The skeletal framework of the human body is made up of bones which are made up of collagen fibers and minerals where calcium is a very important component. As the age advances our bones tend to become weak because of reduced calcium as a result of hormonal changes or any associated disease which affects the bones. Osteoporosis is a medical condition affecting the bones where the bones become weak and fragile and have a greater tendency to break or fracture. Bone densitometry or bone density scan is a metric test which determines the density of your bones thereby helping in predict the possibility of osteoporosis in the future.
What is the age when a bone density scan is indicated ?
Bone density scan is usually indicated in older individuals above 60 years of age or at an early age in individuals who are prone to fractures or other metabolic diseases such as hyperparathyroidism, kidney disease/failure. Bone density scan is also indicated in women of premenopausal age as estrogen plays an important role in maintaining the bone strength in women and reduction of absence of estrogen can lead to weakness in bones and loss of bone matter.
What are the indications of a bone density scan ?
A bone density scan is ideally indicated in individuals who are in their 6-7th decade and might be indicated in younger individuals if required. Bone density scans are usually performed to
- Determine the density or mineral content of bones
- Determine the chances of osteoporosis
- Identify the possibility and risk of fractures in an individual
- To follow up the treatment of osteoporosis
Though bone density scans are performed usually in older age, they are also indicated in individuals who are also experiencing reduction in bone height as detected on X-rays, have a fractured bone, are on medication which can affect the bones, have undergone a transplant surgery and in pre-menopausal women who experience symptoms of menopause and reduced estrogen levels.
What are the contraindications of a bone density scan ?
There are no absolute contraindications for a bone density test, but it is important that you inform your doctor if you are pregnant or are on any medication for any medical condition.
What are the types of bone density scans ?
Bone density scans are performed mainly by two methods:
- Central dual energy x-ray absorptiometry (Central DEXA): This is a common method of doing bone densitometry where your spine and hip bones are scanned to assess the density and risk of fractures.
- Peripheral dual energy x-ray absorptiometry (p-DEXA): As the name suggests this test uses X-rays to scan and assess the density of your peripheral bones such as wrists, heels, fingers, toes, arms and legs.
Though bone density scans use X-ray for scanning, the amount of ionizing radiation is much lesser as compared to a conventional x-ray imaging.
How do you prepare for a bone density scan ?
Your treating doctor will tell you if you need to get a bone density scan done, and actually not much preparation is needed for the test. You must inform your treating surgeon if you are pregnant or are on any medication, have any body piercings or are wearing any jewelry as they may interfere with the outcome of the test. If you are taking any calcium supplements, you will be advised to stop them at least 24hrs before the test.
How is the bone density scan performed ?
The bone density scan or test is performed in a hospital facility and by trained technicians and radiologists. In a central DEXA scan you will be made to wear a loose hospital gown and then lie down on a table which usually has a padding to lift your legs up at the calves or to keep them stationary on the sides. Once you are stationary the arm of the machine will move near the center of your body to scan the spine and the hip bones which are the most common sites of osteoporosis. The scan takes about ten to thirty minutes and the scanned images are then compared with a standard scale to measure the density of bone to assess its correlation with osteoporosis if any is diagnosed or suspected.
In a peripheral DEXA scan only the arms, legs, fingers, heels are scanned as initial signs of osteoporosis may occur there.
How are the results of a bone density scan interpreted ?
The results of a bone density scan are interpreted by assessing mainly two score the T score and the Z score. The T score symbolizes the normal bone density which should be expected in an individual depending upon the gender. The scores range between -1 and -2.5, where -1 is normal and as the score increases the chances of osteoporosis increases. A score of -2.5 and below indicates or confirms osteoporosis.
Another score which is taken into consideration is the Z score which signifies the number of standard deviations which is either above or below the normal as expected according to your age, gender, weight and ethnicity. If a Z-score is -2 it indicates bone loss and that treatment should be started to prevent it.
It is important to ask your treating doctor or the specialist performing the scan to explain to you the need of a bone density scan along with its interpretations.
When are the results of the bone density scan made available ?
The results of a bone density scan are usually made available either within 24hrs of the test or within the timeline decided by the hospital.
Are there any risks associated with a bone density scan ?
No, bone density scan is a rather safe and short procedure and the amount of radiation used in the scan is also minimal. The test should be still avoided or your doctor should be informed if you are pregnant before undergoing the test.
Disclaimer: The content provided here is meant for general informational purposes only and hence SHOULD NOT be relied upon as a substitute for sound professional medical advice, care or evaluation by a qualified doctor/physician or other relevantly qualified healthcare provider.
