Bone density measurement

What is a bone density scan?

During a bone density scan, also referred to as osteodensitometry, the bone mineral content is measured. From this mineral content, conclusions about the density of the bones and their stability can be drawn. In modern medicine, several diagnostic methods are available to assess bone density.

These diagnostic tools are mainly used to diagnose or rule out osteoporosis. A bone density scan is performed to initiate appropriate therapy and to assess disease progression. Osteoporosis affects the stability of the bones, making them susceptible to fractures even with minor force. The prevention of these fractures is the main goal of osteoporosis therapy.

Less commonly, osteodensitometry is also performed for other conditions associated with an altered bone metabolism. These include, among others, primary hyperparathyroidism, osteomalacia or long-term glucocorticoid use.

What examinations can be performed to determine bone density?

Various options and methods are available to determine bone density. The measurement is generally simple and painless since it is performed using x-ray or ultrasound. All these diagnostic methods use radiation. This radiation has a certain intensity, which is then reduced depending on the bone density. This reduction in radiation intensity is measured and compared with standard values.

The most examined bones are the femoral neck, the lumbar spine and the radius (forearm).

Examples of bone density measurement methods include:

• Dual X-ray absorptiometry 

Dual X-ray absorptiometry, abbreviated DXA, is the gold standard for diagnosing osteoporosis. Strictly speaking, rather than measuring the true density of bones, which is given in mass per unit of volume, the bone area density is measured instead. This is usually given in mass per unit of area, usually in grams per square centimeter (g/cm²). 

This procedure is based on the use of ionizing radiation, which is attenuated to a certain degree when passing through bone tissue. The degree of attenuation allows the physician to draw conclusions about the bone mineral content.  The result is then compared to the bone area density of an average healthy bone.

• Quantitative ultrasound measurement

The quantitative ultrasound measurement, abbreviated QUS, is an alternative to DXA. It offers the advantage of being quickly available and free of ionizing radiation. The bone is examined with ultrasound waves, assessing ultrasound velocity and attenuation. The bone structure can be evaluated using these values. While this method allows an estimation of fracture risk, it plays only a minor role in diagnosing osteoporosis.

• Quantitative computed tomography (CT)

CT examinations are based on the use of X-rays, which penetrate various body tissues and are attenuated to a certain degree. The radiation is then detected by a detector. Based on the degree of attenuation conclusions about the type of tissue can be drawn. 

Quantitative computed tomography (QCT) can be used to determine bone density. This method allows for a three-dimensional examination of specific bones. The obtained values are always compared to those of a calibrated phantom, which is a type of reference body. Therefore, results from different devices can be compared with each other.  Among the commonly examined bones are the vertebral bodies, the proximal femur, and the bones of the forearm. In contrast to DXA, QCT can measure the bone mineral content in mass per unit of volume (g/cm³).

• Conventional X-ray

Conventional X-ray allows for evaluation of bone changes caused by reduced bone density. Findings such as increased bone transparency may provide clues about possible osteoporosis but are not sufficient to confirm the diagnosis. This method is more useful for diagnosing and assessing fractures that have resulted from osteoporosis.

• Peripheral densitometry

Peripheral densitometry refers to a measurement of bone density at peripheral body sites, usually the bones of the forearm, less commonly the bones of the lower leg. Both, DXA and quantitative CT (QCT) can be used for this measurement. However, osteoporotic fractures occur most frequently in the vertebral bodies and femoral neck. Since these areas are not included in peripheral measurements, these methods have only limited significance for assessing the risk of fracture.

When is a bone density measurement useful?

A bone density measurement is useful if osteoporosis is suspected or alternatively, if risk factors for osteoporosis are present. Early detection of osteoporosis is crucial to initiate therapy as early as possible to minimize complications associated with this disease. 

Among the most important risk factors for osteoporosis are female sex, the onset of menopause, long term use of glucocorticoids, or certain endocrinological diseases. To prevent osteoporotic fractures, a diagnostic bone density measurement should be performed if indicated by the risk profile.

How does the physician perform a bone density measurement?

The exact procedure varies depending on the chosen method.

Quantitative ultrasound examination is performed using a special ultrasound device. The examination is very simple and quick. For patients, the procedure hardly differs from a conventional ultrasound examination.

Similarly, quantitative computed tomography is performed in the same as a standard CT examination. Patients lie on a movable table while a rotating X-ray tube moves around them.

The most commonly used method for bone density measurement is the DXA, which requires a special bone density scanner. Patients lie down in a supine position with their legs slightly elevated.

Images of the vertebral bodies of the lumbar spine are taken first. It is important that patients lie as still as possible during the imaging. For the examination of the femur, a slight modification of body position is usually required. The examination generally takes about 20 minutes or less and requires no special preparation from the patient.

What are the risks and side effects?

The mentioned bone density measurement procedures are generally considered low risk. This side effect profile depends primarily on the level of radiation used, except for quantitative ultrasound examination, during which patients are not exposed to any radiation.

Radiation exposure depends not only on the procedure used but also on the body region irradiated and the specific device type. The effective radiation dose is generally highest with QCT and lowest with DXA. The radiation exposure of a conventional X-ray usually lies somewhere in between and depends on the body region. However, all of these procedures have overall very low radiation doses, so the risk of long-term damage is very small.

How much does a bone density measurement cost?

The cost depends on the specific bone density measurement procedure. DXA on average costs about 50 to 60 euros. Statutory health insurance covers these costs only when it is clinically indicated. Therefore, prophylactic bone density measurement is generally not covered. The medical costs are only covered if risk factors or indications of osteoporosis are present and drug treatment of osteoporosis is being considered. In case of doubt, it is recommended to clarify cost coverage with the respective health insurance before performing the bone density measurement.

What physicians and clinics perform a bone density measurement?

Specialists in radiology are responsible for performing bone density measurements. The treatment of osteoporosis is usually carried out by specialists and orthopedics with expertise in osteology.

We have made it our mission to connect patients with the right healthcare providers for their specific condition. This way we make medical care of the highest level and in accordance with the latest scientific standards possible. 

All listed specialists are experts in the field of bone density measurement and have extensive experience in performing the different methods. Take advantage of the expertise of our specialists and quickly and easily schedule an initial consultation.