Bone Densitometer
DEXA Bone Densitometry is the gold standard for measuring bones mass and detecting Osteoporosis. Osteoporosis is a bone disorder that can be described as a generalized weakening of the skeleton due to loss of bone and calcium. A skeleton that has been weakened by bone loss is more likely to fracture, and people with osteoporosis have a high incidence of fractures. If all those people with osteoporosis could be identified and treated, a large number of fractures could be prevented.
In India, 1 in 6 women over 50 years old will break their femur (hip), while 1 in 4 will suffer severe fractures in one or more bones.
The death rate from osteoporosis-related fractures is greater than deaths caused by breast and ovarian cancer combined!
It is CT based investigation screening whole body for screening. In contrast, conventional portable machines can only scan single sites.
Indications
An annual DEXA scan is recommended after the age of 40 years (especially for women).
Experts believe you may be at risk for osteoporosis if you have one or more of the following:
Family history of osteoporosis.
Early menopause either natural or surgical.
Amenorrhea (lack of periods) particularly in young woman.
Anti-seizure medicine for many years.
Hyperthyroidism or hyperparathyroidism.
Cushing's syndrome.
Kidney failure colitis.
Stomach or intestinal surgery.
High intake of alcohol, coffee, tea or soft drinks.
Heavy smoking.
Low dietary intake of calcium.
Prepreparations
No preparations is required for this test.
How is the procedure performed?
Bone density tests are a quick and painless procedure. This examination is usually done on an outpatient basis. You will probably be asked to fill out a questionnaire that will help the doctor determine if you have medical conditions or take certain medications that either increase or decrease your risk of a fracture. DEXA is most often performed on the lower spine and hips. In children and some adults, the whole body is sometimes scanned. Peripheral devices that use x-ray or ultrasound are sometimes used to screen for low bone mass.
In the Central DEXA examination, which measures bone density in the hip and spine, the patient lies on a padded table. An x-ray generator is located below the patient and an imaging device, or detector, is positioned above.
To assess the spine, the patient's legs are supported on a padded box to flatten the pelvis and lower (lumbar) spine. To assess the hip, the patient's foot is placed in a brace that rotates the hip inward. In both cases, the detector is slowly passed over the area, generating images on a computer monitor. You must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image. The DEXA bone density test is usually completed within 10 to 30 minutes, depending on the equipment used and the parts of the body being examined.
An additional procedure called Lateral Vertebral Assessment (LVA) is now being done at many centers. LVA is a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DEXA machine. The LVA test adds only a few minutes to the DEXA procedure.
The peripheral tests are simpler. The finger, hand, forearm or foot is placed in a small device that obtains a bone density reading within a few minutes.
What are the limitations of DEXA Bone Densitometry?
A DEXA test cannot predict who will experience a fracture but can provide indications of relative risk.
Despite its effectiveness as a method of measuring bone density, DEXA is of limited use in people with a spinal deformity or those who have had previous spinal surgery. The presence of vertebral compression fractures or osteoarthritis may interfere with the accuracy of the test; in such instances, CT scans may be more useful.
A test done on a peripheral location, such as the heel or wrist, may help predict the risk of fracture in the spine or hip. These tests are not helpful in following response to treatment and if it indicates drug therapy, a baseline central DEXA scan should be obtained.
Your test results will be in the form of two scores:
T score : This number shows the amount of bone you have compared with a young adult of the same gender with peak bone mass. A score above -1 is considered normal. A score between -1 and -2.5 is classified as osteopenia (low bone mass). A score below -2.5 is defined as osteoporosis. The T score is used to estimate your risk of developing a fracture.
Z score : This number reflects the amount of bone you have compared with other people in your age group and of the same size and gender. If this score is unusually high or low, it may indicate a need for further medical tests.
Small changes may normally be observed between scans due to differences in positioning and usually are not significant.
How frequently you should undergo this test?
Routine evaluations every two years may be needed to see a significant change in bone mineral density. Few patients, such as patients on high dose steroid medication, may need follow-up at six months.
Risks
X-rays usually have no side effects in the typical diagnostic range for this exam.
But There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk. Women should always inform the radiologist / physician if she is pregnant.
No other complications are expected with the DXA procedure.