Abstract:Compton and Rayleigh scattering peak intensities and their ratio are used in reflection and transmission experiments to obtain information about the density of the investigated specimen. The ratio is preferred because it allows the reduction of the errors due to attenuation and geometry. In all cases it is fundamental to predict their angular distributions in order to design the optimal experiment for a given material. The code SAP (Scattering Angular distribution Plot) is a graphical tool to compute and plot … Show more
“…3. It is clear that the higher scattering angle and the higher tube voltage are better for the larger intensity measurement as expected from the previous studies on the angular distribution of the scattering intensities of Xrays and the effect of the tube voltage on the X-ray intensity 10,11 .…”
Section: Parameters Affecting the X-ray Scattering Intensitysupporting
“…3. It is clear that the higher scattering angle and the higher tube voltage are better for the larger intensity measurement as expected from the previous studies on the angular distribution of the scattering intensities of Xrays and the effect of the tube voltage on the X-ray intensity 10,11 .…”
Section: Parameters Affecting the X-ray Scattering Intensitysupporting
“…Figure 1 shows the relative scattering fractions of Rayleigh and Compton interactions with water as a function of the scattering angles. The data was from Fernandez et al 8 . CT detectors are located at zero scattering angle or perpendicular to the x direction.…”
Section: Methodsmentioning
confidence: 99%
“… Figure 1 The relative scattering fractions of X-ray Rayleigh and Compton interactions with water deviated from the beam direction (x). The figure was generated using the SAP code 8 . …”
The purpose of this work is to present a body size and tube voltage dependent correction scheme for the Hounsfield Unit, HU, in medical X-ray Computed Tomography imaging. Boltzmann photon transport equation was employed to study X-ray interaction with bulk water in CT imaging. Experimentally measured X-ray output in body of phantoms and attenuation cross sections of water were employed in the derivation of beam intensity in X-ray imaging. A Somatom Emotion CT scanner from Siemens and electron density phantoms from CIRS were employed to acquire CT images of different body sizes and different tissue materials located at different depths from body’s surface. Tube voltage and depth dependent effective attenuation of bulk water was found from theoretical analysis in agreement with measured size-specific correction factors for CTDIvol under different tube voltages. A size and tube voltage dependent correction scheme for the Hounsfield Unit is established. For the same tissue material, body size has much larger impact on the CT number variations than that of depth from the body surface in phantom measurements. Good results were achieved by applying the established correction scheme on the experimentally measured CT number variations under different tube voltages and body sizes.
“…Tabulated values of f (q, Z), s(q, Z) and ðd=dÞ at calculated using different models can be found in the literature (Hubbell et al, 1975). Programs to calculate the cross sections are also available (Fernandez et al, 2011). We have used the SAP program (Fernandez et al, 2011) to calculate the atomic form factor and the incoherent scattering functions of carbon and palladium at 12.4 and 30 keV and obtain the Rayleigh and Compton scattering cross sections.…”
Section: Scattering By An Atommentioning
confidence: 99%
“…Programs to calculate the cross sections are also available (Fernandez et al, 2011). We have used the SAP program (Fernandez et al, 2011) to calculate the atomic form factor and the incoherent scattering functions of carbon and palladium at 12.4 and 30 keV and obtain the Rayleigh and Compton scattering cross sections. The differential cross sections are shown in Fig.…”
Compton scattering is generally neglected in diffraction experiments because the incoherent radiation it generates does not give rise to interference effects and therefore is negligible at Bragg peaks. However, as the scattering volume is reduced, the difference between the Rayleigh (coherent) and Compton (incoherent) contributions at Bragg peaks diminishes and the incoherent part may become substantial. The consequences can be significant for coherent diffraction imaging at high scattering angles: the incoherent radiation produces background that smears out the secondary interference fringes, affecting thus the achievable resolution of the technique. Here, a criterion that relates the object shape and the resolution is introduced. The Compton contribution for several object shapes is quantified, and it is shown that the maximum achievable resolution along different directions has a strong dependence on the crystal shape and size.
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