Lecture 18 - Contrast Agents

Question 1

What is a contrast agent? Used in where

Answer 1

• Clinical agent administered to patient during scan
• Improves contrast resolution
• Helps characterise pathologies
• Used in MRI, CT, angiograms, GI fluoroscopy

Question 2

What are the types of contrast agent?

Answer 2

X-ray:

• Positive: blocks x-rays, heavy elements like iodine/barium (look brighter)
• Negative: X block x-rays, air/Co2

Question 3

What are the ideal characteristics of agents?

Answer 3

• Biologically inert
• Safe/non-toxic
• Stable for storage
• Cheap
• Low osmolality/sol. in H2O

Question 4

Desc diff type of projections in X-ray:

1. Anteroposterior (AP)
2. Posteroanterior (PA)
3. Lateral
4. Oblique

Answer 4

1. X-ray fired at anterior of patient, posterior is detector
   [**Magnify certain structures (heart) so X accurate]
2. Inverse
3. From the side
4. Btw lateral and AP (45 degree)

Question 5

If AP cause magnification of heart, why X use PA everytime?

Answer 5

• Some patients mobility is limited so X

Question 6

What is the effect of increasing energy in ultrasound equipment on quality of image?

Answer 6

• Increases gain: brighter image, reduce contrast btw diff tissue types

Question 7

How to increase resolution of ultrasound?

Answer 7

• Use higher frequency: increases resolution

- Longer wavelength decrease resolution

Question 8

What is the function of Doppler ultrasound?

Answer 8

• Measure flow rate of blood from heart to brain