Generation of hybrid sinograms for the recovery of kV‐CT images with metal artifacts for helical tomotherapy

Jeon, Hosang; Park, Dahl; Youn, Hanbean; Nam, Jiho; Lee, Jayoung; Kim, Wontaek; Ki, Yongkan; Kim, Yong Ho; Lee, Ju Hye; Kim, Dong-Won; Kim, Ho Kyung

doi:10.1118/1.4926552

Cited by 10 publications

(15 citation statements)

References 39 publications

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“…Nevertheless, beam hardening correction methods are generally slow and in any case do not remove all of the artefacts associated with metal in CT data. This is evident from the thorough comparison in Van Slambrouck and Nuyts (2012) which contrasts their polyenergetic reconstruction with other alternatives, and is equally true of dual-energy methods (Jeon et al, 2015). Much of the research into metal artefact reduction (MAR) has instead focused on correcting sinogram data, i.e.…”

Section: Sinogram Interpolation Techniquesmentioning

confidence: 99%

“…Of these sources, beam hardening has probably received the most attention, and most medical CT scans include a physical filter to narrow the range of energies from the X-ray source in order to lessen the consequent effects. Beam hardening artefacts can be further diminished by measuring attenuation independently at different energies (Jeon et al, 2015;Schmidt, 2009;Wu et al, 2014). In medical CT imaging, attenuation is dominated by the photo-electric effect and Compton scattering, and hence it is potentially possible to characterise its energy dependence by measurement at only two different energies (or of two different materials) (Van de Casteele et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Refinement of clinical X-ray computed tomography (CT) scans containing metal implants

Treece

2017

Computerized Medical Imaging and Graphics

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X-ray computed tomography (CT) data contains artefacts from many sources, with sufficient prominence to affect diagnostic utility when metal is present in the scans. These artefacts can be reduced, usually by the removal and in-filling of any sinogram data which has been affected by metal, and several such techniques have been proposed. Most of them are prone to introducing new artefacts into the CT data or may take a long time to correct the data. It is the purpose of this paper to introduce a new technique which is fast, yet can effectively remove most artefacts without introducing significant new ones. The new metal artefact reduction technique (RMAR) consists of an iterative refinement of the CT data by alternately forward- and back-projecting the part of the reconstruction near to metal. The forward-projection is corrected by making use of a prior derived from the reconstructed data which is independently estimated for each projection angle, and smoothed using a newly developed Bitonic filter. The new technique is compared with previously published (LI, NMAR, MDT) and commercial (O-MAR, IMAR) alternatives, quantitatively on phantom data, and qualitatively on a selection of clinical scans, mostly of the hip. The phantom data is from two recently published studies, enabling direct comparison with previous results. The results show an increased reduction of artefacts on the four phantom data sets tested. On two of the phantom data sets, RMAR is significantly better (p<0.001) than all other techniques; on one it is as good as any other technique, and on the last it is only beaten by the Metal Deletion Technique (p<0.001), which is significantly slower. On the clinical data sets, RMAR shows visually similar performance to MDT, with better preservation of bony features close to metal implants, but perhaps slightly reduced homogeneity in the far field. For typical CT data, RMAR can correct each image in 3-8s, which is more than one hundred times faster than MDT. The new technique is demonstrated to have performance at least as good as MDT, with both out-performing other approaches. However, it is much faster then the latter technique, and shows better preservation of data very close to metal.

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Section: Sinogram Interpolation Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Refinement of clinical X-ray computed tomography (CT) scans containing metal implants

Treece

2017

Computerized Medical Imaging and Graphics

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“…Wu et al presented a simulation study in which penalized weighted least‐square iterative image reconstruction was used to optimally combine the data and achieve high quality metal artifact reduction . More recently, Jeon et al studied another hybrid kV/MV CBCT imaging approach on phantoms and three patients with dental implants using a TomoTherapy (TomoTherapy, Inc., Madison, WI) system . They concluded that the hybrid CBCT imaging method outperformed other metal artifact reduction techniques that were based on interpolation of missing data.…”

Section: Introductionmentioning

confidence: 99%

Investigation of combined kV/MV CBCT imaging with a high‐DQE MV detector

et al. 2018

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Purpose Combined kV–MV cone‐beam tomography (CBCT) imaging has been proposed for two potentially important image‐guided radiotherapy applications: (a) scan time reduction (STR) and (b) metal artifact reduction (MAR). However, the feasibility of these techniques has been in question due to the low detective quantum efficiencies (DQEs) of commercially available electronic portal imagers (EPIDs). The goal of the work was to test whether a prototype high DQE MV detector can be used to generate acceptable quality pretreatment CBCT images at acceptable dose levels. Methods 6MV and 100 kVp projection data were acquired on a Truebeam system (Varian, Palo Alto, CA). The MV data were acquired using a prototype EPID containing two scintillators (a) a standard copper‐gadolinium oxysulfide (Cu‐GOS) screen having a zero‐frequency DQE (DQE(0)) value of 1.4%, and (b) a prototype‐focused cadmium tungstate (CWO) pixelated “strip” with a DQE(0) = 22%. The kV data were acquired using the standard onboard imager (DQE(0) = 70%). The angular spacing of the MV projections was 0.81° and the source output was 0.03 MU/projection while the kV projections were acquired with an angular spacing of 0.4° at 0.3 mAs/projection. Image quality was evaluated using (a) an 18‐cm diameter electron density phantom (CIRS, Norfolk, VA) with nine contrast inserts and (b) the resolution section of the 20‐cm diameter Catphan phantom (The Phantom Laboratory, Greenwich, NY). For the MAR studies, two opposing CIRS phantom inserts were replaced by steel rods. The reconstruction methods were based on combining MV and kV data into one sinogram. The MAR reconstruction utilized mostly kV raw data with only those rays corrupted by metal requiring replacement with MV data (total absorbed dose = 0.7 cGy). For the STR study, projections from partially overlapping 105°kV and MV acquisitions were combined to create a complete dataset that could have been acquired in 18 sec (absorbed dose = 2.5 cGy). MV‐only (4.3 cGy) and kV‐only (0.3 cGy) images were also reconstructed. Results The average signal‐to‐noise ratio (SNR) of the inserts in the MV‐only CWO and GOS CIRS phantom images were 0.62× and 0.12× the SNR of the inserts in kV‐only image, respectively. The limiting spatial resolutions in the MV‐only GOS, MV‐only CWO, and kV‐only Catphan images were 3, 6, and 8 lp/cm, respectively. In the combined kV/CWO STR reconstruction, all contrast inserts were visible while only two were detectable in the kV/Cu‐GOS image due to high levels of noise (average SNRs of kV/CWO and kV/GOS inserts were 0.97× and 0.18× the SNR of the kV‐only inserts, respectively). In the kV–MV MAR reconstructions, streaking artifacts were substantially reduced with all inserts becoming clearly visible in the kV/CWO image while only two were visible in the kV/Cu‐GOS image (average SNRs of the kV/CWO and kV/Cu‐GOS CIRS with metal inserts were 0.94× and 0.35× the SNRs of the kV‐only CIRS without metal inserts). Conclusions We have demonstrated that a high‐DQE MV detector can be applied to generating high‐quali...

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“…6 Applying a previously proposed MAR (Wei et al), a variation of 13 and 9 mm, respectively, from the uncorrected datasets were calculated for the beam range and modulation. 19 A compilation of different studies from EBRT, brachytherapy, proton, and heavy ion RT for different metal implants and the benefits of MAR for such investigations are well summarized in the work of Giantsoudi et al 20 Among the MAR methods recently investigated are sinogram inpainting, 1,19,[21][22][23][24][25][26][27][28][29][30] iterative, [31][32][33][34][35][36][37] and hybrid 2,3,[38][39][40][41][42][43][44] 41 Although existing methods may remove metal artifacts in some cases, they may introduce new artifacts or false structures, or even degrade image quality, in other cases.…”

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confidence: 99%

An additional tilted‐scan‐based CT metal‐artifact‐reduction method for radiation therapy planning

Kim

Pua

Lee

et al. 2018

J Applied Clin Med Phys

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PurposeAs computed tomography (CT) imaging is the most commonly used modality for treatment planning in radiation therapy, metal artifacts in the planning CT images may complicate the target delineation and reduce the dose calculation accuracy. Although current CT scanners do provide certain correction steps, it is a common understanding that there is not a universal solution yet to the metal artifact reduction (MAR) in general. Particularly noting the importance of MAR for radiation treatment planning, we propose a novel MAR method in this work that recruits an additional tilted CT scan and synthesizes nearly metal‐artifact‐free CT images.MethodsThe proposed method is based on the facts that the most pronounced metal artifacts in CT images show up along the x‐ray beam direction traversing multiple metallic objects and that a tilted CT scan can provide complementary information free of such metal artifacts in the earlier scan. Although the tilted CT scan would contain its own metal artifacts in the images, the artifacts may manifest in a different fashion leaving a chance to concatenate the two CT images with the metal artifacts much suppressed. We developed an image processing technique that uses the structural similarity (SSIM) for suppressing the metal artifacts. On top of the additional scan, we proposed to use an existing MAR method for each scan if necessary to further suppress the metal artifacts.ResultsThe proposed method was validated by a simulation study using the pelvic region of an XCAT numerical phantom and also by an experimental study using the head part of the Rando phantom. The proposed method was found to effectively reduce the metal artifacts. Quantitative analyses revealed that the proposed method reduced the mean absolute percentages of the error by up to 86% and 89% in the simulation and experimental studies, respectively.ConclusionsIt was confirmed that the proposed method, using complementary information acquired from an additional tilted CT scan, can provide nearly metal‐artifact‐free images for the treatment planning.

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Generation of hybrid sinograms for the recovery of kV‐CT images with metal artifacts for helical tomotherapy

Cited by 10 publications

References 39 publications

Refinement of clinical X-ray computed tomography (CT) scans containing metal implants

Refinement of clinical X-ray computed tomography (CT) scans containing metal implants

Investigation of combined kV/MV CBCT imaging with a high‐DQE MV detector

An additional tilted‐scan‐based CT metal‐artifact‐reduction method for radiation therapy planning

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