Depth distribution of multiple order X-ray scatter

Yao, Weiguang; Leszczyński, Konrad

doi:10.1016/j.radphyschem.2007.12.002

Cited by 7 publications

(7 citation statements)

References 22 publications

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“…This characteristic agrees with the results of Monte Carlo simulations. 22,23 For heterogeneous medium, after applying the same assumptions as in Eqs. ͑18͒ and ͑19͒, Eq.…”

Section: ͑18͒mentioning

confidence: 99%

“…However, our previous work showed that the depth distribution of the first order scatter exponentially increases with zЈ, and the lower the primary photon energy, the faster the first order scatter increases as zЈ does. 23 Therefore, zЈ should be greater than 0.5L and greater for lower energy beams. In this work, for simplicity, we use zЈ = 0.65L for megavoltage beams and 0.95L for kilovoltage beams when the scattering object is a slab.…”

Section: ͑26͒mentioning

confidence: 99%

“…See our previous work for a detailed description. 23 In this work, we used 3 ϫ 10 8 -3ϫ 10 9 histories for each Monte Carlo simulation to obtain stable first order scatter fluences. The typical relative error of the fluence was within 0.5% and could be decreased further by using even more histories.…”

Section: Iic Monte Carlo Codementioning

confidence: 99%

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An analytical approach to estimating the first order x‐ray scatter in heterogeneous medium

Yao

Leszczyński

2009

Medical Physics

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X-ray scatter estimation in heterogeneous medium is a challenge in improving the quality of diagnostic projection images and volumetric image reconstruction. For Compton scatter, the statistical behavior of the first order scatter can be accurately described by using the Klein-Nishina expression for Compton scattering cross section provided that the exact information of the medium including the geometry and the attenuation, which in fact is unknown, is known. The authors present an approach to approximately separate the unknowns from the Klein-Nishina formula and express the unknown part by the primary x-ray intensity at the detector. The approximation is fitted to the exact solution of the Klein-Nishina formulas by introducing one parameter, whose value is shown to be not sensitive to the linear attenuation coefficient and thickness of the scatterer. The performance of the approach is evaluated by comparing the result with those from the Klein-Nishina formula and Monte Carlo simulations. The approximation is close to the exact solution and the Monte Carlo simulation result for parallel and cone beam imaging systems with various field sizes, air gaps, and mono- and polyenergy of primary photons and for nonhomogeneous scatterer with various geometries of slabs and cylinders. For a wide range of x-ray energy including those often used in kilo- and megavoltage cone beam computed tomographies, the first order scatter fluence at the detector is mainly from Compton scatter. Thus, the approximate relation between the first order scatter and primary fluences at the detector is useful for scatter estimation in physical phantom projections.

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“…This characteristic agrees with the results of Monte Carlo simulations. 22,23 For heterogeneous medium, after applying the same assumptions as in Eqs. ͑18͒ and ͑19͒, Eq.…”

Section: ͑18͒mentioning

confidence: 99%

Section: ͑26͒mentioning

confidence: 99%

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An analytical approach to estimating the first order x‐ray scatter in heterogeneous medium

Yao

Leszczyński

2009

Medical Physics

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“…The scatter fluence S͑x , y͒ is very different between the kV and MV energy ranges. 1,21 Generally speaking, in the kV energy range the value of S͑x , y͒ is relatively large but the spatial distribution of S͑x , y͒ is relatively uniform because kV photons have statistically more chance to interact with the scatterer and thus the motion directions of the photons arriving at the detector are more uniformly distributed. Consequently, S͑x , y͒ is more sensitive to the air gap between the scatterer and the detector in kV CBCT than in MV CBCT.…”

Section: Iic Projection Data Acquisitionmentioning

confidence: 99%

An analytical approach to estimating the first order scatter in heterogeneous medium. II. A practical application

Yao

Leszczyński

2009

Medical Physics

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Recently, the authors proposed an analytical scheme to estimate the first order x-ray scatter by approximating the Klein-Nishina formula so that the first order scatter fluence is expressed as a function of the primary photon fluence on the detector. In this work, the authors apply the scheme to experimentally obtained 6 MV cone beam CT projections in which the primary photon fluence is the unknown of interest. With the assumption that the higher-order scatter fluence is either constant or proportional to the first order scatter fluence, an iterative approach is proposed to estimate both primary and scatter fluences from projections by utilizing their relationship. The iterative approach is evaluated by comparisons with experimentally measured scatter-primary ratios of a Catphan phantom and with Monte Carlo simulations of virtual phantoms. The convergence of the iterations is fast and the accuracy of scatter correction is high. For a sufficiently long cylindrical water phantom with 10 cm of radius, the relative error of estimated primary photon fluence was within +/- 2% and +/- 4% when the phantom was projected with 6 MV and 120 kVp x-ray imaging systems, respectively. In addition, the iterative approach for scatter estimation is applied to 6 MV x-ray projections of a QUASAR and anthropomorphic phantoms (head and pelvis). The scatter correction is demonstrated to significantly improve the accuracy of the reconstructed linear attenuation coefficient and the contrast of the projections and reconstructed volumetric images generated with a linac 6 MV beam.

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“…In addition, it has important effects on the patients and workers in an X-ray room. That is to say, the scattered radiation not only reduces the image quality, but also gives additional unwanted dose to the patients and workers in an Xray room [6,7].…”

Section: Introductionmentioning

confidence: 99%

Reduction of Backscattered Radiation in an X-Ray Room by Using Fabricated Iron Steel Grid

Naji¹,

Jaafar²

2013

AMPC

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This study aims to improve a way for reducing backscattered radiation in an X-ray room. An iron steel grid, capable to absorb a significant portion of the backscattered radiation, was used. X-ray machine as a source for radiation was directed normally on the phantom, and the backscattered radiation was measured by using ion chamber. The measurements were recorded at various applied voltages (60 kvp to 120 kvp) and the fabricated grid was designed from iron steel constructed of perpendicular parallel strips mounted on a base. The results indicated that the use of iron steel grid was very effective in the reduction of backscattered radiation in an X-ray room up to about 46% by using fabricated iron steel grid.

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Depth distribution of multiple order X-ray scatter

Cited by 7 publications

References 22 publications

An analytical approach to estimating the first order x‐ray scatter in heterogeneous medium

An analytical approach to estimating the first order x‐ray scatter in heterogeneous medium

An analytical approach to estimating the first order scatter in heterogeneous medium. II. A practical application

Reduction of Backscattered Radiation in an X-Ray Room by Using Fabricated Iron Steel Grid

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