Bone densitometry

Bone densitometry

Bone densitometry

Alternative Names: Bone density test, Bone mineral density test

A bone scan is a test that measures the density (thickness) of bones, either by using the hip or spine (central test) or a peripheral bone such as the heel (peripheral test). It is usually done when osteoporosis (a condition in which there is thinning of the bones) is suspected or a person is at risk for developing the condition e.g. postmenopausal women not on hormonal replacement therapy, long-term steroid treatment and hyperparathyroidism (increased parathyroid hormone in the body). Tests that measure bone density include DEXA scan (measures the amount of radiation absorbed by the bone), QCT (a computer is used to analyse special x-rays) and QUS (sound waves are used to measure bone density). There is no preparation required and the procedure is generally considered safe. While peripheral devices are more convenient and cheaper than central devices, they are not as accurate. Thus if a peripheral device is suggestive of osteoporosis, this finding should be verified using a central device.

What is it?
It is a test that assesses the density (thickness) of your bones.

Why is it done?
A bone density test is usually done in order to assess if a person has osteoporosis (a condition in which there is thinning of bone).

Osteoporosis may be age-related, or may be caused by a number of secondary conditions including Vitamin D or calcium deficiency, alcoholism, thyroid or parathyroid abnormalities and medications such as steroids.

Thus indications for bone mineral testing include:

  • Postmenopausal women with suspected oestrogen deficiency
  • Vertebral abnormalities or fractures associated with bone thinning (seen on plain X-ray)
  • Long term steroid therapy
  • Primary hyperparathyroidism (a condition in which too much parathyroid hormone is released into the body)
  • Monitoring of treatment in existing osteoporosis

What happens?

Before – how to prepare
No real preparation is required. You may have to remove certain articles of clothing or clothing accessories.

During – how the test is done
There are various methods that may be used to measure bone density, some of which measure hip or spine (central devices) and others that measure peripheral bones e.g. the heel (peripheral devices).

These methods include:

  • DEXA (dual energy X-ray absorptiometry) scan – 2 beams of radiation are emitted into the bone after which the amount of radiation energy absorbed by the bone is measured.
  • QCT (quantitative computerised tomography) – a special X-ray is taken of the bone after which a computer program determines bone density.
  • QUS (quantitative ultrasound) – bone density is measured by passing sound waves through the bone (usually the heel).

After the test
You should not experience any untoward side effects.

Risks and Compilations
Bone density tests are generally considered safe, with the levels of radiation being fairly low (in fact less than most X-rays). However, as there is some radiation exposure, caution is advised in pregnant women.

Special Issues
While peripheral devices are more convenient and cheaper than central devices, they are not as accurate. Thus if a peripheral device is suggestive of osteoporosis, this finding should be verified using a central device.

Short Description
A bone scan is a test that measures the density (thickness) of bones, either by using the hip or spine (central test) or a peripheral bone such as the heel (peripheral test).

Keywords
bone densitometry, density scan, osteoporosis



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