 ABCDE






Airway
Bones and breasts
Cardiac and costophrenic
Diaphragm
Edges and extrathoracic
Fields (lung fields and failure)
 ATMLL (“Are There Many Lung Lesions?”)




Abdomen
Thorax – bones and soft tissues
Mediastinum
Lungs – unilateral and bilateral
Cases
Young man with cancer
Young man without symptoms
ICU patient with fever, WBC
Two older women with cough
Dyspnea with sudden CP & fever
Reference:
 Goodman, L.R. (2007)
Felson’s Principles of Chest
Roentgenology: A
Programmed Text. 3rd ed.
Philadelphia: Saunders
Elsevier.