Measurement Tools -- Dual Energy X-Ray Absorptiometry (DEXA)

What It Is

DEXA is based on dividing the body into three compartments: total body mineral (from bones), fat-free soft (lean) mass, and fat tissue mass.

	The person is scanned with photons that are generated by two low-dose x-rays at different energy levels.
	The body's absorption of the photons at the two levels is measured.
	The ratios arecan be then used to predict total body fat, fat-free mass, and total body bone mineral.

Equipment Used

A whole body scanner with the x-ray sources mounted beneath a table and a detector overhead.

How It's Done

Person lies on a table and is scanned. Measurements take about 10 - 20 minutes.

Used with permission from Tanita Corp. of America, Inc.

Pros

	It's considered a reference standard, and the latest body composition research uses this method.
	It's precise, accurate, and reliable.
	It's safe.
	It's noninvasive.
	It can be used to determine body fat distribution.

Cons

	The narrow table limits its use with heavier people.
	The equipment is expensive.
	It's used primarily in laboratory settings.

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