Contrast Media

Question 1

What is contrast media?

Answer 1

Contrast media radiography is a method of using X-rays and a special dye to study organs. The contrast medium, helps radiologists see structures that might not be clear on standard X-rays.

Question 2

Why is contrast media used?

Answer 2

To visualise soft tissues by absorbing more x-ray photons - appearing white on the image.

Question 3

What are the benefits of contrast media?

Answer 3

Attenuate x-ray beam differently to soft tissues.
Non-irritant.
Non-toxic.
Define the organ or viscus.
Persist for a time long enough to be observed on an image.
Excreted from the body.

Question 4

What is negative contrast?

Answer 4

Negative contrast agents are gases such as air, carbon dioxide methyl cellulose, and nitrous oxide.

Question 5

What are the advantages and disadvantages of negative contrast?

Answer 5

Advantages:
- Safer because they are plasma soluble and reduced risk of air embolus
- Decrease the x-ray attenuation within the body
- Allow x-rays to pass through more easily than surrounding tissues

Disadvantages:
- Hypersensitivity
- Adverse reactions
- Can cause stomach cramps, diarrhoea, nausea, vomiting, and constipation

Question 6

What are negative contrasts used for?

Answer 6

It is used mainly in the bladder but can also be used in the gastro-intestinal tract and in joints.

Show the location, size and wall thickness of the organ and will show marked wall thickening and large luminal filling defects such as masses or foreign bodies.

Question 7

What are the advantages and disadvantages of Barium?

Answer 7

Advantages:
Inert and soluble, therapeutic effects if the animal has diarrhoea.

Disadvantages:
May cause a foreign body reaction if leaks. Constipation. Risk of aspiration if secondary condition.

Question 8

What are the advantages and disadvantages of Iodine (water soluble)?

Answer 8

Advantages:
Water soluble, excreted by the kidneys.

Disadvantages:
Difficult to administer for GI studies – unpalatable/irritant. Poor contrast for bowel – contrast diluted in transition to the bowel.
IV may cause fall in blood pressure or anaphylactic reaction.
If animal conscious may cause whining or retching.

Question 9

What is iodine used for? Name 3.

Answer 9

Intravascular studies

Lower urinary tract (bladder most common)

Joints

Salivary glands

Lacrimal sac and ducts

Peripheral sinuses and Fistulae

Myelography

Lymphangiography