Impact of flat panel‐imager veiling glare on scatter‐estimation accuracy and image quality of a commercial on‐board cone‐beam CT imaging system

Lazos, D.; Williamson, Jeffrey F.

doi:10.1118/1.4747260

Cited by 23 publications

(27 citation statements)

References 41 publications

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“…As the beam stop size affects scatter intensity, SPR and T S measurements were performed using four different diameter beam stops (their diameters were 3.5, 7.2, 10.5, and 13.6 mm at the detector plane), and they were linearly extrapolated to "0" beam stop diameter by using least squares polynomial fitting. [34][35][36] In the Results section, SPR and T S values at "0" beam stop diameter, and their standard errors were presented. An example of measured SPR and Ts values versus beam stop diameter was shown in Fig.…”

Section: D Measurement Of Scatter Transmission Fraction and Scattementioning

confidence: 99%

Transmission characteristics of a two dimensional antiscatter grid prototype for CBCT

et al. 2017

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Aim High fraction of scattered radiation in cone-beam CT (CBCT) imaging degrades CT number accuracy and visualization of low contrast objects. To suppress scatter in CBCT projections, we developed a focused, two-dimensional antiscatter grid (2DASG) prototype. In this work, we report on the primary and scatter transmission characteristics of the 2DASG prototype aimed for linac mounted, offset detector geometry CBCT systems in radiation therapy, and compared its performance to a conventional one-dimensional ASG (1DASG). Methods The 2DASG is an array through-holes separated by 0.1 mm septa that was fabricated from tungsten using additive manufacturing techniques. Through-holes’ focusing geometry was designed for offset detector CBCT in Varian TrueBeam system. Two types of ASGs were evaluated: a) a conventional 1DASG with a grid ratio of 10, b) the 2DASG prototype with a grid ratio of 8.2. To assess the scatter suppression performance of both ASGs, Scatter-to-primary ratio (SPR) and scatter transmission fraction (Ts) were measured using the beam stop method. Scatter and primary intensities were modulated by varying the phantom thickness between 10 and 40 cm. Additionally, the effect of air gap and bow tie (BT) filter on SPR and Ts were evaluated. Average primary transmission fraction (TP) and pixel specific primary transmission were also measured for both ASGs. To assess the effect of transmission characteristics on projection image signal-to-noise ratio (SNR) improvement factor was calculated. Improvement in contrast to noise ratio (CNR) was demonstrated using a low contrast object. Results In comparison to 1DASG, 2DASG reduced SPRs by a factor of 3 to 6 across the range of phantom setups investigated. Ts values for 1D and 2DASGs were in the range of 21 to 29%, and 5 to 14%, respectively. 2DASG continued to provide lower SPR and Ts at increased air gap and with BT filter. Tp of 1D and 2DASGs were 70.6% and 84.7%, respectively. Due to the septal shadow of the 2DASG, its pixel specific primary transmission values varied between 32.5% and 99.1%. With respect to 1DASG, 2DASG provided up to factor of 1.7 more improvement in SNR across the SPR range investigated. Moreover, 2DASG provided improved visualization of low contrast objects with respect to 1DASG and NOASG setups. Conclusions When compared to a conventional 1DASG, 2DASG prototype provided noticeably lower SPR and Ts values, indicating its superior scatter suppression performance. 2DASG also provided 19% higher average primary transmission that was attributed to the absence of interseptal spacers and optimized grid geometry. Our results indicate that the combined effect of lower scatter and higher primary transmission provided by 2DASG may potentially translate into more accurate CT numbers and improved contrast resolution in CBCT images.

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Section: D Measurement Of Scatter Transmission Fraction and Scattementioning

confidence: 99%

Transmission characteristics of a two dimensional antiscatter grid prototype for CBCT

et al. 2017

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“…Although initial results showed there was almost no difference in the first‐ and second‐pass Acuros results, future investigations may still be warranted. Indeed, with Acuros’ better scatter correction, other remaining artifacts will become more substantial, such as lag, bone beam hardening, or residual detector scatter (veiling glare) revealing possibly the next “layer of the onion” to be addressed in further improving CBCT image quality.…”

Section: Discussionmentioning

confidence: 99%

Acuros CTS: A fast, linear Boltzmann transport equation solver for computed tomography scatter – Part II: System modeling, scatter correction, and optimization

et al. 2018

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Acuros CTS is a promising new tool for fast and accurate scatter correction for CBCT imaging. By carefully modeling the imaging chain and optimizing several parameters, we achieved high correction accuracies with computation times compatible with the clinical workflow. The improvement in image quality enables better soft-tissue visualization and potentially enables applications such as adaptive radiotherapy.

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“…We used a beam-blocker method(Segui and Zhao, 2006; Niu and Zhu, 2011; Lazos and Williamson, 2012) with blocking disks of 2mm - 7 cm for the case of θ = 0° and for HE and LE exposures equal to that used for the single-pinhole case. The beam blocker method will deliver a scatter value s BB at the pinhole shadow location.…”

Section: Methodsmentioning

confidence: 99%

A scatter correction method for contrast-enhanced dual-energy digital breast tomosynthesis

Peng

Lau

et al. 2015

Phys. Med. Biol.

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Contrast-enhanced dual energy digital breast tomosynthesis (CE-DE-DBT) is designed to image iodinated masses while suppressing breast anatomical background. Scatter is a problem, especially for high energy acquisition, in that it causes severe cupping artifact and iodine quantitation errors. We propose a patient specific scatter correction (SC) algorithm for CE-DE-DBT. The empirical algorithm works by interpolating scatter data outside the breast shadow into an estimate within the breast shadow. The interpolated estimate is further improved by operations that use an easily obtainable (from phantoms) table of scatter-to-primary-ratios (SPR) - a single SPR value for each breast thickness and acquisition angle. We validated our SC algorithm for two breast emulating phantoms by comparing SPR from our SC algorithm to that measured using a beam-passing pinhole array plate. The error in our SC computed SPR, averaged over acquisition angle and image location, was about 5%, with slightly worse errors for thicker phantoms. The SC projection data, reconstructed using OS-SART, showed a large degree of decupping. We also observed that SC removed the dependence of iodine quantitation on phantom thickness. We applied the SC algorithm to a CE-DE-mammographic patient image with a biopsy confirmed tumor at the breast periphery. In the image without SC, the contrast enhanced tumor was masked by the cupping artifact. With our SC, the tumor was easily visible. An interpolation-based SC was proposed by (Siewerdsen et al., 2006) for cone-beam CT (CBCT), but our algorithm and application differ in several respects. Other relevant SC techniques include Monte-Carlo and convolution-based methods for CBCT, storage of a precomputed library of scatter maps for DBT, and patient acquisition with a beam-passing pinhole array for breast CT. Our SC algorithm can be accomplished in clinically acceptable times, requires no additional imaging hardware or extra patient dose and is easily transportable between sites.

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Impact of flat panel‐imager veiling glare on scatter‐estimation accuracy and image quality of a commercial on‐board cone‐beam CT imaging system

Cited by 23 publications

References 41 publications

Transmission characteristics of a two dimensional antiscatter grid prototype for CBCT

Transmission characteristics of a two dimensional antiscatter grid prototype for CBCT

Acuros CTS: A fast, linear Boltzmann transport equation solver for computed tomography scatter – Part II: System modeling, scatter correction, and optimization

A scatter correction method for contrast-enhanced dual-energy digital breast tomosynthesis

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