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Schulze N, Werpy N, Gernhardt J, Fritsch G, Hildebrandt T, Vanderperren K, Klopfleisch R, Ben Romdhane R, Lischer C, Ehrle A. Dynamic three-dimensional computed tomographic imaging facilitates evaluation of the equine cervical articular process joint in motion. Equine Vet J 2023; 55:83-91. [PMID: 35043993 DOI: 10.1111/evj.13560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 11/08/2021] [Accepted: 12/30/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND Dynamic computed tomography (CT) imaging has been introduced in human orthopaedics and is continuing to gain popularity. With dynamic CT, video sequences of anatomical structures can be evaluated in motion. OBJECTIVES To investigate the feasibility of dynamic CT for diagnostic imaging of the equine cervical articular process joints (APJs) and to give a detailed description of the APJ movement pattern. STUDY DESIGN Descriptive cadaver imaging. METHODS Cervical specimens of twelve Warmblood horses were included. A custom-made motorised testing device was used to position and manipulate the neck specimens and perform dynamic 2D and 3D CT imaging. Images were obtained with a 320-detector-row CT scanner with a 160 mm wide-area (2D) solid-state detector design that allows image acquisition of a volumetric axial length of 160 mm without moving the CT couch. Dynamic videos were acquired and divided into four phases of movement. Three blinded observers used a subjective scale of 1 (excellent) to 4 (poor) to grade the overall image quality in each phases of motion cycle. RESULTS With an overall median score of 1 the image quality, a significantly lower score was observed in the dynamic 3D videos over the four phases by the three observers compared with the 2D videos for both flexion (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .007) and extension movement (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .008). Median Translational displacement of the APJ surface was significantly greater in flexion than in extension movement (P = .002). MAIN LIMITATIONS The small number of specimens included. Excision of spines and removal of musculature. CONCLUSIONS The study is a first step in the investigation of the potential of dynamic 3D CT in veterinary medicine, a technique that has only begun to be explored and leaves much room for refinement prior to its introduction in routine practice. CT with a detector coverage of 16 cm and a rotation speed of 0.32 seconds provides high-quality images of moving objects and gives new insight into the movement pattern of equine cervical APJs.
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Affiliation(s)
- Nicole Schulze
- Equine Clinic, Surgery and Radiology, Freie Universität Berlin, Berlin, Germany
| | - Natasha Werpy
- Equine Diagnostic Imaging Inc., Archer, Florida, USA
| | - Jennifer Gernhardt
- Equine Clinic, Surgery and Radiology, Freie Universität Berlin, Berlin, Germany
| | - Guido Fritsch
- Leibniz Institute for Zoo and Wildlife Research, Forschungsverbund Berlin e.V., Berlin, Germany
| | - Thomas Hildebrandt
- Leibniz Institute for Zoo and Wildlife Research, Forschungsverbund Berlin e.V., Berlin, Germany
| | - Katrien Vanderperren
- Department of Veterinary Medical Imaging and Small Animal Orthopaedics, Ghent University, Ghent, Belgium
| | - Robert Klopfleisch
- Institute for Veterinary Pathology, Freie Universität Berlin, Berlin, Germany
| | - Racem Ben Romdhane
- Institute for Veterinary Epidemiology and Biostatistics, Freie Universität Berlin, Berlin, Germany
| | | | - Anna Ehrle
- Equine Clinic, Surgery and Radiology, Freie Universität Berlin, Berlin, Germany
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Lebedev S, Fournié E, Maier J, Stierstorfer K, Kachelrieß M. Motion compensation for aortic valves using partial angle CT reconstructions motion compensation of cardiac valve CT. Med Phys 2021; 49:1495-1506. [PMID: 34822186 DOI: 10.1002/mp.15379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 09/28/2021] [Accepted: 11/02/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE A motion compensation method that is aimed at correcting motion artifacts of cardiac valves is proposed. The primary focus is the aortic valve. METHODS The method is based around partial angle reconstructions and a cost function including the image entropy. A motion model is applied to approximate the cardiac motion in the temporal and spatial domain. Based on characteristic values for velocities and strain during cardiac motion, penalties for the velocity and spatial derivatives are introduced to maintain anatomically realistic motion vector fields and avoid distortions. The model addresses global elastic deformation, but not the finer and more complicated motion of the valve leaflets. RESULTS The method is verified based on clinical data. Image quality was improved for most artifact impaired reconstructions. An image quality study with Likert scoring of the motion artifact severity on a scale from 1 (highest image quality) to 5 (lowest image quality/extreme artifact presence) was performed. The biggest improvements after applying motion compensation were achieved for strongly artifact impaired initial images scoring 4 and 5, resulting in an average change of the scores by -0.59 ± 0.06 and -1.33 ± 0.03, respectively. In case of artifact free images, a chance to introduce blurring was observed and their average score was raised by 0.42 ± 0.03. CONCLUSION Motion artifacts were consistently removed and image quality improved.
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Affiliation(s)
- Sergej Lebedev
- X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Siemens Healthineers, Forchheim, Germany
- Department of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany
| | | | - Joscha Maier
- X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | | | - Marc Kachelrieß
- X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Medical Faculty, University of Heidelberg, Heidelberg, Germany
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Robinson S, Straatman L, Lee TY, Suh N, Lalone E. Evaluation of Four-Dimensional Computed Tomography as a Technique for Quantifying Carpal Motion. J Biomech Eng 2021; 143:061011. [PMID: 33564841 DOI: 10.1115/1.4050129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Indexed: 11/08/2022]
Abstract
Delayed diagnosis of dynamic carpal instability often occurs because early changes in bone alignment and movement are difficult to detect and manifest mainly during a dynamic/functional task. Current diagnostic tools are only able to examine the carpal bones under static or sequential-static conditions. Four-dimensional (three dimensions + time) computed tomography (4DCT) enables quantification of carpal mechanics through 3D volume sequences of the wrist in motion. A comprehensive understanding of carpal mechanics is needed to define normal function and structure and provide targets for treatment of carpal injuries. In this study, measurements of scaphoid translation and joint congruency were taken by creating models from the CT scans of the carpals in extreme frames of motion, registering those models to the neutral position, transforming the models into a local coordinate system, and using software to calculate the joint surface areas (JSA). Results indicated that the centroid of the scaphoid translated 6.4 ± 1.3 mm and extended from extreme radial to extreme ulnar deviation. Results are consistent with the literature. An additional study was performed to measure the responsiveness of the 4DCT technique presented. Bone models from each frame of motion for radio ulnar deviation (RUD) and flexion extension (FE) were created and distinct differences between their JSA were measured qualitatively and quantitatively. The results show that there was statistically significantly different JSA within carpal joints between RUD and FE. These studies provide the first step in developing the methodology when using 4DCT scanning to measure subtle abnormalities in the wrist.
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Affiliation(s)
- Sydney Robinson
- School of Biomedical Engineering, Western University, 1151 Richmond St, London, ON N6A 3K7, Canada; Roth McFarlane Hand and Upper Limb Centre, St Joseph's Health Care London, 268 Grosvenor St, London, ON N6A 4V2, Canada
| | - Lauren Straatman
- Roth McFarlane Hand and Upper Limb Centre, St Joseph's Health Care London, 268 Grosvenor St, London, ON N6A 4V2, Canada; Graduate Program of Health and Rehabilitation Science, Western University, 1151 Richmond St, London, ON N6A 3K7, Canada
| | - Ting-Yim Lee
- Robarts Research Institute, 100 Perth Dr, London, ON N6A 5K8, Canada; Lawson Health Research Institute, 750 Base Line Rd E, London, ON N6C 2R5, Canada; Department of Medical Biophysics, Western University, 1151 Richmond St, London, ON N6A 3K7, Canada
| | - Nina Suh
- Roth McFarlane Hand and Upper Limb Centre, St Joseph's Health Care London, 268 Grosvenor St, London, ON N6A 4V2, Canada; Schulich School of Medicine and Dentistry,Western University, 1151 Richmond St, London, ON N6A 3K7, Canada
| | - Emily Lalone
- School of Biomedical Engineering, Western University, 1151 Richmond St, London, ON N6A 3K7, Canada; Roth McFarlane Hand and Upper Limb Centre, St Joseph's Health Care London, 268 Grosvenor St, London, ON N6A 4V2, Canada
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Lebedev S, Fournie E, Stierstorfer K, Kachelrieß M. Stack transition artifact removal (STAR) for cardiac CT. Med Phys 2019; 46:4777-4791. [PMID: 31444974 DOI: 10.1002/mp.13786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 06/12/2019] [Accepted: 07/03/2019] [Indexed: 11/05/2022] Open
Abstract
INTRODUCTION In cardiac computed tomography (CT), irregular motion may lead to unique artifacts for scanners with a longitudinal collimation that does not cover the entire heart. Given partial coverage, subvolumes, or stacks, may be reconstructed and used to assemble a final CT volume. Irregular motion, for example, due to cardiac arrhythmia or breathing, may cause mismatch between neighboring stacks and therefore discontinuities within the final CT volume. The aim of this work is the removal of the discontinuities that are hereafter referred to as stack transition artifacts. METHOD AND MATERIALS A stack transition artifact removal (STAR) is achieved using a symmetric deformable image registration. A symmetric Demons algorithm was implemented and applied to stacks to remove mismatch and therefore the stack transition artifacts. The registration can be controlled with one parameter that affects the smoothness of the deformation vector field (DVF). The latter is crucial for realistically transforming the stacks. Different smoothness settings as well as an entirely automatic parameter selection that considers the required deformation magnitude for each registration were tested with patient data. Thirteen datasets were evaluated. Simulations were performed on two additional datasets. RESULTS AND CONCLUSION STAR considerably improved image quality while computing realistic DVFs. Discontinuities, for example, appearing as breaks or cuts in coronary arteries or cardiac valves, were removed or considerably reduced. A constant smoothing parameter that ensured satisfactory results for all datasets was found. The automatic parameter selection was able to find a proper setting for each individual dataset. Consequently, no over regularization of the DVF occurred that would unnecessarily limit the registration accuracy for cases with small deformations. The automatic parameter selection yielded the best overall results and provided a registration method for cardiac data that does not require user input.
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Affiliation(s)
- Sergej Lebedev
- X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Siemens Healthineers, 91301, Forchheim, Germany.,Department of Physics and Astronomy, University of Heidelberg, 69120, Heidelberg, Germany
| | | | | | - Marc Kachelrieß
- X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany.,Medical Faculty, University of Heidelberg, 69120, Heidelberg, Germany
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Mori S, Kumagai M, Karube M, Yamamoto N. Dosimetric impact of 4DCT artifact in carbon-ion scanning beam treatment: Worst case analysis in lung and liver treatments. Phys Med 2016; 32:787-94. [DOI: 10.1016/j.ejmp.2016.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 05/03/2016] [Accepted: 05/05/2016] [Indexed: 12/24/2022] Open
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Neo PY, Mat Jais IS, Panknin C, Lau CC, Chan LP, An KN, Tay SC. Dynamic imaging with dual-source gated Computed Tomography (CT): Implications of motion parameters on image quality for wrist imaging. Med Eng Phys 2013; 35:1837-42. [DOI: 10.1016/j.medengphy.2013.05.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 04/17/2013] [Accepted: 05/18/2013] [Indexed: 11/15/2022]
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Enhanced temporal resolution at cardiac CT with a novel CT image reconstruction algorithm: Initial patient experience. Eur J Radiol 2013; 82:270-4. [DOI: 10.1016/j.ejrad.2012.10.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 10/01/2012] [Accepted: 10/03/2012] [Indexed: 11/19/2022]
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8
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Tang Q, Cammin J, Srivastava S, Taguchi K. A fully four-dimensional, iterative motion estimation and compensation method for cardiac CT. Med Phys 2012; 39:4291-305. [PMID: 22830763 PMCID: PMC3396707 DOI: 10.1118/1.4725754] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 05/19/2012] [Accepted: 05/21/2012] [Indexed: 01/18/2023] Open
Abstract
PURPOSE To develop a new fully four-dimensional (4D), iterative image reconstruction algorithm for cardiac CT that alternates the following two methods: estimation of a time-dependent motion vector field (MVF) of the heart from image data and reconstruction of images using the estimated MVF and projection data. METHODS Volumetric image data at different cardiac phase points were obtained using electrocardiogram-gated CT. Motion estimation (ME) and motion-compensated image reconstruction (MCR) were performed alternately until convergence was achieved. The ME method estimated the cardiac MVF using 4D nonrigid image registration between a cardiac reference phase and all the other phases. The nonrigid deformation of the heart was modeled using cubic B-splines. The cost function consisted of a sum of squared weighted differences and spatial and temporal regularization terms. A nested conjugate gradient optimization algorithm was applied to minimize the cost function and estimate the MVFs. Cardiac images were reconstructed using a motion-tracking algorithm that utilized the MVFs estimated by the ME method. The reconstructed images supplied the input to the ME of the next iteration. The performance of the proposed method was evaluated using four patient data sets acquired with a 64-slice CT scanner. The heart rates of the patients ranged from 52 to 71 beats/min. RESULTS Motion artifacts were significantly reduced, and the image quality increased with the number of iterations. Without MCR, the right coronary artery (RCA) was deformed into an arc in axial images of rapid phases. With the proposed method the RCA appeared sharper and was reconstructed similar in shape to the reconstruction at the quiescent phase at mid-diastole. The boundary between the interventricular septum and the right ventricle was also clearer and sharper using the proposed algorithm. The steepness of the transition range at a rapid phase (35% R-R) was increased from 6.8 HU∕pixel to 11.5 HU∕pixel. The ME-MCR algorithm converged in just four iterations. CONCLUSION We developed a fully 4D image reconstruction method that alternates ME and MCR algorithms in an iterative fashion. Performance tests using clinical patient data resulted in reduced motion artifacts.
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Affiliation(s)
- Qiulin Tang
- The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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Isola A, Metz C, Schaap M, Klein S, Grass M, Niessen W. Cardiac motion-corrected iterative cone-beam CT reconstruction using a semi-automatic minimum cost path-based coronary centerline extraction. Comput Med Imaging Graph 2012; 36:215-26. [DOI: 10.1016/j.compmedimag.2011.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 10/14/2011] [Accepted: 12/19/2011] [Indexed: 11/30/2022]
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Isola A, Ziegler A, Schäfer D, Köhler T, Niessen W, Grass M. Motion compensated iterative reconstruction of a region of interest in cardiac cone-beam CT. Comput Med Imaging Graph 2010; 34:149-59. [DOI: 10.1016/j.compmedimag.2009.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 05/27/2009] [Accepted: 08/17/2009] [Indexed: 10/20/2022]
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Isola AA, Grass M, Niessen WJ. Fully automatic nonrigid registration-based local motion estimation for motion-corrected iterative cardiac CT reconstruction. Med Phys 2010; 37:1093-109. [PMID: 20384245 DOI: 10.1118/1.3301600] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Alfonso A Isola
- Philips Technologie GmbH Forschungslaboratorien, Roentgenstrasse 24-26, 22335 Hamburg, Germany.
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12
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Taguchi K, Khaled A. Artifacts in Cardiac Computed Tomographic Images. J Am Coll Radiol 2009; 6:590-3. [DOI: 10.1016/j.jacr.2009.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 05/01/2009] [Indexed: 10/20/2022]
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13
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Isola AA, Ziegler A, Koehler T, Niessen WJ, Grass M. Motion-compensated iterative cone-beam CT image reconstruction with adapted blobs as basis functions. Phys Med Biol 2008; 53:6777-97. [PMID: 18997267 DOI: 10.1088/0031-9155/53/23/009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper presents a three-dimensional method to reconstruct moving objects from cone-beam X-ray projections using an iterative reconstruction algorithm and a given motion vector field. For the image representation, adapted blobs are used, which can be implemented efficiently as basis functions. Iterative reconstruction requires the calculation of line integrals (forward projections) through the image volume, which are compared with the actual measurements to update the image volume. In the existence of a divergent motion vector field, a change in the volumes of the blobs has to be taken into account in the forward and backprojections. An efficient method to calculate the line integral through the adapted blobs is proposed. It solves the problem, how to compensate for the divergence in the motion vector field on a grid of basis functions. The method is evaluated on two phantoms, which are subject to three different known motions. Moreover, a motion-compensated filtered back-projection reconstruction method is used, and the reconstructed images are compared. Using the correct motion vector field with the iterative motion-compensated reconstruction, sharp images are obtained, with a quality that is significantly better than gated reconstructions.
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Affiliation(s)
- A A Isola
- Philips Research Europe - Hamburg, Sector Technical Systems, Roentgenstr. 24-26, D-22335 Hamburg, Germany.
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Understanding the relationship between image quality and motion velocity in gated computed tomography: preliminary work for 4-dimensional musculoskeletal imaging. J Comput Assist Tomogr 2008; 32:634-9. [PMID: 18664854 DOI: 10.1097/rct.0b013e31815c5abc] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To study the effect of motion velocity on image quality to determine the requirements for 4-dimensional (4D; ie, 3D + time) musculoskeletal computed tomographic (CT) imaging. MATERIALS AND METHODS A phantom with resolution targets in both axial (x-y) and coronal (x-z) planes was attached to a motion device and scanned with 64-slice CT using a retrospectively gated CT protocol with pitch values of 0.1 and 0.2. Data were acquired with the phantom at rest and while moving periodically along the x axis at several velocities. Spatial resolution and motion artifacts were assessed both for the axial and coronal targets. RESULTS A linear relationship was found between motion artifact severity and phantom velocity. Spatial resolution was better preserved in the coronal target. However, coronal images displayed banding artifacts, with band displacements being linearly related to motion velocity. CONCLUSIONS The 4D CT imaging of periodically moving objects with velocities up to 20 mm/s is feasible using a pitch value of 0.1 and a motion frequency of 30 cycles per minute.
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King M, Giger ML, Suzuki K, Pan X. Feature-based characterization of motion-contaminated calcified plaques in cardiac multidetector CT. Med Phys 2008; 34:4860-75. [PMID: 18196812 DOI: 10.1118/1.2794172] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In coronary calcium scoring, motion artifacts affecting calcified plaques are commonly characterized using descriptive terms, which incorporate an element of subjectivity in their interpretations. Quantitative indices may improve the objective characterization of these motion artifacts. In this paper, an automated method for generating 12 quantitative indices, i.e., features that characterize the motion artifacts affecting calcified plaques, is presented. This method consists of using the rapid phase-correlated region-of-interest (ROI) tracking algorithm for reconstructing ROI images of calcified plaques automatically from the projection data obtained during a cardiac scan, and applying methods for extracting features from these images. The 12 features include two dynamic, six morphological, and four intensity-based features. The two dynamic features are three-dimensional (3D) velocity and 3D acceleration. The six morphological features include edge-based volume, threshold-based volume, sphericity, irregularity, average margin gradient, and variance of margin gradient. The four intensity-based features are maximum intensity, mean intensity, minimum intensity, and standard deviation of intensity. The 12 features were extracted from 54 reconstructed sets of simulated four-dimensional images from the dynamic NCAT phantom involving six calcified plaques under nine heart rate/multi-sector gating combinations. In order to determine how well the 12 features correlated with a plaque motion index, which was derived from the trajectory of the plaque, partial correlation coefficients adjusted for heart rate, number of gated sectors, and mean feature values of the six plaques were calculated for all 12 features. Features exhibiting stronger correlations ([r] epsilon [0.60,1.00]) with the motion index were 3D velocity, maximum intensity, and standard deviation of intensity. Features demonstrating stronger correlations ([r] epsilon [0.60, 1.00]) with other features mostly involved intensity-based features. Edge-based volume/irregularity and average margin gradient/variance of margin gradient were the only two feature pairs out of 12 with stronger correlations that did not involve intensity-based features. Automatically extracted features of the motion artifacts affecting calcified plaques in cardiac computed tomography images potentially can be used to develop models for predicting image assessability with respect to motion artifacts.
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Affiliation(s)
- Martin King
- Department of Radiology, Committee on Medical Physics, The University of Chicago, Chicago, Illinois 60637, USA.
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Suzuki T, Ota T, Maeda T, Noshi Y, Nakanishi S, Okumura M, Sanda Y, Anno H, Katada K. Development of variable pitch factor scanning for multislice computed tomography. Acad Radiol 2008; 15:1069-74. [PMID: 18620127 DOI: 10.1016/j.acra.2008.02.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 02/07/2008] [Accepted: 02/21/2008] [Indexed: 11/29/2022]
Abstract
RATIONALE AND OBJECTIVES The latest multislice computed tomography (MSCT) scanners permit the chest and abdomen to be scanned continuously. However, conventionally, it has been necessary to perform scanning twice using different pitch factors for the cardiac and abdominal regions. We have developed a new scanning technique known as variable pitch factor scanning, in which the table speed is changed during scanning to obtain continuous images from the heart to the abdomen in a single scan, and have evaluated its physical characteristics. MATERIALS AND METHODS A bead phantom, a comb phantom, and a gold wire placed at an angle were scanned using a 64-row MSCT scanner. The variation in the spatial resolution and continuity of images in the body axis direction because of changes in the pitch factor were evaluated. RESULTS Because reconstruction taking the cone angle into consideration was employed, the spatial resolution in the body axis direction was unchanged and the continuity of images in the body axis direction was maintained at a certain level even when the pitch factor was changed. CONCLUSION Variable pitch factor scanning is a useful technique for obtaining continuous images from the heart to the abdomen in a single scan.
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Affiliation(s)
- Tatsuro Suzuki
- CT Systems Development Department, Toshiba Medical Systems Corporation, Tochigi, Japan
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Taguchi K, Kudo H. Motion compensated fan-beam reconstruction for nonrigid transformation. IEEE TRANSACTIONS ON MEDICAL IMAGING 2008; 27:907-917. [PMID: 18599396 DOI: 10.1109/tmi.2008.925076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We develop an approximate fan-beam algorithm to reconstruct an object with time-dependent nonrigid transformation such as the heart. The method is in the form of derivative backprojection filtering with compensation of affine transformations on a local basis. Computer simulations showed the proposed method significantly reduces image artifact due to nonrigid motion. Therefore, with very little motion artifact, the proposed method allowed us to reconstruct images from projections over about one motion cycle, resulting in reduced image noise level down to 40% of the current level.
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Affiliation(s)
- Katsuyuki Taguchi
- Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, 601 N. Caroline Street, Baltimore, MD21287, USA. ktaguchi@ jhmi.edu
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Tay SC, Primak AN, Fletcher JG, Schmidt B, Amrami KK, Berger RA, McCollough CH. Four-dimensional computed tomographic imaging in the wrist: proof of feasibility in a cadaveric model. Skeletal Radiol 2007; 36:1163-9. [PMID: 17805530 DOI: 10.1007/s00256-007-0374-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Revised: 08/08/2007] [Accepted: 08/12/2007] [Indexed: 02/02/2023]
Abstract
OBJECTIVE High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provide novel insights into the pathophysiology of joint instability. The purpose of this work was to assess the feasibility of using retrospectively gated spiral computed tomography (CT) to perform four-dimensional (4D) imaging of the moving wrist joint. MATERIALS AND METHODS A cadaver forearm from below the elbow was mounted on a motion simulator which performed radioulnar deviation of the wrist at 30 cycles per minute. An electronic trigger from the simulator provided the "electrocardiogram" (ECG) signal required for gated reconstructions. Four-dimensional and 3D images were compared by a blinded observer for image quality and presence of artifacts. RESULTS Image quality of 4D images was found to be excellent at the extremes of radial and ulnar deviation (end-motion phases). Some artifacts were seen in mid-motion phases. CONCLUSION 4D CT musculoskeletal imaging is feasible. Four-dimensional CT may allow clinicians to assess functional (dynamic) instabilities of the wrist joint.
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Affiliation(s)
- Shian-Chao Tay
- Orthopedics Biomechanics Laboratory, Mayo Clinic College of Medicine, Rochester, MN, USA
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Mori S, Chen GTY, Endo M. Effects of Intrafractional Motion on Water Equivalent Pathlength in Respiratory-Gated Heavy Charged Particle Beam Radiotherapy. Int J Radiat Oncol Biol Phys 2007; 69:308-17. [PMID: 17707286 DOI: 10.1016/j.ijrobp.2007.05.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 05/01/2007] [Accepted: 05/06/2007] [Indexed: 10/22/2022]
Abstract
PURPOSE To analyze the water equivalent pathlength (WEL) fluctuations resulting from cardiac motion and display these variations on a beam's-eye-view image; the analysis provides insight into the accuracy of lung tumor irradiation with heavy charged particle beams. MATERIALS AND METHODS Volumetric cine computed tomography (CT) images were obtained on 7 lung cancer patients under free-breathing conditions with a 256-multislice CT scanner. Cardiac phase was determined by selecting systole and diastole. A WEL difference image (DeltaWEL) was calculated by subtracting the WEL image at end-systole from that at end-diastole at respiratory exhalation phase. Two calculation regions were defined: Region 1 was limited to the volume defined by planes bounding the heart; Region 2 included the entire body thickness for a given beam's-eye-view angle. RESULTS The DeltaWEL values observed in Region 1 showed fluctuations at the periphery of the heart that varied from 20.4 (SD, 5.2) mm WEL to -15.6 (3.2) mm WEL. The areas over which these range perturbation values were observed were 36.8 (32.4) mm(2) and 6.0 (2.8) mm(2) for positive and negative WEL, respectively. The WEL fluctuations in Region 2 increased by approximately 3-4 mm WEL, whereas negative WEL fluctuations changed by approximately -4 to -5 mm WEL, compared with WEL for Region 1; areas over 20 mm WEL changes in Region 2 increased by 9 mm(2) for positive DeltaWEL and 2 mm(2) for negative DeltaWEL. CONCLUSIONS Cine CT with a 256-multislice CT scanner captures both volumetric cardiac and respiratory motion with a temporal resolution sufficient to estimate range fluctuations by these motions. This information can be used to assess the range perturbations that charged particle beams may experience in irradiation of lung or esophageal tumors adjacent to the heart.
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Affiliation(s)
- Shinichiro Mori
- Department of Radiation Oncology, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA.
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Mori S, Nishizawa K, Kondo C, Ohno M, Akahane K, Endo M. Effective doses in subjects undergoing computed tomography cardiac imaging with the 256-multislice CT scanner. Eur J Radiol 2007; 65:442-8. [PMID: 17628377 DOI: 10.1016/j.ejrad.2007.05.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Revised: 03/30/2007] [Accepted: 05/02/2007] [Indexed: 11/15/2022]
Abstract
BACKGROUND The 256-multislice CT (256MSCT) obtains volumetric data with 128-mm coverage in a single rotation. This coverage allows satisfactory visualization of the whole heart, allowing the 256MSCT to visualize the cardiac chambers and coronary arteries by cine scan without ECG gating. These characteristics provide a solution to the problems of MSCT. Although a wider beam width provides more efficient imaging over a wider coverage area, patient doses with the 256MSCT are of considerable concern. OBJECTIVE We assessed potential radiation exposure with the 256MSCT in a cardiac CT protocol and compared the results to those with 16- and 64MSCT (collimated 64x0.5mm using 256MSCT). METHODS Organ or tissue doses were measured in an anthropomorphic phantom under a coronary artery imaging protocol with the 256MSCT in cine scan mode without ECG gating, and with the 16- and 64MSCT in helical scan mode with ECG gating. RESULTS Average effective doses were 22.8mSv for the 16MSCT, 27.8mSv for the 64MSCT and 14.1mSv for the 256MSCT. The 16- and 64MSCT doses were thus approximately 1.6- and 2.0-fold higher than those of the 256MSCT. CONCLUSIONS Use of the 256MSCT in cardiac volumetric cine imaging offers lower radiation exposure than 16- and 64MSCT, and suggests the potential of this equipment in single-beat cardiac imaging without ECG gating. This effective dose is acceptable for routine cardiac imaging.
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Affiliation(s)
- Shinichiro Mori
- Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Japan
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