DXA (Dual X-ray Absorptiometry ) scans are used for determining bone
density and thus for diagnosis bone conditions such
as
osteoporosis and osteopenia . The work in much the same way as traditional X-rays – you lay under machine while it scans you. The process is quick, taking around 3 minutes, and completely painless. In fact it’s safer than even low-dose X-rays as less radiation is involved. (DXA was formerly referred to as DEXA.)
Who Will Be Scanned? If you are sent for a DXA scan, it is likely that you will be in one of the following at risk groups:
Post-menopausal women (whether naturally post-menopausal – having gone through “the change” – or surgically, having had a hysterectomy ) – hormonal changes reduce the protection your body gives to your bones
Long-term steroid users – people who have had long-term exposure to oral corticosteroids such as Prednisolone (typically chronic asthmatics and emphysemics ) tend to lose bone
density Ballet dancers (we had a lot of referrals from Birmingham Royal Ballet when I worked in Bone Densitometry) – partly due to the stress their exercises put onto their bones, and partly due to dietary concerns
People who suffer from eating disorders such as anorexia nervosa
People with a history of bone fractures
People with a family history of osteoporosis
(Women have a higher risk of osteoporosis and osteopenia due to endocrine reasons, especially lower testosterone levels. It’s highest instance is in women over 65.)
Evidence of low bone density may also come from machines that measure the bone density in your foot (though some professionals question the value of this type of scan), or evidence may be seen on an X-ray. If so your doctor will probably refer you for a DXA scan.
How is your bone density determined? Unless a special request for a full body scan has been made (or in some cases with children), the scan area is your hips and lower back area. This is because the signs of osteoporosis appear there first, so there’s no need to scan the whole body. As mentioned above, the process is quick and painless. The scan results will be reported by a radiologist.
For crucial points in your skeletal structure – vertebrae L1, L2 etc and both femoral necks – the scan will produce a “T score” and a “Z score”. 1.0 is the average figure for a T score with a normal range within a certain distance of that average at either side. The Z score is adjusted for age, as your bone density tends to go down as you get older. If your bone density is too low (or, rarely, too high) you may be seen by an additional bone expert (an endocrinologist with a special interest in metabolic bone disorders). The most basic treatment for prevention of bone mineral density loss is calcium and vitamin D supplementation , while other drugs such as Bisphosphonates (Alendronate, Risedronate, etc) may also be prescribed with a particular view to prevention of fractures.
That’s really all you need to know if you’re going to have a DXA scan, though normally the hospital will send you an information leaflet before your scan. It’s quick, painless, you don’t need to fast for it, and you can even have this scan if you’re pregnant or in a cast (unless it’s a whole body or possibly above knee cast). It really is one of the simplest, safest types of imaging you could possibly have. So if you were worried… don’t be!