Chapter 26 Workbook
How often should you perform a phantom scan?
A phantom scan is performed daily before any patients are scanned.
Mean
Average
T-score
Comparison with young adult normal values
800 to 1000 U
Daily recommend amount of Vitamin D for patients over 50 years of age.
The two anatomic sites typically used for central DXA scanning are:
Lumbar spine and proximal femur.
ROI
Region of interest
SD
Standard deviation
The T-score is directly related to:
Young-adult population
Radiation exposure for a typical DXA scan is:
1 to 5 mrem (millirems)
Describe the difference between accuracy and precision in bone densitometry:
Accuracy is equipment dependent and relates to the ability to measure the true BMD. Precision is technologist related and involves the ability to reproduce positioning
Z-score
Age-matched BMD
The Z-score is directly related to:
Age-matched population
Why is a baseline scan so important in diagnosis and follow-up?
All the follow-up scans are compared to the baseline scan. The baseline scan must be acquired and analyzed correctly so that when serial scanning is done, the serial can scan can be directly compared to the baseline. Precision and accuracy in both scans are vital to assure correct diagnosis and follow-up.
1200 mg
Amount of daily calcium recommended for patients over 50 years of age.
What does ALARA stand for?
As Low As Reasonably Achievable
Bone mineral density (BMD) is calculated by the following equation:
BMC divided by area.
BMC
Bone mineral content
Secondary osteoporosis
Disease- or medication-induced osteoporosis
Describe the attenuation method used in BMD calculation
Eliminate the contribution of soft tissue, and measure the attenuation due to bone alone. Scan at two different x-ray photon energies, and mathematically manipulate the recorded signal. The density compared to the baseline. Precision and accuracy in both scans are vital to assure correct diagnosis and follow-up.
Weight bearing
Exercise that works against gravity
Two different types of bone in the skeletal region are:
Cortical and Trabecular.
Peak Bone Mass
Reached at about age 30 to 35 years
Name one contraindication to performing a central DXA scan?
Recent barium studies or other contrast media studies, pregnancy.
33%
Region of interest on the forearm DXA scan
Accuracy
Relates to the stability of the DXA system
Precision
Relates to the technologist's ability to reproduce the same positioning.
One of the correct scanning procedures for precision testing is as follows:
Scan 30 patients twice.
What medical condition is an indication for scanning the forearm?
Hyperparathyroidism
What is the purpose of vertebral fracture assessment (VFA)?
It is for the sole purpose of detecting vertebral fractures, not measuring bone density.
LSC
Least significant change
Gray
Measure of absorbed dose of radiation.
kVp
Measure of x-ray voltage
mA
Milliamperage rate of current flow in an x-ray tube.
Describe the process of bone remodeling and its two main components:
Old bone is replaced with new bone. Osteoclasts are the bone destroying cells. Osteoblasts are the bone-building cells.
PA lumbar spine
Position of the patient for the lumbar spine DXA scan.
Primary Osteoporosis
Postmenopausal or age-related osteoporosis
Describe FRAX and why it is used?
The FRAX tool has been developed by the World Health Organization (WHO) to evaluate fracture risks of patients. It is based on individual patient models that integrate the risks associated with clinical risk factors as well as bone mineral density (BMD) at the femoral neck. The algorithim gives the 10-year-old probability of a fracture.
Three factors directly related to radiation safety in DXA scanning are:
Time, distance, and shielding.
WHO
World Health Organization
Archive
Method of saving electronic patient data
Define the difference between primary and secondary osteoporosis:
1) Primary osteoporosis is related to postmenopausal status (type 1) or aging (type 2); Secondary Osteoporosis is caused by other factors, such as medications or disease processes.
What is the minimal distance of a DXA operator should be form the x-ray source of a fan-beam DXA scanner?
9 ft or 3 m
% CV
Coefficient of Variation
Serial scanning
DXA scans performed after the base line scans
The term DXA stands for:
Dual-energy x-ray absorptiometry
NOF
National Osteoporosis Foundation
What is the correct procedure to follow after there has been a failed quality assurance test on any DXA scanner?
Repeat the test and record the problem or corrective action. If the test fails a second time, call the manufacturer's help or applications services line. Cancel all appointments until the problem can be corrected.
What is the primary reason a serial DXA scan is done?
To determine treatment or monitoring response to therapy.
