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Dexa Scan Accuracy



 Submitted by Medical Health Test Team on June 28, 2010
Dexa Scan Accuracy

The Dual Energy X-Ray Absorptiometry test is a test that is conducted to measure the bone density of an individual. Human bone is made up of mineralized tissue. For the structural rigidity of the bone to be maintained, the density of the minerals should be above a certain level. When the density of the bones drops, the individual is likely to suffer from bone related problems such as an increased risk of cracking, fractures and associated pains. Reduced bone density is a problem that affects many aged people and tends to occur in women more frequently than in men.

The DEXA scan uses two different X-ray beams to measure the density of the bone. These two beams are of different strengths which allow the machine to measure how easily the bone is absorbing the X-ray radiation. The results of such a scan are presented in the form of a numerical score. The numerical score is represented either using the T-score which judges people based on gender, or the Z-score which judges people based on gender, ethnic background, age and body mass. The Z-score tends to be more thorough as it takes into consideration factors that may not otherwise be considered. These factors are vital because they play a direct role in the determination of a person’s bone density.

One shortcoming of the DEXA scan which affects DEXA scan accuracy is the method used to measure the density. This method is based on the area of the bone scanned. Actual density is based on the volume of the bone but the DEXA scan accuracy suffers from not measuring the volume of the bone. This can be corrected by assuming the volume of the bone based on the area calculations made by the DEXA scan machine. Even with this shortcoming, the DEXA scan tends to be quite accurate when measuring the bone density of an individual. Another factor affecting the DEXA scan accuracy is the machine being used for the scan. Different machines may have different sensitivities or methods of displaying the results. It is always recommended that a patient use the same machine or similar machines when undergoing subsequent scans. Using a completely different machine could provide confusing results if an attempt is made to match the results with each other.  

In conclusion, it can be assumed that the DEXA scan accuracy is high enough for its results to be diagnostically relevant and for it to be widely used as a diagnostic tool for bone mineral density.

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