CXR Flashcards
How does air look on an xray?
Black
How does fat look on an xray?
Grey
How does bone look on an xray?
White (more white than soft tissue)
How does soft tissue look on an xray?
White
What accounts for the different colors on an xray?
- The less dense the area, the more photons pass through and the blacker the resulting image
- Least dense to most dense: air, fat, soft tissue, bone
What density are most tumors?
soft tissue density (white)
What color are abnormal air pockets?
Still black
When a lung is too back or too white, what abnormalities are suspected?
- Too black: abnormal gas collection
2. Too white: tumor or infection
What color are healthy lungs?
The lungs are dark grey. They are not completely black bc they contain some soft tissue elements like blood vessels
Define contrast resolution
Refers to our ability to see different structures bc they differ in density
Where can tumors hide in the chest so they are undetectable on xray due to poor contrast resolution?
Mediastinum
Define silhouette sign
Loss of the normal interface between the lungs and adjacent soft tissue
What does the presence of the silhouette sign mean?
- An abnormality is present
2. Helps localize the abnormality
If the interface at the right atrium is lost, where is the abnormality located?
Right middle lobe
If the interface at the left ventricle is lost, where is the abnormality located?
Lingula of left lung
If the interface at the left lung and diapraghm is lost, where is the abnormality located?
Left lower lobe
What can cause increased lung density?
- Consolidation
- atelectasis
- nodules/masses
- effusion
What is consolidation? How does it affect lung density and volume?
- consolidation occurs when air is replaced with soft tissue and the lung turns white
- Lung volume remains the same
What processes replace lung with soft tissue?
- pneumonia
- bleeding
- PE from heart failure
- Cancer
Define atelectasis. How does it affect lung density and volume?
- The air has been removed form the lung, leaving only the soft tissue elements like blood behind
- Lung turns white (increased density)
- Decreased volume
What are bronchograms? What condition are bronchograms found in?
- Normally the bronchi are poorly visible on xray bc they are too thin. If they are filled with fluid, the bronchi are visible against the soft tissue density background
- Consolidation
What causes atelectasis?
- passive
A. Caused by a mass or PE pushing on a lung causing decreased lung volume - adhesive
A. Results from inadequate surfactant (respiratory distress of the newborn) - cicatrical
A. volume loss due to scarring after infection or radiation - obstructive
A. Mass like cancer obstructing a bronchus. Air distal to the obstruction is resorbed
How is a mass differentiated from consolidation?
Mass has well defined borders, consolidation is diffuse
What causes lung masses?
Lung cancer, congenital anomaly, pneumonia. depends on history
What is the difference between a nodule and a mass?
Nodule: 3cm
Define pleural effusion
A fluid collection in the potential space between the visceral and parietal pleura
How are pleural effusions recognized?
Conforms to the anatomy of the pleural space. Tend to be peripheral and cause blunting of the cvangles (menisucus appearance)
What causes pleural effusion?
Cancer, infection, heart failure
What is bilateral symmetrical perihilar opacity with small bilateral effusions?
Almost invariably left heart failure
What are the possible causes of a completely opacified hemithorax? How are they differentiated?
- Atelectasis: mediastinum shifts toward atelectasis to compensate for the volume lost by the lung
- massive pleural effusion: mediastinum shifts away from effusion
What happens to the lung volume in a completely opacified hemithorax?
The lung is deflated
How is obstructive atelectasis treated?
removal of obstruction
How is pleural effusion treated?
Thoracentesis
What causes decreased lung density?
- Pneumothorax
- Pneumomediastinum
- Pneumopericardium
- Pulmonary cavitation
Where is the air located in a pneumothorax?
In the pleural space
What happens to the mediastinum in a tension pneumo?
Pushed away from the pneuo
How is a tension pnuemothorax treated?
chest tube
Where is a pneunothorax located in a supine pt?
Air rises over the diapraghm in the lateral sulcus (deep sulcus)
Define bulla
A thin walled, well defined area greater than 1 cm where normal lung has been destroyed and replaced by air. Roughly sphereical in shape
How are skin folds differentiated from pleural lines?
Skin folds are thicker, and may extend into the opposite hemithorax
What causes pneumothoraces?
- Central line puncture
- trauma
- rib fracture
- barotrauma
- Spontaneous, tall thin adolescent males
- Bleb rupture
Define pneumomediastinum. How does it appear on xray?
- Abnormal air collection in mediastinum
2. Streaks of air in the mediastinal area often extending into the neck. May have continuous diaphragm sign
What is a continuous diaphragm sign?
Air is entrapped between the heart and diaphragm, causing you to be able to see an uninterrupted diaphragmatic line across the chest
What causes a pneumomediastinum?
- Rupture of esophagus, trachea or tracheobronchial tree
2. Rupture of overinflated alveoli (most common) in asthmatics, vomiting, or vigorous valsalva maneuver
Define pneumopericardium and its causes
- Air in the pericardium
2. trauma, surgery, infection with gas forming bacteria, positive pressure ventilation
When does a pulmonary cavity occur? Etiology?
- A portion of the lung is destroyed and replaced by air after erosion into a bronchi
- cancer, infections, vasculitis
How can a bulla and cavity be differentiated?
Bulla is usually smooth and thin walled, seen in emphysema
Cavities are thick walled with irregular borders, seen in TB
