Bone Density Scan (DEXA Scan): Preparation and Procedure
Why are Bone Density Scans done?
- Evaluation of persons at risk for osteoporosis
- Follow up for patients with predetermined osteoporosis or known bone demineralization
- Evaluation of response to treatment of osteoporosis
What is a DEXA Scan?
Dual energy X-ray absorptiometry (DEXA) scans are a common technique used to measure bone density. This completely painless procedure is easily performed and exposes the patient to minimal radiation.
DEXA Scan Preparation
- No prior radionuclide studies for 2 weeks
- No barium contrast studies for 2 weeks
- No metal in clothing (i.e. zippers)
DEXA Scan Procedure
A bone density scan or DEXA scan takes approximately 15 minutes. You will be asked to lie down on a table. A small X-ray will scan your lumbar spine and both hips. From the images the doctor will be able to evaluate bone mineral (calcium) content of the bone. The amount of calcium correlates with bony content and with bone strength. The amount of calcium in bone is compared to a database of normal patients, with standard deviations from normal reported as a T-score. A T score of -1 to -2.5 (standard deviations below mean) is considered osteopenia, while T-score of less than -2.5 is considered osteoporosis, based on WHO criteria. Women are especially prone to develop osteoporosis after menopause, when they lose the protective affects of estrogen, while men usually are affected less frequently. Vertebral and hip fractures are common consequences of osteoporosis.
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