The Bone Density test comes in many forms. You may have seen the small machines at Health Fairs or at your local pharmacy. These devices measure bone density by ultrasound technology. It is inexpensive, portable and there is no radiation exposure. Several studies have shown it to be a good predictor of fracture risk. It is sometimes called Quantitative Ultrasound(QUS).
However, ultrasound is not recommended to monitor osteoporosis long term because of limited precision of the machine and the fact that bone mass at peripheral sites (e.g. heel) changes very slowly. If an ultrasound test reveals an abnormal result we suggest obtaining a confirmatory DXA scan of the hip and spine osteochondrozė.
It is also possible to use Quantitative Computed Tomography (QCT) to measure bone density. It is used less often than DXA. It is more expensive, less reproducible and emits a higher radiation dose than DXA.
So let’s talk a little about DXA. DXA is short for Dual X-Ray Absorptiometry. It is also known as DEXA, Bone Densitometry or the Bone Mineral Density (BMD) test/scan. It is really the ‘gold standard’ of bone density measurement techniques. DXA uses a very low radiation dose. The radiation is equivalent to the dose received when flying on an airplane from San Francisco to New York! So as you can see the exposure is minimal, but you should NOT undergo a scan if there is any chance of you being pregnant. DXA measures the BMD in one hip and in the lumbar spine. A few centers will measure both hips. Smaller, more mobile peripheral DXA devices are also used(pDXA). Talk to your physician about which Bone Density Test is available in your area.
Dual X-Ray Absorptiometry (DXA) Scanner
So when you have had your scan you will be given a t-score. This is a statistical number that compares your bone density to that of a young adult. The more negative the t-score the worse your bone density. The lower the t-score the higher your risk of fracture. Take a look at this scale to see where your t-score lies. Take a look at this scale to see where your t-score lies