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
For QCT of the spine…
Can any commercial scanner be used?
Yes
For QCT of the spine…
Is addition of special software required?
Yes
For QCT of the spine…
Is the addition of a reference phantom usually required?
Yes
For QCT of the spine…
What is software used for?
To help place regions of interest within the vertebral bodies (usually L1-L3)
For QCT of the spine…
What is reference phantom used for?
It is used to convert CT attenuation coefficient (Hounsfield Units, HU) to bone equivalent values (BMD).
For QCT of the spine…
If systems don’t require a phantom what do they use?
They use the patient’s fat and muscle as standards.
Does DXA allow volumetric BMD measurement?
No
Does QCT allow volumetric BMD measurement?
Yes
Does size of vertebral body cause error in measurement when measured with QCT?
No
Which is better for patients who are at the extremes for size and weight…
DXA or QCT?
QCT
Which can measure purely cancellous bone…
DXA or QCT?
QCT
Which is less effected by degenerative disease of the spine…
DXA or QCT?
QCT
Which is more precise…
DXA or QCT?
DXA
Which has a higher radiation dose…
DXA or QCT?
DXA
How can the precision of QCT be improved?
With 3D (spiral CT)
Which method of measurement allows true volumetric BMD measurement of the forearm?
Peripheral QCT
Is separation into cortical and cancellous compartments of bone possible with pQCT?
Yes
Does pQCT require a dedicated scanner?
Yes
Which has a lower radiation dose spine/hip QCT or peripheral QCT?
Peripheral QCT
Does pQCT measure areal or volumetric measurement BMD?
Volumetric BMD
Which has greater technology diversity…
DXA or QUS?
QUS
How much radiation does QUS have?
None
It’s ultrasound
Does QUS measure BMD?
No
Is QUS used centrally or peripherally?
Peripherally
Does QUS work better with more or less soft tissue covering over site?
Less soft tissue covering
For QUS transmission:
What two types of sound transmission are there?
- Transverse sound waves (travels through bone)
- Axial sound waves (travels along cortex of bone)
For QUS transmission:
Which machines use transverse sound waves?
- GE, Achilles
- Hologic, Sahara
For QUS transmission:
Which machine uses axial sound waves?
Sunlight
For QUS transmission:
What types of systems are they for transducer coupling?
- Water-based systems
- Gel-based systems
- Systems that use both
How are regions of interest selected in QUS?
Imaging systems
Which two parameters does QUS measure?
- Speed of sound (SOS) in meters per second (m/sec)
- Broadband ultrasound attenuation (BUA) of sound in decibels per megahertz (dB/MHz)
Are calculated parameters in QUS lower in normal patients or those with osteoporosis?
Those with osteoporosis
Correlation of QUS measurements with BMD by DXA.
Calcaneal BMD?
(r = ?)
Moderately high
r = 0.6 - 0.8
Correlation of QUS measurements with BMD by DXA.
Spine or hip BMD?
(r = ?)
Modest
(r
What is one explanation for QUS T-scores and central DXA T-scores not correlating well?
Different reference populations
How is accuracy defined in bone densitometry?
The ability of a measurement to match the accepted reference value.
What two types of error affect accuracy in densitometry?
- Systematic error (trueness)
- Random error (precision)
What is systemic error?
% error between true and measured value
If there is systematic error will the average measurement value, from multiple measurements of the same person, be ‘true’ or ‘untrue’?
Untrue
FDA 510K clearance requires less than ___% error of BMD devices.
10%
Is trueness more important for diagnosis or monitoring serial changes?
Diagnosis
What method is used to determine ‘trueness’?
Bone ash method
What is precision?
Comparison between serial measurements if the same object or person.
Is the average value of random errors ‘true’ or ‘untrue’?
True
Why is precision important?
For reproducibility
What is in-vitro precision best used for?
Monitor the stability of the system for quality assurance.
What is in-vivo precision best used for?
To determine when true change has occurred in serial measurements on the same individual
Least significant change is in-vivo precision.
True or false?
True
Trueness is most affected by…
Technology
Precision is most affected by…
Operator (technologist)
Central DXA:
PA spine…
Precision Error?
1 - 2%
Central DXA:
Lateral spine…
Precision Error?
2 - 3%
Central DXA:
Femur…
Precision Error?
1.5 - 3%
Central DXA:
Forearm…
Precision Error?
1%
Central DXA:
Total body…
Precision Error?
1%
Central DXA:
PA spine…
Trueness Error?
4 - 10%
Central DXA:
Lateral spine…
Trueness Error?
5 - 15%
Central DXA:
Femur…
Trueness Error?
6%
Central DXA:
Forearm…
Trueness Error?
5%
Central DXA:
Total body…
Trueness Error?
3%
Peripheral DXA:
Forearm…
Trueness Error?
4 - 6%
Peripheral DXA:
Calcaneus…
Trueness Error?
4 - 6%
Peripheral DXA:
Hand…
Trueness Error?
5%
Peripheral DXA:
Forearm…
Precision Error?
1 - 2%
Peripheral DXA:
Calcaneus…
Precision Error?
1 - 2%
Peripheral DXA:
Hand…
Precision Error?
1 - 2%
SXA:
Precision Error?
1 - 2%
Spine QCT:
Precision Error?
1.5 - 4%
Peripheral QCT:
Precision Error?
1 - 2%
Peripheral QCT:
Trueness Error?
2 - 8%
Spine QCT:
Trueness Error?
5 - 15%
SXA:
Trueness Error?
4 - 6%
Which has better precision…
SXA/DXA or QUS?
SXA/DXA
What has been proposed as a way to adjust for signal magnitude between x-ray and QUS devices?
Standardized precision error
What is radiation?
Flow of energy through space and matter, in the form of particles or waves.
What kind of radiation are x-rays?
Ionizing radiation
Do x-rays have short or long wavelength?
Short wavelength
Do x-rays have one energy level or multiple?
Multiple energy levels (polyenergetic)
What is the absorbed dose?
Skin entry dose
Measurement if total amount of radiation entering the body.
May skin entry dose be expressed as entrance surface dose?
Yes
What units is skin entry dose/ absorbed dose expressed in?
gray (Gy) or rad
What is the effective dose or dose equivalent?
Calculated dose and calculates the potential biological harm radiation may have on the tissue after being absorbed.
What units is effective dose/ dose equivalent expressed in?
sievert (Sv) or rem
Is the effective dose / dose equivalent corrected for type of radiation and tissue sensitivity?
Yes
Which radiation dose is the correct method to check if your device is working within specifications…
Skin entry dose vs effective dose?
Skin entry dose
Where can you find the effective dose?
In published literature
Which is higher, skin entry dose or effective dose?
Skin entry dose
What is the probability of fatal cancer after radiation exposure?
1% per Sv
1 million DXA
What is the probability of severe genetic effects in succeeding generations after radiation exposure?
1% per Sv
1 million DXA exams
What is the risk of pre-implantation death and congenital anomalies (mental retardation) after radiation exposure?
Minimum dose of 100 mSv (100,000 DXA exams)
What are the two categories of biologic effects of radiation?
- Stochastic
- Deterministic
Do stochastic effects of radiation occur at low dose or high dose?
Low dose
Do deterministic effects of radiation occur at low dose or high dose?
High dose
Do stochastic effects or deterministic effects of radiation cause an increase in random events?
Stochastic effects of radiation
Stochastic effects or deterministic effects of radiation?
Probability of occurrence is a function of dose.
Stochastic effects of radiation
Stochastic effects or deterministic effects of radiation?
Small risk, no threshold dose…
Stochastic effects of radiation
Stochastic effects or deterministic effects of radiation?
Occur in each individual receiving sufficient dose…
Deterministic effects of radiation
Stochastic effects or deterministic effects of radiation?
Examples: cancer and mutation
Stochastic effects of radiation
Stochastic effects or deterministic effects of radiation?
Examples: acute radiation sickness and cataracts
Deterministic effects of radiation
Stochastic effects or deterministic effects of radiation?
Threshold dose (1.2 - 3 Sv) below which effects are insignificant
Deterministic effects of radiation
Is the threshold dose for deterministic effects of radiation smaller or greater than doses used in medical imaging (including DXA and QCT)?
Much greater
Is the dose to patient from central DXA smaller or greater than doses from other radiological exams?
Much smaller (1/50th to 1/1000th of the dose)
At a distance greater than ___ meter away from the scanner table the radiation dose is negligible (no different than background).
1
What is the maximal permissible dose of radiation in the United States…
General public?
5000 microSv per year
Excluding medical or dental
What is the maximal permissible dose of radiation in the International…
General public?
1000 microSv per year
What is the maximal permissible dose of radiation in the United States…
Occupational exposure?
50,000 microSv per year
What does ALARA stand for?
As low as reasonably achievable
For radiation exposure
Intensity of radiation decreases as the square of distance away from source.
True or false?
True
What is used for safety in general radiology?
Shielding
How far should the technologist be from the edge of table of the DXA machine?
Greater than 1 meter
Patients should be pre-screened for contraindications for DXA exams.
True or false?
True
Should pregnant women get DXA scans?
No
Should a pregnant technologist be doing DXA scans?
What steps can be taken?
- Should notify employer and take precautions
- Reassignment of duties or shielding with lead apron
- Badge at abdomen to monitor fetal radiation
What is the permissible dose for a pregnant technologist?
5000 microSv for the duration of the pregnancy
Not to exceed 500 microSv per month
What two calibration methods are used as clinical quality control procedures?
- Internal (continuous)
- External (periodic)
Which scanners use continuous calibration methods?
Hologic scanners
Which scanners use periodic calibration methods?
- GE-Healthcare Lunar
- Norland
Periodic or continuous calibration?
X-ray passes through calibration filter (drum or wheel) while patient is being scanned.
Continuous calibration
Periodic or continuous calibration?
Calibration filter contains bone, tissue, and air equivalent.
Continuous calibration
Periodic or continuous calibration?
Point by point calibration.
Continuous calibration
Periodic or continuous calibration?
Daily scanning of known bone and tissue standards.
Periodic calibration
Periodic or continuous calibration?
Utilises a calibration standard.
Periodic calibration
Periodic or continuous calibration?
May automatically adjust calibration factors as needed.
Periodic calibration
How often are phantom scans recommended as an independent check of system quality assurance?
At least one per week
What three things may cause calibration shift?
- Relocation
- Maintenance
- Change of X-ray tube or detector
What three things may cause calibration drift?
- Change in room conditions (temperature, humidity)
- Change in power supply
- Aging of X-ray tube or detector
What should you do if you have upgraded your software between studies?
Reanalyse the baseline study with the new software before comparing it with follow-up study.
What should be done when changing hardware or when replacing with the same manufacturer and model?
Cross calibration should be performed.
How many phantom scans should one technologist do with repositioning before and after hardware change?
10
If after hardware changes and calibration there is more than __% difference in mean BMD, then the manufacturer should be contacted for service.
1
When does height loss begin?
In the mid 40s
What is the cumulative height loss by age 80 in males?
5 cm
What is the cumulative height loss by age 80 in females?
6.2 cm
Are clinical risk factors a substitute for BMD testing?
No
Do risk factors predict osteoporosis according to the IMPACT trial?
No
Is low BMD an independent risk factor for osteoporotic fractures?
Yes
Is advancing age an independent risk factor for osteoporotic fractures?
Yes
Is prior fracture an independent risk factor for osteoporotic fractures?
Yes
Is family history of osteoporosis or fragility fracture in a first degree relative an independent risk factor for osteoporotic fractures?
Yes
Is being a current smoker an independent risk factor for osteoporotic fractures?
Yes
Is low body weight an independent risk factor for osteoporotic fractures?
Yes
Are falls an independent risk factor for osteoporotic fractures?
Yes
Is sarcopenia an independent risk factor for osteoporotic fractures?
Yes
Is dementia an independent risk factor for osteoporotic fractures?
Yes
Are risk factors for low BMD the same as risk factors for fractures?
No
Decreasing BMD by 1 SD increases fracture risk by ____ times?
1.7 - 2.6
Each decade of aging past age 50 increases fracture risk by ___ times.
2
One prior vertebral fracture increases the risk of subsequent vertebral fracture by approximately ___ fold.
4
Is hypogonadism an indication for BMD measurement?
Yes
Does Medicare give early reimbursement for…
Estrogen-deficient women at clinical risk for osteoporosis (as determined by the physician)
?
Yes
Does Medicare give early reimbursement for…
Individuals with vertebral abnormalities. X-ray evidence of low bone mass / density or vertebral fractures
?
Yes
Does Medicare give early reimbursement for…
Individuals receiving glucocorticoid therapy (expected use over 3 months with 5 mg or more of prednisone or equivalent
?
Yes
Does Medicare give early reimbursement for…
Individuals with primary hyperparathyroidism
?
Yes
Does Medicare give early reimbursement for… And how often…
Individuals monitored for response on a FDA-approved osteoporosis drug therapy
?
Yes
One test every two years
Does Medicare give early reimbursement for…
Exceptions made when medically necessary such as patients on glucocorticoid therapy for more than three months or for baseline testing to allow monitoring if the initial test was performed with a different technique from the proposed monitoring method.
?
Yes
Do chronic inflammatory diseases cause bone loss in adolescents?
Yes
Do some endocrinopathies cause bone loss in adolescents?
Yes
Does a history of childhood cancer cause bone loss in adolescents?
It can
Does thalassemia major cause bone loss in adolescents?
Yes
When should you do BMD testing in children and adolescents with thalassemia major?
At fracture presentation or age 10 whichever earlier.
Should you do BMD testing in children and adolescents prior non-renal transplantation?
Yes
Does chronic immobilization (e.g. cerebral palsy) cause bone loss in adolescents?
Yes
What are the (relative) contra-indications for central DXA?
- Pregnancy
- Recent contrast study (spine DXA)
- Recent nuclear medicine scan (wait at least 72 hours after these studies)
- Extensive orthopedic instrumentation (measure a different site)
- Severe obesity (weight limits of 250 - 450 pounds)
What should you do if the patient is too obese for the central DXA scanner?
Measure forearm density
Name five endocrinopathies associated with low bone mass.
- Hyperparathyroidism
- Hyperthyroidism
- Cushing’s Syndrome
- Hypogonadism (including hyperprolactinemia)
- Hypercalciuria
Are suppressive doses of thyroid hormone associated with low bone mass?
Yes
Is heparin associated with low bone mass?
Yes
Are GnRH agonists associated with low bone mass?
Yes
Is Depo-Provera associated with low bone mass?
Yes
Is phenytoin associated with low bone mass?
Yes
Are exchange resins associated with low bone mass?
Yes
Are thiazolidinediones associated with low bone mass?
In some women
Is excess vitamin A associated with low bone mass?
Yes
Is phenobarbital associated with low bone mass?
Yes
Is cyclosporine associated with low bone mass?
Yes
Is a gastrectomy associated with low bone mass?
Yes
Is inflammatory bowel disease associated with low bone mass?
Yes
Is celiac disease associated with low bone mass?
Yes
Is intestinal bypass surgery associated with low bone mass?
Yes
Is primary biliary cirrhosis associated with low bone mass?
Yes
Is pancreatic insufficiency associated with low bone mass?
Yes
Is rheumatoid arthritis associated with low bone mass?
Yes
Is systemic lupus erythematosus associated with low bone mass?
Yes
Is ankylosing spondylitis associated with low bone mass?
Yes
Is anorexia nervosa associated with low bone mass?
Yes
Is bulimia nervosa associated with low bone mass?
Yes
What is the female athlete triad?
- Disordered eating
- Menstrual irregularity
- Low bone mass
Name two drugs that cause vitamin D deficiency?
- Phenytoin
- Phenobarbital
Is liver and kidney disease associated with vitamin D deficiency?
Yes
Is there an age-related decline in cutaneous production of vitamin D?
Yes
Do gastrointestinal diseases pre-dispose to vitamin D deficiency?
Yes
Is multiple myeloma associated with low bone mass?
Yes
Is hemolytic anemia, hemoglobinopathies associated with low bone mass?
Yes
Is myelo-and lymph-proliferative disorders associated with low bone mass?
Yes
Are skeletal metastases (diffuse or localized) associated with low bone mass?
Yes
Is Gaucher’s disease associated with low bone mass?
Yes
Is mastocytosis associated with low bone mass?
Yes
Is Ehlers-Danlos syndrome associated with low bone mass?
Yes
Is Marfan’s syndrome associated with low bone mass?
Yes
Is homocystinuria associated with low bone mass?
Yes
Is osteogenesis imperfecta associated with low bone mass?
Yes
What could you need a bone biopsy in the case of low bone mass / density?
To differentiate between osteomalacia and osteoporosis.
Which patients with low bone mass / density need a bone biopsy?
- Patients with unusual features of osteoporosis (young men and women with unexplained osteoporosis, patients with very low bone mass, patients with fragility fractures but normal BMD)
- Patients failing conventional therapy (non-responders)
- In renal osteodystrophy when osteomalacia is suspected
What are bone turnover markers?
Products of bone remodelling
Are bone turnover markers independent predictors for fracture?
Yes
Can bone turnover markers be used to diagnose osteoporosis?
No
What are the three markers of bone resorption?
- N-telopeptide (NTX) - serum or urine
- C-telopeptide (CTX) - serum or urine
- Deoxypyridinoline (free, total)
What are the markers of bone formation?
- Bone specific alkaline phosphatase
- Osteocalcin
- Procollagen Type I N-terminal Propeptide (PINP)
Bone turnover markers do not predict hip fracture independently of BMD.
True or false?
False
Bone turnover markers predict bone loss in recently post-menopausal women.
True or false?
True
Bone markers may predict response to estrogen therapy in recently menopausal women.
True or false?
True
How much bone loss must occur before low bone density is seen on x-rays?
About 30% or more
Which study should be done if fracture is equivocal?
MRI or bone scan
Which study should be done if fracture is suspected to be remote?
Bone scan or MRI
Which study should be done if kyphoplasty or vertebroplasty is being considered?
Bone scan and MRI
Which study should be done if metastatic carcinoma is a consideration?
MRI or biopsy
Which study should be done if neurological signs are present?
MRI
How do you diagnose fractures of the mobile type?
By comparing standing lateral radiographs with supine cross-table lateral films.
In which view can you see dynamic mobile fractures?
Standing lateral films
What is ‘Kummels sign’?
Intervertebral clefts associated with dynamic mobile fractures caused by osseous necrosis.
What does Kummels sign look like on conventional radiographs?
Vacuum phenomenon
What does Kummels sign look like on MRI?
Signal void
What percentage of vertebral fractures necessitate admission to the hospital?
10%
Only about ____ of vertebral fractures found on radiographs come to medical attention.
One-third
About what percentage of vertebral fracture events are asymptomatic?
About 50%
Presence of vertebral fractures are a strong indication for pharmacologic therapy.
True or false?
True
The greater the number of prevalent vertebral fractures, the greater the risk of future fractures.
True or false?
True
The greater the severity of prevalent vertebral fractures, the greater the risk of future fractures.
True or false?
True
Pre-existing vertebral fractures predict future fractures independent of BMD.
True or false?
True
VFA can diagnose fractures at the time of DXA.
True or false?
True
Which visual technique is used in VFA…
Qualitative or quantitative?
Qualitative
What does the term ‘Vertebral Fracture Assessment’ denote?
Densitometric spine imaging performed for the purpose of detecting vertebral fractures.
What three types of vertebral fractures are there?
- Wedge
- Biconcave
- Crush
What are the three ways of diagnosing and grading vertebral fractures?
- Qualitative (visual inspection)
- Semiquantitative (visual inspection with assignment of fracture grade)
- Quantitative (morphometry)
What are the three grades of fractures according to the Genant’s chart?
- Mild fracture/Grade 1 ~ 20 - 25%
- Moderate fracture/Grade 2 ~ 25 - 40%
- Severe fracture/Grade 3 ~ 40% or more
What is the main advantage of VFA?
It can be performed during the visit for DXA and the BMD information and fracture status can be integrated.
Spine x-ray or VFA…
Which has a higher radiation dose?
Spine x-ray
Spine x-ray…
Radiation dose?
1800 - 2000 microSv
VFA…
Radiation dose?
30 - 50 microSv
Spine x-ray or VFA…
Which has better access?
VFA
Spine x-ray or VFA…
Which has a higher cost?
Spine x-ray
Spine x-ray or VFA…
Which has a higher resolution?
Spine x-ray
Spine x-ray or VFA…
Which has better visualization above T7?
Spine x-ray
Spine x-ray or VFA…
Which has more parallax effect?
Spine x-ray
Spine x-ray or VFA…
Which has automated morphometry?
VFA
What is the gold standard for vertebral fractures?
Spine x-rays
What is the sensitivity of VFA for moderate and severe fractures?
90 - 94%
What is the sensitivity of VFA for mild fractures?
50%
What is the negative predictive value of VFA?
Over 95%
Name four confounding factors in VFA interpretation.
- Severe scoliosis
- Bowel gas
- Aortic calcification
- Rib and scapular shadows
Name three internal or external artifacts in VFA interpretation.
- Surgical hardware
- Implanted devices
- Bra clips, zippers, buttons
What is the definition of a vertebral fracture according to Genant’s SQ system?
20% reduction in vertebral height
When should VFA be considered?
When the results may influence clinical management
VFA should be considered if there is documented height loss > ___ or historical height loss > ___ since young adulthood.
2 cm (0.75 inches) 4 cm (1.5 inches)
Can patients with normal BMD have osteoporotic fractures?
They may.
Why did the WHO chose T = -2.5?
This cut off value identifies ~ 30% of post menopausal women as having osteoporosis at the spine, hip or forearm.
What’s the lifetime risk of fracture at the spine, hip or forearm?
30%
What is the Z-score?
Number of standard deviations the patient’s BMD is above or below age and sex-matched mean reference value.
Are Z-scores used for diagnosis in adults?
Yes
Is there any evidence to support a specific cut-off point for Z-scores after which you evaluate for secondary causes?
No
What would using Z-score for diagnosis of osteoporosis suggest?
That the prevalence of osteoporosis does not increase with age - this is not true.
Can BMD be used across all devices?
No
Can T-scores be used across all devices?
Yes
Can the lateral spine be used for diagnosis of osteoporosis?
No
Should Ward’s area be used for diagnosis?
No
Should greater trochanter be used for diagnosis?
No
What is the region of interest in the forearm?
Distal 1/3 radius on the non-dominant forearm.
Using DXA young normal men have BMD ~ ____% higher than women (mostly because they have larger bones)
10
Men fracture at the hip at a higher bone density than women.
True or false?
False
They fracture at the same BMD
(Data controversial)
Men fracture at the spine at a higher BMD than women.
True or false?
True
Data controversial
Using DXA young normal blacks have BMD ~ ____% higher than whites.
10
Asians have similar bone density to whites.
True or false?
True
Some manufacturers adjust their T-scores for race while others do not…
Hologic?
Adjusts for men and women
Some manufacturers adjust their T-scores for race while others do not…
Norland?
Adjusts in women but not in men
Some manufacturers adjust their T-scores for race while others do not…
GE-Lunar?
Does not adjust
Some manufacturers adjust their T-scores for race while others do not…
Which machine does not adjust Z-scores in men?
Norland
What is the absolute risk?
Number of events over a defined period of time
What is relative risk?
Ratio of absolute risks of two different groups
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Distal radius
Hip fracture?
1.8
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Distal radius
Vertebral fracture?
1.7
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Proximal radius
Hip fracture?
2.1
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Proximal radius
Vertebral fracture?
2.2
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Calcaneous
Hip fracture?
2
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Calcaneous
Vertebral fracture?
2.4
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Spine
Hip fracture?
1.6
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Spine
Vertebral fracture?
2.3
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Femoral neck
Hip fracture?
2.6
Relative risk of fracture for 1 SD decrease in BMD (age-adjusted):
Site: Femoral neck
Vertebral fracture?
1.8
What is the best measure of the strength of the association between a risk factor and a disease outcome?
Relative risk
What does a relative risk of 1 mean?
Either:
- Absolute risk of both groups is the same
OR
- There is no association between the risk factor and the disease
BMD at any site can predict fracture risk.
True or false?
True
What happens to lifetime risk of fractures with age?
It decreases because life-expectancy decreases.
In Rochester, a hip fracture predicted a ___% risk of a contralateral hip fracture over ___ years.
29%
20 years
What is the average lifetime risk of hip fracture in men?
6%
What is the average lifetime risk of hip fracture in women?
17%
Fracture risk increases _____ gold for each SD decrease in BMD.
1.5 - 3
Is FRAX absolute or relative risk?
Absolute risk
Precision - Manufacturer’s range…
PA spine?
0.5 - 1.5%
Precision - Manufacturer’s range…
Total hip?
0.5 - 1.5%
Precision - Manufacturer’s range…
Femoral neck?
1 - 2.5%
Precision - Clinical Center’s range…
PA spine?
1 - 2.5%
Precision - Clinical Center’s range…
Total hip?
1.5 - 2.5%
Precision - Clinical Center’s range…
Femoral neck?
2 - 3.5%
What does %CV stand for?
Percentage coefficient of variation
Does total body BMD respond well to therapy?
Yes
What is the desirable level of serum 25-OH vitamin D?
30 - 60 ng/mL
What is the prophylactic dose of alendronate?
35 mg per week
Or
5 mg per day
What is the treatment dose of alendronate?
75 mg per week
Or
10 mg per day
Dose of Ibandronate, over what period of time?
3 mg IV over 15 - 30 seconds
How long can you treat with teriparatide for?
2 years
What does teriparatide do to bone markers?
Increases bone markers
Which DXA machine has a One-Scan option that uses a correction factor to compensate for the change in position?
GE-Lunar
