Bone Density (DEXA)

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Bone fracture is always a problem to the old people since it might lead to death or inability to live independently (Geusens, 1998). The test is only necessary for those who risk factors of weak bones, the unnecessary test should not be carried out because it might result in unnecessary treatment instead of discovering the real problem.There are several types of BMD test, and the most advanced type and the most used test is Dual-energy X-ray absorptiometry (DEXA). During the 1960s, the radiologist was only in a position of diagnosing bone mineral loss by analyzing radiographic images. Between 30 to 50 percent analysis was only manageable and a more sensitive method was required to determine the bone mineral loss.Due to the need for better technology, Bone densitometry originated in nuclear science and it was developed by Cameron and Sorenson in 1963. That time it was called single photon absorptiometry (SPA), iodine125 was used and it was capable of emitting 35 keV gamma rays. As a result of further research, X-Ray tube was used instead of the gamma-ray source. this introduced single energy x-ray absorptiometry (SXA). The x-ray beam was filtered so that it can produce a homogenous beam. In the 1970s, dual photon absorptiometry (DPA) was developed, this technology applies radioactive source that can emit gamma radiation in 2 separate energies. DPA in the 1980s was extended to form Dual-energy x-ray absorptiometry (DXA), the system uses fan beam. To achieve the dual energies, the variations of generator signal output are used.There are 2 types of DEXA scanning machines, central DEXA and peripheral DEXA machine. Central DEXA is large and powerful equipment that can measure the BMD at the center of the skeleton (Sawyer, Bachrach, Fung, 2007). Peripheral DEXA is a small machine that can be carried around and can measure the BMD at the peripheral part of the skeleton like a finger.