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Bone quality is a broad term encompassing factors affecting the structural and material properties of bone. X-ray dual-energy method (XDEM) provides one way to explore bone quality in terms of bone tissue material properties. In this study a XDEM is presented for the determination of Ca/P mass ratio, parameter which appears to play an important role in bone health. The low- and high-energy intensity measurements were combined, using a nonlinear mapping function, to cancel out the soft tissue structures and generate the dual energy (DE) Ca/P mass ratio value. The total entrance-skin exposure from low- and high-energy measurements was constrained so that it is similar to diagnostic-examination levels. The DE simulated data were exported using variable Ca and PO4 thicknesses, while the tissue thickness was kept constant. The thickness of each material was fitted separately using a nonlinear least squares minimization algorithm. The functional forms of inverse functions that have been investigated are the linear, quadratic, cubic, and conic functions. The inverse- mapping functions were found to vary as analytic functions of second (conic) and third (conic) order. A nonlinear eight term rational function was selected for dual energy calibration which appeared to be capable of high fitting accuracy while requiring relative few terms. [ABSTRACT FROM AUTHOR]

The Dual energy method, using two different energies generated by an X-ray tube, has been applied in the diagnosis of osteoporosis by determining bone mass or bone density. By measuring parameters that characterize bone quality, such as the Ca/P or Hydroxyapatite/Collagen (HAp/Col) ratios, a potential bone fracture can be predicted more efficiently. The aim of this study was the optimization of dual energy X-ray spectra through the estimation of the Coefficient of Variation (CV) in HAp/Col ratio determination. The upper limit of CVHAp/Col value was set to ≤ 3%. Single and double exposure methods were used in order to obtain polyenergetic spectra. Unfiltered spectra were obtained from Boone et al (1997 Med. Phys. 24 1661-70) for Tungsten (W) anode. For the implementation of the low and high energy beams, several filters were applied to the spectra, based on their K-edges, so as to provide quasi-monochromatic beams. The optimum results, for the single exposure method, were obtained for a 120kVp spectrum with added beam filtration of 800um Ce (CVHAp/Col=1.88%). For the double exposure technique, a CVHAp/Col value of 2.23% was obtained using 40 and 120kVp with added filtration of 250um Cd and 1150um Yb, respectively. [ABSTRACT FROM AUTHOR]

The aim of the present study was the optimization of polyenergetic x-ray spectra for Dual energy imaging. The latter was accomplished by using various combinations of filter thicknesses and kVp. X-ray spectra were optimized by using double track x-ray tubes equipped with Molybdenum (Mo) and Rhodium (Rh), Mo and Tungsten (W), Rh and W, and a W or Rh anode combined with various K-edge filters and combinations. Filtering of energy spectra was implemented by determining the optimum combination and thicknesses of the lanthanides filters. The filtered spectra were normalized at standard exposure conditions. Best performance characteristics were obtained from the combination of Rh anode spectrum at 25kVp filtered with 100 μm Rh for low energy, and W anode spectrum at 50Vp filtered with 400 μm Ce for mammography, with mean energy values 19.57 and 30.10KeV respectively. For bone densitometry, best results were obtained from a W anode filtered spectrum at 110KVp with 900 μm Ce and mean energy values 37.78 and 85.56KeV for low and high energy respectively. [ABSTRACT FROM AUTHOR]

The degradation of X-ray image passing through thin glass substrate was experimentally investigated in term of modulation transfer function (MTF). The screen was prepared by sedimentation of the powder phosphor (Gd2O2S:Eu) on thin glass substrate with thickness 140 μm (Waldemar Knittel-GmbH). The experiment was carried out under X-ray mammographic conditions. The beam quality was 28 kV, 60 mAs, with W/Rh target/filter combination. The screen was coupled to an optical readout device including a CMOS remote RadEye HR photodiode pixel array. Results showed that there is a 40% degradation of the MTF on average, in the whole spatial frequency range, due to the glass substrate. The glass substrate has a low impact on resolution of the image at low frequencies (12% on average, up to 2.7 cy/mm) and a high impact at medium and high frequencies (70% on average). [ABSTRACT FROM AUTHOR]