Chest Radiography

Question 0

What are the different types of CXR?

Answer 0

PA projection:
Radiation travels posterior to anterior
Scapula projecting outwards (patient is standing with arms out/on their hips)
Heart size may be discussed

AP projection:
Radiation travels anterior to posterior
Scapula seen within chest (patient is sitting)
Heart appears magnified, as it is closer to the chest (so heart size is NOT discussed unless PA)

Question 1

Explain how a radiograph is produced.

Answer 1

High energy, short wavelength radiation

Absorbed to different degrees by different tissues, producing a level of contrast

Black = air

White = opaque e.g. bone, metal

Question 2

How is the adequacy of a CXR assessed?

Answer 2

Correct patient name & date

AP or PA?

Inclusion:
1st rib, lateral margin of ribs, & costophrenic angles must be included

Rotation:
CXR needs to be central in order to reliably check for tracheal deviation
- check alignment of spinous processes
- estimate the distance between the clavicles and the trachea (middle of clavicle should bisect the lateral margin of the ribs)

Inspiration: normal = 5-7 anterior ribs at midclavicular line

• incomplete inspiration = big heart, increased lung markings
• exaggerated expiration = diaphragm flattened, 7< ribs visible

Penetration: degree to which X-rays have passed through the body

• complete left hemidiaphragm should be visible
• vertebrae should be just visible through the heart

Question 3

What is an artifact? Give some common examples.

Answer 3

External/iatrogenic material which obstructs view on radiograph

note: except when material has been inhaled/swallowed
e. g. clothes (especially buttons), hair, surgical/vascular lines, pacemaker

Question 4

How is the airway of a CXR assessed?

Answer 4

Trachea central?

Hila equal? (left normally above right; note hilar points)

?masses in trachea/hila

+ carina angle (change could indicate obstruction)

Question 5

How is the breathing on a CXR assessed?

Answer 5

Lungs: equal? normal markings? (note: horizontal fissure may be visible; oblique fissures should not be visible)

Pleural spaces: ?pleural effusion, ?pleural thickening

Lung interfaces

?nodules

?consolidation

Question 6

How is circulation on a CXR assessed?

Answer 6

Aortic arch (aortic knuckle & aortic pulmonary window - may contain lymph nodes)

Pulmonary vessels

?heart enlargement (cardiac index; compare ratio of cardiac width to thoracic diameter, normal < 50% on PA only)

Right heart border: right atrium & middle lobe interface
Left heart border: left ventricle & lingula interface

Paratracheal stripe (azygos vein) - should be ~2cm from trachea

Mediastinal contours

Question 7

How is the diaphragm on a CXR assessed?

Answer 7

?free gas (do not mistake stomach bubble on left)

?nodules (can be hidden if in the lungs behind the diaphragm)

Costophrenic angles/recesses

note: left hemidiaphragm slightly below the right (liver presence)

Question 8

How are the bones on a CXR assessed?

Answer 8

?fractures/dislocations

?masses

No. of ribs visible?

Scapulae visible?

Any missing?

Question 9

What are some important review areas on a CXR?

Answer 9

Apices (?pneumothorax)

Thoracic inlet (?masses)

Paratracheal stripe (?mass/?lymph nodes)

Aortic pulmonary window (?lymph nodes)

Hila (?mass/?collapse)

Behind heart (?mass - should be normal lung tissue)

Edge of film

Below diaphragm (?pneumoperitoneum/?mass)

Bones (?mass/?missing/?fractures)

Question 10

What is silhouette sign? What does it indicate?

Answer 10

Adjacent structures of different density should form crisp silhouettes.

e.g. heart next to lung

Loss of silhouette sign indicates pathology

Question 11

What can cause mediastinal shift? How can mediastinal shift be identified?

Answer 11

Pushed by increased volume/pressure on opposite side
e.g. tension pneumothorax

Pulled by decreased volume/pressure on same side
e.g. pneumonectomy, collapsed lung

Look at tracheal deviation and cardiac shadow

Question 12

What are some important descriptive terms used for CXRs?

Answer 12

Tissue location e.g. lung, heart, aorta, bone

note: lung divided into zones rather lobes

Number

Distribution e.g. focal v.s. widespread

Side e.g. right v.s. left, unilateral v.s. bilateral

Position e.g. anterior v.s. posterior, lung zone

Shape e.g. round, cresenteric

Edge e.g. smooth, irregular, spicated

Pattern e.g. nodular, reticular

Density e.g. air, fat, soft tissue, calcium, metal

Question 13

How does pneumothorax present on a CXR?

Answer 13

Air in pleural cavity causes lung collapse

Visible pleural line, reduced lung markings

+ tension pneumothorax: tracheal/mediastinal shift AWAY from the pneumothorax + depressed hemidiaphragm

Question 14

What are the different types of pneumothorax?

Answer 14

TENSION:
Breach acts like a valve, so air enters the pleural cavity on inspiration but cannot exit during expiration

-> tracheal/mediastinal shift away from pneumothorax -> compressed venous return to heart -> !CARDIAC ARREST!

SPONTANEOUS: occurs in healthy people (often tall, thin males) with no apparent cause

TRAUMATIC: chest wall injury causes pneumothorax

Question 15

How does pleural effusion present on a CXR?

Answer 15

Collection of fluid in pleural space (on erect CXR; fluid pools all along lungs whilst supine)

Meniscus at upper border (presence of fluid)

Uniform white area (fluid) which obscures the hemidiaphragm & costophrenic angle

note:
mediastinal shift AWAY from pleural effusion -> pressure in lung, therefore lung still aerated
mediastinal shift TOWARDS pleural effusion -> reduced pressure in lung, therefore lung has collapsed

Question 16

What are some of the causes of pleural effusion?

Answer 16

Congestive heart failure 
Kidney failure 
Infection 
Malignancy 
Pulmonary embolism 
Hypoalbuminaemia 
Cirrhosis 
Trauma 
etc.

Question 17

How does lobar lung collapse present on a CXR?

Answer 17

Volume loss within lung lobe

Elevation of ipsilateral (same side as…) hemidiaphragm
Crowding of ipsilateral ribs
Mediastinal shift TOWARDS atelectasis (failure of part of lung to expand)
Crowding of pulmonary vessels
Sail sign

note: lower lobe can obscure upper lobe collapse (veiling opacity)

Question 18

What is a sail sign (CXR - retrocardiac) and what does it indicate?

Answer 18

Looks like a double heart border (triangle or “sail” seen between normal and apparent heart borders)

Due to collapsed lower lobe of lung being squashed into a triangular shape

Question 19

What is the presentation of consolidation on a CXR?

Answer 19

Dense opacification due to filling of small airways with:

• pus e.g. pneumonia
• blood e.g. haemorrhage
• fluid e.g. oedema
• cells e.g. cancer

Volume of lungs preserved or increased

note: if air bronchograms are visible (aerated bronchi within consolidation) then it is likely to be an infectious cause

Question 20

What is the presentation of a space occupying lesion on a CXR?

Answer 20

SOL < 3cm = nodule SOL > 3cm = mass

note: bone lesions, cutaneous lesions (e.g. moles), and nipple shadows can mimic

• malignant (primary or metastases)
• benign mass lesion
• inflammatory
• congenital

note: miliary appearance is either TB or metastases

Question 21

How does interstitial lung disease present on CXR?

Answer 21

Too many lung markings

Indistinct cardiac borders

+ CT: “honeycombing” (pulmonary fibrosis)