Introduction
Bone Densitometry also called ‘Dual-Energy X-ray Absorptiometry (DEXA)’, a scan produces the image of the inside of the bone and helps in determining the bone loss, using a small dose of ionizing radiation. DEXA is a simple, quick, and noninvasive standard method for measuring bone mineral density (BMD), diagnosing osteoporosis and also detects the risk of developing osteoporotic fractures. DEXA is the best-standardized method and the radiations produced are small and less than a day’s exposure to natural radiation. In this scan, the two X-ray beams are targeted at the bones, and the DEXA scan can detect 1 percent bone loss, this makes it more accurate and sensitive.
Purpose:
- Osteoporosis is a condition in which the bone becomes fragile, thinner, and structural changes also occur in the bone that makes them fragile, and they are most likely to break. DEXA helps to diagnose osteoporosis, and this condition mostly affects women after the age of 30 years, menopause, and it can also occur in children and men.
- DEXA scan helps to determine the cause of bone loss, and track the progress of the effect of treatment for osteoporosis.
- It also accesses the risk of developing fractures. Several factors like aging, malnutrition, body weight, family history of osteoporotic fractures, unhealthy lifestyle, are also responsible for the loss of bone mass. All these are also taken into consideration before providing therapy to the patient.
- It is recommended for women above 40 years and older and men over 60 years to have a DEXA scan at least once. The bone loss in women is associated with the less reduction of estrogen that occurs because of menopause, so women develop low mineral density earlier than men.
- DEXA scan helps to identify the decrease in bone density. This scan also detects weak or brittle bone and also helps to detect the odds of a future fracture.
The following individuals are advised to undergo a DEXA scan:
- Organ transplant patients, as anti-rejection drugs can cause bone loss.
- Individual suffering from hyperthyroidism and high bone turnover..
- Individuals with a family history of hip fractures.
- Females who’ve reached the stage of menopause.
- Individuals whose mothers smoked during pregnancy period.
- Men who have rheumatoid arthritis and other clinical conditions associated with bone loss.
- Individuals who take medications that cause bone loss, including corticosteroids, anti-seizure medications, and thyroid replacement drugs.
Precautions to take care before DEXA scan:
- Wear loose clothing during the test procedure, and do not wear clothes that have buttons, belts, and zippers.
- Also remove the jewelry, metal objects, coins, keys from the pocket.
- Remove the dental applications, hearing aid, and eyeglasses before the procedure.
- Avoid smoking and alcohol consumption for a few days before the test.
- Avoid taking calcium and certain supplements for about 1-2 days before the test.
- Procedure timing: 10 to 30 minutes, depending upon the body part being examined.
Procedure:
The bone density test is painless and fast, and there is virtually no preparation required before the test. Share with a doctor if you recently have a contrast material injected for a CT Scan or X-ray test, as contrast material might interfere with the bone density test.
Step 1. No anesthesia is required, and the patient has to wear a loose, comfortable gown.
Step 2. The patient is advised to lie on a padded table, and below the table, an imaging device is present an X-ray generator.
Step 3. The scan is focused on the lower spine and hips, and in small children and some adults, the analysis is performed in the whole body. Hips and spine are targeted because, in these sites, most fractures because of bone loss occur. (If the hip or spine cannot be scanned, then the forearm will be scanned instead). Bone density varies in different parts of the body, so more than one body part will be scanned.
Step 4. The patient is advised to stay still to prevent the image from blurring. The hip scan is performed by placing the foot in the device that gently rotates the hip inward.
Step 5. The radiographer, a specialist in taking X-ray images, will send an invisible beam of low dose X-ray containing two energy peaks through the targeted region of the bone. The X-ray detector helps to measure the amount of X-rays passed through the body.
Step 6. The first peak of energy is absorbed by the soft body tissue and the other by the bones. Total bone mineral density is calculated by subtracting the amount of radiation absorbed by the soft tissue from the total radiation emitted or by using the standard deviation (SD) score.
* The baseline scan is compared with the second scan to determine if the bone density is improving or worsening.
Results:
The results are obtained within a week or two, and the results of the bone density test are obtained in the form of Z-score and T-score.
* T score shows the number of units (standard deviations) and determines bone density is higher or lower below the average, compared to the healthy young adult of the same sex.
T score (-1 and above): Bone density normal.
T score (-1 and -2.5): Bone density below normal and may lead to osteoporosis.
T score (-2.5 and below): Osteoporosis.
* Z score compares the bone density to a normal score of the same body size, weight, and age. Helps to determine the unusual contributing factor for bone loss.
Z score (above 2.0): Normal.
Z score (-1.5): Factors other than aging like malnutrition, medications, thyroid abnormalities, tobacco contributing osteoporosis.
Trivitron Bone Densitometer-Discovery Series
- Offers with exceptional precision and accuracy.
- Equipped with high definition digital DXA detectors- It helps improve fracture detection and also help to visualize abdominal aortic calcifications.
- Super visualization.
- Best in Speed and Image quality- The discovery imaging technology help captures the hip and spine with as fast as 10-second regional scanning time.
- Consistency – The Discovery system performs continuous, automatic calibration, ensuring precise measurement results from exam to exam.