Radiology 3 Flashcards
1
Q
DXA scan for diagnosis of osteoporosis
A
- Dual-energy x-ray absorptiometry (DXA) measures bone mineral density of the hip, spine or radius
- Hip and spine because they are weightbearing bones with physiological stress and they are the most commonly
o Lumbar vertebra
o Femoral neck
2
Q
Dual energy mechanism of DXA scan
A
o One image is of bone and soft tissue, one image is just bone
o Take the difference between the two to determine bone density
3
Q
Notes on DXA scan
A
- Precision is superior and takes less of a change to be considered significant (disease progression), making it the gold standard for bone density testing and monitoring
- T-score cannot be used to follow progress
- Each machine is different, should be calibrated to standards, read by certified clinician
- Over the age of 70, spine scan is not accurate
- DXA scan is only 1/3 of the story
4
Q
T score
A
- T- scores represent a standard deviation above/below that of a 30 y.o. of the same sex
- Risk of vertebral fracture based on T-score (2T score)
- Score measures the difference in standard deviation from the mean
o **T-score of –1 indicates 10% decrease in BMD below an average 30-year-old
o **T-score of +1 indicates 10% increase in BMD above an average 30-year-old
5
Q
VFA for diagnosis of osteoporosis
A
- Vertebral Fracture Assessment (VFA) is a new technology using central DXA that permits imaging of the thoracic and lumbar spine to evaluate for the presence of vertebral fractures.
- Patients with prevalent vertebral fractures are at increased risk for future osteoporotic fractures of the spine, wrist and hip.
6
Q
VFA notes
A
- 2/3rds of patients with vertebral fractures are asymptomatic, so patients often do not present with complaints of back pain
o They are cancellous fractures, so they don’t hurt as much, the patient puts up with the pain
o On lateral x-ray, a previous vertebral fracture will make the vertebra wedge shaped, with anterior shortening
o MOST RELIABLE IS VFA X-RAY WHICH CAN CLEARLY DIANOSE OSTEOPOROSIS
o If a patient does not show osteoporosis on DXA, has risk factors for fracture, and has evidence of previous vertebral fracture, VFA is MORE sensitive than DXA and can be a better, more reliable diagnostic modality TEST QUESTION?
7
Q
Sensitivity of VFA
A
- Up to 40% of patients who have osteoporotic vertebral fractures have BMD values that are better than -2.5, the WHO established definition for osteoporosis in post-menopausal women measured by central DXA. – MORE sensitive***
- Prior vertebral fractures are a better predictor of future fracture than low BMD alone
- Patients with prevalent vertebral fracture demonstrate a greater response to medical therapy than patients without prior fracture.
8
Q
IVA for diagnosis of osteoporosis
A
- Instant vertebral assessment (IVA)
- The majority of vertebral fractures are silent, and lateral X-rays (the standard method for identification) are not routinely obtained.
- Instant vertebral assessment (IVA), a technology that utilizes dual X-ray absorptiometry (DXA), provides rapid assessment of vertebral fractures and is highly correlated with vertebral fractures, as assessed on standard lateral spine X-rays.
9
Q
Ultrasound for diagnosis of osteoporosis
A
- DXA has specific limitations (e.g., use of ionizing radiation, large size of the equipment, high costs, limited availability) that hinder its application for population screenings and primary care diagnosis.
- This has resulted in an increasing interest in developing reliable pre-screening tools for osteoporosis such as quantitative ultrasound (QUS) scanners, which do not involve ionizing radiation exposure and represent a cheaper solution exploiting portable and widely available devices.
- Furthermore, the usefulness of QUS techniques in fracture risk prediction has been proven and, with the last developments, they are also becoming a more and more reliable approach for assessing bone quality.
- However, the US assessment of osteoporosis is currently used only as a pre-screening tool, requiring a subsequent diagnosis confirmation by means of a DXA evaluation.
-
Calcaneus is commonly looked at on ultrasound
o If signs of osteoporosis are present, DXA is recommended
10
Q
T and Z scores: What is the normal range of each score?
A
- Normal: T score -1.0 to +1.0 (T compares to Thirty-year-old)
- Z-score < -2.0 indicates secondary cause of osteoporosis (age matched)
11
Q
T and Z scores: Who are the population groups that use T and Z scores?
A
T score – comparison to young adults (30-year-old)
o **Post-menopausal women
o **Men over 50 years old
o Never use in children, pre-menopausal women or men <50 years old
Z score – comparison to age-matched adults
o **Young patients (younger than peak bone mass)
o **Pre-menopausal women (when bone density is lower than expected)
o ***Men < 50 years old
o Evaluating for secondary causes of osteoporosis
12
Q
Most common type of osteoporosis?
A
- MOST COMMON TYPE IS POST-MENOPAUSAL OSTEOPOROSIS
13
Q
T and Z scores: What is the fracture risk of vertebra and hip based on T-scores?
A
- T score > -1.0 = normal
- T score -1.0 - -2.5 = osteopenia (low bone mass)
- T score
14
Q
Visible bone changes
A
- Human eye can see 30-50% bone loss on x-ray
- By the time you see osteoporosis on x-ray, you would already have a score of -3.0, which means they already qualify for the diagnosis of osteoporosis
- This is why you need DXA scan instead of relying on x-ray alone
- A single standard deviation represents a 10% decrease in bone mineral density, so it is much more sensitive
15
Q
Who to treat for osteoporosis
A
- ***FRAX 10-year hip fracture probability ≥3%
- ***FRAX 10-yr all major osteoporosis-related fracture probability of ≥ 20%
