DEXA

Question 1

How does a DEXA scanner calculate the bone density?

Answer 1

The density of bone can be calculated by looking at the amount of photon energy attenuated in the bone at two distinct x-ray photon energies.

Question 2

What is the T-Score?

Answer 2

The number of standard deviations between the bone density of a patient and the bone density which would be expected of a young healthy adult.

Question 3

What is the Z-Score?

Answer 3

The number of standard deviations between the bone density of a patient and the bone density which would be expected of a person of the same age as the patient.

Question 4

What are the units of Bone Mineral Density (BMD)?

Answer 4

grams per centimetre squared

Question 5

What is the typical radiation dose received by the patient undergoing a DXA scan?

Answer 5

10 - 20 microSieverts

Question 6

What factors are associated with low bone density?

Answer 6

• Excess alcohol
• Low serum calcium
• Smoking
• Low oestrogen
• Inactivity

Question 7

Which cells in the body are responsible for the formation of new bone and the resorption of bone?

Answer 7

• Osteoblasts are responsible for the formation of new bone
• Osteoclasts are responsible for bone resorption

Question 8

How often is spongy bone replaced?

Answer 8

Every 3-4 years