Introduction to Chest X-ray Interpretation RAH Radiology
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Introduction toChest X-ray Interpretation
RAH Radiology
How to interpret CXR:
• Film quality
• Anatomic structures
• Basic patterns of disease
Warning:This is a big topic. Important phrases and concepts are bolded.
Film quality:
• Position
• Rotation
• Penetration
Film quality:
• Position
• Rotation
• Penetration
This is a frontal chest xray.
This is a posteroanterior (PA) projection.• The X-rays are generated behind the
patient, and strike the film/screen in front of the patient.
• This reduces magnification of the heart, which is at the front of the chest.
Film quality:
• Position
• Rotation
• Penetration
This is a frontal chest xray.
This is an anteroposterior (AP) projection.• CXR are always performed PA unless
the patient is too unwell to stand.• On AP films the heart is exaggerated
in size, and the lungs are usually under-inspired. AP films are generally poor quality and harder to interpret.
Film quality:
• Position
• Rotation
• Penetration
There are many other aspects of positioning, which can affect assessment. Examples include degree of lordosis (hunching forward) and quality of inspiration.
There is suboptimal inspiration on this film, which makes the heart look bigger (by tilting the axis) and increases lung density (less gas present).
Film quality:
• Position
• Rotation
• Penetration
This film is rotated.
Click forward to see why.
Rotation can distort normal structures and alter how dense the lungs appear.
The spinous processes should be centred between the heads of the clavicles.
The lateral soft tissues should be the same density.
More dense
Less dense
Film quality:
• Position
• Rotation
• Penetration
This film is poorly penetrated.
Everything is grey and washed out.
You can’t see the spine through the heart.
Assessment is difficult (spine, retrocardiac lung etc.)
How to interpret CXR:
• Film quality
• Anatomic structures
• Basic patterns of disease
How to interpret CXR:
• Film quality
• Anatomic structures
• Basic patterns of disease
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
• For example, an enlarged heart suggests you should look for APO, but pneumonia is unlikely to affect the mediastinum.
It is up to you which approach to use, but we suggest:
Mediastinum -> Hilar regions -> Lungs -> Pleura -> Chest wall
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The mediastinum and hilar regions will be covered in more detail next session.
For now, just assess heart size using a rough guesstimate – more or less than 50% of the chest width (rib to rib).
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The lungs are only partially seen on frontal films, and extend behind the mediastinum and diaphragm.
While lobar divisions are often taught, they are not prognostically useful. It is simpler to describe upper, middle and lower lung zones when you are assessing a frontal xray.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The lung vessels are seen as curving lines. They divide every few centimetres, largest centrally and roughly halving at each division.
You should not be able to identify vessels in the peripheral lung.
Gravity pulls blood to the lower zone vessels, so they are larger than the upper zone vessels.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The connective tissue between the airspaces is the pulmonary interstitium. This can be seen as fine lines criss-crossing the lung fields.
Unlike the vessels, these lines are consistent in thickness, and should reach the lung periphery. Normal interstitium is almost invisible.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
We will review the pleura next session.
For now, just look for blunting of the costo-phrenic recesses on erect films.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
We will review the bones and soft tissues next session.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The lateral chest xray is under-appreciated. It is very useful for finding hidden pathology and localising abnormalities.
It is also difficult to orientate yourself to without practice.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
You can approach the film the same way as the frontal film.
The heart / mediastinum extends between the sternum towards the spine, but the posterior border of the heart should be greater than half a vertebral body width away from the spine. Any closer suggests cardiomegaly.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The hilar regions can be appreciated by identifying the left and right pulmonary arteries. Lymphadenopathy is often well demonstrated on the lateral film.
The left pulmonary artery is posterior to the right.
Anatomic structures:
• Radiologists use an “in-to-out” approach. Review the central structures first, the peripheral structures last.
• This approach best matches the patterns of pathology, which aids interpretation.
The vertebral bodies are well seen, and crush fractures are easier to see than on the frontal projection.
The vertebral bodies appear progressively less dense the lower you go down the chest, until the diaphragm. If the lower bodies appear dense, it is often due to pulmonary opacity like pneumonia.
How to interpret CXR:
• Film quality
• Anatomic structures
• Basic patterns of disease
How to interpret CXR:
• Film quality
• Anatomic structures
• Basic patterns of disease• Lung Pathology• Mediastinum (next week)• Pleural disease (next week)
Click to highlight the abnormality.
Increased opacity can be divided into interstitial and alveolar densities.
These can be described as “lines” and “clouds” respectively.
This is an example of cloudy (alveolar) density.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is increased density at the left lung base”
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is increased alveolar opacity at the left lung base”
Alveolar opacities are caused by filling of the terminal airspaces (alveoli).
Alveoli can be filled with simple fluid (alveolar oedema), pus (pneumonia), blood (pulmonary haemorrhage), vomit (aspiration) or cells (some forms of malignancy). Reduced aeration (collapse) can have a similar appearance.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is right upper lobe collapse with elevation of the horizontal fissure”
Collapse typically causes volume loss, that is, the surrounding structures are pulled inwards.
Filled alveoli (called consolidation) should not cause volume loss, although there is usually an element of collapse seen with consolidation (i.e., mucous plugging in pneumonia).
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is left upper zone consolidation with air bronchograms”
Consolidation often demonstrates air bronchograms. The alveoli are filled, but the bronchioles remain aerated, so you see low density tubular structures superimposed over the opacity.
Air bronchograms should not be seen with collapse.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is increased linear density throughout the lungs.”
Interstitial opacities are caused by thickening of the normal pulmonary connective tissue (the interstitium). The alveoli remain aerated, so the thickened interstitium is outlined by gas. Therefore, we see increased linear or reticular density.
Click for a zoomed in view of the increased interstitial markings.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is increased interstitial opacity throughout the lungs.”
Increased interstitial opacity can be caused by heart failure, inflammation / infection, fibrosis or malignancy.
Interstitial opacities can be difficult to appreciate, particularly because they are often symmetrical.
An example case:
Description?• Too many lines?• Clouds?
Interpretation?
An example case:
“This is an AP film with poor penetration showing an enlarged heart and widespread increased interstitial opacity. There is also left basal alveolar opacity.”
This is acute interstitial oedema with cardiomegaly.
The left basal opacity obscures the left hemidiaphragm, consistent with collapse or consolidation (common in unwell patients due to decreased depth of breathing, but can’t exclude infection).
Film the next day, after treatment:
Description?• Too many lines?• Clouds?
Interpretation?
Does this support our earlier diagnosis?
Film the next day, after treatment:
“This is an AP film with poor penetration showing an enlarged heart. There has been interval resolution of the interstitial and alveolar opacities.”
The rapid improvement in the appearance on chest xray following treatment is an important feature to discriminate pulmonary oedema from other interstitial processes such as atypical infection.
Left basal alveolar opacity also often resolves as the patient improves, because they can breathe more deeply.
Click to highlight the abnormality.
Mass lesions typically look like rounded, well defined clouds. This makes sense, as the airspace has been replaced.
Mass lesions can be benign or malignant, and it can be hard to differentiate. Larger lesions, multiple lesions, and new lesions are more likely to be malignant.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is a rounded mass at the left midzone / hilar region”
Click to highlight the abnormality.
Air-fluid levels in masses suggest cavitation in cancer (particularly squamous cancer) or abscess formation. Other causes are rare.
Clinical history is usually very useful to discriminate between these.
High density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is a rounded mass with an air-fluid level at the left midzone”
Low density lung pathology:
Look for asymmetric or otherwise abnormal density:
• “There is generalised lucency and prominence of the bronchovascular markings, consistent with emphysema”
Hyperlucent lungs suggest there is less tissue within the volume. This is usually cause by emphysema.
Associated findings are hyperexpansion of the lungs with flat hemi-daphragms, and increased visibility of the vessels (“coarse bronchovascular markings”).
Low density lung pathology:
We will cover the other major low density thoracic pathology (pneumothorax) next session with pleural disease.
Related Documents
