Bone Density QCT
DEXA and Bone Density
We don’t often think of bones as tissue, but our bones are actually a type of connective tissue, the most common tissue in the human body. Cartilage, bone marrow and blood are also types of connective tissue. In addition to making blood cells (red blood cells, white blood cells and platelets) our bones are so important because they basically hold us together, protect vital organs and allow us to move efficiently.
As with any other human structure, bones can develop problems that may seriously impact our health. The most common bone diseases is osteoporosis, a condition that happens when we lose too much bone, don’t make enough bone, or a combination of both.
Osteoporosis can lead to an increased risk of bone fracture, including hip, spine and wrist. That’s why the National Osteoporosis Foundation (NOF) recommends a bone mineral density test for women age 65 and older, those age 60 to 64 with risk factors for osteoporosis, and women over 45 who have broken any bones. Testing is recommend for men age 50 to 69 with one or more risk factors for osteoporosis, and for men age 70 or older, even without any risk factors.
Osteoporosis can be prevented, treated, and in some cases even partially reversed, and bone mineral density testing can tell patients if they have low bone density or osteoporosis before outward signs appear. But what’s the best test? There are two primary types of bone mineral density tests: DXA and QCT. Both are used in standard medical care and are available in the Flagstaff area. DXA has been around longer and is more common, but QCT can provide more detailed readings, which can be helpful in certain situations. What’s most important is to stay with one method or the other. That makes it easy to track changes in bone density from year to year and determine how treatments and lifestyle changes are affecting osteoporosis or osteopenia (low bone mass, which can lead to osteoporosis).
DXA (or DEXA) stands for dual energy X-ray absorptiometry. DXA uses extremely low energy X-rays and is considered very safe. (As with other procedures, pregnant women should not have X-rays, even at very low doses). Standard X-rays are not used for bone density testing since they can’t detect osteoporosis until it is well advanced. DXA is most often performed on the lower spine and hips, where abnormal bone loss has the most impact.
QCT stands for quantitative computed tomography; it is a low-dose CT scan with special software that can be used to diagnose or monitor osteoporosis. QCT is also most commonly performed on the lower spine. QCT is still less common than DXA scanning; however, the NOF considers both methods as safe and effective for the evaluation of bone mineral density. Other testing methods use ultrasound, CT or X-rays to check for peripheral bone density in the heel, wrist or finger. These methods are often offered for free or low-cost at health fairs, but it’s important to know that they cannot accurately diagnose osteoporosis. These peripheral tests basically let the individual know if he or she needs further testing.
Testing for low bone density is simple, cost-effective and can identify those at increased risk of osteoporosis before outward signs appear. As with many other conditions, early detection is the key to the best diagnosis and treatment possible. While DXA and QCT are both excellent options for bone mineral density testing, the best plan is to talk with your health care provider and stick with one method.
Stephen Ward, M.D.
Dr. Stephen Ward, born in Georgia, graduated from the medical college of Georgia in 1988. He completed his residency in Diagnostic Radiology at the Medical College of Georgia in 1993. He is certified with The American Board of Radiology. He has been a member of Northern Arizona Radiology since 1993.