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Slice-wise reconstruction for low-dose cone-beam CT using a deep residual convolutional neural network

Nuclear Science and Techniques 2019年第4期30卷 53-61页

作者： Hong-Kai Yang Kai-Chao Liang Ke-Jun Kang Yu-Xiang Xing Department of Engineering Physics Tsinghua University Key Laboratory of Particle and Radiation Imaging Ministry of Education Tsinghua University

Because of the growing concern over the radiation dose delivered to patients, X-ray cone-beam CT(CBCT) imaging of low dose is of great interest. It is difficult for traditional reconstruction methods such as Feldkamp to reduce noise and keep resolution at low doses. A typical method to solve this problem is using optimizationbased methods with careful modeling of physics and additional constraints. However, it is computationally expensive and very time-consuming to reach an optimal solution. Recently, some pioneering work applying deep neural networks had some success in characterizing and removing artifacts from a low-dose data set. In this study,we incorporate imaging physics for a cone-beam CT into a residual convolutional neural network and propose a new end-to-end deep learning-based method for slice-wise reconstruction. By transferring 3D projection to a 2D problem with a noise reduction property, we can not only obtain reconstructions of high image quality, but also lower the computational complexity. The proposed network is composed of three serially connected sub-networks: a cone-to-fan transformation sub-network, a 2D analytical inversion sub-network, and an image refinement sub-network. This provides a comprehensive solution for end-to-end reconstruction for CBCT. The advantages of our method are that the network can simplify a 3D reconstruction problem to a 2D slice-wise reconstruction problem and can complete reconstruction in an end-to-end manner with the system matrix integrated into the network design. Furthermore, reconstruction can be less computationally expensive and easily parallelizable compared with iterative reconstruction methods.

关键词： cone-beam CT Slice-wise Residual U-net Low dose Image denoising

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Improvements to conventional X-ray tube-based cone-beam computed tomography system

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Nuclear Science and Techniques 2018年第3期29卷 156-164页

作者： Cui Zhang Xiao-Dong Pan Hong-Jie Shang Yan-Hong Luo Gong-Ping Li School of Nuclear Science and Technology Lanzhou University

Conventional X-ray tube-based cone-beam computed tomography(CX-CBCT) systems have great potential in industrial applications. Such systems can rapidly obtain a three-dimensional(3D) image of an *** X-ray tubes fulfill the requirements for industrial applications, because of their high tube voltage and power. Continuous improvements have been made to CX-CBCT systems, such as imaging time shortening,acquisition strategy optimization, and imaging software development, etc. In this study, a CX-CBCT system is developed. Additionally, some improvements to the CX-CBCT system are proposed based on the hardware conditions of the X-ray tube and detector. A near-detector(ND)geometry condition is employed to obtain a sharper image and larger detection area. An improved acquisition strategy is proposed to simplify operations and reduce total imaging time. In the ND geometry condition, a simplified method called FBP slice stacking(SS-FBP) is proposed, which can be applied to 3D image reconstruction. SS-FBP is timesaving relative to traditional methods. Furthermore, imaging software for the CX-CBCT system is developed in the MATLAB environment. Several imaging experiments were performed. The results suggest that the CX-CBCT system works properly, and that the above improvements are feasible and practical.

关键词： cone-beam CT Conventional X-ray tube Nondestructive testing X-ray imaging

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Dual Energy CT Imaging in cone-beam Micro-CT for Improved Attenuation Coefficient Measurement

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Tsinghua Science and Technology 2011年第4期16卷 352-357页

作者：唐智伟胡广书 Department of Biomedical Engineering Tsinghua University

In order to improve micro-CT＇s capability of accurate quantification of linear attenuation coefficient μ, a dual energy method was developed to correct beam hardening artifacts caused by the polychromatic spectra of X-ray tubes. In this method, two sets of scans, taken at different energy levels, were combined to create a synthetic monochromatic image. A physical polychromatic model of μ in dual energy imaging was developed with an iterative method to solve the model for a few selected pixels. To find a high-speed and effective computing approach, the physics model was approximated by a polynomial function of the measured intensities. The method was tested on a PMMA-aluminum phantom and CaCI2 admixtures. The results show that streak and cupping artifacts are completely eliminated and that the measurement of the reconstructed attenuation coefficient μ is observed to be over 95% accurate.

关键词： micro-CT cone-beam linear attenuation coefficient beam hardening dual energy

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Comparison of bone alignment and fiducial marker alignment for online cone-beam computed tomography-guided radiation therapy for prostate cancer

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Oncology and Translational Medicine 2019年第3期5卷 131-136页

作者： Hussein M.Metwally Clinical Oncology Department Faculty of MedicineFayoum University Dar Al Fouad Hospital Radiation Unit

Objective The aim of the study was to evaluate the coverage of the prostate when prostatic implanted fiducial markers are used to verify setup of the patients in comparison to the pelvic bones while using conebeam computed tomography(CBCT). Methods Seventeen patients with prostate cancer were included. For each patient, daily online CBCT was done. CT planning was matched with CBCT with the help of fiducial markers(3–5 markers) and another matching with done the help of pelvic bony landmarks. Registration of clinical target volume(CTV) 1 including prostate plus seminal vesicles and CTV2 including prostate only was done and were used to confirm the target volume during the process of matching. Delineation of the rectum on every CBCT was done. Two automatic margin representing planning target volume(PTV) were created. PTV1 was generated by adding 1 cm in all directions(PTV1a) and 0.7 cm in the posterior direction(PTV1b). PTV2 was generated by adding 0.5 cm in all directions(PTV2a) and 0.3 cm in the posterior direction(PTV2b). PTV1a was prescribed to receive 46 Gy in conventional fractionation with a boost dose of 30 Gy to PTV1b. The same dose was prescribed to PTV2a and PTV2b. Calculation of the percentage of intersection between CTV1and CTV2 created on CBCT with the original CTV scan was done. A comparison between the two CTVs(CTV1and CTV2) mean dose and the original delineated CTV was done. Then a comparison to the mean dose of the original CTV of PTV1a, PTV2a(CTV1a and CTV2a), and for PTV1b and PTV2b(CTV1b and CTV2b). Calculation of the mean rectal dose and also V60, V70 and V74 was done on the delineated rectum on every CBCT, and then a comparison to the planned original rectal dose. Results The created CTV1and CTV2 intersection percentage with the original CTV1and CTV2 significantly increased by 85%(range, 65%–95%, P < 0.05), when fiducial markers were used. The main difference of the received mean dose was significantly less in comparison to pelvic bone alignment

关键词： cone-beam computed tomography(CBCT) prostate cancer bone alignment fiducial marker alignment

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Method for Converting cone-beam CT Values into Hounsfield Units for Radiation Treatment Planning

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2017年第4期6卷 361-375页

作者： Tadanori Abe Kunihiko Tateoka Yuichi Saito Takuya Nakazawa Masaki Yano Kensei Nakata Masanori Someya Masakazu Hori Koichi Sakata Depertment of Radiation Oncology and Medical Physics Graduate School of Medicine Sapporo Medical University Sapporo Japan Department of Radiology KKR Sapporo Medical Center Sapporo Japan Preparatory Office for Proton Therapy Center Radiation Therapy Research Institute Social Medical Corporation Teishinkai Sapporo Japan Department of Radiology National Hospital Organization Hokkaido Cancer Center Sapporo Japan Department of Radiology Kushiro City General Hospital Kushiro Japan Department of Radiation Oncology School of Medicine Sapporo Medical University Sapporo Japan

cone-beam CT (CBCT) images acquired during radiation treatment can be used to recalculate the dose distribution as well as to confirm the treatment location. However, it is difficult to obtain the electron densities (EDs) necessary for dose calculation from CBCT images because of the effects of scatter contamination during CBCT image acquisition. This paper presents a mathematical method for converting the pixel values of CBCT images (CBCT values) into Hounsfield units (HUs) of radiation treatment simulation CT (simCT) images for use in radiation treatment planning. CBCT values are converted into HUs by matching the histograms of the CBCT values with the histograms of the HUs for each slice via linear scaling of the CBCT values. For prostate cancer and head-and-neck cancer patients, the EDs obtained from converted CBCT values (mCBCT values) show good agreement with the EDs obtained from HUs, within approximately 3.0%, and the dose calculated on the basis of CBCT images shows good agreement with the dose calculated on the basis of the simCT images, within approximately 2.0%. Because the CBCT values are converted for each slice, this conversion method can account for variation in the CBCT values associated with differences in body size, body shape, and inner tissue structures, as well as in longitudinally displaced positions from the isocenter, unlike conventional methods that use electron density phantoms. This method improves on conventional CBCT-ED conversion and shows considerable potential for improving the accuracy of radiation treatment planning using CBCT images.

关键词： cone-beam Computed Tomography Hounsfield Unit Electron Density Ra-diation Treatment Planning

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利用cone-beam CT探讨支抗微螺钉周围骨密度与其稳定性的关系

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口腔医学研究 2013年第6期29卷 547-550页

作者：秦璐邵奕奕赵颖首都医科大学宣武医院口腔科100053

目的:利用cone-beam CT测量支抗微螺钉周围骨密度值,探讨其与微螺钉稳定性的关系。方法:选取颌骨左右对称植入微螺钉后一侧松动而另一侧稳固的7名(共18枚微螺钉)正畸患者。拍摄CBCT,所得三维影像重建后用OnDemand 3DApplication软件对... 详细信息

目的:利用cone-beam CT测量支抗微螺钉周围骨密度值,探讨其与微螺钉稳定性的关系。方法:选取颌骨左右对称植入微螺钉后一侧松动而另一侧稳固的7名(共18枚微螺钉)正畸患者。拍摄CBCT,所得三维影像重建后用OnDemand 3DApplication软件对微螺钉骨内部分周围2mm范围内骨密度(以Hounsfield Unit表示)进行测量,自身对照比较分析双侧对称部位所植入微螺钉周围骨密度测量值间的差异。结果:松动微螺钉与稳定微螺钉骨内部分周围2mm范围内骨密度无统计学差异,两侧微螺钉钉尖部1/3、钉中部1/3及钉颈部1/3周围骨密度均无统计学差异。结论:微螺钉种植支抗的稳定性与其周围骨密度间未发现明显相关性。

关键词：微螺钉 cone-beam CT 骨密度

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Clinical Endodontic Applications of cone beam-Computed Tomography in Modern Dental Practice

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Open Journal of Stomatology 2017年第7期7卷 314-326页

作者： Johnah C. Galicia Jeffrey Kawilarang Peter Z. Tawil Department of Endodontics Arthur A. Dugoni School of Dentistry San Francisco CA USA Endodontic Private Practice Los Angeles CA USA Department of Endodontics School of Dentistry University of North Carolina at Chapel Hill Chapel Hill NC USA

Nearly two decades since cone beam-Computed Tomography (CBCT) was introduced in dentistry, this technology has been proven to be a useful asset in modern dental practice. The information gleaned from a CBCT scan influences treatment decisions and prognostication of challenging endodontic cases. The authors present six cases that utilized CBCT to diagnose vertical root fracture, to assess resorption, to guide the clinician in overcoming anatomical complexities, to hurdle diagnostic dilemmas and to perform pre-surgical evaluation. Initially, a thorough clinical assessment was performed;however, conventional periapical radiographs were not able to provide sufficient information to arrive at a definite diagnosis or a thorough treatment plan. CBCT was therefore deemed helpful for these cases. Clearly, there are advantages to using CBCT. With a better understanding of each case, the clinician can plan a definitive treatment plan and offer a clearer case prognosis to their patient.

关键词： Endodontics cone-beam Computed Tomography Case Reports Radiography

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Usefulness of intra-procedural cone-beam computed tomography in modified balloon-occluded retrograde transvenous obliteration of gastric varices

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World Journal of Radiology 2016年第4期8卷 390-396页

作者： Edward Wolfgang Lee Naomi So Ryan Chapman Justin P McWilliams Christopher T Loh Ronald W Busuttil Stephen T Kee Division of Interventional Radiology Department of RadiologyUCLA Medical CenterDavid Geffen School of Medicine at UCLA Dumont-UCLA Transplant Center Pfleger Liver InstituteDivision of Liver and Pancreas TransplantationDepartment of SurgeryDavid Geffen School of Medicine at University of California

AIM:To evaluate whether intra-procedural conebeam computed tomography(CBCT)performed during modified balloon-occluded retrograde transvenous obliteration(mB RTO)can accurately determine technical success of complete variceal ***:From June 2012 to December 2014,15 patients who received CBCT during m BRTO for treatment of portal hypertensive gastric variceal bleeding were retrospectively ***-dimensional(3D)CBCT images were performed and evaluated prior to the end of the procedure,and these were further analyzed and compared to the pre-procedure contrast-enhanced computed tomography to determine the technical success of m BRTO including:Complete occlusion/obliteration of:(1)gastrorenal shunt(GRS);(2)gastric varices;and(3)afferent feeding ***-mB RTO contrast-enhanced CT was used to confirm the accuracy and diagnostic value of CBCT within 2-3 ***:Intra-procedural 3D-CBCT images were 100% accurate in determining the technical success of m BRTO in all 15 *** demonstrated complete occlusion/obliteration of GRS,gastric varices,collaterals and afferent feeding veins during m BRTO,which was confirmed with post-m BRTO *** patients showed incomplete obliteration of gastric varices and feeding veins on CBCT,which therefore required additional gelfoam injections to complete the *** patient required additional procedures or other interventions during their follow-up period(684 ± 279 d).CONCLUSION:CBCT during mB RTO appears to accurately and immediately determine the technical success of mB *** may improve the technical and clinical success/outcome of m BRTO and reduce additional procedure time in the future.

关键词： Gastric varices Modified balloon-occluded retrograde transvenous obliteration Gastric variceal bleeding cone-beam computed tomography Coilassisted retrograde transvenous obliteration

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Bone mineral density in cone beam computed tomography:Only a few shades of gray

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World Journal of Radiology 2014年第8期6卷 607-612页

作者： Marcio José da Silva Campos Thainara Salgueiro de Souza Sergio Luiz Mota Júnior Marcelo Reis Fraga Robert Willer Farinazzo Vitral Department of Orthodontics Juiz de Fora Federal University 36036-900 Minas Gerais Brasil

cone beam computed tomography(CBCT) has often been used to determine the quality of craniofacial bone structures through the determination of mineral density, which is based on gray scales of the images obtained. However, there is no consensus regarding the accuracy of the determination of the gray scales in these exams. This study aims to provide a literature review concerning the reliability of CBCT to determine bone mineral density. The gray values obtained with CBCT show a linear relationship with the attenuation coefficients of the materials, Hounsfield Units values obtained with medical computed tomography, and density values from dual energy X-ray absorciometry. However, errors are expected when CBCT images are used to define the quality of the scanned structures be-cause these images show inconsistencies and arbitrari-ness in the gray values, particularly when related to abrupt change in the density of the object, X-ray beam hardening effect, scattered radiation, projection data discontinuity-related effect, differences between CBCTdevices, changes in the volume of the field of view(FOV), and changes in the relationships of size and position between the FOV and the object evaluated. A few methods of mathematical correction of the gray scales in CBCT have been proposed; however, they do not generate consistent values that are independent of the devices and their configurations or of the scanned objects. Thus, CBCT should not be considered the ex-amination of choice for the determination of bone and soft tissue mineral density at the current stage, par-ticularly when values obtained are to be compared to predetermined standard values. Comparisons between symmetrically positioned structures inside the FOV and in relation to the exomass of the object, as it occurs with the right and left sides of the skull, seem to be viable because the effects on the gray scale in the re-gions of interest are the same.

关键词： Tomography cone-beam computed tomography Bone mineral density Reproducibility of results

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Long-term clinical performance of flapless implant surgery compared to the conventional approach with flap elevation:A systematic review and meta-analysis

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World Journal of Clinical Cases 2020年第6期8卷 1087-1103页

作者： He Cai Xing Liang Dong-Yuan Sun Jun-Yu Chen Department of Prosthodontics State Key Laboratory of Oral DiseasesNational Clinical Research Center for Oral DiseasesWest China Hospital of StomatologySichuan UniversityChengdu 610041Sichuan ProvinceChina Botnar Research Centre University of OxfordWindmill RoadOxford OX37LDUnited Kingdom Kennedy Institute of Rheumatology University of OxfordRoosevelt DriveOxford OX37FYUnited Kingdom

BACKGROUND The conventional implant approach involves flap elevation,which may result in increased soft tissue and bone loss and postoperative *** flapless surgical technique,aided by three-dimensional medical imaging equipment,is regarded as a possible alternative to the conventional approach to alleviate the above *** studies have been performed regarding the role of flapless implant ***,the results are inconsistent and there is no robust synthesis of long-term evidence to better inform surgeons regarding which type of surgical technique is more beneficial to the long-term prognosis of patients in need of implant *** To compare the long-term clinical performance after flapless implant surgery to that after the conventional approach with flap *** PubMed,EMBASE,Cochrane Central Register of Controlled Trials,and grey literature databases were searched from inception to 23 September *** controlled trials (RCTs) and cohort studies comparing the long-term clinical performance after flapless implant surgery to that after the conventional approach over a follow-up of three years or more were ***-analyses were conducted to estimate the odds ratios (ORs) or mean differences (MDs) and their 95 To confidence intervals (CIs) between the long-term implant survival rate,marginal bone loss,and complication rate of the flapless and conventional *** analyses were carried out to account for the possible effects of the guided or free-hand method during flapless *** Ten articles,including four RCTs and six cohort studies,satisfied the eligibility criteria and nine of them were inclded in the *** was no significant difference between the long-term implant survival rate [OR=1.30,95%CI (0.37,4.54),P=0.68],marginal bone loss [MD=0.01,95%CI (-0.42,0.44),P=0.97],and complication rate [OR=1.44,95%CI (0.77,2.68),P=0.25] after flapless implant surgery and the conventional appro

关键词： Flapless implant surgery Dental implantation Minimally invasive surgical procedures Computer-assisted surgery cone-beam computed tomography Implant survival rate Marginal bone loss Complication rate

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