SDL: Thoracic Imaging

Question 1

What are the standard views for radiography of the small animal thorax?

Answer 1

Minimum of 2 orthogonal views, but the views will depend on the pathology you suspect

• Routine incl. cardiac cases: RL and DV
• Screening for mets: RL, LL and VD/DV
• Lung pathology: RL, LL, VD

Question 2

What is the cranio-caudal centring point for the primary beam when taking a lateral view of a small animal thorax?

Answer 2

Thoracic radiography: centre beam slightly caudal to caudal border of scaupula. collimate to thoracic inlet, thoracic spine, sternum and diaphragm.

DV/VD views: make sure spine nad sternum are symmetrical. centre beam slightly caudal to caudal border of scapula. collimate to thoracic inlet, diaphragm and body wall.

Question 3

How can you prevent axial rotation in lateral views of thorax in dogs?

Answer 3

Place a foam pad under the sternum to correct axial rotation.

Important to extend the forelimbs cranimally and secure to prevent excessive tissue overlying the cranial thorax.

Question 4

Most reliatable way to assess axial rotation on lateral and DV views?

Answer 4

Lateral: superimposition of the rib heads of the caudal ribs

DV/VD: if well positioned, the dorsal spinous processes are ovoid or fusiform in shape and lie centrally within the vertebral bodies. The sternum overlies the spine.

Question 5

At what point should you make exposure for a standard radiograph of the thorax?

Answer 5

Should be taken at peak inspiration. Gives the best visualisation of the lung fields and accurate portrail of the cardiac silhouette.

Question 6

How do you assses if a lateral throacic radiograph is inspiratory or expiratory?

Answer 6

Inspiratory:

• Diaphragmatic line: straight dorsally, little contact with cardiac silhouette
• Vertebral - diaphragmatic angle: Open
• Dorsal diaphragmatic line: T12/T13
• Caudal vena cava: Relatively horizontal - ventral border less well defined
• Tracheal-vertebral angle: Increased

Expiratory

• Diaphragmatic line: Domed, incrased contact with the cardiac silhouette
• Vertebral - diaphragmatic angle: closed
• Dorsal diaphragmatic line: T10/T11
• Caudal vena cava: cranioventral slope to heart - ventral border well defined
• Tracheal-vertebral angle: Decreased

Hear will look smaller on inspiration and the lungs will look relatively radiolucent and vasculature promient during inspiration cf. expiration where the heart will look larger and the lungs will look less radiolucent with diminished vasculature.