A DEXA scan may also report results using a Z-score, which reports the amount of bone a person has in comparison with other people of the same size, age, and sex. It can help determine whether something uncommon is leading to bone loss.
A score that is below When the test also measures body composition, results include a total fat mass and total body fat percentage. The DEXA scan is a useful diagnostic test that doctors use to determine whether a person has low bone density and or a higher risk of experiencing fractures. The results of the scan can help a doctor determine whether treatment is necessary for osteoporosis and help monitor the effectiveness of treatment.
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It is a painless and low risk procedure. Learn more here. Too little body fat is linked to problems with normal, healthy functioning in both men and women.
It can also lead to problems with reproduction in women. Too much body fat, especially when located around the abdomen, increases the risk of many diseases, including the following:.
By knowing your body fat percentage, and the range it falls in, you can take measures to improve your health and reduce your risk for various diseases. On the day of the exam you may eat normally. You should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. You will be asked to remove objects such as keys or wallets that would be in the area being scanned.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. The differential attenuation of the X-ray beam at these two energies is used to calculate the bone mineral content BMC and soft tissue composition in the scanned region. DEXA uses ionising radiation but the effective dose equivalents of contemporary instrumentation are below or equivalent to background levels, allowing for safe longitudinal studies in both children and adults.
The difference in attenuation between the two energy peaks is particular to each element, and thus to each tissue. In all systems, the differential attenuation of the two energies is used to estimate bone mineral content and soft tissue composition. Training in DEXA operation, positioning of the participants and data management is essential to obtain reliable data.
Training is generally provided by each company along with an electronic standard operating manual embedded in the DEXA software. DEXA was created for and continues to be used as a clinical tool to assess bone mineral density and bone mineral content to diagnose osteoporosis thinner bones. Other body sites e. DEXA estimates bone mineral mass, lean mass and fat mass from the differential absorption of X-rays of two different energies using instruments specific algorithms.
Manufacturers of DEXA systems also include correction algorithms for the effect of body thickness. Although, readjustments may be required and the standardised protocol in Figure 3 can be adopted. A data extraction tool can be set up to access the raw data and reconstruct body composition variables where necessary. Table 1 World Health Organization cut off values to indicate presence of osteoporosis. Some software allows automated estimations of body composition for scans where the symmetry method was applied e.
However, it is preferable to switch this feature off as the estimation can occur even if, for example, small tissue is clipped from the scanning area. After the missing tissue has been rebuilt, percentage body fat can be derived. The procedure below removes the bone, the fat and the lean masses of the left arm from total mass, left total mass and left arm mass values and replaces it with the right arm values.
There are published translation regression equations to tackle the systematic differences in the absolute values of body composition variables between different manufactures [2, 9]. However, these equations have been derived from healthy individuals and they might not be generalised to other populations.
Cross-calibration study of different instruments is therefore recommended to derive translation regression equations. When replacing an instrument, the ISCD International Society of Clinical Densitometry guidelines recommend carrying out cross-calibrations between the old and new instruments in at least 30 participants scanned on each instrument, twice on the new instrument to test precision and accuracy and derived cross-calibration equations. Considerations relating to the use of DEXA for anthropometry in specific populations are described in Table 4.
Refer to section: practical considerations for objective anthropometry. A method specific instrument library is being developed for this section.
In the meantime, please refer to the overall instrument library page by clicking here to open in a new page. Whole body DEXA scan. What is assessed? There are two approaches: Some instruments Hologic have a switching pulse system that rapidly alternate the voltage of the X-ray generator, producing two beams of high and low energies. The attenuated X-rays that have passed through the participant are measured sequentially with a detector situated on the scanning arm above the participant.
Learn more about body composition analysis exam preparation and find the clinic most convenient for you. Body Composition Dexa Scan. Dexa Scan Body Fat Analysis. Body fat Mineral in your bones Lean tissue such as organs and muscles. Dexa Scan Results. Summary Statistics. T-score and Z-score Meaning. Enhanced Composition Analysis Breakdown.
What Happens During my Dexa Scan? At the time of booking, you will be asked to wear clothing that does not contain any metal snaps, buttons, zippers for your appointment. If you forget on the day of your exam, you may be asked to change into a gown when you arrive; we do not want any metal on your clothing.
You will be weighed and your height measured before your scan. Our scanning beds have a maximum weight restriction of pounds.
You will be positioned on a bed by our technologist. The scan should take approximately 10 minutes. Please remain as still as possible for your scan, as movement may blur the exam images. Using dexa or dual-energy X-ray absorptiometry, we will calculate your body composition. If there is any chance that you are pregnant, please talk to your doctor before coming in for your body composition.
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