Bone density scanning, also called dual-energy x-ray absorptiometry (DEXA) or bone densitometry, is a form of x-ray technology used to measure bone loss. DEXA is most often used to diagnose osteoporosis, a gradual loss of calcium that causes bones to become thinner, more fragile and more likely to break. It is typically used to measure bone density of the hip and lumbar spine areas. DEXA can also be useful in the detection of bone loss due to prolonged steroid use, long-term thyroid replacement therapy, and to aid in the decision of pursuing hip replacement. The results of the scan may help your physician to determine what type of replacement therapy may be needed (e.g. estrogen, calcium, etc.).

A DEXA Scan is relatively easy to perform and the amount of radiation exposure is low (approximately 10% of a routine chest X-ray). The scanning procedure on average takes 20 minutes to complete and is painless and noninvasive. 

The DEXA machine produces two X-ray beams, each with different energy levels. One beam is high energy while the other is low energy. The amount of X-rays that pass through the bone is measured for each beam, which will vary depending on the thickness of the bone. Based on the difference between the two beams, the bone density is measured.

Physicians normally suggest a baseline test at age 65 (or after menopause for women), with follow-up exams as recommended by your doctor based on your results.

Drs. Aaron Douglas and Amy Servais are Certified Clinical Densitometrists (CCD), a professional certification in the field of bone densitometry designated by the International Society For Clinical Densitometry (ISCD).

For more information on bone health, the National Osteoporosis Foundation has many resources available, including two handouts: "Healthy Bones for Life" patient guide, and "Questions to Ask Your Healthcare Provider about Bone Health and Osteoporosis" checklist. Any additional questions or concerns should be discussed furthe with your healthcare provider.