Introduction to the Imaging of the Thorax

Question 1

What exposure settings should be used for radiographs of the thorax?

Answer 1

• High kV technique
• Low mAs

Question 2

What are the ideal exposure times for taking thoracic radiographs?

Answer 2

• Very fast exposure settings
• High mA output machines for shorter periods of time

Question 3

What phase of the respiratory cycle should thoracic radiographs be taken in?

Answer 3

• Taken in full inspiration

Question 4

What are the normal collimation margins for taking thoracic radiographs?

Answer 4

• Thoracic inlet (2cm) cranial to the lung tips

Question 5

Describe the normal patient positioning for taking X-rays of the lateral thorax, the central ray landmarks for dogs and cats and the collimation margins used for dogs and cats:

Answer 5

1. Forelegs should be well forward (clear cranial thorax)
2. Central ray landmarks: Dog: Just caudal to caudal proximal scapula, Cat: 2.5cm caudal to caudal proximal scapula
3. Collimation landmarks: thoracic inlet cranial to manubrium to L1-L2 vertebrae caudal to dorsocaudal lung tips

Question 6

What structures should be seen on a well exposed thoracic radiograph?

Answer 6

1. Heart and mediastinum
2. Bronchovesicular markings
3. Lung background (hot light)
4. Lung in the thinnest part of the thorax
5. Thoracic dorsal spinous processes [just]

Question 7

What are the beam centering landmarks for a VD/DV view of the thorax?

Answer 7

• Just caudal to the caudal proximal scapula
• 5th to 6th ICS

Question 8

Describe how a patient positioning assessment should be done on a DV/VD view of the thorax:

Answer 8

• Dorsal spinous processes should be central to the vertebrae
• Sternum should be superimposed over the thoracic vertebrae
• Spine should be straight from cranial to caudal

Question 9

Asssess the study below for positioning:

Answer 9

• The study is very poorly positioned - the spinous processes of the thoracic vetebrae are of to one side and the sternum can be seen quite visibly

Question 10

What is the normal position of the diaphragm dorsal crus (vertebrae) on the lateral view for each of the following?

1. Full expiration
2. Mid inspiration
3. Full inspiration

Answer 10

1. Full expiration: T9 - T10
2. Mid inspiration: T11 - T12
3. Full inspiration: T13-L1