What is bone densitometry (DEXA)?
Bone densitometry (also called dual-energy X-ray absorptiometry, DEXA or DXA) is a type of imaging exam that uses a very small amount of radiation to measure the density of your bones. Like other types of X-ray exams, DEXA is noninvasive and painless. DEXA is most commonly used to determine if a person has osteoporosis (a condition that causes your bones to become porous and weak) or is at risk for developing osteoporosis. In fact, DEXA is the most commonly used method for diagnosing the disease.
How DEXA works
DEXA uses “simple math” to calculate the mineral density of your bones. During the exam, the DEXA machine emits a beam of X-ray energy that passes through your bones. Another device measures the amount of energy as the X-rays exit your body. Since bone tissue is dense, it absorbs more X-ray energy than the surrounding soft tissue. By measuring the amount of X-ray energy that leaves your body, the DEXA machine can calculate how much has been absorbed, and that data can be used to determine the density of your bones. DEXA is usually performed on your hip or your spine, two areas that are especially prone to fractures due to osteoporosis.
DEXA uses very low levels of X-ray radiation to minimize your exposure. In fact, the amount is so low, the technician can remain next to you at the DEXA console throughout the exam. At the end of the scan, the DEXA machine provides both graphic and numerical data that can be used to evaluate your risk for osteoporosis and fractures. Your data can also be compared to a database of other people of the same age and sex to determine your relative risk.
What to expect during a DEXA scan
Windsor Radiology uses the most advanced DEXA technology for precise and accurate results. During your exam, you’ll lie on an exam table with the “arm” of the DEXA machine positioned above you. The exam itself takes just a few moments and it’s completely painless. You’ll need to lie still for a few moments while the X-rays are being emitted. Once your exam is complete, the DEXA computer will analyze the data and prepare a report which will be analyzed by one of our board-certified radiologists. The final findings will then be forwarded to your doctor. The report will contain both your bone mineral density or BMD, as well as your FRAX report, which provides a 10-year probability for hip and osteoporotic fractures (including fractures in your spine, arm, shoulder or hip). Since the exam measures the mineral content of your bones, you shouldn't take calcium supplements for 24 hours prior to your scan.
DXA for body composition analysis
Body composition analysis is conducted in much the same way as a standard bone density exam, but in addition to measuring your bone density, this analysis also determines the amount of fat, lean muscle, and visceral fat (fat located in your belly area). Large amounts of visceral fat have been linked with higher risks for diseases, including cardiovascular disease and type 2 diabetes. Body composition provides you with your fat mass index or FMI, which reflects the amount of fat you have in your body in relation to your height. Body composition analysis can be very useful in managing obesity, for helping athletes train better and it's also very useful for determining age-related muscle loss.