Module 14 Flashcards
What filter do GE lunar systems use
Cerium
The cerium filter spectrum at 80KV produces 2 photo electric peaks at about what value
40keV and 70keV
Norland Swissray uses what type of filter
Samarium
The Samarium filter spectrum at 100kV a low energy peak and high energy peak at what range
47keV low, Less than 100keV high
Hologic scanners use what type of filter system
Energy switching xray beam between 100 and 140kVp
Two dimensional scan area is also known as
Projectional or areal
Three dimensional scans are also known as
Volumetric
A decrease in the BMC also results in a decrease in
BMD
A decrease in area causes an increase in
BMD
This is the sum of the data values, divided by the number of values
Mean
Measure of variability, it shows how spread out the data is around the mean
Standard deviation
This is A statistic that helps compare a variability between different datasets whether or not they have the same mean
Percent coefficient of variation
This refers to an inconvenient anomaly in which T scores from different atomic sites within the same patient fall into different diagnostic classifications
Discordance
This describes how closely a measurement approximates with things that is measuring
Accuracy
This measures how closely a test`s results approximate the correct value
Trueness
This is the measure of how likely a test is to achieve the same result when repeated on the same subject in the same conditions
Precision
This is used to describe the consistency of measurement
Precision
This is used to describe how closely it measures the expected values
Trueness
What are the rules for in vivo scans
Either 15 patients 3 times each or 30 patients 2 times each
What is the maximum acceptable precision error for technologies performing a lumbar spine scan
1.9% with an associated LSC of 5.3%
What is the maximum precision error for a scan of the total hip
1.8% with an LSC of 5%
What is the maximum precision error for a scan of the femoral neck
2.5% with an LSC of 6.9%
How do you cross calibrate machines
Scan 30 patients representative of the facility’s patient population on the original system and then twice on the new system for this method all scan should be completed within 60 days
This is a measure of bone micro texture and is a marker for the risk of osteoprosis
Trabecular bone score
What does QC on DXA units consist of
Scanner calibration test, Phantom test, and precision assessments
This is a comprehensive program that sets guidelines for monitoring and evaluating medical systems. This includes the scanner’s function and the technologies technique
QA, quality assurance
When values are plotted mathematical rules are applied to detect any failures that indicate a change in a machine’s performance the result of this QC is called what
Shewhart or control chart
This is a statistical method of Quality control, the purpose of this is to evaluate scanner stability
Shewhart rules
The upper lower controls on control chart represent plus and minus ____ percent of the main
1.5
What type of Phantom does a hologic unit use
Anthropomorphic (made of hydroxyapatite)
What type of spine Phantom does GE use
Aluminum
What are the 3 basic statistical terms used in analysis of QC results
The mean, the standard deviation, and the percent coefficient variation
Precision assessment measures
Reproducibility
True or false DXA scanning exposes patients to < one day’s worth of natural background radiation
True
Which skeletal site offers the highest precision in the most rapid response treatment
Lumbar spine
When should cross calibration be performed
When changing DXA hardware
How many Phantom scans must be performed to verify Phantom BMD following scanner maintenance
10
Serial scanning of a patient’s bone mineral density values can be used to monitor
Response to therapy
What is the main purpose of Shewhart rules as they apply to bone Densitometry
Evaluating scanner precision
