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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

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chest x ray interpretation for the internist

Chest X-Ray Interpretation for the Internist

Theresa Cuoco, MD

Medical University of South Carolina

February 22, 2012

why do we need to know
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
  • 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
  • PA and lateral
  • AP
  • Which is preferred and why?
  • Lateral film – left side of chest against x-ray cassette
  • Decubitus films
the tions
The “tions”
  • IdentificaTION
  • InspiraTION
  • PenetraTION
  • RotaTION
inspiration vs expiration
Inspiration vs Expiration

Any indications for an expiratory film?




  • Heavy light exposure causes the film to be black (A)
  • Little light exposure causes the film to be white (B)
alveolar vs interstitial
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
Lobar Anatomy



the silhouette sign
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
Localizing Lesions

Where is the silhouette sign?

localizing lesions4
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
    • Pseudosilhouette of diaphragm in underpenetrated film
    • Right heart border my overlap spine
    • Heart obscures anterior left diaphragm on lateral
the air bronchogram
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
NO Air Bronchograms…
  • In pneumonia if bronchi are filled with secretions
  • If cancer obstructs a bronchus
  • Interstitial fibrosis
  • Asthma/emphysema (hyperinflation)
lung and lobar collapse
Lung and Lobar Collapse
  • When a whole lung collapses, the trachea deviates TOWARD the side of collapse (due to volume loss)
  • 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
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
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
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
What is the pattern?

A: Focal/linear

B: Diffuse/nodular

C: Alveolar

the mediastinum1
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 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
the heart
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 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)
  • 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
Systematic approach
    • 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
  • Goodman, L.R. (2007) Felson’s Principles of Chest Roentgenology: A Programmed Text. 3rd ed. Philadelphia: Saunders Elsevier.