Chest X-Ray
Interpretation for the
Internist
Theresa Cuoco, MD
August 2, 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
 Initial basics and type of film
 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
The Basics (“the TIONS”)
 IdentificaTION
 InspiraTION
 PenetraTION
 RotaTION
Inspiration vs. Expiration
Indications for an expiratory film?
-To detect pneumothorax or look for air trapping
(would remain inflated and black instead of white)
Penetration
A
B
Heavy light exposure causes the film
to be black (A)
Little light exposure causes the film
to be white (B)
Rotation
Technique
 PA and lateral
 AP
 Which is preferred and why?
 Less magnification, sharper images
 Better inspiratory effort, pleural fluid and air easier to see
 Lateral film – left side of chest against x-ray cassette
 Decubitus films
Which is which?
Crisp CPA
More magnification, dull images,
poor inspiratory effort
Normal Anatomy
A.
B.
C.
D.
E.
CPA
Left diaphragm
Heart
Aortic knob
Trachea
F. Hilum
G. Carina
H. Stomach bubble
J. Ascending aorta
The Normal Chest X-Ray
A. Gas in splenic flexure B. CPA C. Heart
D. Descending aorta E. Trachea F. Carina
G. Hilum H. Aortic knob J. Ascending aorta K. Right diaphragm
The left hilum is slightly higher than the right – this is normal
Alveolar vs. Interstitial
 Alveolar = air sacs
 Radiolucent
 Can contain blood, mucous,
tumor, or edema (“airless
lung”)
 Interstitial = vessels,
lymphatics, bronchi, and
connective tissue
 Radiodense
 Interstitial disease:
prominent lung markings
with aerated lungs
Lobar Anatomy
Anterior
Right:
Upper, middle, lower
Left:
Upper and lower
Posterior
The fissure has to be parallel to the x ray beam for it to be seen on the film.
The oblique (major) fissures are not visible on the normal frontal projection
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?
• Obscured right heart border
• Right middle lobe infiltrate
Localizing Lesions
You can still see right heart border
Localizing Lesions
A: lost heart border = lingular
B: lost hemidiaphragm = LLL
Localizing Lesions
A: loss of right hilum;
ascending aorta
B: lost aortic knob
Localizing Lesions: Review
 Ascending aorta, upper R heart border = RUL
 R heart border = RML
 R anterior hemidiaphragm = RLL
 Aortic knob = LUL
 L heart border = lingula
 L anterior hemidiaphragm or descending aorta = LLL
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)
 Left lung consolidated and collapsed
Fissures
 Formed by 2 visceral pleural layers
 Demarcate the boundaries of the lobes
 Shift of fissures is best sign of lobar collapse
Minor fissure shifts up: RUL collapse
Minor fissure shifts down: RML collapse
Major fissures shift down: LL 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
The Mediastinum
A. Ascending aorta B. Aortic knob
C. Descending aorta D. R heart border
E. SVC F. R tracheal wall G. L heart
X. retrosternal clear space
Outside mediastinum:
L. L pulmonary artery
R. R pulmonary artery
The Mediastinum
 I: Anterior Mediastinum
 Heart
 Retrosternal clear space
 4 T’s
 II: Middle Mediastinum
 Esophagus
 Arch and descending aorta
 Trachea
 III: Posterior Mediastinum
 Paravertebral area; most
masses neurogenic
 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?
Pneumothorax
Air enters pleural space with each breath
but cant escape, increasing intrapleural
pressure – increased pressure depresses
the diaphragm, collapses the lung, and
shifts the mediastinum away
Clinical signs: rapid onset respiratory
failure, decreased breath sounds,
deviated trachea, JVD
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)
Cases
Young man with cancer
Osteosarcoma w Pulmonary Met
Metal nipple markers have been
placed
1. pulmonary nodule below right
nipple marker where ribs cross
2. Right shoulder amputated:
pulmonary met from
osteosarcoma
Young man without symptoms
Anterior Mediastinal Mass
Strange cardiomediastinal shape on left - causes silhouette of
left atrium ,pulmonary artery, and aortic arch
Lateral shows density in retrosternal clear space
Dyspnea with sudden CP & fever
Heart Failure and Perf Ulcer
Cephalization, enlarged heart, free air