What is a bone density scan (DEXA, DXA)?
Bone density test, also called dual-energy X-ray absorptiometry (DXA) or bone density measurement, is an improved form of X-ray technology used to measure bone loss. Dual-energy X-ray absorptiometry (DXA) is the standard in force today for measuring bone mineral density (BMD).
X-ray (radiography) is a non-invasive medical test that helps doctors diagnose and treat medical conditions. X-ray imaging involves exposing a part of the body to a small dose of ionizing radiation to produce images inside the body. X-rays are the oldest and most widely used form of medical imaging.
Dual-energy X-ray absorptiometry (DXA) is nearly often performed on the lower spine and hips. In children and some adults, the whole body is sometimes examined. Peripheral devices that use X-rays or ultrasound are sometimes used to detect a low bone mass, mostly in the forearm. In some societies, CT may also be used with special software to diagnose or monitor low bone mass (QCT). This is accurate but is less frequently used than the DXA scan.
How the dual-energy x-ray absorptiometry is performed?
A bone density test can be done in several ways. The most common and accurate method uses dual-energy X-ray absorptiometry (DEXA) scanning. DEXA uses a low-dose X-ray. (She receives more radiation from a chest X-ray.)
There are two types of Dual-energy X-ray absorptiometry (DEXA) assays:
- Central DEXA: You lie on a soft table. The scanner passes over the lower part of the spine and the hip. In most cases, you do not need to take off your clothes. This scan is the best test for predicting the risk of developing a fracture, especially of the hip.
- Peripheral DEXA (p-DEXA): These smaller devices measure the density of the bone in your wrist, fingers, leg, or heel. These machines are found in health care offices, pharmacies, malls, and health fairs.
How to prepare for the dual-energy x-ray absorptiometry?
- If you are or could be pregnant, tell your provider before having this test. Do not take calcium supplements for 24 hours before the test.
- You will be required to remove all metal items from your body, such as jewellery and buckles.
Who interprets the results and how will I get them?
A radiologist, a physician specially trained to supervise and interpret radiology examinations, analyzes the images and sends a signed report to your primary care or referring physician, who will discuss the results with you.
Dual-energy X-ray absorptiometry (DXA) scans are also interpreted by other doctors such as rheumatologists and endocrinologists. A physician should review your DXA scan while evaluating the presence of clinical risk factors such as:
- Rheumatoid arthritis
- Chronic renal and liver disease
- Respiratory disease
- Inflammatory bowel disease
Your test results will be in two degrees:
- T score: This number shows the amount of bone that I compared a young adult of the same sex with a peak bone mass. A grade of -1 and above is considered normal. A score between -1.1 and -2.4 is classified as osteopenia (low bone mass). A score of -2.5 and below is known as osteoporosis. The T score is used to estimate your risk of a fracture and also to determine whether treatment is required.
- Z score: This number reflects the amount of bone that you compared with other people of your age group and the same size and sex. If this score is unusually high or low, it may indicate the need for further medical tests.
Small changes are usually noticed between scans due to differences in positioning and are usually insignificant.
Risks of dual-energy X-ray absorptiometry
Bone mineral density uses a small amount of radiation. Most experts feel the risk is very low compared to the benefits of detecting osteoporosis before a bone is broken.