Antiscatter grids in mobile C-arm cone-beam CT: Effect on image quality and dose

Schäfer, Sebastian; Stayman, J. Webster; Zbijewski, Wojciech; Schmidgunst, Christian; Kleinszig, Gerhard; Siewerdsen, J. H.

doi:10.1118/1.3666947

Cited by 45 publications

(46 citation statements)

References 14 publications

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“…Although the presence of a grid did not seem to improve the SNR in relation to applied radiation dose (Schafer et al, 2012), a significant decrease in cupping artefacts was observed (Kyriakou and Kalender, 2007). However, in certain high-scatter conditions, the grid could lead to a reduction in dose of up to 50% (Kyriakou and Kalender, 2007).…”

Section: Anti-scatter Gridmentioning

confidence: 84%

ICRP Publication 129: Radiological Protection in Cone Beam Computed Tomography (CBCT)

Rehani¹,

Gupta²,

Bartling³

et al. 2015

Ann ICRP

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The objective of this publication is to provide guidance on radiological protection in the new technology of cone beam computed tomography (CBCT). Publications 87 and 102 dealt with patient dose management in computed tomography (CT) and multi-detector CT. The new applications of CBCT and the associated radiological protection issues are substantially different from those of conventional CT. The perception that CBCT involves lower doses was only true in initial applications. CBCT is now used widely by specialists who have little or no training in radiological protection. This publication provides recommendations on radiation dose management directed at different stakeholders, and covers principles of radiological protection, training, and quality assurance aspects. Advice on appropriate use of CBCT needs to be made widely available. Advice on optimisation of protection when using CBCT equipment needs to be strengthened, particularly with respect to the use of newer features of the equipment. Manufacturers should standardise radiation dose displays on CBCT equipment to assist users in optimisation of protection and comparisons of performance. Additional challenges to radiological protection are introduced when CBCT-capable equipment is used for both fluoroscopy and tomography during the same procedure. Standardised methods need to be established for tracking and reporting of patient radiation doses from these procedures. The recommendations provided in this publication may evolve in the future as CBCT equipment and applications evolve. As with previous ICRP publications, the Commission hopes that imaging professionals, medical physicists, and manufacturers will use the guidelines and recommendations provided in this publication for implementation of the Commission's principle of optimisation of protection of patients and medical workers, with the objective of keeping exposures as low as reasonably achievable, taking into account economic and societal factors, and consistent with achieving the necessary medical outcomes.

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Section: Anti-scatter Gridmentioning

confidence: 84%

ICRP Publication 129: Radiological Protection in Cone Beam Computed Tomography (CBCT)

Rehani¹,

Gupta²,

Bartling³

et al. 2015

Ann ICRP

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“…Although scatter was fairly low due to the extended geometry (Schafer et al 2012), incorporation of scatter-correction as well as beam-hardening correction methods is the subject of ongoing work, with image quality from both analytic and iterative reconstruction methods expected to improve. Furthermore, statistical reconstruction methods have been adapted to include an electronic noise model (La Rivière and Billmire 2005, Xu and Tsui 2009), which may play an important role for improving image quality in the ultra-low dose regime.…”

Section: Discussionmentioning

confidence: 99%

Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction

et al. 2014

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The potential for statistical image reconstruction methods such as penalized-likelihood (PL) to improve C-arm cone-beam CT (CBCT) soft-tissue visualization for intraoperative imaging over conventional filtered backprojection (FBP) is assessed in this work by making a fair comparison in relation to soft-tissue performance. A prototype mobile C-arm was used to scan anthropomorphic head and abdomen phantoms as well as a cadaveric torso at doses substantially lower than typical values in diagnostic CT, and the effects of dose reduction via tube current reduction and sparse sampling were also compared. Matched spatial resolution between PL and FBP was determined by the edge spread function of low-contrast (~40–80 HU) spheres in the phantoms, which were representative of soft-tissue imaging tasks. PL using the non-quadratic Huber penalty was found to substantially reduce noise relative to FBP, especially at lower spatial resolution where PL provides a contrast-to-noise ratio increase up to 1.4–2.2 × over FBP at 50% dose reduction across all objects. Comparison of sampling strategies indicates that soft-tissue imaging benefits from fully sampled acquisitions at dose above ~1.7 mGy and benefits from 50% sparsity at dose below ~1.0 mGy. Therefore, an appropriate sampling strategy along with the improved low-contrast visualization offered by statistical reconstruction demonstrates the potential for extending intraoperative C-arm CBCT to applications in soft-tissue interventions in neurosurgery as well as thoracic and abdominal surgeries by overcoming conventional tradeoffs in noise, spatial resolution, and dose.

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“…In breast imaging, Kwan et al 43 measured ∼50% SPR at the detector for an average-size breast (14 cm diameter) and showed the benefit of a bowtie filter in reducing scatter. For mobile C-arm imaging, Schafer et al 44 showed that an antiscatter grid did not offer an improvement in CNR per unit square root dose. Similarly, Kyriakou et al 45 found that for low-to medium-scatter levels in C-arm CT, an increase in x-ray exposure was needed to compensate for primary absorption in the grid.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo study of the effects of system geometry and antiscatter grids on cone‐beam CT scatter distributions

et al. 2013

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Purpose:The proliferation of cone-beam CT (CBCT) has created interest in performance optimization, with x-ray scatter identified among the main limitations to image quality. CBCT often contends with elevated scatter, but the wide variety of imaging geometry in different CBCT configurations suggests that not all configurations are affected to the same extent. Graphics processing unit (GPU) accelerated Monte Carlo (MC) simulations are employed over a range of imaging geometries to elucidate the factors governing scatter characteristics, efficacy of antiscatter grids, guide system design, and augment development of scatter correction. Methods: A MC x-ray simulator implemented on GPU was accelerated by inclusion of variance reduction techniques (interaction splitting, forced scattering, and forced detection) and extended to include x-ray spectra and analytical models of antiscatter grids and flat-panel detectors. The simulator was applied to small animal (SA), musculoskeletal (MSK) extremity, otolaryngology (Head), breast, interventional C-arm, and on-board (kilovoltage) linear accelerator (Linac) imaging, with an axis-todetector distance (ADD) of 5, 12, 22, 32, 60, and 50 cm, respectively. Each configuration was modeled with and without an antiscatter grid and with (i) an elliptical cylinder varying 70-280 mm in major axis; and (ii) digital murine and anthropomorphic models. The effects of scatter were evaluated in terms of the angular distribution of scatter incident upon the detector, scatter-to-primary ratio (SPR), artifact magnitude, contrast, contrast-to-noise ratio (CNR), and visual assessment. Results: Variance reduction yielded improvements in MC simulation efficiency ranging from ∼17-fold (for SA CBCT) to ∼35-fold (for Head and C-arm), with the most significant acceleration due to interaction splitting (∼6 to ∼10-fold increase in efficiency). The benefit of a more extended geometry was evident by virtue of a larger air gap-e.g., for a 16 cm diameter object, the SPR reduced from 1.5 for ADD = 12 cm (MSK geometry) to 1.1 for ADD = 22 cm (Head) and to 0.5 for ADD = 60 cm (C-arm). Grid efficiency was higher for configurations with shorter air gap due to a broader angular distribution of scattered photons-e.g., scatter rejection factor ∼0.8 for MSK geometry versus ∼0.65 for C-arm. Grids reduced cupping for all configurations but had limited improvement on scatterinduced streaks and resulted in a loss of CNR for the SA, Breast, and C-arm. Relative contribution of forward-directed scatter increased with a grid (e.g., Rayleigh scatter fraction increasing from ∼0.15 without a grid to ∼0.25 with a grid for the MSK configuration), resulting in scatter distributions with greater spatial variation (the form of which depended on grid orientation). Conclusions: A fast MC simulator combining GPU acceleration with variance reduction provided a systematic examination of a range of CBCT configurations in relation to scatter, highlighting the magnitude and spatial uniformity of individual scatter components, illustrating trad...

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Antiscatter grids in mobile C-arm cone-beam CT: Effect on image quality and dose

Cited by 45 publications

References 14 publications

ICRP Publication 129: Radiological Protection in Cone Beam Computed Tomography (CBCT)

ICRP Publication 129: Radiological Protection in Cone Beam Computed Tomography (CBCT)

Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction

Monte Carlo study of the effects of system geometry and antiscatter grids on cone‐beam CT scatter distributions

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