Thoracic Imaging Radiology

What structures can you not normally see in the mediastinum?

• Cranial vena cava

• Brachiocephalic trunk

• Left subclavian artery

• Azygous vein

• Lymph nodes

What is the order of opacity on radiographs from radio-lucent to radio-dense?

1. Air

2. Soft tissue

3. Fat

4. Bone

5. Metal

What is the relative size of the cranial mediastinum in dogs?

No wider than 2x the width of the vertebral column

What is the relative size of the cranial mediastinum in cats?

No wider than the width of the vertebral column

What is seen of the diaphragm in VD?

• Cupula

• Right crus

• Left crus

What is seen of the diaphragm in DV?

One arch

What is seen of the diaphragm in right lateral?

Crura are parallel with right crus slightly shifted cranially

What is seen of the diaphragm in left lateral?

Crura form a Y and the left crus is shifted cranially

What is the angle of divergence of the trachea from the vertebral column?

15-30 degrees in most dogs; can be parallel in brachycephalic breeds

Where is the esophagus located in the caudal thorax?

Between the aorta and caudal vena cava

What does the cardiac silhouette consist of?

• Heart

• Pericardium

• Pericardial contents

• Major blood vessels

Within what intercostal spaces does the heart sit?

Between 3rd/4th and 6th/7th

Which cardiac chambers are positioned more cranially?

Right cardiac chambers

Which cardiac chambers are positioned more caudally?

Left cardiac chambers

How do you measure the long axis of the heart?

From carina to apex

How do you measure the short axis of the heart?

Starting at the caudal vena cava and perpendicular to the long axis

What structure is located between 11 and 1

Aortic arch

What structure is located between 1 and 2

Main pulmonary artery

What structure is located between 2:30 and 3

Left auricle

What structure is located between 3 and 5

Left ventricle

What structure is located between 5 and 9

Right ventricle

What structure is located between 9 and 11

Right atrium

What is VHS?

Sum of the long and short heart axis in vertebral units

VHS in dogs vs cats

• Dogs: 9.7 plus or minus 0.5

  • Cats: 7.5 plus or minus 0.03

What is the order of pulmonary vasculature in a lateral view?

• Artery located dorsally

• Bronchus

• Vein located ventrally

What is the order of pulmonary vasculature in a VD view?

• Artery located laterally

• Bronchus

• Vein located medially

What is the relative size of an artery to rib in a VD view?

Artery should be no wider than the 9th rib where they cross

What is the relative size of an artery to rib in a lateral view?

Vessels should be no wider than the proximal 1/3 of the 4th rib

What does it mean if you can visualize lymph nodes on a radiograph?

Lymphadenopathy possibly due to erlichia, anaplasma, septicemia