Medical Imaging

Question 1

Colour of each type of material in x-rays

Answer 1

Black - air
Dark grey - fat
grey - soft tissue
light grey - bone
white - metal

Question 2

Contrast media in x-rays

Answer 2

Used to improve contrast resolution in tissues, have high atomic number

Question 3

Idiosyncratic contrast reactions

Answer 3

Allergic type reactions to drug used

Question 4

Non-idiosyncratic contrast reactions

Answer 4

“metallic” taste or sensation of warmth, nausea

Question 5

Advantages of x-rays

Answer 5

• Quick
• Simple
• Cheap

Question 6

Disadvantages of x-rays

Answer 6

• Low dose of radiation
• 2D
• Contrast reactions

Question 7

How does fluoroscopy work?

Answer 7

Continuous x-rays are used, creating real-time image

Question 8

Uses of fluoroscopy

Answer 8

Diagnostic and interventional uses (vascular, GI, MSK)

Question 9

Disadvantages of fluoroscopy

Answer 9

• Multiple x-rays = higher radiation dose
• 2D
• Contrast reactions

Question 10

CT scans

Answer 10

Uses x-rays on one side of the rotating ring, detectors on the other side

Question 11

Hounsfield unit numbers

Answer 11

Air = -1000HU
Fat, water, blood, soft tissue = 0HU
Cortical bone = 1000HU
Metal = 2000HU

Question 12

Clinical uses of CT

Answer 12

• infection
• cancer
• obstruction
• haemorrhage

Question 13

Advantages of CT

Answer 13

• fairly quick
• can scan most body parts well

Question 14

Disadvantages of CT

Answer 14

• Radiation
• requires breath-holding
• contrast reactions

Question 15

Advantages of ultrasound

Answer 15

• no radiation
• low cost
• can see movement

Question 16

Disadvantages of ultrasound

Answer 16

• no bone or gas penetration
• difficult with obese or frail patients