Thoracic spine (AP view)

The thoracic spine anteroposterior (AP) view images the thoracic spine, which consists of twelve vertebrae.

Indications

This projection is utilized in many imaging contexts including trauma, postoperatively, and for chronic conditions. It can help to visualize any compression fractures, subluxation or kyphosis.

Patient position

• the patient is erect or supine, depending on clinical history
  • ideally, spinal imaging should be taken erect in the setting of non-trauma to give a functional overview of the thoracic spine
  • all imaging of patients with a suspected spinal injury must occur in the supine position without moving the patient
• hands are placed by the patient's side

Technical factors

• anteroposterior projection
• arrested inspiration​ (to push the diaphragm downwards over the upper lumbar vertebra)
• centering point
  • the level of the 7th thoracic vertebra at the MSP 
  • the central ray is perpendicular to the image receptor 
• collimation
  • superiorly to include the C7/T1 junction
  • inferiorly to include the T12/L1 junction
  • lateral to include the costotransverse joints and left and right paraspinal lines 
• orientation  
  • portrait
• detector size
  • 35 cm x 43 cm 
• exposure
  • 70-80 kVp
  • 25-40 mAs 
• SID
  • 110 cm
• grid
  • yes (ensure the correct grid is selected if using focused grids)

Image technical evaluation

The entire thoracic spine should be visible from T1 to T12:

• no patient rotation as evident by central spinous processes with sternoclavicular joints appearing equidistant
• intervertebral joints are seen in profile 
• adequate image penetration and image contrast is evident by clear visualization of thoracic vertebral bodies, with both trabecular and cortical bone demonstrated

Practical points

• the three-column concept of thoracolumbar spinal fractures is of particular importance when assessing this image for pathology
• take particular care when imaging patient on a trauma trolley that the image receptor is aligned to the central ray to prevent anatomy exclusion and grid cut-off
• flexing the patient's legs or providing a pillow under the knees may improve patient comfort, whilst reducing spinal lordosis