(Bone Mineral Density [BMD] Test, Bone Density Test, Bone Mineral Content, Bone Absorptiometry)
What is bone densitometry?
Bone densitometry is used to measure the bone mineral content and density. This measurement can indicate decreased bone mass, a condition in which bones are more brittle and more prone to break or fracture easily. Bone densitometry is used primarily to diagnose osteoporosis and to determine fracture risk. The testing procedure measures the bone density of the bones of the spine, pelvis, lower arm, and thigh.
Bone densitometry testing may be done using X-rays, dual-energy X-ray absorptiometry (DEXA or DXA) or by quantitative CT scanning using special software to determine bone density of the hip or spine.
Standard X-rays may detect weakened bones. However, at the point where bone weakness is obvious on standard X-rays, the bone weakness may be too far advanced for treatment to be effective. Bone densitometry testing can determine decreasing bone density and strength at a much earlier stage when treatment of the bone weakness can be beneficial.
Before the procedure
Generally, no prior preparation, such as fasting or sedation, is required. However, you may be advised to stop taking calcium supplements 24-48 hours prior to your bone density test.
Notify the technologist if you are pregnant or suspect you may be pregnant.
During the procedure
Generally, bone densitometry follows this process:
In some cases, you may stay dressed but will be asked to remove all metallic objects, such as belt buckles, zippers, coins, keys, and jewelry. In other cases, you will be given a gown to wear so that no buttons, zippers, or hooks will interfere with the imaging process.
You will be positioned on an X-ray table, lying flat. Your legs will be supported on a padded box which serves to flatten the pelvis and lumbar spine.
Under the table, a photon generator will pass slowly beneath you, while an X-ray detector camera will pass above the table parallel to the photon generator beneath, projecting images of the lumbar and hip bones onto a computer monitor.
The computer will calculate the amount of photons that are not absorbed by the bones to determine the bone mineral content. The bone mineral density will then be reported by the radiologist.
While the bone densitometry procedure itself causes no pain, the manipulation of the body part being examined may cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
After the procedure
There is no special type of care following bone densitometry testing. You may resume your usual diet and activities, unless your doctor advises you differently.