Two‐dimensional antiscatter grid: A novel scatter rejection device for Cone‐beam computed tomography

Alexeev, Timur; Kavanagh, Brian D.; Miften, Moyed; Altunbas, Cem

doi:10.1002/mp.12724

Cited by 22 publications

(53 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The cadaver heads all had a complete oral cavity, with the mandibula, the maxilla, the palate, soft tissues and some teeth present. As metallic restoration materials cause scattering on CBCT images, and hence reduce soft-tissue visualization by loss of contrast resolution and image artifacts [2], all metallic materials were removed prior to CBCT scanning.…”

Section: Cadaversmentioning

confidence: 99%

Determination of intra-oral surface areas by cone-beam computed tomography analysis and their relation with anthrometric measurements of the head

et al. 2020

View full text Add to dashboard Cite

Purpose Determination of intra-oral surface areas might contribute to our understanding of the physiology of the oral cavity and oral diseases. In previous studies, the intra-oral surface area was determined using a laborious and technically challenging method. Our aim was to develop an easy and non-invasive method to determine the intra-oral surface areas. Methods In this study, we used cone-beam computed tomography (CBCT) and digital analysis in 20 human cadavers to determine various intra-oral surface areas, based on digital segmentation. Next, we explored whether there was a relationship between various intra-oral surface areas and anthropometric measurements of the head using Pearson correlation coefficient. Results Using CBCT and digital analysis, it was possible to determine various intra-oral surface areas. On average, the total intra-oral surface area was 173 ± 19 cm 2. Moderate, statistical significant correlations were observed between (1) the length of the head and the palatal surface area, as well as (2) the depth of the head and the surface area of the tongue. These correlations suggest the feasibility of estimating intra-oral surface areas without relying on CBCT imaging. Conclusions This study presents a technique for measuring the intra-oral surface areas by CBCT imaging in combination with digital analysis. The results of this study suggest that anthropometric measurements of the head might be used to estimate the surface areas of the palate and tongue.

show abstract

Section: Cadaversmentioning

confidence: 99%

Determination of intra-oral surface areas by cone-beam computed tomography analysis and their relation with anthrometric measurements of the head

et al. 2020

View full text Add to dashboard Cite

show abstract

“…In this work, we developed a novel method to reduce ring artifacts in CBCT images acquired with 2DASG prototypes. 2,3 Although the general formulation is presented as the full biharmonic form, in this work, we considered a special case solution by decoupling the "x" and "y" directions in the projections. Artifacts caused by 2DASG septa shadows appear as GLA in projections, and may spread to more than one adjacent pixel row or column.…”

Section: Discussionmentioning

confidence: 99%

“…In this work, we developed a novel method to reduce ring artifacts in CBCT images acquired with 2DASG prototypes . Although the general formulation is presented as the full biharmonic form, in this work, we considered a special case solution by decoupling the “x” and “y” directions in the projections.…”

Section: Discussionmentioning

confidence: 99%

“…To address this problem, two‐dimensional antiscatter grids (2DASG), a 2D array of through‐holes separated by tungsten septa, have been investigated recently. With respect to conventional ASGs, we have shown that 2DASG provides substantially better scatter rejection and primary x‐ray transmission performance, and therefore, has the potential to further improve CBCT image quality …”

Section: Introductionmentioning

confidence: 99%

“…With respect to conventional ASGs, we have shown that 2DASG provides substantially better scatter rejection and primary x-ray transmission performance, and therefore, has the potential to further improve CBCT image quality. 3 One of the main challenges in implementation of 2DASG are the artifacts caused by its septa shadows. Since the 2DASG is placed on the FPD surface, its footprint is impinged in the projection imagesthat is, detector pixels underneath the 2DASG's footprint receive lower x-ray fluence and produce artifacts.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A novel total variation based ring artifact suppression method for CBCT imaging with two‐dimensional antiscatter grids

et al. 2019

Self Cite

View full text Add to dashboard Cite

Purpose Two‐dimensional antiscatter grids (2DASG) for cone beam computed tomography (CBCT) is a new area of research to reduce scatter intensity, and consequently improve CBCT image quality. One of the challenges in implementation of 2DASGs is their septa shadows that are impinged on the projections. If these artifacts are not corrected, they may lead to ring artifacts in CBCT images. In this work, we present a novel method to suppress ring artifacts in FPD‐based CBCT images. Methods Briefly, our method first detects the locations of 2DASG’s septa shadows in projections and then, reduces projection pixel values in septa shadows iteratively until a residual‐based convergence criterion is met. To suppress the 2DASG’s septa shadows, we developed a total variation minimization (TVM) formulation, referred to as adaptive‐diffusive total variation minimization (adTVM), where the diffusivity regularization parameter was adaptively adjusted during each iteration based on the magnitude of the local pixel gradients. To test our method, we have acquired CBCT scans of phantoms using three 2DASG prototypes with different grid geometries. Projections were acquired with a linac mounted CBCT system, operated in offset detector geometry. These projections were then corrected in the following steps: first, projections were corrected using a gantry angle‐specific gain correction map; next, projections were corrected by applying our adTVM method. CBCT images were reconstructed using FDK filtered backprojection algorithm. To evaluate adTVM’s performance, pixel value statistics and contrast‐to‐noise ratio (CNR) were compared in CBCT images corrected with and without our adTVM method. Results Without our adTVM method, all three 2DASG prototypes introduced ring artifacts with varying intensities in CBCT images. With our method, significant reduction in ring artifacts was observed in all test cases. Standard deviation of CT numbers was reduced by 7–74% in uniform density phantom CBCT images, CNR was increased by 8–67%, and CT number accuracy of contrast objects embedded in the phantom was preserved. Conclusion We propose a new method to suppress ring artifacts caused by the 2DASG's septa shadows in CBCT images. Our initial investigations indicated that adTVM method could substantially reduce such ring artifacts while preserving CT number accuracy and maintaining good spatial resolution. Therefore, our method may potentially play an important role in enabling the implementation of 2DASGs in flat panel detector based CBCT systems.

show abstract

A unified scatter rejection and correction method for cone beam computed tomography

Altunbas

Park

et al. 2021

Medical Physics

Self Cite

View full text Add to dashboard Cite

Purpose Scattered radiation is a major cause of image quality degradation in flat panel detector‐based cone beam CT (CBCT). While recently introduced 2D antiscatter grids reject the majority of scatter fluence, the small percentage of scatter fluence still transmitted to the detector remains a major challenge for implementation of quantitative imaging techniques such as dual energy imaging in CBCT. Additionally, this residual scatter is also a major source of grid‐induced artifacts, which impedes implementation of 2D grids in CBCT. We therefore present a new method to achieve both robust scatter rejection and residual scatter correction using a 2D antiscatter grid; in doing so, we expand the role of 2D grids from mere scatter rejection devices to scatter measurement devices. Method In our method, the radiopaque septa of the 2D grid emulate a micro array of beam‐stops placed on the detector which introduce spatially periodic septal shadows. By selecting sufficiently thin grid septa, the primary intensity can be reduced while preserving the uniformity of scatter intensity. This enables us to correlate the modulated pixel signal intensity in septal shadows with local scatter intensity. Our method then exploits this correlation to measure and remove residual scatter intensity from projections. No assumptions are made about the object being imaged. We refer to this as Grid‐based Scatter Sampling (GSS). In this work, we evaluate the principle of signal modulation with grid septa, the accuracy of scatter estimates, and the effect of the GSS method on image quality using simulations and measurements. We also implement the GSS method experimentally using a 2D grid prototype. Results Our results demonstrate that the GSS method increased CT number accuracy and reduced image artifacts associated with scatter. With 2D grid and residual scatter correction, HU nonuniformity was reduced from 65 HU to 30 HU in pelvis sized phantoms, and HU variations due to change in phantom size were reduced from 59 HU to 20 HU, when compared to use of only a 2D grid. With residual scatter correction via GSS method, grid‐induced ring artifacts were suppressed, leading to a 41% reduction in noise. The shape of the modulation transfer function (MTF) was preserved before and after suppression of ring artifacts. Conclusions Our grid‐based scatter sampling method enables utilization of a 2D grid as a scatter measurement and correction device. This method significantly improves quantitative accuracy in CBCT, further reducing the image quality gap between CBCT and multi‐detector CT. By correcting residual scatter with the proposed method, grid‐induced line artifacts in projections and associated ring artifacts in CBCT images were also suppressed with no compromise of spatial resolution.

show abstract

Two‐dimensional antiscatter grid: A novel scatter rejection device for Cone‐beam computed tomography

Cited by 22 publications

References 14 publications

Determination of intra-oral surface areas by cone-beam computed tomography analysis and their relation with anthrometric measurements of the head

Determination of intra-oral surface areas by cone-beam computed tomography analysis and their relation with anthrometric measurements of the head

A novel total variation based ring artifact suppression method for CBCT imaging with two‐dimensional antiscatter grids

A unified scatter rejection and correction method for cone beam computed tomography

Contact Info

Product

Resources

About