Bone Density Registry Exam Prep Newest Actual Exam With Complete Questions
And Correct Detailed Answers (Verified Answers) |Already Graded A+
Question 1
Bone Mineral Density (BMD) as measured by DXA is expressed as "areal" density. What are the
specific units used?
A) mg/cm³
B) g/cm²
C) mg/dL
D) g/mm
E) HU (Hounsfield Units)
Correct Answer: B) g/cm²
Rationale: DXA is a two-dimensional projection technique. It measures the bone mineral
content (BMC) in grams and divides it by the area of the bone being scanned in square
centimeters. Because it lacks a "depth" or volume component, it is considered an "areal"
measurement rather than a true volumetric density (which would be mg/cm³ as seen in
QCT).
Question 2
According to the World Health Organization (WHO), what T-score range defines "Osteopenia" or
low bone mass?
A) -1.0 and above
B) Between -1.0 and -2.5
C) -2.5 and below
D) -2.5 and below with a history of a fragility fracture
E) -3.0 and below
Correct Answer: B) Between -1.0 and -2.5
Rationale: The WHO classification for bone density in postmenopausal women and men
over 50 is: Normal (T-score ≥ -1.0), Osteopenia (T-score between -1.0 and -2.5), and
Osteoporosis (T-score ≤ -2.5). A score of -2.5 or lower with a fragility fracture is categorized
as "Severe" or "Established" Osteoporosis.
, 2
Question 3
Which of the following describes the "Z-score" in a DXA report?
A) Comparison to a young-adult peak bone mass population.
B) Comparison to an age-matched, sex-matched, and ethnicity-matched population.
C) The absolute risk of a fracture over the next 10 years.
D) The percentage of bone lost since the patient’s last scan.
E) The coefficient of variation for the facility's precision.
Correct Answer: B) Comparison to an age-matched, sex-matched, and ethnicity-matched
population.
Rationale: The Z-score compares the patient to others of their own age. This is useful for
identifying "secondary" causes of bone loss. If a Z-score is -2.0 or lower, it is considered
"below the expected range for age" and warrants a medical workup for underlying
conditions like hyperparathyroidism or vitamin D deficiency.
Question 4
In the context of DXA quality control, what is a "Shewhart Chart" used for?
A) To determine the patient’s 10-year fracture risk.
B) To track and plot daily phantom BMD values to monitor machine stability.
C) To calculate the Least Significant Change (LSC).
D) To compare Hologic values to GE-Lunar values.
E) To measure the thickness of the patient’s soft tissue.
Correct Answer: B) To track and plot daily phantom BMD values to monitor machine
stability.
Rationale: Quality Control (QC) is performed by scanning a phantom of known density.
The results are plotted on a Shewhart chart, which uses statistical limits (Standard
Deviations) to identify if the machine’s calibration is drifting or if it has "shifted" out of
acceptable range, which would invalidate patient results.
Question 5
Which of the following refers to the "Least Significant Change" (LSC)?
A) The smallest bone in the lumbar spine.
, 3
B) The magnitude of BMD change required to be 95% confident that the change is real.
C) The change in a T-score from -2.4 to -2.5.
D) The minimum amount of calcium a patient must take daily.
E) The difference between the 33% radius and the ultra-distal radius.
Correct Answer: B) The magnitude of BMD change required to be 95% confident that the
change is real.
Rationale: Because of inherent "noise" or error in scanning (precision error), not every
change in BMD from one year to the next is biological. The LSC is a mathematical
threshold calculated from a facility's precision study. If a patient's change exceeds the LSC,
it is statistically significant; if not, it must be attributed to measurement error.
Question 6
What is the primary function of the "Dual-Energy" X-ray beam in DXA?
A) To scan two patients at once.
B) To provide a color image of the bone.
C) To separate bone from soft tissue by utilizing different attenuation at different energies.
D) To reduce the radiation dose to the technologist.
E) To allow the scan to be performed through lead shielding.
Correct Answer: C) To separate bone from soft tissue by utilizing different attenuation at
different energies.
Rationale: X-rays are absorbed differently by bone and soft tissue. By using two energy
peaks (High and Low), the DXA system can solve mathematical equations to "subtract" the
soft tissue components (fat and lean mass), allowing the remaining attenuation data to
represent bone mineral only.
Question 7
Which lumbar vertebra typically has the largest transverse processes and is often used as a
landmark for identifying the lumbar spine?
A) L1
B) L2
C) L3
, 4
D) L4
E) L5
Correct Answer: C) L3
Rationale: In a standard PA spine scan, L3 is usually the "anchor" or central vertebra. It
typically features the largest and most distinct transverse processes. Recognizing this helps
the technologist correctly label the spine from L1 to L4.
Question 8
Why is the hip (proximal femur) scan usually performed with the foot internally rotated 15 to 25
degrees?
A) To make the patient more comfortable.
B) To maximize the length of the femoral neck and place it parallel to the table.
C) To minimize the amount of soft tissue over the femur.
D) To allow the greater trochanter to be hidden behind the shaft.
E) To ensure the femoral head is not seen in the scan.
Correct Answer: B) To maximize the length of the femoral neck and place it parallel to the
table.
Rationale: Anatomically, the femoral neck is angled anteriorly. By rotating the foot inward
(toes in), the neck is moved into a position parallel to the scan table. This allows for the
most accurate and reproducible measurement of the femoral neck area, which is a critical
ROI for diagnosing osteoporosis.
Question 9
What does the "FRAX" tool calculate?
A) The patient's exact bone mineral content in grams.
B) The 10-year probability of a major osteoporotic fracture.
C) The percentage of cortical bone in the forearm.
D) The amount of radiation absorbed by the patient (Gys).
E) The effectiveness of bisphosphonate medications.
Correct Answer: B) The 10-year probability of a major osteoporotic fracture.
Rationale: FRAX (Fracture Risk Assessment Tool) is a computer algorithm developed by
And Correct Detailed Answers (Verified Answers) |Already Graded A+
Question 1
Bone Mineral Density (BMD) as measured by DXA is expressed as "areal" density. What are the
specific units used?
A) mg/cm³
B) g/cm²
C) mg/dL
D) g/mm
E) HU (Hounsfield Units)
Correct Answer: B) g/cm²
Rationale: DXA is a two-dimensional projection technique. It measures the bone mineral
content (BMC) in grams and divides it by the area of the bone being scanned in square
centimeters. Because it lacks a "depth" or volume component, it is considered an "areal"
measurement rather than a true volumetric density (which would be mg/cm³ as seen in
QCT).
Question 2
According to the World Health Organization (WHO), what T-score range defines "Osteopenia" or
low bone mass?
A) -1.0 and above
B) Between -1.0 and -2.5
C) -2.5 and below
D) -2.5 and below with a history of a fragility fracture
E) -3.0 and below
Correct Answer: B) Between -1.0 and -2.5
Rationale: The WHO classification for bone density in postmenopausal women and men
over 50 is: Normal (T-score ≥ -1.0), Osteopenia (T-score between -1.0 and -2.5), and
Osteoporosis (T-score ≤ -2.5). A score of -2.5 or lower with a fragility fracture is categorized
as "Severe" or "Established" Osteoporosis.
, 2
Question 3
Which of the following describes the "Z-score" in a DXA report?
A) Comparison to a young-adult peak bone mass population.
B) Comparison to an age-matched, sex-matched, and ethnicity-matched population.
C) The absolute risk of a fracture over the next 10 years.
D) The percentage of bone lost since the patient’s last scan.
E) The coefficient of variation for the facility's precision.
Correct Answer: B) Comparison to an age-matched, sex-matched, and ethnicity-matched
population.
Rationale: The Z-score compares the patient to others of their own age. This is useful for
identifying "secondary" causes of bone loss. If a Z-score is -2.0 or lower, it is considered
"below the expected range for age" and warrants a medical workup for underlying
conditions like hyperparathyroidism or vitamin D deficiency.
Question 4
In the context of DXA quality control, what is a "Shewhart Chart" used for?
A) To determine the patient’s 10-year fracture risk.
B) To track and plot daily phantom BMD values to monitor machine stability.
C) To calculate the Least Significant Change (LSC).
D) To compare Hologic values to GE-Lunar values.
E) To measure the thickness of the patient’s soft tissue.
Correct Answer: B) To track and plot daily phantom BMD values to monitor machine
stability.
Rationale: Quality Control (QC) is performed by scanning a phantom of known density.
The results are plotted on a Shewhart chart, which uses statistical limits (Standard
Deviations) to identify if the machine’s calibration is drifting or if it has "shifted" out of
acceptable range, which would invalidate patient results.
Question 5
Which of the following refers to the "Least Significant Change" (LSC)?
A) The smallest bone in the lumbar spine.
, 3
B) The magnitude of BMD change required to be 95% confident that the change is real.
C) The change in a T-score from -2.4 to -2.5.
D) The minimum amount of calcium a patient must take daily.
E) The difference between the 33% radius and the ultra-distal radius.
Correct Answer: B) The magnitude of BMD change required to be 95% confident that the
change is real.
Rationale: Because of inherent "noise" or error in scanning (precision error), not every
change in BMD from one year to the next is biological. The LSC is a mathematical
threshold calculated from a facility's precision study. If a patient's change exceeds the LSC,
it is statistically significant; if not, it must be attributed to measurement error.
Question 6
What is the primary function of the "Dual-Energy" X-ray beam in DXA?
A) To scan two patients at once.
B) To provide a color image of the bone.
C) To separate bone from soft tissue by utilizing different attenuation at different energies.
D) To reduce the radiation dose to the technologist.
E) To allow the scan to be performed through lead shielding.
Correct Answer: C) To separate bone from soft tissue by utilizing different attenuation at
different energies.
Rationale: X-rays are absorbed differently by bone and soft tissue. By using two energy
peaks (High and Low), the DXA system can solve mathematical equations to "subtract" the
soft tissue components (fat and lean mass), allowing the remaining attenuation data to
represent bone mineral only.
Question 7
Which lumbar vertebra typically has the largest transverse processes and is often used as a
landmark for identifying the lumbar spine?
A) L1
B) L2
C) L3
, 4
D) L4
E) L5
Correct Answer: C) L3
Rationale: In a standard PA spine scan, L3 is usually the "anchor" or central vertebra. It
typically features the largest and most distinct transverse processes. Recognizing this helps
the technologist correctly label the spine from L1 to L4.
Question 8
Why is the hip (proximal femur) scan usually performed with the foot internally rotated 15 to 25
degrees?
A) To make the patient more comfortable.
B) To maximize the length of the femoral neck and place it parallel to the table.
C) To minimize the amount of soft tissue over the femur.
D) To allow the greater trochanter to be hidden behind the shaft.
E) To ensure the femoral head is not seen in the scan.
Correct Answer: B) To maximize the length of the femoral neck and place it parallel to the
table.
Rationale: Anatomically, the femoral neck is angled anteriorly. By rotating the foot inward
(toes in), the neck is moved into a position parallel to the scan table. This allows for the
most accurate and reproducible measurement of the femoral neck area, which is a critical
ROI for diagnosing osteoporosis.
Question 9
What does the "FRAX" tool calculate?
A) The patient's exact bone mineral content in grams.
B) The 10-year probability of a major osteoporotic fracture.
C) The percentage of cortical bone in the forearm.
D) The amount of radiation absorbed by the patient (Gys).
E) The effectiveness of bisphosphonate medications.
Correct Answer: B) The 10-year probability of a major osteoporotic fracture.
Rationale: FRAX (Fracture Risk Assessment Tool) is a computer algorithm developed by
