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Bone densitometry, or dual-energy X-ray absorptiometry, is the most commonly used non-invasive test to diagnose osteoporosis.
What does it consist of?
Bone densitometry consists of obtaining images, using X-rays, to quantify bone mineral density (BMD). The two areas usually analysed are those where fractures most frequently occur, the lumbar spine and the hip.
What is it for?
Bone densitometry is used to diagnose osteoporosis, mainly in postmenopausal women(according to the World Health Organization,WHO),to monitor the patients and to assess the fracture risk.
It is also indicated for elderly men and anyone who has an illness or is undergoing treatment that can increase bone fragility (anorexia nervosa, chemotherapy treatments, glucocorticoid treatments).
The areasthat canbe assessed are the lumbar spine, hip, forearm and entire body. A whole body analysis also quantifies body fat and its distribution.
A lateral image of the thoracic and lumbar spine may also be carried out forsubsequent identification and analysis of possible vertebral fractures (Vertebral Fracture Assessment, VFA).
How it is performed?
The patient lies down on a stretcher and any metal objects they have on them are removed; their legs are bent on a special cushion for the first test, and for the second, their legs are straightened and their hips are rotated and supported by a special device. It is ensured that the patient is comfortable.
The table has a detector behind it and the X-ray source in front, which moves so that it can adequately track the study area. Two images are usually taken, similar to X-rays, but less radiation for the patient.
Two X-ray beams pass through the bone and the amount of energy that is sent back to the detector more or less relates to their density (the more dense the bone, the less energy). These data are used to measure and quantify the bone mineral density (BMD). The bone mineral density obtained is compared to a group of people of the same sex, race and age (Z Scale) and with a group of young individuals of the same sex and race (T Scale). From these comparisons, a diagnosis of osteoporosis, osteopenia or low bone mass is given or not.
How long does it last?
Approximately 5- 10 minutes.
How do you prepare for it?
No preparation is necessary. However, if the patient has recently undergone a barium swallow test, it is recommended to wait 10-14 days before undergoing a densitometry.
Like any X-ray examination, it should not be performed on pregnant women. In certain clinical circumstances, such as, for example, patients with large degenerative changes in the spine or those who have had two hip replacements, an examination of the non-dominant arm should be added.
In patients with suspected or a history of vertebral fractures, a vertebral fractures assessment (VFA) can be added to the standard bone densitometry to visualise the fractures and measure the height of the vertebral bodies.
Who performs the test?
A bone densitometry is performed by a specialised imaging technician.