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Erath J, Vöth T, Maier J, Fournié E, Petersilka M, Stierstorfer K, Kachelrieß M. Deep learning-based forward and cross-scatter correction in dual-source CT. Med Phys 2021; 48:4824-4842. [PMID: 34309837 DOI: 10.1002/mp.15093] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 06/17/2021] [Accepted: 07/02/2021] [Indexed: 11/08/2022] Open
Abstract
PURPOSE Dual-source computed tomography (DSCT) uses two source-detector pairs offset by about 90°. In addition to the well-known forward scatter, a special issue in DSCT is cross-scattered radiation from X-ray tube A detected in the detector of system B and vice versa. This effect can lead to artifacts and reduction of the contrast-to-noise ratio of the images. The purpose of this work is to present and evaluate different deep learning-based methods for scatter correction in DSCT. METHODS We present different neural network-based methods for forward and cross-scatter correction in DSCT. These deep scatter estimation (DSE) methods mainly differ in the input and output information that is provided for training and inference and in whether they operate on two-dimensional (2D) or on three-dimensional (3D) data. The networks are trained and validated with scatter distributions obtained by our in-house Monte Carlo simulation. The simulated geometry is adapted to a realistic clinical setup. RESULTS All DSE approaches reduce scatter-induced artifacts and lead to superior results than the measurement-based scatter correction. Forward scatter, under the presence of cross-scatter, is best estimated either by our network that uses the current projection and a couple of neighboring views (fDSE 2D few views) or by our 3D network that processes all projections simultaneously (fDSE 3D). Cross-scatter, under the presence of forward scatter, is best estimated using xSSE XDSE 2D, with xSSE referring to a quick single scatter estimate of cross scatter, or by xDSE 3D that uses all projections simultaneously. By using our proposed networks, the total scatter error in dual could be reduced from about 18 HU to approximately 3 HU. CONCLUSIONS Deep learning-based scatter correction can reduce scatter artifacts in DSCT. To achieve more accurate cross-scatter estimations, the use of a cross-scatter approximation improves the results. Also, the ability to leverage across different projection angles improves the precision of the algorithm.
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Affiliation(s)
- Julien Erath
- Division of X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Computed Tomography Division, Siemens Healthcare, Forchheim, Germany.,Medical Faculty, Ruprecht-Karls-University, Heidelberg, Germany
| | - Tim Vöth
- Division of X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Department of Physics and Astronomy, Ruprecht-Karls-University, Heidelberg, Germany
| | - Joscha Maier
- Division of X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Eric Fournié
- Computed Tomography Division, Siemens Healthcare, Forchheim, Germany
| | - Martin Petersilka
- Computed Tomography Division, Siemens Healthcare, Forchheim, Germany
| | - Karl Stierstorfer
- Computed Tomography Division, Siemens Healthcare, Forchheim, Germany
| | - Marc Kachelrieß
- Division of X-Ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Medical Faculty, Ruprecht-Karls-University, Heidelberg, Germany
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Becker AE, Hernandez AM, Schwoebel PR, Boone JM. Cone beam CT multisource configurations: evaluating image quality, scatter, and dose using phantom imaging and Monte Carlo simulations. ACTA ACUST UNITED AC 2020; 65:235032. [DOI: 10.1088/1361-6560/abc306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Gong C, Zeng L, Wang C, Ran L. Design and Simulation Study of a CNT-Based Multisource Cubical CT System for Dynamic Objects. SCANNING 2018; 2018:6985698. [PMID: 30228852 PMCID: PMC6136499 DOI: 10.1155/2018/6985698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/27/2018] [Accepted: 07/12/2018] [Indexed: 06/08/2023]
Abstract
The purpose of this paper is to design and simulate a new computed tomography (CT) system with a high temporal resolution for dynamic objects. We propose a multisource cubical CT (MCCT) system with X-ray tubes and detectors installed on a cube. Carbon nanotube- (CNT-) based X-ray focal spots are distributed on the twelve edges of the cube. The distribution of X-ray focal spots and detectors completely avoids mechanical movements to scan an object under inspection. CNTs are excellent electron field emitters because the use of a "cold" cathode makes it possible to fabricate a cathode with multiple electron emission points, and the CNT-based X-ray focal spots possess little response time and programmable emission. The proposed rotation-free MCCT system can acquire a high scanning speed when using a high frame rate detector. A three-dimensional (3D) reconstruction algorithm with tensor framelet-based L0-norm (TF-L0) minimization is developed for the simulation study of the MCCT. Simulation experiment results demonstrate the feasibility of the MCCT system.
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Affiliation(s)
- Changcheng Gong
- Key Laboratory of Optoelectronic Technology and Systems of the Ministry of Education of China, Chongqing University, Chongqing 400044, China
- Engineering Research Centre of Industrial Computed Tomography Nondestructive Testing of the Ministry of Education of China, Chongqing University, Chongqing 400044, China
| | - Li Zeng
- Engineering Research Centre of Industrial Computed Tomography Nondestructive Testing of the Ministry of Education of China, Chongqing University, Chongqing 400044, China
- College of Mathematics and Statistics, Chongqing University, Chongqing 401331, China
| | - Chengxiang Wang
- College of Mathematical Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China
| | - Lei Ran
- Engineering Research Centre of Industrial Computed Tomography Nondestructive Testing of the Ministry of Education of China, Chongqing University, Chongqing 400044, China
- College of Mechanical Engineering, Chongqing University, Chongqing 400030, China
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Chen M, Yu H. Analytic reconstruction algorithms for triple-source CT with horizontal data truncation. Med Phys 2015; 42:6062-73. [PMID: 26429281 DOI: 10.1118/1.4931408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This paper explores a triple-source imaging method with horizontal data truncation to enlarge the field of view (FOV) for big objects. METHODS The study is conducted by using theoretical analysis, mathematical deduction, and numerical simulations. The proposed algorithms are implemented in c + + and matlab. While the basic platform is constructed in matlab, the computationally intensive segments are coded in c + +, which are linked via a mex interface. RESULTS A triple-source circular scanning configuration with horizontal data truncation is developed, where three pairs of x-ray sources and detectors are unevenly distributed on the same circle to cover the whole imaging object. For this triple-source configuration, a fan-beam filtered backprojection-type algorithm is derived for truncated full-scan projections without data rebinning. The algorithm is also extended for horizontally truncated half-scan projections and cone-beam projections in a Feldkamp-type framework. Using their method, the FOV is enlarged twofold to threefold to scan bigger objects with high speed and quality. The numerical simulation results confirm the correctness and effectiveness of the developed algorithms. CONCLUSIONS The triple-source scanning configuration with horizontal data truncation cannot only keep most of the advantages of a traditional multisource system but also cover a larger FOV for big imaging objects. In addition, because the filtering is shift-invariant, the proposed algorithms are very fast and easily parallelized on graphic processing units.
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Affiliation(s)
- Ming Chen
- School of Mathematics and System Science, Shandong University of Science and Technology, Qingdao, Shandong 265590, China and Department of Electrical and Computer Engineering, University of Massachusetts Lowell, Lowell, Massachusetts 01854
| | - Hengyong Yu
- Department of Electrical and Computer Engineering, University of Massachusetts Lowell, Lowell, Massachusetts 01854
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Kuchenbecker S, Faby S, Sawall S, Lell M, Kachelrieß M. Dual energy CT: how well can pseudo-monochromatic imaging reduce metal artifacts? Med Phys 2015; 42:1023-36. [PMID: 25652515 DOI: 10.1118/1.4905106] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Dual Energy CT (DECT) provides so-called monoenergetic images based on a linear combination of the original polychromatic images. At certain patient-specific energy levels, corresponding to certain patient- and slice-dependent linear combination weights, e.g., E = 160 keV corresponds to α = 1.57, a significant reduction of metal artifacts may be observed. The authors aimed at analyzing the method for its artifact reduction capabilities to identify its limitations. The results are compared with raw data-based processing. METHODS Clinical DECT uses a simplified version of monochromatic imaging by linearly combining the low and the high kV images and by assigning an energy to that linear combination. Those pseudo-monochromatic images can be used by radiologists to obtain images with reduced metal artifacts. The authors analyzed the underlying physics and carried out a series expansion of the polychromatic attenuation equations. The resulting nonlinear terms are responsible for the artifacts, but they are not linearly related between the low and the high kV scan: A linear combination of both images cannot eliminate the nonlinearities, it can only reduce their impact. Scattered radiation yields additional noncanceling nonlinearities. This method is compared to raw data-based artifact correction methods. To quantify the artifact reduction potential of pseudo-monochromatic images, they simulated the FORBILD abdomen phantom with metal implants, and they assessed patient data sets of a clinical dual source CT system (100, 140 kV Sn) containing artifacts induced by a highly concentrated contrast agent bolus and by metal. In each case, they manually selected an optimal α and compared it to a raw data-based material decomposition in case of simulation, to raw data-based material decomposition of inconsistent rays in case of the patient data set containing contrast agent, and to the frequency split normalized metal artifact reduction in case of the metal implant. For each case, the contrast-to-noise ratio (CNR) was assessed. RESULTS In the simulation, the pseudo-monochromatic images yielded acceptable artifact reduction results. However, the CNR in the artifact-reduced images was more than 60% lower than in the original polychromatic images. In contrast, the raw data-based material decomposition did not significantly reduce the CNR in the virtual monochromatic images. Regarding the patient data with beam hardening artifacts and with metal artifacts from small implants the pseudo-monochromatic method was able to reduce the artifacts, again with the downside of a significant CNR reduction. More intense metal artifacts, e.g., as those caused by an artificial hip joint, could not be suppressed. CONCLUSIONS Pseudo-monochromatic imaging is able to reduce beam hardening, scatter, and metal artifacts in some cases but it cannot remove them. In all cases, the CNR is significantly reduced, thereby rendering the method questionable, unless special post processing algorithms are implemented to restore the high CNR from the original images (e.g., by using a frequency split technique). Raw data-based dual energy decomposition methods should be preferred, in particular, because the CNR penalty is almost negligible.
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Affiliation(s)
| | - Sebastian Faby
- German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Stefan Sawall
- German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Michael Lell
- Friedrich-Alexander-University (FAU), Erlangen 91054, Germany
| | - Marc Kachelrieß
- German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
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Abstract
PURPOSE To discuss options in designing detector shapes in third generation CT and to quantify potential cost savings for compact third generation CT systems, and to extend the work from two-dimensional fan-beam CT to three-dimensional cone-beam CT for circular, sequential, and spiral scan trajectories. METHODS Third generation CT scanners typically comprise detectors which are flat or whose shape is the segment of a cylinder or a sphere that is focused onto the focal spot of the x-ray source. There appear to be two design criteria that favor this choice of detector shape. One is the possibility of performing fan-beam and cone-beam filtered backprojection in the native geometry (without rebinning) and the other criterion could be to enable the early use of focused antiscatter grids. It is less known, however, that other detector shapes may also have these properties. While these designs have been evaluated for 2D CT from a theoretical standpoint more than one decade ago the authors revisit and generalize these considerations, extend them to 3D circular, sequential, and spiral cone-beam CT and propose an optimal design in terms of detector costs while keeping image quality constant. Their considerations and conclusions are based on considering the sampling density of the x-rays, including the effects of finite focal spot and finite detector element size. Proposing image reconstruction algorithms or numerically evaluating the results by reconstructing simulated projection data is not within the scope of this work. RESULTS If the detector arc is curved to be nearly concentric with the circle describing the edge of the field of measurement significantly less detector area and detector pixels are required compared to today's third generation CT systems where the detector arc is centered about the focal spot. Combined with a detector that just covers the spiral Tam window cost savings of 60% or more are possible in compact CT systems. In terms of practicability the new designs appear to be nearly as easy to realize as today's third generation systems. CONCLUSIONS Compact CT systems, which require the focal spot to be mounted close to the edge of the field of measurement, may significantly benefit from using detector shapes other than the typical equiangular detector that is focused onto the focal spot.
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Affiliation(s)
- Marc Kachelrieß
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.
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Iterative Reconstruction Techniques: What do they Mean for Cardiac CT? CURRENT CARDIOVASCULAR IMAGING REPORTS 2013. [DOI: 10.1007/s12410-013-9203-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Bhagalia R, Pack JD, Miller JV, Iatrou M. Nonrigid registration-based coronary artery motion correction for cardiac computed tomography. Med Phys 2012; 39:4245-54. [PMID: 22830758 DOI: 10.1118/1.4725712] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE X-ray computed tomography angiography (CTA) is the modality of choice to noninvasively monitor and diagnose heart disease with coronary artery health and stenosis detection being of particular interest. Reliable, clinically relevant coronary artery imaging mandates high spatiotemporal resolution. However, advances in intrinsic scanner spatial resolution (CT scanners are available which combine nearly 900 detector columns with focal spot oversampling) can be tempered by motion blurring, particularly in patients with unstable heartbeats. As a result, recently numerous methods have been devised to improve coronary CTA imaging. Solutions involving hardware, multisector algorithms, or β-blockers are limited by cost, oversimplifying assumptions about cardiac motion, and populations showing contraindications to drugs, respectively. This work introduces an inexpensive algorithmic solution that retrospectively improves the temporal resolution of coronary CTA without significantly affecting spatial resolution. METHODS Given the goal of ruling out coronary stenosis, the method focuses on "deblurring" the coronary arteries. The approach makes no assumptions about cardiac motion, can be used on exams acquired at high heart rates (even over 75 beats/min), and draws on a fast and accurate three-dimensional (3D) nonrigid bidirectional labeled point matching approach to estimate the trajectories of the coronary arteries during image acquisition. Motion compensation is achieved by employing a 3D warping of a series of partial reconstructions based on the estimated motion fields. Each of these partial reconstructions is created from data acquired over a short time interval. For brevity, the algorithm "Subphasic Warp and Add" (SWA) reconstruction. RESULTS The performance of the new motion estimation-compensation approach was evaluated by a systematic observer study conducted using nine human cardiac CTA exams acquired over a range of average heart rates between 68 and 86 beats/min. Algorithm performance was based-lined against exams reconstructed using standard filtered-backprojection (FBP). The study was performed by three experienced reviewers using the American Heart Association's 15-segment model. All vessel segments were evaluated to quantify their viability to allow a clinical diagnosis before and after motion estimation-compensation using SWA. To the best of the authors' knowledge this is the first such observer study to show that an image processing-based software approach can improve the clinical diagnostic value of CTA for coronary artery evaluation. CONCLUSIONS Results from the observer study show that the SWA method described here can dramatically reduce coronary artery motion and preserve real pathology, without affecting spatial resolution. In particular, the method successfully mitigated motion artifacts in 75% of all initially nondiagnostic coronary artery segments, and in over 45% of the cases this improvement was enough to make a previously nondiagnostic vessel segment clinically diagnostic.
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Tang J, Hsieh J, Chen GH. Temporal resolution improvement in cardiac CT using PICCS (TRI-PICCS): Performance studies. Med Phys 2010; 37:4377-88. [DOI: 10.1118/1.3460318] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Steckmann S, Knaup M, Kachelriess M. Algorithm for hyperfast cone-beam spiral backprojection. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2010; 98:253-260. [PMID: 19765852 DOI: 10.1016/j.cmpb.2009.08.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 07/14/2009] [Accepted: 08/14/2009] [Indexed: 05/28/2023]
Abstract
Cone-beam spiral backprojection is computationally highly demanding. At first sight, the backprojection requirements are similar to those of cone-beam backprojection from circular scans such as it is performed in the widely used Feldkamp algorithm. However, there is an additional complication: the illumination of each voxel, i.e. the range of angles the voxel is seen by the X-ray cone is a complex function of the voxel position. The weight function has no analytically closed form and must be numerically determined. Storage of the weights is prohibitive since the amount of memory required equals the number of voxels per spiral rotation times the number of projections a voxel receives contributions and therefore is in the order of 10(9) to 10(11) floating point values for typical spiral scans. We propose a new algorithm that combines the spiral symmetry with the ability of today's 64 bit CPUs to store large amounts of precomputed weights. Using the spiral symmetry in this way allows to exploit data-level parallelism and thereby to achieve a very high level of vectorization. An additional postprocessing step rotates these slices back to normal images. Our new backprojection algorithm achieves up to 24.6 Giga voxel updates per second (GUPS) on our systems that are equipped with two standard Intel X5570 quad core CPUs (Intel Xeon 5500 platform, 2.93 GHz, Intel Corporation). This equals the reconstruction of 410 images per second assuming each slice consists of 512 x 512 pixels, receiving contributions from 512 projections.
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Affiliation(s)
- Sven Steckmann
- Institute of Medical Physics (IMP), University of Erlangen-Nürnberg, 91052 Erlangen, Germany.
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Lu Y, Katsevich A, Zhao J, Yu H, Wang G. Fast exact/quasi-exact FBP algorithms for triple-source helical cone-beam CT. IEEE TRANSACTIONS ON MEDICAL IMAGING 2010; 29:756-770. [PMID: 19923043 PMCID: PMC2885857 DOI: 10.1109/tmi.2009.2035617] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Cardiac computed tomography (CT) has been improved over past years, but it still needs improvement for higher temporal resolution in the cases of high or irregular cardiac rates. Given successful applications of dual-source cardiac CT scanners, triple-source cone-beam CT seems a promising mode for cardiac CT. In this paper, we propose two filtered-backprojection algorithms for triple-source helical cone-beam CT. The first algorithm utilizes two families of filtering lines. These lines are parallel to the tangent of the scanning trajectory and the so-called L lines. The second algorithm utilizes two families of filtering lines tangent to the boundaries of the Zhao window and L lines, respectively, but it eliminates the filtering paths along the tangent of the scanning trajectory, thus reducing the required detector size greatly. The first algorithm is theoretically exact for r < 0.265R and quasi-exact for 0.265R <or= r < 0.495R, and the second algorithm is quasi-exact for r < 0.495R , where r and R denote the object radius and the trajectory radius, respectively. Both algorithms are computationally efficient. Numerical results are presented to verify and showcase the proposed algorithms.
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Affiliation(s)
- Yang Lu
- Asterisk indicates corresponding author
| | - Alexander Katsevich
- Department of Mathematics, University of Central Florida, Orlando, FL 32816 USA ()
| | - Jun Zhao
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China ()
| | - Hengyong Yu
- SBES Division & ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, VA 24061 USA ()
| | - Ge Wang
- SBES Division & ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, VA 24061 USA ()
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Stenner P, Schmidt B, Bruder H, Allmendinger T, Haberland U, Flohr T, Kachelriess M. Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase-correlated CT. Med Phys 2009; 36:5683-94. [PMID: 20095281 DOI: 10.1118/1.3259734] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Ertel D, Pflederer T, Achenbach S, Kalender WA. Real-time determination of the optimal reconstruction phase to control ECG pulsing in spiral cardiac CT. Phys Med 2009; 25:122-7. [DOI: 10.1016/j.ejmp.2008.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Revised: 07/10/2008] [Accepted: 08/19/2008] [Indexed: 10/21/2022] Open
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Chen GH, Tang J, Hsieh J. Temporal resolution improvement using PICCS in MDCT cardiac imaging. Med Phys 2009; 36:2130-5. [PMID: 19610302 DOI: 10.1118/1.3130018] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The current paradigm for temporal resolution improvement is to add more source-detector units and/or increase the gantry rotation speed. The purpose of this article is to present an innovative alternative method to potentially improve temporal resolution by approximately a factor of 2 for all MDCT scanners without requiring hardware modification. The central enabling technology is a most recently developed image reconstruction method: Prior image constrained compressed sensing (PICCS). Using the method, cardiac CT images can be accurately reconstructed using the projection data acquired in an angular range of about 120 degrees, which is roughly 50% of the standard short-scan angular range (approximately 240 degrees for an MDCT scanner). As a result, the temporal resolution of MDCT cardiac imaging can be universally improved by approximately a factor of 2. In order to validate the proposed method, two in vivo animal experiments were conducted using a state-of-the-art 64-slice CT scanner (GE Healthcare, Waukesha, WI) at different gantry rotation times and different heart rates. One animal was scanned at heart rate of 83 beats per minute (bpm) using 400 ms gantry rotation time and the second animal was scanned at 94 bpm using 350 ms gantry rotation time, respectively. Cardiac coronary CT imaging can be successfully performed at high heart rates using a single-source MDCT scanner and projection data from a single heart beat with gantry rotation times of 400 and 350 ms. Using the proposed PICCS method, the temporal resolution of cardiac CT imaging can be effectively improved by approximately a factor of 2 without modifying any scanner hardware. This potentially provides a new method for single-source MDCT scanners to achieve reliable coronary CT imaging for patients at higher heart rates than the current heart rate limit of 70 bpm without using the well-known multisegment FBP reconstruction algorithm. This method also enables dual-source MDCT scanner to achieve higher temporal resolution without further hardware modifications.
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Affiliation(s)
- Guang-Hong Chen
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
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Ertel D, Kyriakou Y, Lapp RM, Kalender WA. Respiratory phase-correlated micro-CT imaging of free-breathing rodents. Phys Med Biol 2009; 54:3837-46. [PMID: 19491456 DOI: 10.1088/0031-9155/54/12/015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We provide a dedicated phase-correlated imaging procedure for respiratory gating in micro-CT imaging with automatic detection of the optimal data window providing the least amount of motion blurring. A rawdata-based motion function (kymogram) was used for synchronization purposes and for identification of the optimal data window used for phase-correlated image reconstruction. Measurements were performed on a dual-source micro-CT scanner. Projection data were acquired over ten rotations for multi-segment phase-correlated reconstruction. Visual assessment was performed on datasets of ten free-breathing subjects. The kymogram approach provided a reliable synchronization signal for phase-correlated image reconstruction. Also, it allowed for the identification of phase intervals of increased and decreased motion and the corresponding detection of the optimal reconstruction phase. Phase-correlated images showed a strong improvement with respect to motion blurring compared to standard image reconstruction. A reconstruction for the calculated optimal data window provided the least amount of motion blurring and even allowed for the assessment of small structures in the lung. The dedicated retrospective phase-correlated image reconstruction procedure for respiratory gating is a feasible approach for motion-free imaging. A subject-specific optimal reconstruction phase can minimize motion blurring and further improve image quality.
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Affiliation(s)
- Dirk Ertel
- Institute of Medical Physics, University of Erlangen-Nürnberg, Erlangen, Germany.
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Zhao J, Jin Y, Lu Y, Wang G. A filtered backprojection algorithm for triple-source helical cone-beam CT. IEEE TRANSACTIONS ON MEDICAL IMAGING 2009; 28:384-93. [PMID: 19244010 PMCID: PMC2876985 DOI: 10.1109/tmi.2008.2004817] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Multisource cone-beam computed tomography (CT) is an attractive approach of choice for superior temporal resolution, which is critically important for cardiac imaging and contrast enhanced studies. In this paper, we present a filtered-backprojection (FBP) algorithm for triple-source helical cone-beam CT. The algorithm is both exact and efficient. It utilizes data from three inter-helix PI-arcs associated with the inter-helix PI-lines and the minimum detection windows defined for the triple-source configuration. The proof of the formula is based on the geometric relations specific to triple-source helical cone-beam scanning. Simulation results demonstrate the validity of the reconstruction algorithm. This algorithm is also extended to a multisource version for (2N + 1)-source helical cone-beam CT. With parallel computing, the proposed FBP algorithms can be significantly faster than our previously published multisource backprojection-filtration algorithms. Thus, the FBP algorithms are promising in applications of triple-source helical cone-beam CT.
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Affiliation(s)
- Jun Zhao
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yannan Jin
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yang Lu
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Ge Wang
- Biomedical Imaging Division, Virginia Tech/Wake Forest University (VT-WFU) School of Biomedical Engineering and Science, Virginia Tech, Blacksburg, VA 24061 USA
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Lapp RM, Kachelriess M, Ertel D, Kyriakou Y, Kalender WA. Cardiac phase-correlated image reconstruction and advanced image processing in pulmonary CT imaging. Eur Radiol 2008; 19:1035-42. [PMID: 19082602 DOI: 10.1007/s00330-008-1237-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 09/03/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
Image quality in pulmonary CT imaging is commonly degraded by cardiac motion artifacts. Phase-correlated image reconstruction algorithms known from cardiac imaging can reduce motion artifacts but increase image noise and conventionally require a concurrently acquired ECG signal for synchronization. Techniques are presented to overcome these limitations. Based on standard and phase-correlated images that are reconstructed using a raw data-derived synchronization signal, image-merging and temporal-filtering techniques are proposed that combine the input images automatically or interactively. The performance of the approaches is evaluated in patient and phantom datasets. In the automatic approach, areas of strong motion and static areas were well detected, providing an optimal combination of standard and phase-correlated images with no visible border between the merged regions. Image noise in the non-moving regions was reduced to the noise level of the standard reconstruction. The application of the interactive filtering allowed for an optimal adaptation of image noise and motion artifacts. Noise content after interactive filtering decreased with increasing temporal filter width used. We conclude that a combination of our motion-free merging approach and a dedicated interactive filtering procedure can highly improve pulmonary imaging with respect to motion artifacts and image noise.
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Maaß C, Knaup M, Lapp R, Karolczak M, Kalender WA, Kachelrieß M. A new weighting function to achieve high temporal resolution in circular cone-beam CT with shifted detectors. Med Phys 2008; 35:5898-909. [DOI: 10.1118/1.3013700] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Ertel D, Kröber E, Kyriakou Y, Langner O, Kalender WA. Modulation transfer function-based assessment of temporal resolution: validation for single- and dual-source CT. Radiology 2008; 248:1013-7. [PMID: 18632531 DOI: 10.1148/radiol.2482072173] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study was to determine a manufacturer-independent quality assurance measurement for temporal resolution with a three-dimensional cardiac motion robot; validation was with single-source (SS) and dual-source (DS) computed tomography (CT). Image acquisition was performed by using standard cardiac protocols. Image contrast-based modulation transfer function (MTF) was assessed as function of time. For motion frequency of 60 beats per minute, MTF slightly decreased by 14% and 6% for SS CT and DS CT, respectively. For higher frequencies, a stronger decrease of MTF (eg, by 50% [SS CT] and 18% [DS CT] at 120 beats per minute) was detected. Effect of manufacturer's adaptive bisegment algorithm for SS CT and corresponding resonance effects of rotation time and heart rate were quantified. The robot-based approach is a reproducible, objective way to assess temporal resolution; it allows practical measurement of temporal resolution and comparison of CT scanners and protocols.
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Affiliation(s)
- Dirk Ertel
- Institute of Medical Physics, University of Erlangen-Nürnberg, Henkestrasse 91, 91052 Erlangen, Germany
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Engel KJ, Herrmann C, Zeitler G. X-ray scattering in single- and dual-source CT. Med Phys 2007; 35:318-32. [DOI: 10.1118/1.2820901] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Kyriakou Y, Kalender WA. Intensity distribution and impact of scatter for dual-source CT. Phys Med Biol 2007; 52:6969-89. [DOI: 10.1088/0031-9155/52/23/014] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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