DEXA (Bone Density Measurement)
The DEXA (Dual Energy X-ray Absorptiometry) device is used to determine bone density. Unlike standard X-ray images, DEXA scans emit X-ray beams at two different energies, allowing the system to measure two different attenuation values at each measurement point. Through calculations, these data provide information about the calcium content of the skeleton and the distribution of bone, muscle, and fat tissue within the scanned volume.
The Horizon WI DEXA device by Hologic, compared to other bone density measurement devices on the market, offers several new options for the diagnostic evaluation of the spine and peripheral skeleton. The duration of the examination is shortened.
Early detection and prevention are crucial because osteoporosis, when identified early, is a treatable disease. The only way to diagnose it before fractures occur is by quantifying bone density. Bone density measurements analyze the bone density in various skeletal areas, providing a risk assessment for future fractures.
If fractures are already present, density measurement can confirm the diagnosis and determine the severity of the bone break. There are various methods for measuring bone density. According to the World Health Organization (WHO) and the Dachverband Osteologie (DVO), the DEXA method is currently the most accurate and informative procedure for early detection of osteoporosis. It is an X-ray method with very low radiation exposure that measures the calcium hydroxylapatite content of the bone, thus allowing conclusions about bone mass.
Applications
With the introduction of bone density measurement, the diagnosis of osteoporosis can be made in an early, asymptomatic phase. Low bone density is recognized as a significant risk factor for fractures – akin to blood pressure and cholesterol levels as risk factors for cardiovascular diseases. The examination is particularly recommended for patients at increased risk of osteoporosis, including:
- Women after menopause
- Women with early loss of ovarian function (due to surgery, radiation, premature menopause, extreme menstrual disorders)
- Men with testosterone deficiency in old age
- Men after surgery, radiation, or chemotherapy of the testes
- Patients with a family history of osteoporosis
- Patients with high alcohol and nicotine consumption
- Patients with calcium deficiency or metabolic disorders
- Patients with low body weight or physical activity
- Use of corticosteroid medications
- Diseases of the intestines, kidneys, liver, or thyroid
- Type 1 diabetes mellitus
- Significant osteoporosis symptoms (e.g., bone pain)
Moreover, regular measurements are useful for monitoring the progression of osteoporosis or for therapy control.
Procedure
During the examination, you lie on your back on the examination table. With a small amount of X-ray radiation, about one hundredth of a chest X-ray, the device scans the area of interest. Typically, bone density is measured at two sites (the lumbar spine and femoral neck). The evaluation is done by computer, comparing your individual values to standard values. There are mainly two key figures: The T-Score indicates how your measured mineral salt content in a specific skeletal segment compares to the average value of young healthy individuals of your gender. The Z-Score is the measured difference in your bone density compared to patients in the same age group. In patients with osteoporosis, this value is in the negative range. The examination is painless, not stressful, and takes about 15 minutes. There are no known risks; however, pregnancy should be excluded.