X-ray of the thorax

Author: Mikael Häggström

Planning

Choice of investigation

• X-ray of the thorax is generally the initial investigation of choice in dyspnea.
• CT of the thorax is generally the investigation of choice in pulmonary embolism and aortic dissection. It is recommended as complementary to X-ray in chest trauma.

Evaluation

Quality checking

The frontal X-ray should be straight enough to avoid excessive coverage of the lung fields by the mediastinum.

The diaphragm should be intersected by the 5th to 7th anterior ribs in the mid-clavicular line.

Magnification

In projectional radiography ("X-ray") of the thorax (chest), the estimated geometric magnification factor is generally between 1.05 and 1.40, meaning that measurements made in the image will be this much larger than the real distance in the patient. Therefore, compare to other structures (such as pleural fluid reaching half way to hilar level) where possible rather than giving numbers.

Normal anatomy

• 

  A normal posteroanterior (PA) chest radiograph.

• 

  Normal lateral chest radiograph.

• 

  Projectionally rendered CT, showing the transition of thoracic structures between the anteroposterior and lateral view.

Basic screening

One method uses an alphabetic order:

• Airways: Any shift to the side?
• Bones: Check for obvious fractures

Cardiothoracic ratio = (MRD + MLD)/ID}
where:
MRD = greatest perpendicular diameter from midline to right heart border
MLD = greatest perpendicular diameter from midline to left heart border
ID = internal diameter of chest at level of right hemidiaphragm

• Cardiac: Check both cardiothoracic ratio and any dilation of blood vessels.
• Diaphragm: Check for any pleural fluid
• Edges: Check for pneumothorax and, if not already evaluated under C, also Kerley B lines.

• 

  Subtle pneumothorax, only determined by absence of vascularity in upper left lung region.

• 

  Kerley B lines

• Fields: Any lung consolidations
• Gastric: Whether there is any apparent hiatal hernia

• 

  Hiatal hernia.

• Hili: Prominence, such as by lymphadenopathy
• In lateral image: as a reminder to check the lateral projection, if available, mainly in the lung fields, for any apparent pathology

Report

• Even absence of lung opacities and pleural fluid.
• Upright images: Normal or increased heart size, and generally even absence of congestion.
• Supine: Report suspected cardiomegaly and/or dilated vessels only if the referral specifically requests it. Even then, note that it is difficult to determine with patient lying down.

See also: General notes on reporting

Diseases and targets

If specifically suspected or requested in the referral:

• X-ray of the thorax in sarcoidosis
• X-ray of the thorax in tuberculosis
• X-ray of cardiac pacemakers
• X-ray of central venous catheters

Regions

• Ribs

• X-ray of rib fractures

• Sternoclavicular joint

• X-ray of sternoclavicular osteoarthritis