Abstract
At CEA-LETI, a DEXA approach for systems using a digital 2D radiographic detector has been developed. It relies on
an original X-rays scatter management method, based on a combined use of an analytical model and of scatter
calibration data acquired through different thicknesses of Lucite slabs. Since Lucite X-rays interaction properties are
equivalent to fat, the approach leads to a scatter flux map representative of a 100% fat region. However, patients’ soft
tissues are composed of lean and fat. Therefore, the obtained scatter map has to be refined in order to take into account
the various fat ratios that can present patients. This refinement consists in establishing a formula relating the fat ratio to
the thicknesses of Low and High Energy Lucite slabs leading to same signal level. This proportion is then used to
compute, on the basis of X-rays/matter interaction equations, correction factors to apply to Lucite equivalent X-rays
scatter map. Influence of fat ratio correction has been evaluated, on a digital 2D bone densitometer, with phantoms
composed of a PVC step (simulating bone) and different Lucite/water thicknesses as well as on patients. The results
show that our X-rays scatter determination approach can take into account variations of body composition.
