Wednesday, August 14, 2013

Benefits of Bone Density Examination (densitometry)

Prevent Osteoporosis with Benefits of Bone Density Examination (densitometry)

If you are post-menopausal women or older men with risk factors such as glucocorticoid therapy, history of fractures by minor trauma, family history of hip fracture, low body mass index (<20 kg / m²), a history of smoking or heavy alcohol consumption, menopause Early on female or male hypogonadism, rheumatoid arthritis, malabsorption, liver disease or chronic kidney disease, you may need to do a bone density test. In fact, even if you were younger but want to perform special steps to prevent osteoporosis, you may well need it.

Examination to measure the bone mineral density is known as densitometry, appliance called a densitometer. Bone mineral density is determined by the amount of calcium and other bone minerals (in mg) were collected in each unit area (cm2) of the bone. The higher the mineral content, the more solid bone mass and the stronger your bones. The rapid development of medical technology has resulted in techniques of non-invasive technique for measuring bone mineral density.

Commonly, There are two ways to measure the bone mineral density by DEXA densitometer (Dual Energy X-ray absorptiometry) and ultrasound densitometer.

1. DEXA Scan

Benefits of Bone Density Examination (densitometry)

Benefits of Bone Density Examination (densitometry)

Spine and hips surrounded by soft tissue, including fat, muscle, blood vessels, and abdominal organs. DEXA densitometer allows us to measure bone mass was hidden by utilizing differences in attenuation of low energy X-rays and high energy by the bone mineral and soft tissue.

DEXA Scan or DEXA scan is the gold standard for diagnosis of osteoporosis because it provides a very high accuracy, reaching 98-99%. The test is performed by DEXA machine at risk of bone fractures due to osteoporosis. This section covers the lumbar spine is the lower back, part of the femur that joins the hip, spine and wrist forearm.

Scanning takes a few minutes, with no anesthesia, no injection, no pain, and only describe levels of radiation in limited (well below the levels of X-rays for chest x-rays). However, under the recommendations of the International Society of Clinical Densitometry (ISCD), with a DEXA scan to Skiring and diagnosis should be no more frequently than once every two years.

Portable version of this machine is sometimes used for bone density screening at clinics and health fairs, but as they only scan smaller bones, such as the heel or finger, the result is not as accurate as a standard DEXA machine.

Scanned image is used to calculate bone mineral density in mg/cm2, which is then compared with the bone density in the comparison group:

Value of T

T values ​​(T-score) is a unit number (standard deviation) in which bone density is above or below the bone mineral density of healthy young adults, regardless of race or gender memadang. If you are experiencing bone loss, a negative value of T you because you have a bone mineral density that is less than standard. Interpret the value of T is as follows:

T Value Meaning

-1 Above normal bone mass density.
Value between -1 and -2.5 indicates osteopenia sign, the condition in which bone density is below normal and may lead to osteoporosis.
Below -2.5 indicates osteoporosis bone mass density.

Each one-point decrease in the value of T indicates bone loss between 10 to 15 percent, which means to increase the risk of hip fracture 3 times and 2.5 times the fractured vertebra.

Your doctor may suggest a traditional X-ray X-rays to examine further if there is a fracture or broken bone. X-rays can not diagnose osteoporosis until a serious fracture occurs (over 30 percent).

Z values ​​(Z-Score)

Z value is the ratio of the number density of your bones with bone density in the reference group who have the same age and sex with you. Race and weight are sometimes also included. Z value is calculated according to the percentile, the percent of people in the population who have a lower bone density. 

Here is a complete list of Z values ​​and percentile. If you have a Z value of zero then you are in the 50% percentile. If your Z value is -0.84% ​​then 20 others have lower bone density than you. The larger the negative value of Z, the more brittle your bones.

2. Ultrasound densitometer

Benefits of Bone Density Examination (densitometry)
Densitometer with ultrasound (USG) is a new method for diagnosing osteoporosis. Scanning is done with a device that emits sound waves on the heels of the patient and takes about one minute. The device used is smaller and cheaper than traditional DEXA systems. 

Scan results are then used to calculate the bone mineral density, which is compared with the standard density in young adults to get the value of T. T values ​​below -2.5 indicates you have osteoporosis.

Because the measure bone density in the heel, ultrasound is not as accurate as DEXA densitometer which measures the spine or hip. However, with a negative predictive value of 95% is an effective tool for screening. If you get a negative result, then you should feel confident not have osteoporosis. 

If the result is positive, further testing with DEXA scans are required because the positive predictive value of only 27%. This device can save costs by preventing examination of DEXA scans are not necessary for you that are not at risk of osteoporosis. (DEXA scan can cost hundreds of thousands to over a million dollars).

Bone density tests can detect when you have low bone density but can not explain the cause. To answer these questions, you need a complete medical examination including medical history, physical examination and laboratory. This information can help your doctor interpret the results of a bone density test.

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