What is a densiometry?

The densiometry o Bone densitometry is a diagnostic test, similar to an X-ray, that allows to accurately measure bone mineral density (BMD), or amount of bone mineral present in the tissue, to detect a possible pathology.

Densitometry is also called dual energy X-ray absorptiometry (DEXA) and is commonly performed in the radiology or nuclear medicine areas of health centers, using a low dose of ionizing radiation (10 times less than in an x-ray ).

This test is done to determine whether or not you are, in the presence of some degree of osteopenia, osteoporosis or risk of fracture, as well as to evaluate the progress of a treatment in the bone system.

It is not a procedure that helps prevent osteoporosis, and although it is not 100% accurate, it does help predict whether a person will have a fracture in the future.

Risk factors for fractures include: age, body weight, previous fracture, family history of osteoporotic fractures, smoking, and alcoholism.

Procedure to carry out a densiometry

The apparatus used to carry out this examination is called a densitometer and it concentrates the radiation on the area to be evaluated; usually that area is the lumbar region of the spine (lower back) and / or the hip. However, it can also be done on the forearm.

It is a painless and relatively fast procedure (lasts between 15-20 minutes), which is usually indicated to people over 40 years of age, especially if they are women because they are the population most affected by bone pathologies.

It is an evolution of X-ray technology and is performed with the person lying on their back, wearing a surgical gown and without clothing of any kind..

You are asked to lie still and hold your breath for a moment, just as you do during an X-ray or CT scan..

Although it does not require special preparation, since you can maintain your diet and normal activity prior to the exam, it is advisable not to take calcium supplements at least 24 hours before the test..

Typically, the person can resume their usual activities immediately after the examination..

During the procedure, the device used for the study sends a thin, invisible beam of X-rays with two different energy peaks through the bones; one is absorbed by soft tissue, while the other is absorbed by bone tissue.

From there, images are obtained with values ​​that reflect the mineral density of the patient's bones..

These results are contrasted with the values ​​considered normal (those of a healthy 30-year-old adult) and this is measured in units called standard deviations (SD).

The results of this study will allow the specialist to decide which prevention or treatment options are the most appropriate..

The specialists who analyze the results of this examination are radiologists, but there are cases in which the interpretation of a rheumatologist or an endocrinologist is used..

Equipment to perform a densiometry

There are two types of equipment to perform bone de-synthometry:

1. DEXA core devices: It consists of a large, smooth table and an “arm” that is over the patient's head. This is the most common because it is used to evaluate the hip and spine..
2. Peripheral devices: It consists of a kind of portable box of approximately 27 kg, with space to place the foot or the forearm and that is used to measure bone density in the wrist, heel, forearm or finger. Special ultrasound machines have also been designed for these cases..

In both cases, the device has software that computes and displays bone density measurements on the computer monitor..

Advantage?

It is fast and accurate. It is not invasive, does not require anesthesia, and does not leave radiation residue on the patient's body.

Risks?

Those linked to radiation, although currently X-ray systems, have very controlled beams and filtration control methods to minimize the deflection (scattering) of radiation.

When should a bone de-synthometry be performed?

This test is recommended in the following cases:

• Post-menopause without estrogen treatment.
• Maternal or personal history of smoking or hip fracture.
• Post-menopausal woman tall (more than 1.70 meters) or thin (less than 56.77 kilograms).
• Man with a history of bone loss.
• Treatment with corticosteroids such as prednisone or anticonvulsants such as Dilantin and certain barbiturates.
• Type 1 diabetes, liver or kidney disease.
• Family history of osteoporosis.
• Hyperthyroidism or hyperparathyroidism.
• Mild trauma fractures.

Contraindications of bone de-synthometry

The cases in which a bone de-synthometry is counterproductive are:

• Pregnant and / or breastfeeding.
• People older than 60 years unless there is a risk of fracture greater than 10%.

Medical personnel should be advised if you have recently had a barium exam or have received an injection of contrast material for a CT or radioisotope scan..

Osteoporosis

That is to say that osteoporosis is associated with a decrease in the mineral salts of calcium that form the bones, making them less thick and more fragile and prone to breaks or fractures.

It is a pathology that affects women to a greater extent after menopause, although it also affects men and, less frequently, children.

According to the World Health Organization, there are four types or levels of osteoporosis:

1. Normal: There is no osteoporosis when bone mineral density is greater than -1 SD.
2. Osteopenia: When the results show a bone mineral density between -1 and -2.5 SD.
3. Osteoporosis: If the bone mineral density is less than -2.5 SD, it is referred to as osteoporosis.
4. Established osteoporosis: When the results are well below -2.5 SD, the patient can, very surely, suffer from fragility fractures.

According to this, the higher the negative number, the more serious the osteoporosis suffered by the patient..

When evaluating these values, it should be borne in mind that there are diseases that decrease bone mass, such as: rheumatoid arthritis, hyperthyroidism, hyperparathyroidism, anorexia nervosa, gastrectomy, pernicious anemia.

Risk factors should also be ruled out such as: the person being 6 months or older on corticosteroids, or a woman who reached menopause before 45 years of age (early menopause).

To prevent or delay the onset of osteoporosis, it is best to:

• Ingest calcium: at least 1200 to 1500 g per day.
• Eat foods rich in calcium and vitamin D.
• Work out.
• Avoid tobacco and alcohol consumption.
• Sunbathe for at least 10 minutes each day.

References

1. Bonilla Escobar, Angélica (2015). Osteoporosis prevention. Recovered from: saluspot.com.
2. Niams (2015). Bone mass measure. Recovered from: niams.nih.gov.
3. Radiology info (s / f). Dexa. Recovered from: radiologyinfo.org.
4. Zelman, David (2017). Bone densitometry. Recovered from: webmd.com.