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Department of Radiology Department of Radiology
  1. Department of Radiology
  2. Divisions
  3. Musculoskeletal Imaging
  4. Imaging & Services
  5. DEXA

Musculoskeletal Imaging & Interventional Services: DEXA

DEXA (Dual-emission X-ray absorptiometry)

DEXA (or DXA) is an x-ray examination used to calculate bone mineral density and diagnose osteoporosis. Osteoporosis may be diagnosed in postmenopausal women and in men age 50 and over. Osteoporosis increases one’s fracture risk, and DEXA can be used to calculate this risk.

Why Come to UCSD?

Our radiologists will provide expert interpretations of your DEXA exam, enabling your doctor to employ the appropriate treatment if you are diagnosed with osteoporosis or low bone mass.

How to Prepare for Your Exam?

You will be asked to fill out a questionnaire that includes personal history relevant to fracture risk. Please list any relevant medications, especially those that may affect bone mineral health. These include supplements, medications to treat osteoporosis, sex hormone treatments, cancer medications, and steroids. For women, it is important to know whether you have gone through menopause.

What do my Results Mean?

If you are a postmenopausal woman or a man aged 50 or older, your bone mineral density is compared to that of a young adult population to calculate the T-score. If your T-score greater than or equal to -1.0, your bone mineral density is normal. If your T-score is less than or equal to -2.5, you have osteoporosis and will typically need treatment to reduce fracture risk. If your T-score is in between -1.0 and -.2.5, your classification is low bone mass (osteopenia). In this case, we may calculate the FRAX score based on your hip bone mineral density and risk factors for fracture to determine the probability that you will sustain a fracture in 10 years, which can help your doctor determine whether or not you need to be treated.

If you are a premenopausal woman or a man under age 50, your bone mineral density is compared to that of a population of similar age, sex, and ethnicity to calculate the Z-score. If your Z-score is greater than -2.0, your bone mineral density is normal. If your Z-score is less than or equal to -2.0, your bone mineral density is below the expected range for age and you  may need treatment.   

Advanced Testing of Bone Strength with TBS

TBS means Trabecular Bone Score. This is a more recently developed test of your bone structure that is complementary to standard bone density testing. When TBS is combined with bone density testing, we learn more about your bone health than with bone density testing alone. TBS is important because about one-half of people who break bones do not have bone density that is classified as osteoporosis. TBS can help recognize these people and allow for more personalized care to prevent broken bones.

Below is an example of how TBS can help. These are two different patients with similar bone density. The one on the right has very poor bone structure compared with the one on the left and has a much higher risk of breaking bones. TBS can detect this degradation of bone structure. It can help us decide whether treatment is needed and what kind of treatment is best.

Bone

Good Bone

Good Bone Structure

 Poor Bone

Poor Bone

Poor Bone Structure

TBS does not require any additional scanning. It uses advanced software cleared by the FDA to measure your bone structure with the same scan that measures your bone density.