Introduction
Bone density scans are used to assess bone strength. DEXA scan is the most commonly used kind of bone density scan. DEXA stands for dual energy X-ray absorptiometry. It is a painless medical procedure whose use is to quantify mineral content in the bones. It utilizes a minimal dose of ionizing radiation to produce images of the internal body parts, usually the spine and hips.
Often times, DEXA scan is used to assess chances of osteoporosis or bone fractures.
Facts & Figures
According to the Centers for Disease Control and Prevention (CDC), 1 in 5 women and 1 in 20 men above 50 years are affected by osteoporosis.
This test bone strength and thickness (density) by passing high-energy and low-energy X-ray beams through the spine and hip region.
Indications/Uses
The purpose of a DEXA scan is to diagnose osteopenia and osteoporosis, apart from predicting possibility of future fractures.
- Women older than 65 years and men aged above 70 years are at risk of osteoporosis. In these individuals, a DEXA scan is recommended.
- Women younger than 65 years who are at risk of developing osteoporosis should also be scanned.
- Young people can have increased chance of developing osteoporosis because of:
- Estrogen deficiency.
- Low body weight.
- Lack of periods for more than a year before age of 42 years.
Other recommendations for DEXA scan are:
- Intake of medicines such as long-term heparin that may affect bone mineral density.
- Medical conditions such as hyperthyroidism and rheumatoid arthritis thyat can affect bone mineral density.
Preparation & Details
- DEXA scan does not require any special or complicated preparation.
- Your healthcare provider needs to know some important information from you, such as:
- Being on periods.
- Being a smoker or an alcoholic.
- Using medication that might thin bones such as steroids.
- Being on treatment to strengthen the bones.
- Carrying a pregnancy.
Before the test:
- Height and weight are measured by the radiographer.
- The patient changes clothes into hospital gowns. However, this is not a necessity in some hospitals.
- Metallic belongings such as piercings or metallic objects on clothes such as zips and buckles on the belt must be removed.
During the test:
- The patient is asked to lie on the scanning couch on his or her back and correctly positioned by the help of a radiographer.
- The machine is lined to put it in the right position.
- The patient must remain still, and communicate any issue that might cause disturbances during the procedure.
- The DEXA scan then is made to pass over the lower part of the spine and the hips. It sends X-rays into your body, a completely painless process. For persons who have had hip replacement surgery the forearm is scanned.
Results
- A bone density scan is used in comparison of a patient’s bone density with the expected bone density for a young healthy individual of the same age, sex and race.
- The difference obtained is calculated as a standard deviation score. This quantifies the difference between the individual’s bone density and their expected value.
- T score is the difference measured between an individual’s bone density and that of a young healthy individual.
- Z score is the difference measured between bone densities of two individuals of the same age. It is usually used for children and persons under the age of 30 who are still growing/maturing.
The following is the categorization of T scores according to the World Health Organization (WHO):
- -1 and above: Normal SD.
- -2.5 to -1: Mildly decreased bone density as compared to peak bone mass.
- -2.5 and below: Osteoporosis
For Z scores, when the result is below -2, then the individual’s bone density is lower than it should be for an individual of similar age.
Merits
- It aids in preventing fractures by identifying weak or brittle bones.
- It is used to determine the condition of the bone (bone density).
Risks
There is a very small increased chance of developing cancers in the future (same as risks from X-rays). This risk of radiation is incredibly minimal.