Bone densitometry is also known as osteodensitometry. It enables the painless measurement of bone quality based on the mineral content. Bone density measurement helps to estimate the risk of bone fractures, for example due to osteoporosis. Various methods are used for this, which work with the help of radiation, usually X-rays.
You can find further information and selected specialists for bone density measurement here.
The measurement reveals the extent to which radiation is attenuated by the bones. This allows conclusions to be drawn about the level of mineral salts in the bone.
By measuring bone density, doctors can determine the general risk of bone fractures. It also plays an important role in the diagnosis and control of osteoporosis. Osteoporosis (bone loss) is an age-related bone disease that increases the risk of fractures.
Clinically significant fractures can occur in the lumbar spine and femoral neck. This is why bone density measurement is usually carried out here to assess the risk of fractures.
The various procedures that can be used to measure bone density include
Ideally, bone density measurements should be carried out at regular intervals. They should be carried out by the same doctor and with the same device. This makes it possible to determine how quickly the bone substance is disappearing.
A bone density measurement for diagnosis is recommended if osteoporosis is suspected. A bone density measurement should also be carried out if certain risk factors for osteoporosis are present. The risk factors include
There are also some high-risk factors for which regular bone density measurements are recommended:
This examination is usually called DXA or DEXA. This is the abbreviation for Dual Energy X-Ray Absorptiometry. DXA is the most commonly used method for measuring bone density.
For the examination, two X-rays of different strengths are sent through the body. The X-rays penetrate the bone, but are attenuated by it. The bone density is calculated according to how much the bone has been affected by the X-ray beam.
DXA is a very reliable and accurate measurement method. In addition, only low levels of ionizing (radioactive) radiation are used.
In principle, the examination can be carried out on the whole body, provided there are no metal implants in the areas concerned.
DXA is a very reliable variant of bone density measurement © Robert Kneschke | AdobeStock
This examination, also abbreviated to QCT, is carried out in the area of the lumbar spine. X-rays are used to produce a tomographic image of the bones. These images can be used to separately determine the bone density of the outer bone layer and the inner so-called bone balls.
The metabolic activity is higher in the bone beams than in the outer layer. This means that QCT can also be used to detect changes in bone metabolism. This is its advantage over DXA.
However, the radiation exposure is higher with QCT and it is less accurate than DXA. For this reason, QCT is only used for patients with very specific problems.
Peripheral QCT (pQCT) can also be performed. In this case, the measurement is not taken on the lumbar spine, but on the forearm. The radiation exposure with this method is lower than with normal QCT, but in contrast to DXA, it is locally limited.
In contrast to the other examinations, this method, QUS for short, does not use X-rays but ultrasound waves. There are two different procedures for this:
The great advantage of QUS is that there is no radiation exposure.
However, the method is still very new, which is why it is not yet fully developed. It is not yet used as standard.
Peripheral densitometry can be performed using DXA or pQCT. The measurement is usually carried out on the forearm . As no clinically important fractures occur here, the measurement is only of limited significance with regard to the risk of fractures.
After a bone density measurement, the determined bone density value is given as a so-called T-value. This value is standardized for all examinations in order to ensure comparability of the various procedures.
The T-value indicates how far the patient's values deviate from the average values of a 30-year-old. The level of the T-value can then be interpreted as follows:
In addition, a so-called Z-score can also be calculated from the data. This indicates the extent to which the patient's findings deviate from healthy test subjects of the same age. The result therefore shows whether the existing bone loss is within the normal range of findings for this age.
From this, the doctor can determine the next steps to be taken, for example whether drug treatment is indicated.
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