Chest Imaging

Created by

Beth

Cards (76)

Trachea
Hilum
Lungs
Diaphragm
Heart
Aortic knuckle
Ribs
Scapulae
Breasts
Bowel gas
Important obscured/invisible structures
sternum
oesophagus
spine
pleura
fissures
aorta
The trachea and bronchi are visible - branching at the carina
The trachea passes to the right of the aorta and so may be slightly off mid-line to the right
Large airways
A) Right main bronchus
B) Trachea
C) Aortic knuckle
D) Left main bronchus
E) Carina
Start assessment of every chest X-ray by looking at the airways. The trachea should be central or slightly to the right at the level of the aortic knuckle.
If the trachea is deviated, it is important to establish if this is because of patient rotation or if it is due to pathology. If the trachea is genuinely deviated you should then try to decide if it has been pushed or pulled by a disease process.
Normal hilar position
Each hilar point is the angle formed where the upper and lower lobe pulmonary vessels meet
They are useful points of reference to determine the position of the hila
Commonly the left hilum is higher than the right
Not every normal patient has a clearly-defined hilar point on both sides
Hilar points
A) Right hilar point
B) Left hilar point
Pulmonary arteries
Deoxygenated blood is pumped upwards out of the right ventricle via the main pulmonary artery
The main PA divides into left pulmonary artery and right pulmonary artery which pass into the lungs via the hila
The left PA hooks backwards over the left main bronchus
The right PA passes anterior to the right main bronchus
Pulmonary arteries
A) Trachea
B) Left PA
C) Right PA
D) Main PA
E) RV
Chest X-ray assessment routinely involves checking the hilar structures for normal, size, density and position. The hila are often wrongly called abnormal when normal and normal when abnormal. An awareness of the range of normal is important, but the best tip is to look for increase in density as well as size. If the hila are out of position, ask yourself if they are pushed or pulled, just as you would when assessing the trachea.
Lung zones
Note that the lower zones reach below the diaphragm – the lungs pass behind the dome of the diaphragm into the posterior sulcus of each hemithorax
Lung zones
A) Upper zones
B) Middle zones
C) Lower zones
Assessing the lung zones
Each zone is compared with its opposite side. If lungs appear asymmetrical it should be determined if this is due to asymmetry of normal structures, technical factors, such as rotation, or lung pathology.
If genuine asymmetry, decide which side is abnormal. Often dense area is abnormal, such as pneumonia or lung cancer, but some diseases cause reduced density, such as pneumothorax.
Some diseases result in bilateral lung abnormalities making comparison of left with right difficult. In these cases it is still important to assess each zone in turn, to avoid missing subtle abnormalities on the background of abnormal lungs.
Normal pleura and pleural spaces
Trace round the entire edge of the lung where pleural abnormalities are more readily seen
Start and end at the hila
Is there pleural thickening?
Is there a pneumothorax? The lung markings should be visible to the chest wall
Is there an effusion? The costophrenic angles and hemidiaphragms should be well defined
The pleura and pleural spaces are only clearly visible when abnormal. Some diseases, such as mesothelioma, cause pleural thickening. Other pleural diseases lead to fluid accumulation (pleural effusion) or air gathering in the pleural spaces (pneumothorax)
Normal pleura and pleural spaces
Pleural abnormalities can be subtle, so it is important to check carefully around the edge of each lung where abnormalities are seen more easily.
Make sure you can see lung markings all the way to the edge of the chest wall. If the lung edge (visceral pleura) is visible and there is black surrounding this edge, then a pneumothorax should be suspected -immediate assessment of trachea and mediastinum. Deviation of midline structures away from pneumothorax suggests tension pneumothorax which is medical emergency.
Also check for pleural thickening and pleural effusions.
Right lung
A) upper lobe
B) middle lobe
C) lower lobe
Left lung
A) Upper lobe
B) Lower lobe
The horizontal fissure separates the right upper lobe from the right middle lobe
It may be seen on a normal chest X-ray as a thin line running roughly horizontally from the edge of the lung towards the right hilum
The oblique (major) fissures overlie each other on a lateral view and are not always seen in entirety
If seen at all, the lower end is usually seen most clearly
Accessory fissures
A) Azygos fissure
B) Azygos lobe
C) Azygos vein
Azygos fissure is most common accessory fissure visible on chest X-ray
In most people azygos vein passes horizontally along right side of mediastinum
In those with an azygos fissure, small section of right upper lobe develops medial to vein which is pushed away from mediastinum
The azygos vein appears to pass through the lung and is surrounded by both parietal and visceral pleura
Azygos fissure consists of four layers of pleura, two parietal and two visceral
Tadpole-shaped - head is azygos vein, tail is azygos fissure
Azygos lobe is not separate - part of right upper lobe
Occasionally lung disease is limited in extent by a fissure. This can help locate a disease process more specifically to a lobe. For most cases this degree of accuracy is not clinically important, unless further action such as biopsy or surgery is required, in which case other imaging such as CT would probably be performed. In most cases it is still best to refer to the location of lung abnormalities seen on a chest X-ray in terms of lung zones rather than lobes.
The diaphragm separates the lungs from the abdominal organs
Abdominal organs are denser (whiter) than the air-filled lungs (blacker)
Each hemidiaphragm should appear as a smooth, domed contour
The right hemidiaphragm is usually slightly higher than the left
The liver is located immediately inferior to the right hemidiaphragm
The stomach and spleen are located immediately inferior to the left hemidiaphragm
The stomach is often visible as a gas-filled 'bubble' below the left hemidiaphragm
The lowest portion of the lungs extends below the level of the contours of the hemidiaphragms
The stomach bubble forms a window through which the lower part of the lungs is visible on the left
The right hemidiaphragm is slightly higher than the left
The liver is located inferior to the right hemidiaphragm
The stomach and spleen are located inferior to the left hemidiaphragm
Lung markings are visible below the diaphragm on both sides – most clearly through the stomach bubble
The cardiophrenic angles are the points at which the hemidiaphragms meet the heart
On both sides the contour of the hemidiaphragm should be seen passing medially as far as the spine
Hemidiaphragms
A) Cardiophrenic angles
B) Right hemidiaphragm
C) Left hemidiaphragm
D) stomach bubble
E) spleen
F) liver
Lateral X-rays show the right hemidiaphragm extending from posterior to anterior
The left hemidiaphragm becomes indistinct at the lower edge of the heart and the stomach bubble may be seen below it
Lateral view of hemidiaphragms
A) Right hemidiaphragm
B) stomach bubble
C) left hemidiaphragm
The hemidiaphragms are domed structures that should be well defined and visible to the midline on a frontal view. The contours of the hemidiaphragms do not demarcate the bottom of the lungs; lung markings can be seen below the hemidiaphragms. This area of the lungs should be checked whenever assessing a chest X-ray.
Inferior displacement of the diaphragm is a sign of lung hyperexpansion.
Raised position of a single hemidiaphragm may indicate phrenic nerve palsy
The costophrenic angles are formed by the points at which the chest wall and diaphragm meet.
The costophrenic recesses contain the lower edges of the lungs which contact the diaphragm.