Validation of a Monte Carlo code system for grid evaluation with interference effect on Rayleigh scattering

Zhou, Abel; White, Graeme L.; Davidson, Rob

doi:10.1088/1361-6560/aaa44b

Cited by 9 publications

(22 citation statements)

References 45 publications

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“…The simulation determinations of Tp, Ts, and Tt were in the broad‐beam condition without a blocker in accordance with the IEC 60627 Standards 25 . This simulation setup identified forward scatter arising in a narrow‐beam condition as well as in blocked primary radiation in a broad‐beam condition, hence avoiding the influence of forward scatter on Tp and Ts 13 …”

Section: Methodsmentioning

confidence: 99%

“…In planar radiography, a notation of a linear‐focused grid is often given as its strip frequency ( N ) and grid ratio ( r ), for example, Nxry where x and y are their respective values 13–16 . The grid‐strip frequency, N = 1/( d + D ), is a measure of the number of strips per unit length, and the grid ratio, r = h / D , is the ratio of the strip height ( h ) to the interspace distance ( D ) 25 .…”

Section: Theory Of Optimal Thicknesses Of Grid Stripsmentioning

confidence: 99%

“…However, grids also reduce primary radiation (the useful information or signal) reaching the image receptor and hence when used, an increase in patient exposures is needed to maintain image diagnostic quality 10,11 . Grid performance can be expressed with grid‐physical parameters, such as the transmission of the primary radiation (Tp); the transmission of scatter radiation (Ts); and the transmission of the total radiation (Tt) 12,13 . Tp, Ts, and Tt vary from grid designs; and for the same grid‐ratio and the same grid materials, Tp, Ts, and Tt vary a great extent, up to 13%, 23%, and 21%, respectively 14–16 .…”

Section: Introductionmentioning

confidence: 99%

“…There is no information found about grid design to optimize grid performance. It is accepted that forward scatter radiation in the narrow‐beam method 12 influences Tp and forward scatter radiation which should arise in the materials underneath the blocker affects Ts 13,17 . Tp, Ts, and Tt are used to calculate the combined effects of the differential attenuation of the primary radiation and scatter reduction (noise reduction) on image diagnostic quality.…”

Section: Introductionmentioning

confidence: 99%

“…Tp, Ts, and Tt are used to calculate the combined effects of the differential attenuation of the primary radiation and scatter reduction (noise reduction) on image diagnostic quality. Some measures of these combined effects are the image contrast improvement factor ( K ) 12 and the quantum signal‐to‐noise ratio (SNR) improvement factor ( K SNR ) 13,15,18,19 …”

Section: Introductionmentioning

confidence: 99%

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The determination of the optimal strip‐thickness of anti‐scatter grids for a given grid ratio and strip height

Zhou

Yin

Tan

et al. 2020

Int J Imaging Syst Tech

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In X‐ray imaging, anti‐scatter grids are used to reduce scatter radiation reaching image receptors, hence improving image quality. Optimization of grid performance is essential for improving image diagnostic quality and minimizing radiation doses to patients. This work investigated the performance of a series of grid designs modeled from the design of typically focused grid with grid ratio 8:1 (r8) and strip height 1.7 mm (h1.7) for high‐energy radiographic applications. Monte Carlo simulation was used to evaluate designs (r8h1.7) which had the strip thickness changed from 6 to 150 μm in 2 μm increments and the interspace distance fixed at 214 μm. The transmissions of radiation in grid materials were modeled by using a regression with radial‐basis‐function‐networks (RBFNS). KSNR was then determined from RBFNS models of radiation transmissions. The optimal strip‐thickness was obtained at the maximum signal‐to‐noise ratio (SNR) improvement factor (KSNR). For high‐energy applications at 100 peak‐kilo‐voltage (kVp) and 30 cm PMMA thickness, the optimal lead‐strip‐thickness was found approximately 74 μm resulting in a strip‐frequency approximately 35 per cm (N35). Using the optimal thickness for imaging condition at 100 kVp and 30 cm thickness, the KSNR would increase by approximately 5.3%. This work showed the existence of optimal strip‐thickness for a series of grids with a given grid‐ratio, strip‐height, strip‐, and interspace materials. The findings are useful and provide guidance to improve grid designs for better performance that will essentially lead to better image quality and better radiation protection for patients.

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Section: Methodsmentioning

confidence: 99%

Section: Theory Of Optimal Thicknesses Of Grid Stripsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The determination of the optimal strip‐thickness of anti‐scatter grids for a given grid ratio and strip height

Zhou

Yin

Tan

et al. 2020

Int J Imaging Syst Tech

Self Cite

View full text Add to dashboard Cite

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New antiscatter grid design by optimization of strip thickness and height

Zhou

Tan

White

et al. 2020

Int J Imaging Syst Tech

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Antiscatter grids are used in biomedical X-ray imaging to improve image quality by reducing scatter radiation reaching the image receptor. However, this comes at the cost of increasing radiation exposure. Grid performance can be improved by optimizing strip-thickness, which reduces radiation exposure, leading to greater benefits achieved by the grid. Evidence has shown that strip height may also affect grid performance. This work investigates optimization of grid performance by varying both the strip thickness and height for a constant grid-ratio of 15:1 (r15). A series of grid designs using lead strips and carbon-fiber-interspace materials for grids for high-energy use was evaluated. The performance of these designs was determined by adopting a Monte Carlo simulation. For each grid design, the signal-to-noise ratio improvement factor (K SNR ) was determined. A maximum value of K SNR (1.895) was found among these designs at a strip height of 6.8 mm and a thickness of 66.8 μm. The best performance of the r15-series grids is 6% greater than that of a grid design with a grid ratio of 15:1 and a strip frequency of 44 cm −1 (found in the literature); consequently, the transmission of scatter radiation is reduced by 40%. The results show that grid designs can be optimized by both the strip height and thickness. If the optimization of the strip height and thickness cannot be done simultaneously, the recommendation is to optimize the strip height for better radiation protection without compromising the grid performance. The findings provide useful guidance for designing high-performance antiscatter grids to reduce radiation exposure of patients.

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Impact of bowtie filter and detector collimation on multislice CT scatter profiles: A simulation study

et al. 2020

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Purpose: To investigate via Monte Carlo simulations, the impact of scan subject size, antiscatter grid (ASG), collimator size, and bowtie filter on the distribution of scatter radiation in a typical realistically modeled third generation 16 slice diagnostic computed tomography (CT) scanner. Methods: Full radiation transport was simulated with Geant4 in a realistic CT scanner geometric model, including the imaging phantom, bowtie filter (BTF), collimators and detector assembly, except for the ASGs. An analytical method was employed to quantify the probable transmission through the ASG of each photon intersecting the detector array. Normalized scatter profiles (NSP) and scatter-to-primary-ratio (SPR) profiles were simulated for 90 and 140 kVp beams for different size phantoms and slice thicknesses. The impact of CT scatter on the reconstructed attenuation coefficient factor was also studied as were the modulating effects of phantom-and patient-tissue heterogeneities on scatter profiles. A method to characterize the relative spatial frequency content of sinogram signals was developed to assess the latter. Results: For the 21.4-cm diameter phantom, NSP and SPR increase linearly with collimator opening for both tube potentials, with the 90 kVp scan exhibiting slightly larger NSP and SPR. The BTF modestly modulates scatter under the phantom center, reducing the prominent off-axis lobes by factors of 1.1-1.3. The ASG reduces scatter on the central axis NSP threefold, and reduces scatter at the detectors outside the phantom shadow by factors of 25 to 500. For the phantoms with diameters of 27 and 32 cm, the scatter increases roughly three-and fourfold, respectively, demonstrating that scatter monotonically increases with phantom size, despite deployment of the ASG and BTF. In the absence of a scan subject, the ASG reduces the signal profile arising photons scattered by the BTF. Without ASG, the in-air scatter profile is relatively flat compared to the scatter profile when the ASG is present. For both 90 and 140 kVp photon spectra, the calculated attenuation coefficient decreases linearly with increasing collimation size. For both homogeneous and heterogeneous objects, NSPs are dominated by low spatial frequency content compared to the primary signal. However, the SPR, which quantifies the local magnitude of nonlinear detector response and is dominated by the high frequency content of the primary profile, can contribute strongly to high-spatial frequency streaking artifacts near high-density structures in reconstructed image artifacts. Conclusion: Public-domain Monte Carlo codes, Geant-4 in particular, is a feasible method for characterizing CT detector response to scattered-and off-focal radiation. Our study demonstrates that the ASG substantially reduces the scatter radiation and reshapes scatter-radiation profiles and affects the accuracy with which the detector array can measure narrow-beam attenuation due its inability to distinguish between true uncollided primary and narrow-angle coherently scattered photons. Hence...

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Validation of a Monte Carlo code system for grid evaluation with interference effect on Rayleigh scattering

Cited by 9 publications

References 45 publications

The determination of the optimal strip‐thickness of anti‐scatter grids for a given grid ratio and strip height

The determination of the optimal strip‐thickness of anti‐scatter grids for a given grid ratio and strip height

New antiscatter grid design by optimization of strip thickness and height

Impact of bowtie filter and detector collimation on multislice CT scatter profiles: A simulation study

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