ISCD Certified Bone Densitometry Technologist (CBDT®) — Questions and Answers

Question 1: Which patients need extra precaution during a scan?

Smokers
Children
Elderly
Pregnant patients (Correct answer)

Correct answer: Pregnant patients

Pregnant patients require extra precaution during any procedure involving radiation, including DEXA scans. Although DEXA uses a very low dose of radiation, there is still a potential risk to the developing fetus. Therefore, pregnancy should always be screened for, and the scan should typically be postponed or performed only if absolutely medically necessary and with appropriate shielding after consultation with a radiologist.

Question 2: Which condition requires DEXA monitoring and is caused by elevated endogenous cortisol due to a pituitary or adrenal tumor?

Cushing's syndrome (Correct answer)
Hyperparathyroidism
Fibrous dysplasia
Paget's disease of bone

Correct answer: Cushing's syndrome

Cushing's syndrome causes endogenous glucocorticoid excess, leading to secondary osteoporosis that requires BMD monitoring via DEXA.

Question 3: Which anabolic agent used for osteoporosis treatment stimulates new bone formation by mimicking parathyroid hormone?

Teriparatide (Forteo) (Correct answer)
Denosumab (Prolia)
Raloxifene (Evista)
Zoledronic acid (Reclast)

Correct answer: Teriparatide (Forteo)

Teriparatide is a recombinant PTH(1-34) analog that activates osteoblasts to build new bone, making it an anabolic (bone-building) therapy.

Question 4: When a DEXA professional identifies a potential regulatory violation, the CORRECT first step is to:

Wait to see if it resolves on its own
Address it only if directly affected
Document the violation and report through proper channels (Correct answer)
Discuss it casually with coworkers

Correct answer: Document the violation and report through proper channels

Proper documentation and reporting through established channels ensures accountability.

Question 5: In a serial DEXA report, the phrase 'statistically significant decrease in BMD' should only be used when:

Any decrease in T-score is observed
The patient's physician requests it
The Z-score drops below -2.0
The BMD change exceeds the facility-specific Least Significant Change (LSC) (Correct answer)

Correct answer: The BMD change exceeds the facility-specific Least Significant Change (LSC)

A statistically significant change is defined as BMD change exceeding the LSC, which accounts for measurement precision at that specific facility.

Question 6: Denosumab (Prolia) reduces bone resorption by inhibiting which signaling molecule?

Interleukin-6 (IL-6)
Calcitonin receptor
RANK ligand (RANKL) (Correct answer)
Sclerostin

Correct answer: RANK ligand (RANKL)

Denosumab is a monoclonal antibody that binds and neutralizes RANKL, blocking osteoclast differentiation and activity.

Question 7: A patient with severe obesity (BMI > 40) presents for a DXA body composition scan. The main technical limitation to address is:

The radiation dose will be too high for the patient to receive the scan
The patient may exceed the table weight limit and scan field width, causing tissue truncation (Correct answer)
The DXA software cannot generate a body composition report above a BMI of 35
The scan will overestimate bone mineral density due to beam hardening

Correct answer: The patient may exceed the table weight limit and scan field width, causing tissue truncation

Obese patients may exceed the weight limit of the DXA table (commonly 350–450 lbs) and may be wider than the scan field, leading to truncation artifacts that invalidate body composition results.

Question 8: What does a Z-score compare?

Water weight
Fat mass
Daily height changes
Bone density of age-matched peers (Correct answer)

Correct answer: Bone density of age-matched peers

A Z-score in DEXA scanning compares a patient's Bone Mineral Density (BMD) to the average BMD of individuals of the same age, sex, and ethnic background. This score is primarily used for children, premenopausal women, and men under 50 to determine if their bone density is lower than expected for their age, helping identify secondary causes of low bone mass.

Question 9: A patient has severe scoliosis affecting the lumbar spine. What is the most appropriate alternative site for BMD measurement?

Femoral neck only
Distal forearm (33% radius) (Correct answer)
Calcaneus
Thoracic spine

Correct answer: Distal forearm (33% radius)

The distal forearm (33% radius site) is the recommended alternative when the lumbar spine cannot be accurately measured due to scoliosis or other artifacts.

Question 10: In DEXA Bone Density Scan Certification, what is the PRIMARY purpose of conducting regular safety drills and exercises?

To ensure personnel can respond effectively in emergencies (Correct answer)
To reduce daily workload
To satisfy insurance requirements only
To evaluate employee performance reviews

Correct answer: To ensure personnel can respond effectively in emergencies

Regular safety drills ensure that all personnel are prepared to respond effectively during actual emergencies.

Question 11: Which reference database should be used when generating Z-scores for DXA body composition parameters in a 30-year-old female patient?

The young-adult peak reference (T-score style)
A BMI-matched reference cohort regardless of age
An age- and sex-matched reference population (Z-score) (Correct answer)
The NHANES pediatric reference database

Correct answer: An age- and sex-matched reference population (Z-score)

Z-scores for body composition compare the patient to an age- and sex-matched normative population, which is the appropriate reference for adults of all ages.

Question 12: Which position is commonly used in a DEXA scan?

Prone
Supine (Correct answer)
Sitting
Standing

Correct answer: Supine

During a DEXA scan, the patient is most commonly positioned supine, meaning lying flat on their back on the examination table. This position ensures optimal alignment and stability for accurate imaging of the lumbar spine and hip, which are the most frequently scanned areas. The supine position minimizes movement artifacts and allows for consistent measurements.

Question 13: A DXA report shows an Android/Gynoid (A/G) fat ratio of 1.4 in a 55-year-old male patient. This finding is clinically significant because:

This ratio reflects bone density rather than fat distribution
A/G ratios above 1.0 are normal in males and require no clinical action
An elevated A/G ratio is associated with increased cardiovascular and metabolic disease risk (Correct answer)
It indicates the patient has a favorable fat distribution pattern

Correct answer: An elevated A/G ratio is associated with increased cardiovascular and metabolic disease risk

An elevated A/G ratio indicates disproportionate central (abdominal) fat accumulation relative to peripheral fat, a pattern strongly associated with insulin resistance, dyslipidemia, and cardiovascular disease.

Question 14: Which of the following best describes trabecular (cancellous) bone architecture?

Solid cortical shell with no internal pores
Avascular tissue composed of hyaline cartilage
Dense, solid matrix with haversian canals
Sponge-like network of plates and rods called trabeculae (Correct answer)

Correct answer: Sponge-like network of plates and rods called trabeculae

Trabecular bone consists of an interconnected lattice of bony struts (trabeculae) enclosing spaces filled with bone marrow.

Question 15: In male osteoporosis, which hormone deficiency is a critical secondary cause that should be assessed before starting treatment?

Thyroid hormone deficiency (hypothyroidism)
Estrogen excess
Growth hormone excess
Testosterone deficiency (hypogonadism) (Correct answer)

Correct answer: Testosterone deficiency (hypogonadism)

Hypogonadism is the most important secondary cause of male osteoporosis and must be evaluated before initiating pharmacotherapy.

Question 16: Which metric best describes the ratio of appendicular lean mass to body weight squared, commonly used to screen for sarcopenia?

Relative skeletal muscle index (RSMI) (Correct answer)
Fat mass index (FMI)
Visceral fat area (VFA)
Body mass index (BMI)

Correct answer: Relative skeletal muscle index (RSMI)

The Relative Skeletal Muscle Index (RSMI) is calculated as appendicular lean mass (kg) divided by height squared (m²) and is a primary DXA-based criterion for diagnosing sarcopenia.

Question 17: What is the recommended action if the femoral neck region of interest (ROI) is placed incorrectly during analysis?

Use the trochanter value as a substitute
Accept the result because software auto-corrects errors
Rescan the patient immediately
Reposition the ROI manually and reanalyze the scan (Correct answer)

Correct answer: Reposition the ROI manually and reanalyze the scan

Manual repositioning and reanalysis of the ROI is required to ensure accurate femoral neck BMD measurement without repeating radiation exposure.

Question 18: On a DXA whole-body scan printout, the 'gynoid' region of interest (ROI) encompasses primarily the:

Upper arms and shoulders
Hips, buttocks, and upper thighs (Correct answer)
Lumbar spine and pelvis
Lower legs and ankles

Correct answer: Hips, buttocks, and upper thighs

The gynoid ROI covers the hips, buttocks, and upper thighs, capturing fat distribution characteristic of the pear-shaped body pattern.

Question 19: A DEXA report includes a FRAX® score. What does this score estimate?

10-year probability of major osteoporotic fracture (Correct answer)
Bone mineral content in grams
Rate of bone loss per year
Trabecular bone score

Correct answer: 10-year probability of major osteoporotic fracture

FRAX® calculates the 10-year probability of a major osteoporotic or hip fracture using BMD and clinical risk factors.

Question 20: On a DEXA report, the Z-score compares bone density to which reference population?

The same patient's prior scan
Age-matched and sex-matched peers (Correct answer)
Young adult peak bone mass
Postmenopausal women only

Correct answer: Age-matched and sex-matched peers

The Z-score compares a patient's BMD to age-matched and sex-matched reference norms.

Question 21: A technologist notices the DXA table laser alignment light does not activate during startup. What is the correct response?

Manually estimate patient positioning without the laser
Document and report the malfunction; do not scan until serviced (Correct answer)
Replace the laser module immediately and continue scanning
Continue scanning; the laser is only for convenience

Correct answer: Document and report the malfunction; do not scan until serviced

Malfunctioning positioning lasers should be reported and the unit should not be used for clinical scanning until the equipment is serviced and verified.

Question 22: A patient's follow-up spine BMD shows a statistically significant decrease despite 2 years of bisphosphonate therapy. What does this indicate?

Normal expected response to bisphosphonate therapy
Possible treatment failure, non-adherence, or secondary cause of bone loss requiring clinical evaluation (Correct answer)
The DEXA machine needs recalibration
The patient must switch to calcium supplements only

Correct answer: Possible treatment failure, non-adherence, or secondary cause of bone loss requiring clinical evaluation

A significant BMD decrease despite therapy signals potential treatment failure, poor adherence, or an undiagnosed secondary cause of bone loss.

Question 23: The EWGSOP2 (European Working Group on Sarcopenia in Older People) recommends which DXA-based cutoff for low appendicular lean mass index (ALM/ht²) in men?

Less than 7.0 kg/m² (Correct answer)
Less than 4.0 kg/m²
Less than 5.5 kg/m²
Less than 9.0 kg/m²

Correct answer: Less than 7.0 kg/m²

EWGSOP2 recommends an ALM/ht² cutoff of < 7.0 kg/m² in men and < 5.5 kg/m² in women to define low muscle mass as part of the sarcopenia diagnosis.

Question 24: Why calibrate the DEXA machine regularly?

Avoid overheating
Speed up scan time
Reduce radiation
Ensure accurate scan results (Correct answer)

Correct answer: Ensure accurate scan results

Regular calibration of a DEXA machine is absolutely essential to ensure the accuracy and reliability of scan results. Calibration maintains the precision of the X-ray beams and detectors, guaranteeing that the measured bone mineral density values are consistent and correct over time. This is critical for accurate diagnosis, monitoring treatment effectiveness, and comparing results across different scans.

Question 25: What is the primary reason DEXA uses dual-energy X-ray rather than single-energy X-ray?

To reduce patient radiation dose
To differentiate bone mineral from soft tissue (Correct answer)
To increase image resolution
To shorten scan acquisition time

Correct answer: To differentiate bone mineral from soft tissue

Dual-energy X-ray allows mathematical subtraction of soft tissue attenuation, isolating bone mineral density values accurately.

Question 26: Which of the following findings on a DEXA scan report would most indicate the need for a Vertebral Fracture Assessment (VFA)?

BMI greater than 30
Height loss of 1.5 inches or more since peak height (Correct answer)
T-score of -1.2 at the femoral neck
Age under 50 with normal Z-scores

Correct answer: Height loss of 1.5 inches or more since peak height

ISCD indications for VFA include historical height loss ≥1.5 inches, which suggests possible vertebral compression fractures.

Question 27: On a pediatric DEXA report, which skeletal sites are recommended by ISCD for BMD assessment in children?

Total hip and lateral spine
Calcaneus and distal radius
Femoral neck and Ward's triangle
Lumbar spine (PA) and total body less head (TBLH) (Correct answer)

Correct answer: Lumbar spine (PA) and total body less head (TBLH)

ISCD recommends PA lumbar spine and total body less head (TBLH) as the primary sites for pediatric DXA, since hip norms for children are less robust.

Question 28: Which factor MOST significantly affects the quality of technical outcomes in DEXA practice?

The practitioner's training, preparation, and attention to detail (Correct answer)
Speed of procedure completion
The brand of equipment
The time of day

Correct answer: The practitioner's training, preparation, and attention to detail

Quality depends primarily on training, preparation, and attention to detail.

Question 29: In body composition DEXA reporting, lean mass, fat mass, and bone mineral content should sum to approximately what value?

Total soft tissue mass excluding bone
Total bone mass only
Total body water content
Total body weight as measured on a scale (Correct answer)

Correct answer: Total body weight as measured on a scale

In DEXA body composition, lean mass + fat mass + bone mineral content equals total body weight, which should closely match scale weight.

Question 30: Which FRAX input variable directly represents the skeletal impact of chronic glucocorticoid use?

Body mass index (BMI)
Spine fracture history field
Secondary osteoporosis checkbox and glucocorticoid input field (Correct answer)
Femoral neck BMD T-score only

Correct answer: Secondary osteoporosis checkbox and glucocorticoid input field

FRAX includes a secondary osteoporosis field and a separate glucocorticoid input that adjusts fracture probability upward for chronic steroid users.

Question 31: A patient with a pacemaker reports for a DEXA scan. How should the technologist proceed?

Perform only a peripheral forearm scan to avoid the chest
Consult the cardiologist before performing the scan
Refuse the scan; pacemakers are an absolute contraindication
Proceed with the scan; DEXA poses no known risk to pacemakers (Correct answer)

Correct answer: Proceed with the scan; DEXA poses no known risk to pacemakers

DEXA uses very low-dose X-rays with no electromagnetic fields that would interfere with pacemaker function, so the scan can proceed normally.

ISCD Certified Bone Densitometry Technologist (CBDT®)

The CBDT® exam certifies technologists in performing and analyzing DEXA bone density scans, covering bone physiology, radiation safety, DXA equipment, scan acquisition, and clinical data interpretation for osteoporosis assessment.

Questions

35 min

Time Limit

70%

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