Bone Densitometry Course Flashcards
What percentage of bone matrix is collagen?
90%
What type of collagen is found in bone matrix?
Type 1 collagen
Type 1 collagen contains cross links which three thing?
- N-telopeptides
- C-telopeptides
- deoxypyridinolines
What percentage of bone matrix is made of proteins?
10%
What three proteins are present in bone matrix?
- osteocalcin
- osteonectin
- osteopontin
What is bone mineral composed of?
Hydroxyapatite
Calcium and phosphorus
Name four types of bone cells.
- Osteoblasts
- Osteoclasts
- Osteocytes
- Lining cells
Where are osteoclasts derived from?
Bone marrow precursors
Where are osteoblasts derived from?
Mesenchymal precursors
What is the process of mineralization of bone called?
Formation
What happens to bone mineral density during adolescence?
It dramatically increases
What happens to bone mineral density during late teens and early twenties?
Peak bone mass is achieved.
What happens to bone mineral density during after menopause?
There is accelerated bone loss.
How long does the accelerated phase of bone loss after menopause last?
5 - 10 years
Is bone mineral density higher in men or women?
Men
Is bone mineral density higher in blacks or whites?
Blacks
How variable are average bone densities?
Very variable
Above-average white women have higher BMD than below average black men.
What percentage of cortical bone is renewed each year?
3%
What percentage of cancellous bone is renewed each year?
25%
What percentage of the skeleton is being remodeled at any one time?
10%
Which type of bone loss is rapid in early menopause?
Cancellous bone loss
Which body part fractures increase in frequency as cancellous bone loss begins in early menopause?
Wrist fractures
Which bone loss is more gradual after menopause, cancellous or cortical?
Cortical
Does the risk of hip fractures after menopause increase as a result of cancellous or cortical bone loss?
Bone
Why does bone loss occur with increasing age?
Because resorption is greater than formation.
If a bone breaks under conditions that would not cause a normal bone to break - what kind of fracture is it?
Fragility fracture
Does bone loss have any symptoms?
No
What is the prevalence of disease?
Frequency of disease at a specific point in time.
Number with disease/risk
What is the prevalence of women over age 50 years with osteoporosis?
30%
What is the incidence of a disease?
The new cases of a disease over a specific period of time.
New cases within the period of time/number of risk
What is the incidence of hip fractures in the elderly population?
12 per 1000 person-years
How many people are estimated to have osteoporosis worldwide?
200 million
Hip fracture is projected to increase ____ % in women by 2050.
240%
Hip fracture is projected to increase ____ % in men by 2050.
320%
Even if there is no increase in age-related hip fracture risk, the number of hip fractures will increase from _____ in 1990 to _____ in 2050.
1.7 million to 6.3 million
Is it easier to diagnose osteoporosis in the spine or the hip as you get older?
The hip. Spine becomes harder to use because of degenerative changes.
Rochester Osteoporosis Project: Prevalence
At younger ages, the prevalence of osteoporosis at the _____ is higher than the prevalence at the _____.
Spine higher than hip
Rochester Osteoporosis Project: Prevalence
At older ages, the prevalence of osteoporosis at the _____ is higher than the prevalence at the _____.
Hip higher than spine
Rochester Osteoporosis Project: Prevalence
Overall is the prevalence of osteoporosis higher at the hip or the spine.
Overall, the prevalence is similar.
Which skeletal sites did the NHANES III use?
Only proximal femur (hip)
What was the NHANES III reference population?
White men and women, aged 20 - 29, from multiple geographic regions of the US.
What was the study population of the NHANES III?
Men and women aged 50 years or more, difference races, from multiple regions of the US.
NHANES III
Prevalence of osteoporosis based on femoral neck measurements in white women aged 50 and older?
22%
NHANES III
Prevalence of osteoporosis based on femoral neck measurements in Hispanic women aged 50 and older?
10%
NHANES III
Prevalence of osteoporosis based on femoral neck measurements in black women aged 50 and older?
5%
NHANES III
Prevalence of osteoporosis based on femoral neck measurements in men aged 50 and older?
6%
NHANES III
Prevalence of low bone mass in women aged 50 - 59 years?
40%
NHANES III
Prevalence of low bone mass in women aged older than 80 years?
Over 90%
National Osteoporosis Foundation (NOF)
How many people in the US have osteoporosis?
10 million people
National Osteoporosis Foundation (NOF)
How many women in the US have osteoporosis?
8 million women
National Osteoporosis Foundation (NOF)
How many men in the US have osteoporosis?
2 million men
National Osteoporosis Foundation (NOF)
How many people in the US have low bone mass?
34 million people
National Osteoporosis Foundation (NOF)
How many people in the US will there be with osteoporosis in 2020?
(Estimate)
Almost 14 million people
What is a pathological fracture?
A fracture that occurs in an area of bone already weakened by another process i.e. tumor, infection, inherited bone disorder etc.
What is a stress fracture?
A hairline fracture resulting from repeated stress.
What is an osteoporotic fracture?
Fracture occurring with minimal trauma such as a force less than or equal to falling from standing height.
Fracture incidence is bimodal - when are the two peaks?
Youth: 15 - 25 years
Over age 45 years
Which fractures pre-dominate in young people?
Fractures of long bones
In young people is the incidence of traumatic fractures greater in women or men?
Men
What type of fractures increase after age 45 years?
Fragility fractures
Do men or women have more fragility fractures?
Women
NOF
Approximately how many osteoporosis fractures per year are there in the US (incidence)?
1.5 million
NOF
Approximately how many osteoporosis spine fractures per year are there in the US (incidence)?
700,000 spine fractures
NOF
Approximately how many osteoporosis hip fractures per year are there in the US (incidence)?
300,000 hip fractures
NOF
Approximately how many osteoporosis wrist fractures per year are there in the US (incidence)?
250,000
NOF
Approximately how many osteoporosis fractures other than spine, hip and wrist per year are there in the US (incidence)?
300,000
Asymptomatic fractures account for about _____ % of all vertebral fractures.
65 - 75%
When does the incidence of forearm fractures begin to rise in women?
Age 45 - 50 years
When does the incidence of forearm fractures level off in women?
Around age 65 years
Is there an increase in the rate of foreman fractures in men?
No
When does the incidence of clinical vertebral fractures begin to rise in women?
Age 55 - 60
It rises linearly after this
When does the incidence of clinical vertebral fractures begin to rise in men?
Age 60 - 70 years
When does the incidence of hip fractures begin to rise in women?
Age 65
Increases exponentially
When does the incidence of hip fractures begin to rise in men?
Age 70 - 75
What kind of fracture is more likely when you fall forward (younger women)?
Wrist fracture
What kind of fracture is more likely when you fall sideways (older women)?
Hip fracture
What is the third most common osteoporotic fracture?
Distal forearm fracture
If you have a distal forearm fracture, then what is the risk of future fracture?
Relative risk of forearm fracture?
3.3
If you have a distal forearm fracture, then what is the risk of future fracture?
Relative risk of vertebral fracture?
1.7
If you have a distal forearm fracture, then what is the risk of future fracture?
Relative risk of hip fracture?
1.9
Reflex sympathetic dystrophy is a complication of which fracture?
Distal forearm fracture
In distal forearm fractures, what percentage report fair/poor recovery in functional recovery 6 months after fracture?
23%
6 months following ER presentation of wrist fracture in untreated patients, what percentage of patients had a DXA in the control group?
Majumdar CAMJ 2008; 178:569-575
18%
6 months following ER presentation of wrist fracture in untreated patients, what percentage of patients were given bisphosphonates in the control group?
Majumdar CAMJ 2008; 178:569-575
7%
What three types of vertebral fractures are they?
- Wedge
- Biconcave
- Crush
If you have a vertebral fracture, then what is the risk of future fracture?
Relative risk of hip fracture?
2.3
If you have a vertebral fracture, then what is the risk of future fracture?
Relative risk of vertebral fracture?
4.4
If you have a vertebral fracture, then what is the risk of future fracture?
Relative risk of forearm fracture?
1.4
What percentage of vertebral fractures seen on x-ray are diagnosed clinically?
25 - 30%
By what percentage does vital capacity decrease as a consequence of vertebral fractures?
9%
What percentage of hip fractures occur at the femoral neck?
40%
What percentage of hip fractures occur at the intertrochanteric region?
40%
What is the second most common osteoporotic fracture?
Hip fracture
What percentage of osteoporotic fractures are spontaneous?
5%
What percentage of falls lead to hip fractures?
1%
What is the excess mortality within 1 year after a hip fracture?
24 - 30%
How many American women die from complications of hip fracture every year?
65,000
What percentage of hip fracture survivors are permanently incapacitated?
50%
What percentage of hip fracture survivors require long-term nursing home care?
20%
Kamel HK, et al. Am J Med. 2000; 109:326-328
In this study of 170 patients hospitalized for hip fracture, diagnosis and treatment for osteoporosis occurred in less than ___%.
10
After hip fracture, mortality is in the first _____ months.
6 - 12
Is the increase in mortality sudden or gradual after a vertebral fracture?
Gradual
By what percentage is five-year excess mortality increased by in both hip and spine fractures?
About 20%
What percentage of health care dollars for osteoporosis are spent for hospitalisation?
62%
What percentage of health care dollars for osteoporosis are spent for nursing home care?
28%
What percentage of health care dollars for osteoporosis are spent for outpatient care?
10%
What was the cost of osteoporosis in 1997?
13.8 billion dollars
What was the cost of osteoporosis in 2005?
19 billion dollars
What is the projected cost (annually) for total fractures by 2025?
25 billion dollars
How many people in the United States have low bone density and osteoporosis?
(2010 estimate)
42.4 million
How many people in the United States have hypercholestrolemia?
(2010 estimate)
98.6 million
How many people in the United States have hypertension?
2010 estimate
73.5 million
How many people in the United States have diabetes?
2010 estimate
23.6 million
In older women, the incidence of osteoporotic fractures (about ___ million) is ______ than the incidence of myocardial infarction, stroke, and breast cancer combined.
2 million
Greater
What is the clinical utility of bone densitometry?
- Diagnosis (WHO T-score classification)
- Prognosis (Fracture risk assessment)
- Monitoring (Requires knowledge of precision and LSC)
Do all patients with T-score -2.5 or below have osteoporosis?
No
Do all patients with T-score above -2.5 not have osteoporosis?
No
T-scores may differ at different skeletal sites.
True or false?
True
Does the diagnosis of osteoporosis explain the etiology of it?
No
Does everyone with osteoporosis have the same fracture risk?
No
Does a low bone mineral density equal bone loss?
No
Can a single BMD examination distinguish between low peak BMD followed by normal rate of loss or normal peak BMD with accelerated rate of loss?
No
What is the rationale for using BMD to predict fracture risk?
(2 points)
- BMD is correlated with bone strength in biomechanical studies.
- BMD is predictive of future fractures in epidemiologic studies.
The strength of cortical bone decreases by _____ % per decade after age 20.
2 - 5%
In cancellous bone _____ % variability in elastic modulus explained by apparent density (bone mass per unit volume of marrow and bone tissue).
60 - 80%
Is the correlation between vertebral BMD and failure load better for DXA or QCT?
DXA
Is there a strong correlation between femoral BMD and failure load?
Yes
What are the two best predictors of fracture load at the distal radial?
- Cortical width
- Cortical area
Which two reference populations is the 10-year probability of fracture risk assessment based on?
- NHANES III
- Swedish population
What are the four features of an ideal skeletal site to serially monitor changes in BMD?
- Rapid bone turnover
- Low precision error
- Rapid response to therapy
- Greatest response to therapy
What is the best site to use for monitoring serial changes in BMD?
Lumbar spine
Central devices can measure bone density of which regions of interest?
(Four areas)
- Spine
- Hip
- Forearm
- Total body
Peripheral devices can measure bone density of which regions of interest?
(Three examples)
- Heel
- Finger
- Wrist
What are bone density instruments classified by?
Their primary technology platform
What two technology platforms exist for bone density?
- X-ray based
- Ultrasound based
Is the proximal femur a peripheral or central skeletal site?
Central
Which lumbar vertebrae does bone density analysis include?
L1 - L4
Which lumbar vertebrae looks like a ‘bow-tie’ or a ‘dog bone’?
L5
Which lumbar vertebrae is ‘box’ or ‘X-shaped’?
L4
Which lumbar vertebrae are ‘U-shaped’?
L1 - L3
What are the four regions of interest in the hip?
- Femoral neck box
- Total hip
- Greater and lesser trochanters
- Ward’s area
Name two central densitometry devices.
- Dual-energy x-ray absorptiometry (DXA)
- Quantitative computed tomography (QCT)
What is the ‘gold standard’ for bone density measurement?
Central DXA
Central DXA has excellent reproducibility.
True or false?
True
What is the radiation dose from central DXA?
1 - 3 microSv (low radiation dose)
Which technique for bone density measurement as been used in most epidemiological studies?
Central DXA
Is it well known how DXA-measured BMD relates to fracture risk?
Yes
Which method of bone density measurement is used to select subjects for therapy and to document response to treatment over time in pharmaceutical trials?
Central DXA
Name five peripheral densitometry devices.
- Peripheral DXA
- Single x-ray absorptiometry (SXA)
- Peripheral QCT (pQCT)
- Quantitative ultrasound (QUS)
- Radiographic absorptiometry (RA)
What is attenuation?
A reduction in the number and energy of photons in an x-ray beam (decreased intensity of x-ray beam)
What is attenuation determined by?
Tissue density and thickness
Does denser tissue contain more of less electrons?
More electrons
What else can you quantify when degree of attenuation is quantified?
Tissue density
Can you separate how much mass is due to bone, soft tissue or both with single energy x-ray beam?
No
With dual energy x-ray beams the proportion of radiation transmitted through the patient depends on which three factors?
- Energy of x-ray photons
- Physical density of the body
- Body thickness
What is the difference between a single energy and dual energy x-ray beams?
Single energy x-rays have one photon energy while dual energy x-rays have two different photon energies.
What two energies are used in dual energy x-ray absorptiometry?
- Low energy (30 - 50 keV)
- High energy (>70 keV)
Which is greater at low energy…
Bone attenuation or soft tissue attenuation?
Bone attenuation
Which is greater at high energy…
Bone attenuation or soft tissue attenuation?
Bone attenuation is similar to soft tissue attenuation.
Can dual x-ray attenuation distinguish bone and soft-tissue?
Yes
What three parts do DXA systems have?
- X-ray tube
- Collimator
- X-ray detector
What are x-ray photons produced by?
X-ray tube
What does an X-ray tube consist of?
An X-ray tube consists if a cathode (negative charged) and an anode (positively charged) encased in a vacuum tube.
What percentage of X-ray tube energy appears as x-rays?
Less than 1%
What percentage of X-ray tube energy is lost as heat?
99%
What does the collimator do?
Focuses the x-ray beam
The type of detector depends on the type of system — what types are they?
K-edge filter vs voltage switching
Pencil-beam vs fan-beam
What are the x-ray tube, collimator, and detector aligned and mechanically linked using?
Scanner arm
Which detector/system is used in GE and Norland DXA?
K-edge filtering
Which detector/system is used in Hologic DXA?
Voltage switching
What do K-edge filtering systems use?
Constant-potential generator and a k-edge filter to split the polyenergetic x-ray beam into high and low energy components.
What type of filter does GE-Healthcare Lunar use?
Cerium filter that results in energy peaks of 40 and 70 keV.
What type of filter does Norland use?
A samarium filter that results in energy peaks of 45 and 80 keV.
What is pulse counting?
The energy discriminating detector counts the high and low energy photons at each image position.
How are high and low energy photons differentiated in a DXA machine?
With an energy discriminating detector.
Do photon counting systems have limited count rate capabilities?
Yes
What do voltage-switching systems use?
Switch the high-voltage generator, that is connected to the x-ray source, between high and low peak voltage (kVp) during alternate half-cycles of the main power supply.
Which system does not require differentiation of high and low energy photons in a DXA machine?
Voltage-switching system
What do current-integrating detectors do?
They sum all the signal during the half cycle since all the photons are either high (or low) photons.
Which system is better for low photon count rate?
K-edge filtering systems
How are voltage switching systems calibrating?
Continuously calibrated using a rotating wheel or drum (internal calibration)
Is the clinical utility affected by method of dual-energy production or type of detectors used?
No
Can clinical results between manufacturers be compared?
No
What two types of central DXA scanners are they?
- Pencil-beam
- Fan-beam
Scanning occurs point by point.
Which type of scanner?
Pencil-beam scanners
Scanning occurs line by line.
Which type of scanner?
Fan-beam (or array) scanners
What two types of fan-beam scanners are there?
- Wide-angle fan-beam (oriented transverse to the long axis of the body)
- Narrow-angle fan-beam (oriented parallel to the long axis of the body)
Does Hologic use wide-angle or narrow-angle fan-beam?
Wide-beam
Does GE use wide-angle or narrow-angle fan-beam?
Narrow-angle fan-beam
Which one is cheaper…
Pencil-beam or fan-beam?
Pencil-beam
Which one has faster acquisition…
Pencil-beam or fan-beam?
Fan-beam
Which one has multiple detectors…
Pencil-beam or fan-beam?
Fan-beam
Which one is more accurate…
Pencil-beam or fan-beam?
They are comparable
Which one is more precise…
Pencil-beam or fan-beam?
They are comparable
Do pencil-beam scanners have a rotating gantry?
No
Which one has better resolution…
Pencil-beam or fan-beam?
Fan-beam
Which one has higher radiation dose…
Pencil-beam or fan-beam?
Fan-beam
Why are BMD values of different manufacturers not comparable?
(Five reasons)
Because of different:
- Methods of dual-energy production
- Calibration
- Detectors
- Edge detection software
- Regions of interest
Compared to central devices, SXA and peripheral DXA are:
Smaller or larger?
Smaller
Compared to central devices, SXA and peripheral DXA are:
Portable or non-portable?
Portable
Compared to central devices, SXA and peripheral DXA have:
Lower or higher radiation doses?
Lower radiation doses
Compared to central devices, SXA and peripheral DXA have:
Shorter or longer scan times?
Shorter scan times
Compared to central devices, SXA and peripheral DXA are:
Easier or harder to operate?
Easier to operate
Compared to central devices, SXA and peripheral DXA are:
Cheaper or more expensive?
Cheaper
What two types of peripheral DXA device configurations are there?
- Pencil-beam configuration
- Cone-beam configuration
Do peripheral DXA use different normative databases?
Yes
Which one uses a water bath for soft tissue equalization…
SXA or DXA?
SXA
Which three parts of the body do peripheral DXA measure BMD in?
- Forearm
- Finger
- Heel