FM Radiology Case - Osteoporosis Flashcards
Be familiar with: 1. Imaging procedures considered for early detection of osteoporosis 2. Mechanism and limitation of bone densitometry scan 3. Radiological criteria for osteoporosis 4. Sensitivity and specificity of bone densitometry studies 5. Identification of high risk individuals 6. Annual screen (cost for population, screening cost per procedure, number of potential subjects) 7. Morbidity advantage of early detection
Osteoporosis is characterized by a decrease in ___, with preservation of ___.
Bone matrix; mineralization
List 3 risk factors for osteoporosis.
- Age
- Long term use of steroids
- Smoking
When should you suspect osteoporosis?
- Loss of height with aging
- Kyphosis with aging (asymptomatic)
- Compression fractures of vertebra
- Any fracture after age 40
- Adult weighing less than 125 lbs
- Fracture of wrist, spine, or hip in a first-degree relative after age 50
List the 2 commonly used types of peripheral bone density measurements.
- Dual-energy X-ray Absorptiometry (DXA)
2. Quantitative CT (QCT)
What is the gold standard for measuring peripheral bone density?
DXA scan
Compare the parts of the body studied with DXA vs. QCT.
DXA - posteroanterior lumbar spine and proximal femur
QCT - lumbar spine
How does a DXA scan work?
X-rays with two energy peaks are produced, allowing different absorption of radiation by bone and soft tissue, from which bone mineral density (BMD) is calculated
What is unique about a QCT?
Measures trabecular bone density
QCT is probably the most ___ test in measuring changes in bone density. However, it is not as precise as DXA and is not as widely used - why?
Sensitive; higher radiation dose
What bone density measurement site correlates best with clinically important fractures?
The hip is the best site for predicting clinically important fractures.
What is a T-score?
The number of standard deviations the bone mineral density measurement is above or below the young (30 y/o) normal mean bone mineral density
T-score = ?
(Patient’s BMD - Young adult mean BMD)/Standard deviation of young adult BMD
What is a Z-score?
The number of standard deviations the measurement is above or below the age-matched mean bone mineral density
Z-score = ?
(Patient’s BMD - Peer age group mean BMD)/Standard deviation of peer age group BMD
T-score is the standard used to determine the risk for ___.
Fractures
T-score normal range?
-1 to +1
T-score range for osteopenia?
-1 to -2.5
T-score range for osteoporosis?
-2.5
Which site is used in clinical decisions?
Hip
If the T-score is the standard used to determine the risk for fractures, what is the Z-score used for?
Determining whether the BMD is less than the age-related bone loss - this would call for investigation of causes of osteoporosis unrealted to age
What is the clinical recommendation regarding osteoporosis screening?
For women over 50 and under 65, you need at least one risk factor to recommend DXA scan.
What factors contribute to the estimate of the annual cost of screening all potential subjects in the US?
- # of F over 65
- # of F between 50-65 with risk factor
- Cost of DXA
How do you justify the cost of annual screening for osteoporosis?
Prevention of morbidity due to vertebral fractures
