Chest radiograph

The chest radiograph (also known as the chest x-ray or CXR) is thought to be the most frequently-performed radiological investigation globally ^ref.

For paediatric chest radiograph see: chest radiograph (paediatric)

Indications

The chest radiograph is performed for a broad content of indications, including but not limited to ^1-4:

• respiratory disease
• cardiac disease
• haemoptysis
• suspected pulmonary embolism
• investigation of tuberculosis
• pneumonia
• pneumothorax
• suspected metastasis
• follow up of known disease to assess progress
• chronic dyspnoea
• trauma
• pneumoperitoneum
• evaluation of symptoms that could relate to abdominopelvic pathology
• thoracic disease processes
• monitoring of patients in intensive care units
• post-operative imaging
• immigration screening
• check position of nasogastric tubes, endotracheal tubes, PICCs etc.
• exclude radiopaque foreign bodies (MRI safety screen)

Projections

Standard projectionsPA projection

• PA view
   with x-ray beam traversing from posterior to anterior
• it is performed standing and in full inspiration
• it examinesis the best general radigographic technique to examine the lungs, bony thoracic cavity, mediastinum and great vessels
• disadvantages: must patient must be able to stand erect
• advantages: betterexcellent visualisation of the mediastinum and lungs, with accurate assessment of heart size

Standard lateral projection

• lateral view
  •  is performed erect left lateral, and labelled with the side closest to the cassette
  • ideala paravertebral gutter technique involves rotating the right side 5-10° anterior to align the posterior ribs along the divergent beam
  • allows for localisation of suspected lung lesions when takenassessed in conjunction with the PA view
  • examines the retrosternal and retrocardiac spaces
  • used to confirmallows assessment of the presence & location of opacities on frontal X-raysposterior costophrenic recesses
  • salient points
    • gastric bubble is under the left hemidiaphragm; left hemidiaphragm is less distinct anteriorly due to the cardiac silhouette
    • right hemidiaphragm appears higher and more complete (as the right is closer to the beam)

Additional projections

Other forms of the chest radiographs are performed in a variety of clinical scenarios, usually if the patient is unable to tolerate a standing PA radiograph:

• AP erect
  • sitting up on the bed; can be performed outside the radiology department, by a mobile x-ray unit
  • disadvantages: mediastinal structures may appear magnified, poorly inspired, rotated; poor inspiration causes crowding of the vessels
  • advantages: better for intubated, sick patients
  • disadvantages: heart is further away from the detector which leads to magnification and inaccurate size assessment
• supine
  •  usually for trauma and critical care patients
• lateral decubitus
  • the patient is laying either left lateral or right lateral on a trolley on top of a radiolucent sponge.
  • the detector is placed landscape posterior to the patient running parallel with the long axis of the thorax.
  • the patient’s hands should be raised to avoid superimposing on the region of interest, legs may be flexed for balance.
  • problem-solving film, used to differentiate pneumothorax vs. pleural effusion; pneumothorax vs. pneumomediastinum.
  • air trapping due to inhaled foreign bodies, and showing and quantifying pleural effusions
• expiration view
  •  for pneumothorax and air trapping due to inhaled foreign bodies
• lordotic view
  • demonstrates areas of the lung apices that appear obscured on thePA/AP chest radiographic views
• right anterior oblique (RAO)/left anterior oblique (LAO) view
  •  for rib fractures and intrathoracic lesions (RAO also used routinely used in barium oesophagography)
• ribs AP view
  • for suspected posterior rib fractures 
• ribs PA view
  • for suspected anterior rib fractures 
• sternum lateral view 
  • a lateral projection often used to query fractures or infection
• sternum oblique view 
  • an RAO projection that is orthogonal to the lateral sternum view 

Pitfalls

• rotation of the frontal projection can markedly affect the appearance of the CXR
  • apparent mediastinal widening
  • tracheal deviation
  • apparent increased thickness of the paratracheal stripes
  • asymmetric lung density
• supine positioning of the patient will alter the appearance of the CXR
  • enlarge the heart (cardiothoracic ratio)
  • alter the appearance of fluid or gas in the pleural space
    • pneumothorax
    • pleural effusion
  • alter the appearance of fluid in the lung air spaces
    • upper lobe vascular redistribution
    • alveolar fluid distribution

Patient preparation

The patient should be asked to remove all clothing and jewellery from the waist up and dress in a hospital gown. Long hair should be worn up.