• Medial parts of clavicles should be horizontal and equidistant from spinous processes –  if closer to one clavicle then rotated towards that side
• Spinous processes should be vertical against vertebral bodies

• 5 – 6 anterior ribs should be present
• Both costophrenic angles should be present
• Apices should be present

• The standard way to do a chest x-ray is PA (posterior anterior). This means that the plate is held in front of the patient and the X-Ray beam is aimed from behind them. 
• The CXR will usually state if it is taken PA or AP. As PA is the norm, if there is nothing written, then you can assume that it is taken PA
• If patient’s are unable to stand, then this is a time when it might be taken AP. Therefore, an anterior-posterior X-Ray is an indication that the patient may not be very mobile and so it more likely to be sick.
• The problem will PA X-Rays is that due to dispersion, the heart may appear larger than it is. Therefore, you will not be able to comment on the size of the heart and say that there is cardiomegaly present, as this might just be due to the projection of the chest X-Ray

• Exposure is how well you can see the structures. 
• You should be able to see the vertebral bodies visible behind the heart. This is a well exposed X-Ray
• If you cannot see the vertebrae, this is underexposed and means you could miss key pathology

In a healthy patient the trachea should be in the middle between the two lungs and not deviated. Tracheal deviation signifies that either something is pulling the trachea in one direction or pushing it away from something. It is important to look at the direction the trachea is deviated in consideration with where the opacification is seen in the lungs:

• • Deviated away from opacification (white): Large pleural effusion, thoracic mass 
  • Deviated towards opacification: Collapse, pneumonectomy 
  • Deviated away from black area: Tension pneumothorax 
  • Central trachea: Seen in conditions like consolidation (pneumonia/oedema), pleural effusion, pneumothorax, fibrosis 

The carina is located at T4/T5. It is an important landmark for assessing whether an NG tube is placed correctly. A correctly placed NG tube should bisect the carina on CXR. This suggest that the NG tube is in the oesophagus and not in the airways.

Once you have seen the trachea, you can follow the bronchi into the lungs and assess for any masses.  

Scan the edges of the lungs and assess if the lung markings go all the way to the edge of the thorax. In healthy individuals, the intrapleural space should not be visible as the lungs are fully expanded and there is no air in the space. 

If there is air in the pleural space, then you will be able to see increased lucency (blackness) and the white lung markings will not go all the way to the costal margins. This indicates that there is a pneumothorax.

Divide R and L lungs into upper, middle and lower zones and Inspect each zone in turn looking for asymmetry. You will be looking to find areas of opacification.

Opacification (increased white) can be due to a variety of pathologies. It can be due to a mass (tumour). Often it is due to infection, where inflammation caused pus and nectrotic debris to clog up the airways. This is more dense than air and so appears whiter on X-Rays.  

Upper/Apex:

• Check lung markings extend to the end – pneumothorax and 
• Check for apical opacification – Pancoast tumour, apical fibrosis seen in ankolysing spondylitis 

Middle and lower zones:

• Check for opacification that maps to lobes – indicates lobar pneumonia, collapse or is diffuse
• Bilateral opacification is seen in conditions like pulmonary oedema, bronchial pneumonia
• Check for isolated spots of opacification – these may show tumours (cancer), granulomas (TB), pulmonary haemorrhages (seen in Wegener’s GoodPastures syndrome)

The hilum is an important structure that contains pulmonary vessels and lymph nodes. The hilum is usually not prominently visible on a CXR in healthy indivuals. Increased hilar opacification is associated with several conditions

• • Unilateral hilar opacification: Lung cancer, lymphoma, early TB 

  • Bilateral hilar opacification: TB, Sarcoidosis, Lung cancer, lymphoma

• If Anterior-Posterior projection, then you cannot comment on size 

• If Posterior-Anterior film, then heart should be less than half the width of the thorax. If the heart is larger than this, this signifies caridomegaly (an enlarged heart). This often occurs secondary to heart failure, pulmonary hypertension and pericardial effusions

Looking for the heart borders helps to identify any consolidation that might be affecting the lungs. This is because consolidation here will cause loss of the heart border definition, as the white from the consolidation merges with the increased opacification due to the heart muscle.

• The right atrium makes up the right heart border. Loss of right heart border definition = Right middle lobe consolidation

• Left ventricle makes up left heart border. Loss of left heart border definition = Left lingual consolidation

You can look at the mediastinum to identify any gross pathologies. These include:

• Aortic dissection – this shows up as a widened mediastinum on CXR
  

• Hiatus hernia – this is when part of the stomach herniates into the thorax through the diaphragm. It will be seen behind the heart

In a normal patient, the right and left hemidiaphragms should be clearly visible as two domes. The right side is often a little bit higher than the left as it is pushed upwards by the liver. When analysing the hemidiaphrgams, look out for the following features:

• Flattened hemidiaphragms – seen in COPD due to hyperexpanded lungs
• Opacification against the diagphrams – seen in lower lobe pneumonia
• Raised hemidiaphragm – seen in lung collapse, lung removal surgery (pneumonectomy)

Gas under diaphragm suggests pneumoperitoneum, air in the peritoneum. This is serious as it is suggestive of bowel perofration, causing gas to rise and collect under the diaphragm.

On the left side, you may also see a gas bubble. It is important to realise that a gas bubble in the stomach is a normal finding

The costophrenic angles are the part at the edges where the diaphragm meets the costal margin. They should be clearly visible in a health individual. Look out for blunting of the angles – as this is associated with pleural effusions and consolidation.

Pleural effusions can be unilateral or bilateral:

• Unilateral ones are often due to exudative processes e.g. parapneumonic, secondary to malignancy
• Bilateral are often due to transudates caused by increased hydrostatic or reduced oncotic pressure e.g.  heart failure, liver failure, renal failure

If you see a pneumonthorax, remember that this could be caused by a rib fracture

This involves checking for a variety of different things. These are very easily identifiable on a chest X-Ray as they are usually radio-opaque and give a big indication of the underlying pathology present.

• ECG electrodes
• Pacemakers
• PICC lines
• Chest drains
• NG tubes

D – This is a Chest X-Ray taken on ….., of the following patient….. Is there a previous CXR to compare to

R – Commenting first on the quality, it is not rotated, there is adequate inspiration, the projection is posterior-anterior and it is adequately exposed as I can see the vertebral bodies clearly

On initial inspection, there is no obvious pathology, but I will proceed to go through it systematically.

A – Starting with the airways, the trachea is not deviated, and the carina is visible. 

B – The pleural markings go all the way to the costal margin so there is no evidence of a pneumothorax. Going through the lung zones, there is no area of increased opacification and both hila appear normal.

C – The heart is not enlarged and the borders are clearly visible. 

D – The hemidiaphragms are clearly visible and there is no blunting of the costophrenic angles. There is no free air under the diaphragm.

E – There are no foreign objects or bone fractures.

There is no abnormality in the review areas, including the apices, behind the lung

In summary this is a normal chest X-Ray

Image 1:Mikael Häggström, CC0, via Wikimedia Commons