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Bone Densitometry: exam detects osteoporosis

Bone Densitometry: exam detects osteoporosis

Bone densitometry is the ideal exam for the diagnosis of osteoporosis and osteopenia because it detects bone mass reduction early and accurately. It is the most widely used method for assessing bone mineral density and uses an apparatus known to use the Dual-Energy X-ray Absorptiometry (DXA) technique. Bone densitometry evaluates the lumbar spine, the proximal femur, and the distal third of the radius. This is because these areas are most at risk of fractures. This method uses sophisticated devices that have two important advantages: they are fast and produce low radiation exposure - up to ten times less than the exposure generated by a normal chest x-ray. Bone densitometry is a rapid test (lasting about 5 minutes) and painless for the measurement of bone mineral density.


The bone densitometry test is indicated for women over 65 years and men over 70 years. However, it may be indicated for women under 65 and men under 70 who meet one of the criteria below:

  • Low Weight (Body Mass Index <18.5 kg / m²)
  • Previous Fracture
  • Medications that increase the risk of osteoporosis
  • Diseases that increase the risk of osteoporosis
  • Monitor already diagnosed osteoporosis
  • Monitor treatment.

The procedure also has application in pediatrics, to follow the growth of the child and the adolescent Pediatricians ask for densitometry to evaluate bone mass and how much lean mass and fat mass the patient has, functioning as a complement to the classic evaluation of bone age of the X-ray of hands and wrists. In children and adolescents up to 20 years old, the sites used are spine and whole body (the femur is still growing and is not evaluated). In this group, we compare the bone mass of the patient with children of the same age and we do not use the term osteoporosis as in adults.


  • Pregnant or pregnant women due to radiation
  • People which have been taken with iodine or barium contrast, can not perform bone densitometry for one to two weeks depending on the contrast used (time to be removed from the body), as this interferes with the result. Other radiological examinations such as scintigraphy should have a range of elimination determined by the physician.
  • Extensive orthopedic surgery or extensive prosthesis in the assessed region: in the case of people who have prostheses in one femur, the other is evaluated. For people with a prosthesis in the spine, an analysis of the femur and another of the forearm is performed.
  • Severe obesity: most bone densitometry devices support up to 160 kg. Some devices support up to 200 kg.

Exam Preparation

On the day of the bone densitometry examination, avoid wearing button-down clothing or metal buckles for the test, as these can be inferred from the result. Jewelry such as necklaces and bracelets should also be avoided as well as bras with iron hoops. It is also recommended that the person does not take any calcium supplementation on the day because the pill may appear on the spinal examination and interfere with the result.

How is it done?

Bone densitometry can be done by a radiographer or physician trained in bone densitometry. At the time of the examination, you will be asked to change your clothes into a hospital gown, suitable for testing. The technician will ask you to lie on the device on a padded table, and will position your legs in a sponge holder, aligning your pelvis and spine. The laser of the device will zick over the organs to be analyzed, scan its bones and measure the amount of radiation they absorb.The bone densitometry test should be done on at least two different bones, preferably the hip and spine. In the case of children, the scanner is made of the entire body and spine. Bone densitometry does not cause pain. If you have back pain, it may be uncomfortable to stand still during the check.

Bone Densitometry Duration - Photo: Getty Images

Bone densitometry lasts on average five minutes for spine and femur and ten minutes


Bone densitometry is performed every one or two years, depending on the control of osteopenia / osteoporosis determined by the attending physician. Shorter intervals may occur in cases of rapid bone loss, such as in people using corticosteroid medicines.

Post-examination recommendations

There are no special recommendations following the bone densitometry examination.

What the results mean?

The test is done to identify your bone density, whether you have osteopenia or osteoporosis, and to help you evaluate your risk. of fracture. You get the results like the photos of an X-ray, but the images are a little less sharp because of the diminished amount of radiation. It's like a radiograph at a lower resolution. Your bones are compared to that of a healthy young person and provide the distance of your bone mass from the normal mean. From this the T-score, an international reference standard developed by the World Health Organization, is calculated. It shows how close or far you are to this ideal. The T-score starts from number zero (which represents the mean) and departs for a scale of negative or positive numbers - the more negative the number is, the further away your bone mass is from the ideal.

The result for children uses the Z-score and not the T-score. The Z-score compares the child's bone mass with the mean for the same age. The result is not osteopenia or osteoporosis, but within the mean or below the mean for the age.

Reference values:

For adults ie men aged 50 years and over and women over 40 (menopausal transition period) or menopausal women. Osteopenia: T-Score of - 1.0 to -2.4 SD

Normality: T-Score from 0 to -1.0 SD (Standard Deviation)

> Osteoporosis: T-Score of -2.5 or less.

  • For young adults (Men between 20 and 49 years and women from 20 to 40 years with normal menstrual cycles) we used Z-score. Used site: column, femur or forearm:
  • Z-Score equal to or lower than -2.0 SD is considered to be below the standards for age. Above this, the values ​​are considered within the standards for age.
  • For children (Men and Women from 5 to 19 years). Sites used: column and total body

Z-Score equal to or lower than -2.0 SD is considered below the standards for age. Above this, values ​​are considered within the standards for age.

Can pregnant woman do?

Pregnant women should not do bone densitometry because of the radiation involved in the examination. If the woman has osteoporosis diagnosed and becomes pregnant, she will be followed up with densitometry after pregnancy.

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