AbstractID: 9733 Title: How to avoid DEXA limitations: introduction of x-ray
spectroscopy in diagnostic absorptiometry
In attempts to determine bone mineral density (BMD) in vivo, dual energy x-ray
absorptiometry shows a lot of advantages compared with other non-invasive radiological
techniques: improved precision, good spatial resolution, short scanning time, reduced
radiation dose to patient, etc. But, poly-energetic nature of two separated energy region of
x-ray spectra, could be a reasons of some inherent limitations of technique. Simplified
model of the body, consisting of only two components: mineral and nonmineral as one
consequence of only two mean energies used limits a precision and accuracy of method.
Hardening of two relatively brad energy regions contributes to additional systematic
inaccuracy.
In this work, an attempt was made to use full energy spectra of x-ray beam transmitted
through three different material layers to calculate areal densities of each of them. Test
objects made from different thicknesses of aluminium, Plexiglas and petrolatum were
used to simulate part of body consisting from cortical bone, soft tissue and bone marrow
respectively. Three different types of detectors were used in study: planar HPGe, CZT
and NaI. It was shown that spectra obtained by HPGe and NaI detectors, with small
correction (mostly for summing effect at high count rates) can be used in calculation of
areal densities in transmission measurements. Method is not limited to only two nonmineral components and in most cases, even in simplified calculations, areal density of
aluminium (simulating solid bone) was reconstructed correctly with same precision
obtained in DEXA phantom measurements.