Norland Elite 437A150, Operator'S Manual

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Dual Energy X-Ray Absorptiometry (DXA)
Dual Energy X-ray Absorptiometry (DXA) is a method of estimating bone mineral utilizing a pencil beam x-ray
beam filtered to provide the two distinct energy peaks necessary to distinguish bone from soft tissue.
SimulCount
TM
ensures a more accurate measure of BMD. Dual NaI scintillation crystals are used to sep-
arately detect the two x-ray energies.
The technique for separating x-ray output into two distinct energy levels is known as K-edge filtration. In K-edge
filtering, a rare earth element is placed in the beam path and x-rays are sharply attenuated at energy levels par-
ticular to that element. Norland uses samarium as the filter material because it produces energy peaks at
46.8keV and 80keV, which have proven to be most effective at differentiating between soft tissue and bone tis-
sue.
Dynamic Filtering
DynaFlux
TM
is another Norland innovation that is complementary to its pencil-beam design. Norland has
developed a method of optimizing the photon count rate for varying patient thickness by automatically selecting
the proper samarium filter combination. This filter selection feature prevents starvation or saturation of the
detector assembly.
Operator's Guide
437D140 Rev. I
2-4 General Information