DEXA Body Composition Analysis & DXA Clinical Applications 2

Question 1

What is the primary clinical significance of a high fat mass index (FMI) combined with a low lean mass index (LMI) on DXA body composition analysis?

Accepted Answer

It suggests sarcopenic obesity, a condition associated with increased metabolic and functional risk

Answer

It indicates primary hyperparathyroidism

Answer

It confirms a diagnosis of anorexia nervosa

Answer

It is a normal finding in elite endurance athletes

Question 2

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

Accepted Answer

Hips, buttocks, and upper thighs

Answer

Lumbar spine and pelvis

Answer

Upper arms and shoulders

Answer

Lower legs and ankles

Question 3

Which DXA-derived measurement is most useful for monitoring response to resistance training in a clinical exercise program?

Accepted Answer

Appendicular lean mass (ALM)

Answer

Total bone mineral density (BMD)

Answer

Visceral adipose tissue (VAT) volume

Answer

Fat mass index (FMI)

Question 4

When comparing DXA body composition results across serial scans, the technologist should ensure:

Accepted Answer

The same DXA system and software version are used for each scan

Answer

The patient fasts for 24 hours before each scan to standardize hydration

Answer

The patient wears the same clothing for all follow-up scans

Answer

Scans are always performed in the morning to control circadian variation

Question 5

The precision error (CV%) for DXA whole-body fat mass measurement in a well-controlled clinical setting is typically:

Accepted Answer

1–3%

Answer

Less than 1%

Answer

5–10%

Answer

Greater than 15%

Question 6

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

Accepted Answer

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

Answer

The scan will overestimate bone mineral density due to beam hardening

Answer

The radiation dose will be too high for the patient to receive the scan

Answer

The DXA software cannot generate a body composition report above a BMI of 35

Question 7

In DXA body composition analysis, the 'R-value' (or tissue ratio) is used to:

Accepted Answer

Differentiate lean soft tissue from fat based on differential X-ray attenuation at two energy levels

Answer

Calculate the patient's 10-year fracture risk

Answer

Measure the ratio of android to gynoid fat

Answer

Estimate visceral fat from subcutaneous fat thickness