Chest Radiography Flashcards
What are the different types of CXR?
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)
Explain how a radiograph is produced.
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
How is the adequacy of a CXR assessed?
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
What is an artifact? Give some common examples.
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
How is the airway of a CXR assessed?
Trachea central?
Hila equal? (left normally above right; note hilar points)
?masses in trachea/hila
+ carina angle (change could indicate obstruction)
How is the breathing on a CXR assessed?
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
How is circulation on a CXR assessed?
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
How is the diaphragm on a CXR assessed?
?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)
How are the bones on a CXR assessed?
?fractures/dislocations
?masses
No. of ribs visible?
Scapulae visible?
Any missing?
What are some important review areas on a CXR?
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)
What is silhouette sign? What does it indicate?
Adjacent structures of different density should form crisp silhouettes.
e.g. heart next to lung
Loss of silhouette sign indicates pathology
What can cause mediastinal shift? How can mediastinal shift be identified?
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
What are some important descriptive terms used for CXRs?
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
How does pneumothorax present on a CXR?
Air in pleural cavity causes lung collapse
Visible pleural line, reduced lung markings
+ tension pneumothorax: tracheal/mediastinal shift AWAY from the pneumothorax + depressed hemidiaphragm
What are the different types of pneumothorax?
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
How does pleural effusion present on a CXR?
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
What are some of the causes of pleural effusion?
Congestive heart failure Kidney failure Infection Malignancy Pulmonary embolism Hypoalbuminaemia Cirrhosis Trauma etc.
How does lobar lung collapse present on a CXR?
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)
What is a sail sign (CXR - retrocardiac) and what does it indicate?
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
What is the presentation of consolidation on a CXR?
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
What is the presentation of a space occupying lesion on a CXR?
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
How does interstitial lung disease present on CXR?
Too many lung markings
Indistinct cardiac borders
+ CT: “honeycombing” (pulmonary fibrosis)
