A Bone Densitometry (BMD) test measures the mineral density such as calcium in your bones using a special X-ray scan. From this information, an estimate of the strength of your bones can be made.
Calcium is constantly being added to and taken away from bone. When calcium is taken away faster than it is added, the bones become lighter, less dense, and more porous. This makes the bones weaker and increases their risk of fracture.
Loss of bone mass occurs as part of the natural process of aging. Bones naturally become thinner as you grow older, because existing bone is broken down faster than new bone is made. This process is called osteopenia. As this occurs, the bones lose minerals, heaviness, and structure, making them weaker. With further bone loss, osteopenia develops into osteoporosis. The thicker your bones are, the longer it takes to develop osteoporosis. Although osteoporosis can occur in men, it is most common in women older than age 65.
Regular X-rays cannot detect mild bone loss. A bone must lose at least a quarter of its weight before a regular X-ray can detect the problem.
The bones most commonly measured in this scan, are those in the lower spine and hip. These bones generally have the greatest amount of bone loss and are at the highest risk of fracture. In special cases, bones in the wrist may be used.
Is there any preparation?
There is no preparation for this procedure. It is recommended that you wear clothing without metal zippers or clips as these can interfere with the image. If you have a hip replacement you should inform the technician, as that hip cannot be used for scanning purposes.
What will happen?
A DEXA scan is a simple procedure. Two scans are performed, one of the hip and the other of the lower spine. These two areas are most commonly used as they are the first areas to be affected by osteoporosis, as well as being the areas most at risk from a fracture.
You will be placed on a bed - underneath is an X-ray source that produces very low energy X-rays. The scanning arm, which houses the X -ray detectors, will pass over you as the scan is performed. The detectors read the energy level of the X-ray beam after it has passed through your body and can thus calculate the density of the bone.
The radiographer will then process this information to produce a representative image of the area with calculations of bone density and fracture risk.
Contra-indications
Patients who have recently had a nuclear medicine scan performed must wait 3 weeks from that procedure before having the DEXA study performed.
Even though the radiation levels are extremely low, a DEXA study still uses ionising radiation and so is not recommended for women who are pregnant.
Results
Your referring doctor will receive a report from the Radiologist. This usually takes 2- 3 working days.
Please Ask
We know that most patients are anxious about having tests performed. If you have any questions or concerns, please ask our staff.