302 Nuclear medicine

Question 1

What are the different methods of imaging osteoporosis?

Answer 1

DEXA scan
Trabecular bone score
High resolution peripheral CT

Question 2

What is primary osteoporosis?

Answer 2

F>M
Type 1-post menopausal.
Type 2 -senile (>age 70-75)

Question 3

What is Secondary osteoporosis?

Answer 3

F=M any age
Chronic predisposing medical disease e.g. Rheumatoid, anorexia

Prolonged use of medications e.g. steroids, aromatase inhibitors, anti-epileptics, thyroxine, proton pump inhibitors

Question 4

What does bone mass rely on?

Answer 4

-Oestrogen levels
-resorption
-Calcium/Vitamin metabolism
-bone deposition
-PTH- bone resorption to ensure adequate Ca in blood

Question 5

When is peak bone mass reached?

Answer 5

30 years of age

Followed by progressive bone loss and increased risk of fracture

Question 6

What does DEXA stand for?

Answer 6

Dual-energy X-ray absorptiometry

Question 7

How does a DEXA scan show bone density?

Answer 7

Uses low dose X-rays to measure bone mass per area (g/cm2)

Reduced BMD is a strong predictor of fracture risk

Question 8

What are the clinically relevant skeletal sites for a DEXA scan?

Answer 8

Lumbar Spine (L1-L4)
Hip
Forearm

Question 9

What does a DEXA scan take into account?

Answer 9

Compares BMD with:
that expected for a young healthy adult a healthyadult of the same age.

Takes into account gender and ethnicity.

The difference is calculated as a standard deviation (SD) score:
T Score- SD between measured BMD and that of a young healthy adult.
Z Score- SD between measured BMD and that of someone of the same age

Question 10

What are the normal T and Z scores measured by DEXA?

Answer 10

T-score:
Normal =equal or greater than -1
Osteopenia=T score between -1 and -2.5
Osteoporosis= T score equal to or below -2.5.

Z score of < -2.0 means BMD is lower than it shouldbe for someone age matched

Question 11

Which artifacts can interfere with the results of a DEXA?

Answer 11

metallic rings/buttons, compression fractures, osteophytes

Question 12

What are osteophytes?

Answer 12

Bony lumps that grow on the bones in the spine or around joints that form when a joint or bone has been damaged by arthritis

Question 13

What is the FRAX tool?

Answer 13

Calculates the 10 year probability of hip fracture or ‘major osteoporotic fracture’

Question 14

What are the determinants of bone strength?

Answer 14

Macroarchitecture:
Bone size (cross-sectional area)
-Bone shape (hip axis)

Microarchitecture:
-Cortical bone
-Trabecular bone

Material properties of bone:
-Skeletal mineralisation
-Collagen crosslink formation

Question 15

What is trabecular bone?

Answer 15

Less dense inner lattice-like structure of bone

It’s for thickness, number and connectivity

Question 16

What is cortical bone?

Answer 16

The dense outer shell

It’s for thickness and porosity

Question 17

What is the trabecular bone score?

Answer 17

A raised TBS represents strong, fracture-resistant microarchitecture. A low TBS reflects weak, fracture-prone microarchitecture.

TBS decreases with age from about 45yrs.

Can be used to compute FRAX score adjusted for TBS- more accurate in fracture risk assessment

Question 18

How is High Resolution Peripheral CT (HRpQCT) to diagnose osteoporosis?

Answer 18

A sensitive 3-D high resolution CT of the peripheries (wrist and ankle).

Provides quantitative volumetric bone mineral density (vBMD, g/cm3) rather than areal BMD (DEXA).

Can assess bone micro-architecture (separate cortical and trabecular bone assessment).
Cortical bone- thickness, density and porosity.
Trabecular bone-trabecular thickness, number and separation.

Provides information previously only obtained from bone biopsy.