DXA FINAL EXAM PREP NEWEST ACTUAL EXAM WITH COMPLETE QUESTIONS
AND CORRECT DETAILED ANSWERS (VERIFIED ANSWERS) |ALREADY GRADED A+
Question 1
Which of the following is true regarding bone density values obtained from different DXA
manufacturers (e.g., GE-Lunar, Hologic, Norland)?
A) Values are identical across all devices.
B) Values obtained by different manufacturers will not be the same.
C) Hologic values are always higher than GE-Lunar values.
D) Values are only comparable if the patient is the same age.
E) Different manufacturers use the exact same reference databases.
Correct Answer: B) Values obtained by different manufactures will not be the same.
Rationale: Each DXA manufacturer uses proprietary methods for bone edge detection,
different calibration standards, and different dual-energy beam generation technologies.
Consequently, a BMD of 0.850 g/cm² on a Hologic scanner does not represent the same
physical density as 0.850 g/cm² on a GE-Lunar scanner. Standardized BMD (sBMD) was
developed to help bridge these differences, but raw values remain unique to the device.
Question 2
How is bone densitometry classified as a diagnostic tool?
A) Qualitative measurement technique
B) Quantitative measurement technique
C) Subjective assessment tool
D) Visual interpretation study only
E) Non-mathematical analysis
Correct Answer: B) Bone densitometry is considered a quantitative measurement technique.
Rationale: Unlike standard radiography, which is qualitative (visual assessment), DXA
provides a numerical value (g/cm²) representing bone mineral content divided by the area
of the bone. It involves precise mathematical calculations of X-ray attenuation, allowing for
the comparison of data against reference populations and serial measurements over time.
Question 3
Why do clinical guidelines recommend reporting the average BMD for L1-L4 rather than
, 2
focusing on individual lumbar vertebrae?
A) Because it is faster for the technologist to analyze.
B) Because individual vertebrae have higher precision.
C) Because accuracy and precision for contiguous vertebrae is superior to that of individual
vertebra.
D) To avoid seeing the ribs on the scan.
E) Because L1 always has the highest BMD.
Correct Answer: C) Average BMD for L1-L4 is reported rather than individual vertebra
because accuracy and precision for contiguous vertebrae is superior to that of individual
vertebra.
Rationale: The statistical reliability of the measurement increases as the area being
measured increases. By averaging L1 through L4, the "noise" or minor positioning errors
of a single vertebra are minimized, providing a more stable and reproducible number for
diagnosing osteoporosis and monitoring the effects of therapy.
Question 4
If the "percent young adult" value for a patient is 90%, which of the following is the correct
interpretation?
A) The patient has lost exactly 10% of their bone density.
B) The patient has 10% more bone than a young adult.
C) The patient's BMD is 90% of the peak bone mass of the reference population.
D) The patient has a T-score of -1.0.
E) The patient is in the 90th percentile for their age.
Correct Answer: C) The patient's BMD is 90% of the peak bone mass of the reference
population.
Rationale: The percent young adult value compares the patient to the expected peak bone
mass (100%). However, a value of 90% does not necessarily mean that specific patient
"lost" 10% of their bone; they may have never achieved 100% peak bone mass to begin
with due to genetics or lifestyle. Therefore, the statement that they "lost" 10% is false.
, 3
Question 5
What should be suspected if a patient has a significantly poor "percentage age-matched" (Z-
score) value?
A) Natural aging processes
B) Menopause/Estrogen loss
C) A secondary cause of bone loss other than age or estrogen loss
D) Excessive exercise
E) High calcium intake
Correct Answer: C) If a patient has a poor percentage age matched value, a cause other than
age or estrogen loss should be suspected.
Rationale: The Z-score compares the patient to others of the same age and sex. If a patient
is significantly below the average for their own age group, it suggests that something other
than "normal aging" is occurring, such as hyperparathyroidism, vitamin D deficiency, or
long-term steroid use.
Question 6
When comparing Dual-Energy X-ray Absorptiometry (DXA) with the older Dual Photon
Absorptiometry (DPA), DXA is preferred because:
A) It uses a radioactive source.
B) It is much slower than DPA.
C) It offers improved precision and shorter scan times.
D) It cannot measure the spine.
E) It has a higher radiation dose to the patient.
Correct Answer: C) When compared with DPA, DXA offers improved precision.
Rationale: DPA used a radioactive isotope (Gadolinium-153) which decayed over time,
leading to inconsistent beam intensity and poorer precision. DXA uses a stable X-ray tube
source, which provides a higher photon flux, much better image resolution, and superior
reproducibility (precision), which is critical for monitoring small changes in BMD.
Question 7
The image generated during a PA (Posteroanterior) spine DXA study consists primarily of which
, 4
elements?
A) The anterior elements (vertebral bodies)
B) The posterior elements (spinous processes and neural arch)
C) The transverse processes only
D) The intervertebral discs
E) The spinal cord tissue
Correct Answer: B) The appearance of the image on the PA spine DXA study consists mainly
of the posterior elements of the spine.
Rationale: In a PA projection, the X-ray beam passes through the posterior elements first.
Because these structures (the lamina, pedicles, and spinous processes) are highly
mineralized, they contribute significantly to the total BMD measured in a PA scan,
potentially masking bone loss that occurs primarily in the trabecular-rich vertebral body.
Question 8
Which of the following is true regarding lumbar anatomy in DXA patients?
A) Every patient has 5 lumbar vertebrae.
B) Ribs are always located on T12.
C) Anatomic variations, such as 4 or 6 lumbar vertebrae, occur in the population.
D) S1 is always the largest vertebra.
E) The pelvis never interferes with L5.
Correct Answer: C) All patients have 5 lumbar vertebrae and the lowest set of ribs on T12
(False).
Rationale: The technologist must be aware of anatomical variants. Some patients have
"lumbarized" T12 or "sacralized" L5. Assuming every patient has 5 lumbar vertebrae can
lead to mislabeling, which results in comparing the wrong vertebrae in follow-up studies
and inaccurate BMD calculations.
Question 9
What is the effect of a vertebral compression fracture on the BMD measurement of that specific
vertebra?
A) Falsely decreases the BMD.
AND CORRECT DETAILED ANSWERS (VERIFIED ANSWERS) |ALREADY GRADED A+
Question 1
Which of the following is true regarding bone density values obtained from different DXA
manufacturers (e.g., GE-Lunar, Hologic, Norland)?
A) Values are identical across all devices.
B) Values obtained by different manufacturers will not be the same.
C) Hologic values are always higher than GE-Lunar values.
D) Values are only comparable if the patient is the same age.
E) Different manufacturers use the exact same reference databases.
Correct Answer: B) Values obtained by different manufactures will not be the same.
Rationale: Each DXA manufacturer uses proprietary methods for bone edge detection,
different calibration standards, and different dual-energy beam generation technologies.
Consequently, a BMD of 0.850 g/cm² on a Hologic scanner does not represent the same
physical density as 0.850 g/cm² on a GE-Lunar scanner. Standardized BMD (sBMD) was
developed to help bridge these differences, but raw values remain unique to the device.
Question 2
How is bone densitometry classified as a diagnostic tool?
A) Qualitative measurement technique
B) Quantitative measurement technique
C) Subjective assessment tool
D) Visual interpretation study only
E) Non-mathematical analysis
Correct Answer: B) Bone densitometry is considered a quantitative measurement technique.
Rationale: Unlike standard radiography, which is qualitative (visual assessment), DXA
provides a numerical value (g/cm²) representing bone mineral content divided by the area
of the bone. It involves precise mathematical calculations of X-ray attenuation, allowing for
the comparison of data against reference populations and serial measurements over time.
Question 3
Why do clinical guidelines recommend reporting the average BMD for L1-L4 rather than
, 2
focusing on individual lumbar vertebrae?
A) Because it is faster for the technologist to analyze.
B) Because individual vertebrae have higher precision.
C) Because accuracy and precision for contiguous vertebrae is superior to that of individual
vertebra.
D) To avoid seeing the ribs on the scan.
E) Because L1 always has the highest BMD.
Correct Answer: C) Average BMD for L1-L4 is reported rather than individual vertebra
because accuracy and precision for contiguous vertebrae is superior to that of individual
vertebra.
Rationale: The statistical reliability of the measurement increases as the area being
measured increases. By averaging L1 through L4, the "noise" or minor positioning errors
of a single vertebra are minimized, providing a more stable and reproducible number for
diagnosing osteoporosis and monitoring the effects of therapy.
Question 4
If the "percent young adult" value for a patient is 90%, which of the following is the correct
interpretation?
A) The patient has lost exactly 10% of their bone density.
B) The patient has 10% more bone than a young adult.
C) The patient's BMD is 90% of the peak bone mass of the reference population.
D) The patient has a T-score of -1.0.
E) The patient is in the 90th percentile for their age.
Correct Answer: C) The patient's BMD is 90% of the peak bone mass of the reference
population.
Rationale: The percent young adult value compares the patient to the expected peak bone
mass (100%). However, a value of 90% does not necessarily mean that specific patient
"lost" 10% of their bone; they may have never achieved 100% peak bone mass to begin
with due to genetics or lifestyle. Therefore, the statement that they "lost" 10% is false.
, 3
Question 5
What should be suspected if a patient has a significantly poor "percentage age-matched" (Z-
score) value?
A) Natural aging processes
B) Menopause/Estrogen loss
C) A secondary cause of bone loss other than age or estrogen loss
D) Excessive exercise
E) High calcium intake
Correct Answer: C) If a patient has a poor percentage age matched value, a cause other than
age or estrogen loss should be suspected.
Rationale: The Z-score compares the patient to others of the same age and sex. If a patient
is significantly below the average for their own age group, it suggests that something other
than "normal aging" is occurring, such as hyperparathyroidism, vitamin D deficiency, or
long-term steroid use.
Question 6
When comparing Dual-Energy X-ray Absorptiometry (DXA) with the older Dual Photon
Absorptiometry (DPA), DXA is preferred because:
A) It uses a radioactive source.
B) It is much slower than DPA.
C) It offers improved precision and shorter scan times.
D) It cannot measure the spine.
E) It has a higher radiation dose to the patient.
Correct Answer: C) When compared with DPA, DXA offers improved precision.
Rationale: DPA used a radioactive isotope (Gadolinium-153) which decayed over time,
leading to inconsistent beam intensity and poorer precision. DXA uses a stable X-ray tube
source, which provides a higher photon flux, much better image resolution, and superior
reproducibility (precision), which is critical for monitoring small changes in BMD.
Question 7
The image generated during a PA (Posteroanterior) spine DXA study consists primarily of which
, 4
elements?
A) The anterior elements (vertebral bodies)
B) The posterior elements (spinous processes and neural arch)
C) The transverse processes only
D) The intervertebral discs
E) The spinal cord tissue
Correct Answer: B) The appearance of the image on the PA spine DXA study consists mainly
of the posterior elements of the spine.
Rationale: In a PA projection, the X-ray beam passes through the posterior elements first.
Because these structures (the lamina, pedicles, and spinous processes) are highly
mineralized, they contribute significantly to the total BMD measured in a PA scan,
potentially masking bone loss that occurs primarily in the trabecular-rich vertebral body.
Question 8
Which of the following is true regarding lumbar anatomy in DXA patients?
A) Every patient has 5 lumbar vertebrae.
B) Ribs are always located on T12.
C) Anatomic variations, such as 4 or 6 lumbar vertebrae, occur in the population.
D) S1 is always the largest vertebra.
E) The pelvis never interferes with L5.
Correct Answer: C) All patients have 5 lumbar vertebrae and the lowest set of ribs on T12
(False).
Rationale: The technologist must be aware of anatomical variants. Some patients have
"lumbarized" T12 or "sacralized" L5. Assuming every patient has 5 lumbar vertebrae can
lead to mislabeling, which results in comparing the wrong vertebrae in follow-up studies
and inaccurate BMD calculations.
Question 9
What is the effect of a vertebral compression fracture on the BMD measurement of that specific
vertebra?
A) Falsely decreases the BMD.
