A DEXA scan (Dual X-ray Absorptiometry) determines the bone mineral density (BMD) of a patient, with the intent of detecting signs of, or the existence of osteopenia, or osteoporosis, a progressive bone disease that decreases bone density and mass to the point where bones can fracture. DEXA Scans (or DXA scans) are also utilized to measure the total body composition and fat content of a patient with a high degree of accuracy.
There are several different factors that can measure a patient’s risk. The World Health Organization’s FRAX calculator is able to include several different clinical risk factors such as:
- Prior fragility fractures.
- Usage of glucocorticoids.
- Heavy smoking.
- Excess usage and intake of alcohol.
- Rheumatoid arthritis.
- A history of parental hip fracture.
- Chronic renal disease.
- Chronic liver disease.
- Chronic respiratory disease.
- Long-term usage of phenobarbital.
- Long-term usage of phenytoin.
- Celiac disease.
- Inflammatory bowel disease.
- Other related risks.
The scan is relatively easy to perform with little preparation needed, and the amount of exposure to radiation is low for patients. The dexa scanner creates two types of X-ray beams, each with different energy levels. One beam is high energy, and the other is low energy. Each beam is aimed at a patient’s bones and measures the level of X-rays that passes through the bone structure regarding density.
DEXA Scanning focuses on two main areas: the hip and spine regions. If either area can’t be measured, then the forearm can be used to substitute. Even though osteoporosis can affect the entire body, the BMD measurements of one area can be predictive of fractures that are located at other sites.
On average, scanning will usually take about 10 to 20 minutes to run through, and the procedure is noninvasive and painless for patients. There is also less radiation exposure performed from this test, especially in comparison to CAT scans or Radiographic Absorptiometry. In fact, the radiation received from a dexa scan is less than an airline flight to California to New York and back.
There are some limitations and reasons to withhold from using this test if the patient is pregnant (or believes that they are pregnant), previously had another X-ray that made use of contrast media within the last seven days (examples of cases: barium enema, upper GI, as well as some CAT scans), or if the patient has had a nuclear scan (including bone scans or thyroid studies) within the last seven days. Any patient that meets one of these conditions should not have a dexa scan performed.
In regards to the current clinical practice in paediatrics, dexa scans are one of the most widely utilized techniques used for bone measurement, as the procedure itself is more cost efficient than other types of tests, accessible, easy to use, and is able to provide an accurate estimation of bone mineral density in adults. The scans are more also more accurate than regular X-rays (to get the accuracy that a dexa scan can create, a patient would need to lose twenty to thirty percent of their bone density to show up on X-ray).
Some clinics will routinely perform scans on pediatric patients with conditions such as nutritional rickets, lupus, and Turner Syndrome. DEXA scans have been able to demonstrate the successful measurement of skeletal maturity and body fat composition, as well as to evaluate the effects of pharmaceutical therapy. It can also assist pediatricians in diagnosing and monitoring treatment of disorders of bone mass acquisition in childhood development.
On average, the U. S. Preventative Services Task Force recommends that women aged 65 and older should have a dexa scan performed. The scanning age for men isn’t quite as specific, though 70 years is the commonly preferred age, especially if they have causes of osteopenia or osteoporosis.