9/8- Chest Imaging in Lung Disease Flashcards
What is the reference substance for x-ray?
Water
Describe relative absorption of x-rays by different tissues:
- Bone
- Tissue (fluid, muscle)
- Air
- Bone: high absorption (white)
- Tissue (fluid, muscle): grey
- Air: low absorption (black)
What is silhouette sign in x-ray?
Tissues or structures with similar density, adjacent to each other, cannot be differentiated (e.g. blood filled heart) If fluid is obscuring heart/aorta, it’s in the same plane as what is no longer seen
(B- see aorta outline but not heart; in plane of heart. C- see heart border but not aorta; in plan of aorta)
Under what position/conditions is a CXR taken?
- Upright
- Full inspiration
- 72” from x-ray source
- Plate in front of patient
Characteristics of a normal CXR (postero-anterior)?
- Stomach
- Scapula
- Clavicles
- Vertebral bodies
- Lung lobes
Postero-anterior film
- Air in stomach
- Scapulae at edge of thorax
- Well centered – clavicles equidistant from spinous processes
- Lower vertebral bodies barely visible
- LLL visible (behind heart
What is different in antero-posterior view as opposed to postero-anterior?
- Opposite
- Anterior structure magnified: heart, mediastinum
- Scapula in thorax
Features of lateral CXR?
What is abnormal?
Elevated diaphragm
What can cause an elevated diaphragm?
- Collapse/ volume loss of lung
- Subpulmonic effusion
- Subphrenic abscess
- Herniation/eventration
What are diseases of increased radiographic density?
- Alveolar filling (blood, fluid, cellular components in pneumonia)
- Atelectasis/Volume loss
- Interstitial infiltrates
- Masses
What is seen here?
Silhouette Sign: RML pneumonia
- We are missing the right heart border
What is seen here?
Infiltrate in upper lobe
- Opacity above minor fissure (separating upper lobe from middle lobe)
- Possibly additional infiltrate in left lower lobe
Which lobes correspond to:
- Right heart border
- Left heart border
- Right heart border: right lower lobe
- Left heart border: left lingula
What is seen here?
Uremic lung disease (not a specific finding)
- Diffuse increase in density; bilateral
What is seen here?
Collapsed left lung (due to tumor)
- Ipsilateral pulling of midline structures due to collapse
- Heart, diaphragm, aorta/midline structures are all silhouetted out
What is seen here?
Pulmonary vascular congestion (turns out he had mitral stenosis)
- Predominant upper lobe density
- Bilateral
What does the meniscus sign suggest?
Presence of pleural fluid
What is seen here?
Tumor causing obstruction of right main bronchus
- Trachea and heart deviated to the right
- Right lung is smaller and more opaque
What are diseases of decreased radiographic density?
- Air trapping: asthma, emphysema, foreign body
- Pneumothorax
- Cysts/bullae
- Loss of soft tissue (e.g. mastectomy pts)
What is seen here
Overinflation- severe bullous emphysema
- Diaphragm low and flat
- Streaks are due to upper lung tissue being pulled down (bullae); crowding of lung markings in lower thorax; absence of lung markings (upper)
- Hilum has been pushed down (below aortic knob)
What is seen here?
Overinflation- severe bullous emphysema
- Increased retrosternal air space
- Flat diaphragms
What is seen here?
Pneumothorax- compression atalectasis of the lung
- Right apex might be considered normal (no markings, but mostly collapsed/compressed lung
- See pneumonic infiltrates on right
What is seen here?
Pneumothorax
- Can see pleura line on the lower right with effusion just external
What is seen here?
Cavitation of the lung (lucency within density)
- Commonly from infection (also, sometimes from cancers)
What is seen here?
Cavity with development of air-fluid level… this is an ABSCESS
When would you want decubitus film?
- Demonstrate pleural effusion fluid layers/air rises
- Sub-pulmonic effusion
- Air/fluid levels
- Subtle pneumothorax
If there is a pleural effusion on the right, which side do you want down?
Want pneumothorax side DOWN
When would inspiratory/expiratory films be helpful?
- Small/subtle pneumothorax
- Unilateral air trapping
CT is test of choice for what?
- Pulmonary embolism
- Vascular malformations
Also:
- Evaluation of hilar and mediastinal structures: LNs, tumors, central airways
- Radiologic diagnosis of bronchiectasis
What is seen here?
- “Generous” hilum
What is seen here?
Large homogeneous density of a mass/LN
Angiography of the chest shows what vessels?
Contrast studies help diagnose vascular diseases such as pulmonary embolism
- Pulmonary
- Bronchial
- A 41 yo presents with dyspnea for 3 weeks-
- On physical exam there are decreased breath sound, decreased tactile fremitus, and dullness to percussion on the right lower lung field
- Chest x-ray show increased radiographic density and obliterated costophrenic angle.
- You suspect pleural effusion.
- What radiographic test would you order next to confirm the diagnosis?
Pleural diseases, pneumothorax and pleural effusion are better assessed by decubitus films
- For a pneumothorax: air rises when lying on unaffected side, fluid layers when lying on the affected side
How does pneumothorax affect absorption of X-ray photons and what is the resulting effect on the X ray density on the affected side?
Air rises when lying on unaffected side, fluid layers when lying on the affected side
Name 3 respiratory conditions associated with increased and 3 associated with decreased radiographic density.
Increased radiographic density:
- Alveolar filling
- Atalectasis/volume loss
- Interstitial infiltrates
- Masses
Decreased radiographic density:
- Air trapping: asthma, emphysema, foreign body
- Pneumothorax
- Cysts/bullae
- Loss of soft tissue
