Medical Imaging

Question 1

Which uses more ionising radiation - CT or MRI?

Answer 1

CT

Question 2

Give x2 examples of diagnostic imaging which do not use ionising radiation.

Answer 2

Ultrasound and MRI.

Question 3

Approximately what percentage of background radiation exposure is from ionising sources?

Answer 3

15%

Question 4

What affects the attenuation of x-rays?

Answer 4

The type of tissue

Question 5

How does air appear on the x-ray?

Answer 5

Black

Question 6

How does soft tissue appear on the x-ray?

Answer 6

Grey

Question 7

How does bone appear on the x-ray?

Answer 7

White

Question 8

How does fat appear on the x-ray?

Answer 8

Black

Question 9

How does metal appear on the x-ray?

Answer 9

White

Question 10

Which are the two commonly used contrast agents?

Answer 10

Barium and iodine

Question 11

Why do we use a contrast agent in x-rays?

Answer 11

To enhance the differences between tissues of similar densities.

Question 12

How is CT different to X-ray?

Answer 12

CT can differentiate between soft tissue and water.

Question 13

Which are the three CT windows?

Answer 13

Soft tissue, bone and lung windows

Question 14

What are the two main risks for using contrast agents?

Answer 14

Kidney damage and allergic reactions.

Question 15

Do ultrasound scans use x-rays?

Answer 15

No.

Question 16

How do MRIs work?

Answer 16

The MRI is made up of a strong magnet which is supercooled with liquid helium. Radiowaves are transmitted into the patient and interact with protons (water) in the patient’s body.

Question 17

How would fat appear in a CT vs. MRI?

Answer 17

CT = Black, MRI = White.

Question 18

How would air appear in a CT vs. MRI?

Answer 18

Both would appear black.

Question 19

How would fluid appear in a CT vs. MRI?

Answer 19

CT = Dark grey
MRI = Black

Question 20

How would bone marrow appear in a CT vs. MRI?

Answer 20

CT = Grey
MRI = White

Question 21

What is the difference in the way bones appear in CT vs MRI?

Answer 21

CT = White
MRI = Black

Question 22

What is PET?

Answer 22

Positron emission tomography = detects metabolic changes rather than structural changes. Particularly used in locating cancer.

Question 23

In relation to the anterior and posterior positions, what do dorsal and ventral relate to?

Answer 23

Dorsal = posterior
Ventral = anterior

Question 24

What are the upper and lower surfaces of the foot called?

Answer 24

The dorsal and plantar surfaces.
Dorsal = upper
Plantar = lower