CT chest non contrast (technique)

The non-contrast CT chest is a commonly performed diagnostic examination. It is often performed to evaluate conditions impacting the lungs or preferenced over a contrast enhanced scan when iodinated contrast is contraindicated.

NB: This article is intended to outline some general principles of protocol design. The specifics will vary depending on CT hardware and software, radiologists' and referrers' preference, institutional protocols, patient factors (e.g. allergy) and time constraints.

Indications

• respiratory disease
• hemoptysis
• pneumonia
• pneumothorax
• suspected metastasis
• chronic dyspnea
• assessment of lung nodules 
• nodule follow up
• chest trauma  

Technique

• patient position
  • supine with their arms above their head
• scout 
  • apices to diaphragm
• scan extent 
  • apices to diaphragm
• scan direction
  • caudocranial
• scan delay
  • minimal scan delay
• ​respiration phase
  • suspended ​inspiration 

Practical points

• if patients cannot place arms above head, ensure to place arms on a pillow or saline bag ventrally to maintain image quality
• consider utilizing a high pitch technique if suspended inspiration is an issue
• 'high-resolution CT' can be achieved from thin sections defined as <1.5 mm: usually 1 mm, but ranging between 0.625-1.25 mm although this is not the traditional axial technique and will depend on your institution