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Xin L, Zhuo W, Liu Q, Xie T, Zaidi H. Triple-source saddle-curve cone-beam photon counting CT image reconstruction: A simulation study. Z Med Phys 2024; 34:408-418. [PMID: 36336554 PMCID: PMC11384087 DOI: 10.1016/j.zemedi.2022.10.003] [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: 06/19/2022] [Revised: 09/18/2022] [Accepted: 10/05/2022] [Indexed: 11/06/2022]
Abstract
PURPOSE The most common detector material in the PC CT system, cannot achieve the best performance at a relatively higher photon flux rate. In the reconstruction view, the most commonly used filtered back projection, is not able to provide sufficient reconstructed image quality in spectral computed tomography (CT). Developing a triple-source saddle-curve cone-beam photon counting CT image reconstruction method can improve the temporal resolution. METHODS Triple-source saddle-curve cone-beam trajectory was rearranged into four trajectory sets for simulation and reconstruction. Projection images in different energy bins were simulated by forward projection and photon counting CT respond model simulation. After simulation, the object was reconstructed using Katsevich's theory after photon counts correction using the pseudo inverse of photon counting CT response matrix. The material decomposition can be performed based on images in different energy bins. RESULTS Root mean square error (RMSE) and structural similarity index (SSIM) are calculated to quantify the image quality of reconstruction images. Compared with FDK images, the RMSE for the triple-source image was improved by 27%, 21%, 14%, 8%, and 6% for the reconstrued image of 20-33, 33-47, 47-58, 58-69, 69-80 keV energy bin. The SSIM was improved by 1.031%, 0.665%, 0.396%, 0.235%, 0.174% for corresponding energy bin. The decomposition image based on corrected images shows improved RMSE and SSIM, each by 33.861% and 0.345%. SSIM of corrected decomposition image of iodine reaches 99.415% of the original image. CONCLUSIONS A new Triple-source saddle-curve cone-beam PC CT image reconstruction method was developed in this work. The exact reconstruction of the triple-source saddle-curve improved both the image quality and temporal resolution.
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Affiliation(s)
- Lin Xin
- Institute of Radiation Medicine, Fudan University, Shanghai, China
| | - Weihai Zhuo
- Institute of Radiation Medicine, Fudan University, Shanghai, China
| | - Qian Liu
- School of Biomedical Engineering, Hainan University, Haikou, China.
| | - Tianwu Xie
- Institute of Radiation Medicine, Fudan University, Shanghai, China; Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland.
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland; Geneva Neuroscience Center, Geneva University, Geneva, Switzerland; Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
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Bal NJS, Chitra Ragupathy I, Tramm T, Nijkamp J. A Novel and Reliable Pixel Response Correction Method (DAC-Shifting) for Spectral Photon-Counting CT Imaging. Tomography 2024; 10:1168-1191. [PMID: 39058061 PMCID: PMC11281142 DOI: 10.3390/tomography10070089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 07/02/2024] [Accepted: 07/16/2024] [Indexed: 07/28/2024] Open
Abstract
Spectral photon-counting cone-beam computed tomography (CT) imaging is challenged by individual pixel response behaviours, which lead to noisy projection images and subsequent image artefacts like rings. Existing methods to correct for this either use calibration measurements, like signal-to-thickness calibration (STC), or perform a post-processing ring artefact correction of sinogram data or scan reconstructions without taking the pixel response explicitly into account. Here, we present a novel post-processing method (digital-to-analogue converter (DAC)-shifting) which explicitly measures the current pixel response using flat-field images and subsequently corrects the projection data. The DAC-shifting method was evaluated using a repeat series of the spectral photon-counting imaging (Medipix3) of a phantom with different density inserts and iodine K-edge imaging. The method was also compared against polymethyl methacrylate (PMMA)-based STC. The DAC-shifting method was shown to be effective in correcting individual pixel responses and was robust against detector instability; it led to a 47.4% average reduction in CT-number variation in homogeneous materials, with a range of 40.7-55.6%. On the contrary, the STC correction showed varying results; a 13.7% average reduction in CT-number variation, ranging from a 43.7% increase to a 45.5% reduction. In K-edge imaging, DAC-shifting provides a sharper attenuation peak and more uniform CT values, which are expected to benefit iodine concentration quantifications.
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Affiliation(s)
- Navrit Johan Singh Bal
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark; (N.J.S.B.); (I.C.R.); (T.T.)
- Danish Centre for Particle Therapy, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Imaiyan Chitra Ragupathy
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark; (N.J.S.B.); (I.C.R.); (T.T.)
- Danish Centre for Particle Therapy, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Trine Tramm
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark; (N.J.S.B.); (I.C.R.); (T.T.)
- Department of Pathology, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Jasper Nijkamp
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark; (N.J.S.B.); (I.C.R.); (T.T.)
- Danish Centre for Particle Therapy, Aarhus University Hospital, 8200 Aarhus, Denmark
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3
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Kronfeld A, Rose P, Baumgart J, Brockmann C, Othman AE, Schweizer B, Brockmann MA. Quantitative multi-energy micro-CT: A simulation and phantom study for simultaneous imaging of four different contrast materials using an energy integrating detector. Heliyon 2024; 10:e23013. [PMID: 38148814 PMCID: PMC10750148 DOI: 10.1016/j.heliyon.2023.e23013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 11/23/2023] [Accepted: 11/23/2023] [Indexed: 12/28/2023] Open
Abstract
Emerging from the development of single-energy Computed Tomography (CT) and Dual-Energy Computed Tomography, Multi-Energy Computed Tomography (MECT) is a promising tool allowing advanced material and tissue decomposition and thereby enabling the use of multiple contrast materials in preclinical research. The scope of this work was to evaluate whether a usual preclinical micro-CT system is applicable for the decomposition of different materials using MECT together with a matrix-inversion method and how different changes of the measurement-environment affect the results. A matrix-inversion based algorithm to differentiate up to five materials (iodine, iron, barium, gadolinium, residual material) by applying four different acceleration voltages/energy levels was established. We carried out simulations using different ratios and concentrations (given in fractions of volume units, VU) of the four different materials (plus residual material) at different noise-levels for 30 keV, 40 keV, 50 keV, 60 keV, 80 keV and 100 keV (monochromatic). Our simulation results were then confirmed by using region of interest-based measurements in a phantom-study at corresponding acceleration voltages. Therefore, different mixtures of contrast materials were scanned using a micro-CT. Voxel wise evaluation of the phantom imaging data was conducted to confirm its usability for future imaging applications and to estimate the influence of varying noise-levels, scattering, artifacts and concentrations. The analysis of our simulations showed the smallest deviation of 0.01 (0.003-0.15) VU between given and calculated concentrations of the different contrast materials when using an energy-combination of 30 keV, 40 keV, 50 keV and 100 keV for MECT. Subsequent MECT phantom measurements, however, revealed a combination of acceleration voltages of 30 kV, 40 kV, 60 kV and 100 kV as most effective for performing material decomposition with a deviation of 0.28 (0-1.07) mg/ml. The feasibility of our voxelwise analyses using the proposed algorithm was then confirmed by the generation of phantom parameter-maps that matched the known contrast material concentrations. The results were mostly influenced by the noise-level and the concentrations used in the phantoms. MECT using a standard micro-CT combined with a matrix inversion method is feasible at four different imaging energies and allows the differentiation of mixtures of up to four contrast materials plus an additional residual material.
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Affiliation(s)
- Andrea Kronfeld
- University Medical Center of the Johannes Gutenberg University Mainz, Department of Neuroradiology, Langenbeck 1, 55131, Mainz, Germany
| | - Patrick Rose
- University Medical Center of the Johannes Gutenberg University Mainz, Department of Neuroradiology, Langenbeck 1, 55131, Mainz, Germany
- RheinMain University of Applied Sciences, Faculty of Engineering, Am Brückweg 26, 65428, Rüsselsheim am Main, Germany
| | - Jan Baumgart
- University Medical Center of the Johannes Gutenberg University Mainz, Translational Animal Research Center, Hanns-Dieter-Hüsch-Weg 19, 55128, Mainz, Germany
| | - Carolin Brockmann
- University Medical Center of the Johannes Gutenberg University Mainz, Department of Neuroradiology, Langenbeck 1, 55131, Mainz, Germany
| | - Ahmed E. Othman
- University Medical Center of the Johannes Gutenberg University Mainz, Department of Neuroradiology, Langenbeck 1, 55131, Mainz, Germany
| | - Bernd Schweizer
- RheinMain University of Applied Sciences, Faculty of Engineering, Am Brückweg 26, 65428, Rüsselsheim am Main, Germany
| | - Marc Alexander Brockmann
- University Medical Center of the Johannes Gutenberg University Mainz, Department of Neuroradiology, Langenbeck 1, 55131, Mainz, Germany
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Knäusl B, Belotti G, Bertholet J, Daartz J, Flampouri S, Hoogeman M, Knopf AC, Lin H, Moerman A, Paganelli C, Rucinski A, Schulte R, Shimizu S, Stützer K, Zhang X, Zhang Y, Czerska K. A review of the clinical introduction of 4D particle therapy research concepts. Phys Imaging Radiat Oncol 2024; 29:100535. [PMID: 38298885 PMCID: PMC10828898 DOI: 10.1016/j.phro.2024.100535] [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: 10/11/2023] [Revised: 12/12/2023] [Accepted: 01/04/2024] [Indexed: 02/02/2024] Open
Abstract
Background and purpose Many 4D particle therapy research concepts have been recently translated into clinics, however, remaining substantial differences depend on the indication and institute-related aspects. This work aims to summarise current state-of-the-art 4D particle therapy technology and outline a roadmap for future research and developments. Material and methods This review focused on the clinical implementation of 4D approaches for imaging, treatment planning, delivery and evaluation based on the 2021 and 2022 4D Treatment Workshops for Particle Therapy as well as a review of the most recent surveys, guidelines and scientific papers dedicated to this topic. Results Available technological capabilities for motion surveillance and compensation determined the course of each 4D particle treatment. 4D motion management, delivery techniques and strategies including imaging were diverse and depended on many factors. These included aspects of motion amplitude, tumour location, as well as accelerator technology driving the necessity of centre-specific dosimetric validation. Novel methodologies for X-ray based image processing and MRI for real-time tumour tracking and motion management were shown to have a large potential for online and offline adaptation schemes compensating for potential anatomical changes over the treatment course. The latest research developments were dominated by particle imaging, artificial intelligence methods and FLASH adding another level of complexity but also opportunities in the context of 4D treatments. Conclusion This review showed that the rapid technological advances in radiation oncology together with the available intrafractional motion management and adaptive strategies paved the way towards clinical implementation.
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Affiliation(s)
- Barbara Knäusl
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Gabriele Belotti
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - Jenny Bertholet
- Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland
| | - Juliane Daartz
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | | | - Mischa Hoogeman
- Department of Medical Physics & Informatics, HollandPTC, Delft, The Netherlands
- Erasmus MC Cancer Institute, University Medical Center Rotterdam, Department of Radiotherapy, Rotterdam, The Netherlands
| | - Antje C Knopf
- Institut für Medizintechnik und Medizininformatik Hochschule für Life Sciences FHNW, Muttenz, Switzerland
| | - Haibo Lin
- New York Proton Center, New York, NY, USA
| | - Astrid Moerman
- Department of Medical Physics & Informatics, HollandPTC, Delft, The Netherlands
| | - Chiara Paganelli
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy
| | - Antoni Rucinski
- Institute of Nuclear Physics Polish Academy of Sciences, PL-31342 Krakow, Poland
| | - Reinhard Schulte
- Division of Biomedical Engineering Sciences, School of Medicine, Loma Linda University
| | - Shing Shimizu
- Department of Carbon Ion Radiotherapy, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kristin Stützer
- OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden – Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany
| | - Xiaodong Zhang
- Department of Radiation Physics, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Ye Zhang
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Katarzyna Czerska
- Center for Proton Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland
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Healy J, Searle E, Panta RK, Chernoglazov A, Roake J, Butler P, Butler A, Gieseg SP. Ex-vivo atherosclerotic plaque characterization using spectral photon-counting CT: Comparing material quantification to histology. Atherosclerosis 2023; 378:117160. [PMID: 37495488 DOI: 10.1016/j.atherosclerosis.2023.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 06/06/2023] [Accepted: 06/07/2023] [Indexed: 07/28/2023]
Abstract
BACKGROUND AND AIMS Atherosclerotic plaques are characterized as being vulnerable to rupture based on a series of histologically defined features, including a lipid-rich necrotic core, spotty calcification and ulceration. Existing imaging modalities have limitations in their ability to distinguish between different materials and structural features. We examined whether X-ray spectral photon-counting computer tomography (SPCCT) images were able to distinguish key plaque features in a surgically excised specimen from the carotid artery with comparison to histological images. METHODS An excised carotid plaque was imaged in the diagnostic X-ray energy range of 30-120 keV using a small-bore SPCCT scanner equipped with a Medipix3RX photon-counting spectral X-ray detector with a cadmium telluride (CdTe) sensor. Material identification and quantification (MIQ) images of the carotid plaque were generated using proprietary MIQ software at 0.09 mm volumetric pixels (voxels). The plaque was sectioned, stained and photographed at high resolution for comparison. RESULTS A lipid-rich core with spotty calcification was identified in the MIQ images and confirmed by histology. MIQ showed a core region containing lipid, with a mean concentration of 260 mg lipid/ml corresponding to a mean value of -22HU. MIQ showed calcified regions with mean concentration of 41 mg Ca/ml corresponded to a mean value of 123HU. An ulceration of the carotid wall at the bifurcation was identified to be lipid-lined, with a small calcification identified near the breach of the artery wall. CONCLUSIONS SPCCT derived material identification and quantification images showed hallmarks of vulnerable plaque including a lipid-rich necrotic core, spotty calcifications and ulcerations.
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Affiliation(s)
- Joe Healy
- Free Radical Biochemistry Laboratory, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; MARS Bioimaging Ltd., Christchurch, New Zealand
| | - Emily Searle
- Free Radical Biochemistry Laboratory, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; MARS Bioimaging Ltd., Christchurch, New Zealand
| | - Raj Kumar Panta
- Department of Radiology, University of Otago, Christchurch, New Zealand; MARS Bioimaging Ltd., Christchurch, New Zealand; European Organization for Nuclear Research (CERN), Geneva, Switzerland
| | | | - Justin Roake
- Department of Surgery, University of Otago, Christchurch, New Zealand
| | - Phil Butler
- Department of Physics and Astronomy, University of Canterbury, New Zealand; MARS Bioimaging Ltd., Christchurch, New Zealand; European Organization for Nuclear Research (CERN), Geneva, Switzerland
| | - Anthony Butler
- Department of Physics and Astronomy, University of Canterbury, New Zealand; Department of Radiology, University of Otago, Christchurch, New Zealand; MARS Bioimaging Ltd., Christchurch, New Zealand; European Organization for Nuclear Research (CERN), Geneva, Switzerland
| | - Steven P Gieseg
- Free Radical Biochemistry Laboratory, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; Department of Radiology, University of Otago, Christchurch, New Zealand; European Organization for Nuclear Research (CERN), Geneva, Switzerland.
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6
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Li B, Luo N, Zhong A, Li Y, Chen A, Zhou L, Xu Y. A prior image constraint robust principal component analysis reconstruction method for sparse segmental multi-energy computed tomography. Quant Imaging Med Surg 2021; 11:4097-4114. [PMID: 34476191 DOI: 10.21037/qims-20-844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 04/16/2021] [Indexed: 11/06/2022]
Abstract
Background Multi-energy computed tomography (MECT) is a promising technique in medical imaging, especially for quantitative imaging. However, high technical requirements and system costs barrier its step into clinical practice. Methods We propose a novel sparse segmental MECT (SSMECT) scheme and corresponding reconstruction method, which is a cost-efficient way to realize MECT on a conventional single-source CT. For the data acquisition, the X-ray source is controlled to maintain an energy within a segmental arc, and then switch alternately to another energy level. This scan only needs to switch tube voltage a few times to acquire multi-energy data, but leads to sparse-view and limited-angle issues in image reconstruction. To solve this problem, we propose a prior image constraint robust principal component analysis (PIC-RPCA) reconstruction method, which introduces structural similarity and spectral correlation into the reconstruction. Results A numerical simulation and a real phantom experiment were conducted to demonstrate the efficacy and robustness of the scan scheme and reconstruction method. The results showed that our proposed reconstruction method could have achieved better multi-energy images than other competing methods both quantitatively and qualitatively. Conclusions Our proposed SSMECT scan with PIC-RPCA reconstruction method could lower kVp switching frequency while achieving satisfactory reconstruction accuracy and image quality.
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Affiliation(s)
- Bin Li
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China.,State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Ning Luo
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China.,The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Anni Zhong
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China
| | - Yongbao Li
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Along Chen
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Linghong Zhou
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China
| | - Yuan Xu
- School of Biomedical Engineering, Southern Medical University, Guangzhou, China
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Wang AS, Pelc NJ. Spectral Photon Counting CT: Imaging Algorithms and Performance Assessment. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021; 5:453-464. [PMID: 35419500 PMCID: PMC9000208 DOI: 10.1109/trpms.2020.3007380] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Photon counting x-ray detectors (PCDs) with spectral capabilities have the potential to revolutionize computed tomography (CT) for medical imaging. The ideal PCD provides accurate energy information for each incident x-ray, and at high spatial resolution. This information enables material-specific imaging, enhanced radiation dose efficiency, and improved spatial resolution in CT images. In practice, PCDs are affected by non-idealities, including limited energy resolution, pulse pileup, and cross talk due to charge sharing, K-fluorescence, and Compton scattering. In order to maximize their performance, PCDs must be carefully designed to reduce these effects and then later account for them during correction and post-acquisition steps. This review article examines algorithms for using PCDs in spectral CT applications, including how non-idealities impact image quality. Performance assessment metrics that account for spatial resolution and noise such as the detective quantum efficiency (DQE) can be used to compare different PCD designs, as well as compare PCDs with conventional energy integrating detectors (EIDs). These methods play an important role in enhancing spectral CT images and assessing the overall performance of PCDs.
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Affiliation(s)
- Adam S Wang
- Departments of Radiology and, by courtesy, Electrical Engineering, Stanford University, Stanford, CA 94305 USA
| | - Norbert J Pelc
- Department of Radiology, Stanford University, Stanford, CA 94305 USA
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Baer K, Kieser S, Schon B, Rajendran K, Ten Harkel T, Ramyar M, Löbker C, Bateman C, Butler A, Raja A, Hooper G, Anderson N, Woodfield T. Spectral CT imaging of human osteoarthritic cartilage via quantitative assessment of glycosaminoglycan content using multiple contrast agents. APL Bioeng 2021; 5:026101. [PMID: 33834156 PMCID: PMC8018795 DOI: 10.1063/5.0035312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/22/2021] [Indexed: 01/06/2023] Open
Abstract
Detection of early osteoarthritis to stabilize or reverse the damage to articular cartilage would improve patient function, reduce disability, and limit the need for joint replacement. In this study, we investigated nondestructive photon-processing spectral computed tomography (CT) for the quantitative measurement of the glycosaminoglycan (GAG) content compared to destructive histological and biochemical assay techniques in normal and osteoarthritic tissues. Cartilage-bone cores from healthy bovine stifles were incubated in 50% ioxaglate (Hexabrix®) or 100% gadobenate dimeglumine (MultiHance®). A photon-processing spectral CT (MARS) scanner with a CdTe-Medipix3RX detector imaged samples. Calibration phantoms of ioxaglate and gadobenate dimeglumine were used to determine iodine and gadolinium concentrations from photon-processing spectral CT images to correlate with the GAG content measured using a dimethylmethylene blue assay. The zonal distribution of GAG was compared between photon-processing spectral CT images and histological sections. Furthermore, discrimination and quantification of GAG in osteoarthritic human tibial plateau tissue using the same contrast agents were demonstrated. Contrast agent concentrations were inversely related to the GAG content. The GAG concentration increased from 25 μg/ml (85 mg/ml iodine or 43 mg/ml gadolinium) in the superficial layer to 75 μg/ml (65 mg/ml iodine or 37 mg/ml gadolinium) in the deep layer of healthy bovine cartilage. Deep zone articular cartilage could be distinguished from subchondral bone by utilizing the material decomposition technique. Photon-processing spectral CT images correlated with histological sections in healthy and osteoarthritic tissues. Post-imaging material decomposition was able to quantify the GAG content and distribution throughout healthy and osteoarthritic cartilage using Hexabrix® and MultiHance® while differentiating the underlying subchondral bone.
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Affiliation(s)
| | - Sandra Kieser
- Christchurch Regenerative Medicine and Tissue Engineering (CReaTE), Department of Orthopaedic Surgery and Musculoskeletal Medicine, University of Otago Christchurch, Christchurch 8011, New Zealand
| | | | | | | | - Mohsen Ramyar
- Department of Radiology, University of Otago Christchurch, Christchurch 8011, New Zealand
| | | | - Christopher Bateman
- Department of Radiology, University of Otago Christchurch, Christchurch 8011, New Zealand
| | | | | | | | - Nigel Anderson
- Department of Radiology, University of Otago Christchurch, Christchurch 8011, New Zealand
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Willemink MJ, Varga-Szemes A, Schoepf UJ, Codari M, Nieman K, Fleischmann D, Mastrodicasa D. Emerging methods for the characterization of ischemic heart disease: ultrafast Doppler angiography, micro-CT, photon-counting CT, novel MRI and PET techniques, and artificial intelligence. Eur Radiol Exp 2021; 5:12. [PMID: 33763754 PMCID: PMC7991013 DOI: 10.1186/s41747-021-00207-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 01/22/2021] [Indexed: 12/24/2022] Open
Abstract
After an ischemic event, disruptive changes in the healthy myocardium may gradually develop and may ultimately turn into fibrotic scar. While these structural changes have been described by conventional imaging modalities mostly on a macroscopic scale-i.e., late gadolinium enhancement at magnetic resonance imaging (MRI)-in recent years, novel imaging methods have shown the potential to unveil an even more detailed picture of the postischemic myocardial phenomena. These new methods may bring advances in the understanding of ischemic heart disease with potential major changes in the current clinical practice. In this review article, we provide an overview of the emerging methods for the non-invasive characterization of ischemic heart disease, including coronary ultrafast Doppler angiography, photon-counting computed tomography (CT), micro-CT (for preclinical studies), low-field and ultrahigh-field MRI, and 11C-methionine positron emission tomography. In addition, we discuss new opportunities brought by artificial intelligence, while addressing promising future scenarios and the challenges for the application of artificial intelligence in the field of cardiac imaging.
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Affiliation(s)
- Martin J. Willemink
- grid.168010.e0000000419368956Department of Radiology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94035 USA
| | - Akos Varga-Szemes
- grid.259828.c0000 0001 2189 3475Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC USA
| | - U. Joseph Schoepf
- grid.259828.c0000 0001 2189 3475Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC USA
| | - Marina Codari
- grid.168010.e0000000419368956Department of Radiology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94035 USA
| | - Koen Nieman
- grid.168010.e0000000419368956Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA USA ,Stanford Cardiovascular Institute, Stanford, CA 94305 USA
| | - Dominik Fleischmann
- grid.168010.e0000000419368956Department of Radiology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94035 USA ,Stanford Cardiovascular Institute, Stanford, CA 94305 USA
| | - Domenico Mastrodicasa
- Department of Radiology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA, 94035, USA. .,Stanford Cardiovascular Institute, Stanford, CA, 94305, USA.
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Abstract
The introduction of photon-counting detectors is expected to be the next major breakthrough in clinical x-ray computed tomography (CT). During the last decade, there has been considerable research activity in the field of photon-counting CT, in terms of both hardware development and theoretical understanding of the factors affecting image quality. In this article, we review the recent progress in this field with the intent of highlighting the relationship between detector design considerations and the resulting image quality. We discuss detector design choices such as converter material, pixel size, and readout electronics design, and then elucidate their impact on detector performance in terms of dose efficiency, spatial resolution, and energy resolution. Furthermore, we give an overview of data processing, reconstruction methods and metrics of imaging performance; outline clinical applications; and discuss potential future developments.
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Affiliation(s)
- Mats Danielsson
- Department of Physics, KTH Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden. Prismatic Sensors AB, AlbaNova University Center, SE-106 91 Stockholm, Sweden
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Lau LCM, Lee WYW, Butler APH, Chernoglazov AI, Chung KY, Ho KKW, Griffith J, Butler PH, Yung PSH. Multi-energy spectral photon-counting computed tomography (MARS) for detection of arthroplasty implant failure. Sci Rep 2021; 11:1554. [PMID: 33452309 PMCID: PMC7810731 DOI: 10.1038/s41598-020-80463-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 12/21/2020] [Indexed: 01/22/2023] Open
Abstract
To determine whether state-of-the-art multi-energy spectral photon-counting computed tomography (MARS) can detect knee arthroplasty implant failure not detected by standard pre-operative imaging techniques. A total knee arthroplasty (TKA) removed from a patient was reviewed. The extracted prosthesis [NexGen Legacy Posterior Stabilized (LPS) TKA] was analyzed as were pre-operative imaging examination and compared with a MARS-CT examination obtained of the extracted TKA prosthesis. Radiographs, fluoroscopy, ultrasound and MRI preoperatively did not reveal the cause of the implant failure. MARS CT images of the extracted prosthesis clearly showed the presence of posteromedial polyethylene and tibial tray wear which is compatible with the clinical appearance of the extracted TKA. MARS can identify polyethylene insert and metallic tibial tray wear as a cause of TKA failure, that could not be identified with on standard pre-operative imaging. Although clinical MARS CT system is still under development, this case does illustrate its potential clinical usefulness. This is the first study to document how MARS CT imaging can detect orthopedic implant failure not detected by standard current imaging techniques. This system has a potential clinical application in orthopedic patients.
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Affiliation(s)
- Lawrence Chun Man Lau
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Wayne Yuk Wai Lee
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
- Li Ka Shing Institute of Health Sciences, The Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Anthony P H Butler
- University of Otago, 2 Riccarton Ave, Christchurch, 8140, New Zealand
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand
- The European Organization for Nuclear Research (CERN), Geneva, Switzerland
- MARS Bioimaging Ltd, 29a Clyde Rd, Christchurch, New Zealand
| | | | - Kwong Yin Chung
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Kevin Ki Wai Ho
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - James Griffith
- Department of Radiology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
| | - Philip H Butler
- School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand.
- The European Organization for Nuclear Research (CERN), Geneva, Switzerland.
- MARS Bioimaging Ltd, 29a Clyde Rd, Christchurch, New Zealand.
| | - Patrick Shu Hang Yung
- Department of Orthopaedics and Traumatology, Faculty of Medicine, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
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12
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Review of Technical Advancements and Clinical Applications of Photon-counting Computed Tomography in Imaging of the Thorax. J Thorac Imaging 2021; 36:84-94. [PMID: 33399350 DOI: 10.1097/rti.0000000000000569] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Photon-counting computed tomography (CT) is a developing technology that has the potential to address some limitations of CT imaging and bring about improvements and potentially new applications to this field. Photon-counting detectors have a fundamentally different detection mechanism from conventional CT energy-integrating detectors that can improve dose efficiency, spatial resolution, and energy-discrimination capabilities. In the past decade, promising human studies have been reported in the literature that have demonstrated benefits of this relatively new technology for various clinical applications. In this review, we provide a succinct description of the photon-counting detector technology and its detection mechanism in comparison with energy-integrating detectors in a manner understandable for clinicians and radiologists, introduce benefits and some of the existing challenges present in this technology, and provide an overview of the current status and potential clinical applications of this technology in imaging of the thorax by providing example images acquired with an investigational whole-body photon-counting CT scanner.
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13
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Persson M, Wang A, Pelc NJ. Detective quantum efficiency of photon-counting CdTe and Si detectors for computed tomography: a simulation study. J Med Imaging (Bellingham) 2020; 7:043501. [PMID: 32715022 DOI: 10.1117/1.jmi.7.4.043501] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 06/30/2020] [Indexed: 11/14/2022] Open
Abstract
Purpose: Developing photon-counting CT detectors requires understanding the impact of parameters, such as converter material, thickness, and pixel size. We apply a linear-systems framework, incorporating spatial and energy resolution, to study realistic silicon (Si) and cadmium telluride (CdTe) detectors at a low count rate. Approach: We compared CdTe detector designs with 0.5 × 0.5 mm 2 and 0.225 × 0.225 mm 2 pixels and Si detector designs with 0.5 × 0.5 mm 2 pixels of 30 and 60 mm active thickness, with and without tungsten scatter blockers. Monte-Carlo simulations of photon transport were used together with Gaussian charge sharing models fitted to published data. Results: For detection in a 300-mm-thick object at 120 kVp, the 0.5- and 0.225-mm pixel CdTe systems have 28% to 41% and 5% to 29% higher detective quantum efficiency (DQE), respectively, than the 60-mm Si system with tungsten, whereas the corresponding numbers for two-material decomposition are 2% lower to 11% higher DQE and 31% to 54% lower DQE compared to Si. We also show that combining these detectors with dual-spectrum acquisition is beneficial. Conclusions: In the low-count-rate regime, CdTe detector systems outperform the Si systems for detection tasks, whereas silicon outperforms one or both of the CdTe systems for material decomposition.
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Affiliation(s)
- Mats Persson
- Stanford University, Department of Bioengineering, Stanford, California, United States.,Stanford University, Department of Radiology, Stanford, California, United States
| | - Adam Wang
- Stanford University, Department of Radiology, Stanford, California, United States
| | - Norbert J Pelc
- Stanford University, Department of Bioengineering, Stanford, California, United States.,Stanford University, Department of Radiology, Stanford, California, United States.,Stanford University, Department of Electrical Engineering, Stanford, California, United States
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14
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Grönberg F, Lundberg J, Sjölin M, Persson M, Bujila R, Bornefalk H, Almqvist H, Holmin S, Danielsson M. Feasibility of unconstrained three-material decomposition: imaging an excised human heart using a prototype silicon photon-counting CT detector. Eur Radiol 2020; 30:5904-5912. [PMID: 32588212 PMCID: PMC7554013 DOI: 10.1007/s00330-020-07017-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 05/11/2020] [Accepted: 06/05/2020] [Indexed: 11/05/2022]
Abstract
Rationale and objectives The purpose of this study was to evaluate the feasibility of unconstrained three-material decomposition in a human tissue specimen containing iodinated contrast agent, using an experimental multi-bin photon-counting silicon detector. It was further to evaluate potential added clinical value compared to a 1st-generation state-of-the-art dual-energy computed tomography system. Materials and methods A prototype photon-counting silicon detector in a bench-top setup for x-ray tomographic imaging was calibrated using a multi-material calibration phantom. A heart with calcified plaque was obtained from a deceased patient, and the coronary arteries were injected with an iodinated contrast agent mixed with gelatin. The heart was imaged in the experimental setup and on a 1st-generation state-of-the-art dual-energy computed tomography system. Projection-based three-material decomposition without any constraints was performed with the photon-counting detector data, and the resulting images were compared with those obtained from the dual-energy system. Results The photon-counting detector images show better separation of iodine and calcium compared to the dual-energy images. Additional experiments confirmed that unbiased estimates of soft tissue, calcium, and iodine could be achieved without any constraints. Conclusion The proposed experimental system could provide added clinical value compared to current dual-energy systems for imaging tasks where mix-up of iodine and calcium is an issue, and the anatomy is sufficiently small to allow iodine to be differentiated from calcium. Considering its previously shown count rate capability, these results show promise for future integration of this detector in a clinical CT scanner. Key Points • Spectral photon-counting detectors can solve some of the fundamental problems with conventional single-energy CT. • Dual-energy methods can be used to differentiate iodine and calcium, but to do so must rely on constraints, since solving for three unknowns with only two measurements is not possible. Photon-counting detectors can improve upon these methods by allowing unconstrained three-material decomposition. • A prototype photon-counting silicon detector with high count rate capability allows performing unconstrained three-material decomposition and qualitatively shows better differentiation of iodine and calcium than dual-energy CT.
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Affiliation(s)
- Fredrik Grönberg
- Department of Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE-106 91, Stockholm, Sweden.
| | - Johan Lundberg
- Department of Clinical Neuroscience, Karolinska Institutet and the Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Martin Sjölin
- Department of Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE-106 91, Stockholm, Sweden
| | - Mats Persson
- Department of Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE-106 91, Stockholm, Sweden.,Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA
| | - Robert Bujila
- Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - Hans Bornefalk
- Department of Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE-106 91, Stockholm, Sweden
| | - Håkan Almqvist
- Department of Clinical Neuroscience, Karolinska Institutet and the Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Staffan Holmin
- Department of Clinical Neuroscience, Karolinska Institutet and the Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Mats Danielsson
- Department of Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE-106 91, Stockholm, Sweden
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15
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Ishiguro A, Sato K, Taura M, Hoshi H. Quantitative evaluation of the effect of changes in effective energy on the image quality in X-ray computed tomography. Phys Eng Sci Med 2020; 43:567-575. [PMID: 32524441 DOI: 10.1007/s13246-020-00857-4] [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: 10/23/2019] [Accepted: 03/09/2020] [Indexed: 10/24/2022]
Abstract
The X-ray effective energy differs for each computed tomography (CT) scanner even at the same tube voltage because of differences in the bow-tie filter and additional filter. Even when scanning with the same tube voltage and dose setting, these differences in effective energy result in different image noise levels. Although this qualitative change is known, the related quantitative changes have not been clarified. In this study, using two CT scanners with the same geometric specifications and detector configurations, we quantitatively assessed the reduction in image noise accompanying the increase in effective energy. We also clarified the fluctuations in CT number. For both CT scanners, the effective energy, the standard deviation (SD) of the noise image when using two water phantoms with diameters of 240 mm and 320 mm, and CT numbers of the sensitometry module were measured. Further, the dose required to obtain the same image noise level in each CT scanner was calculated. The effective energy difference was 5.5 keV to 10.7 keV, and the difference tended to be larger when the scan field of view was larger. The SD differences were 24% and 14% for the 320-mm and 240-mm phantoms, respectively. For converting to the dose required to obtain the same SD, the dose can be reduced by 42% and 24% for the 320-mm and 240-mm phantoms, respectively. The CT number difference of both CT scanners was small. Therefore, higher effective energy contributes to the reduction of image noise.
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Affiliation(s)
- Ayana Ishiguro
- Sendai Open Hospital, 5-22-1 Tsurugaya, Miyagino-ku, Sendai, Miyagi, 983-0824, Japan.
| | - Kazuhiro Sato
- Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Masaaki Taura
- Tohoku Medical and Pharmaceutical University Hospital, 1-12-1 Fukumuro, Miyagino-ku, Sendai, Miyagi, 983-8512, Japan
| | - Hideki Hoshi
- Sendai Open Hospital, 5-22-1 Tsurugaya, Miyagino-ku, Sendai, Miyagi, 983-0824, Japan.,Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi Aoba-ku, Sendai, Miyagi, 980-8575, Japan
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16
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Simard M, Panta RK, Bell ST, Butler AP, Bouchard H. Quantitative imaging performance of MARS spectral photon‐counting CT for radiotherapy. Med Phys 2020; 47:3423-3434. [DOI: 10.1002/mp.14204] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 04/03/2020] [Accepted: 04/19/2020] [Indexed: 12/23/2022] Open
Affiliation(s)
- Mikaël Simard
- Département de physique Université de Montréal, Complexe des sciences 1375 Avenue Thérèse‐Lavoie‐Roux Montréal Québec H2V 0B3 Canada
- Centre de recherche du Centre hospitalier de l’Université de Montréal 900 Rue Saint‐Denis Montréal Québec H2X 3H8 Canada
| | - Raj Kumar Panta
- MARS Bioimaging Ltd Christchurch New Zealand
- Department of Radiology University of Otago Christchurch New Zealand
- European Organisation for Nuclear Research (CERN) Geneva Switzerland
| | | | - Anthony P.H. Butler
- MARS Bioimaging Ltd Christchurch New Zealand
- Department of Radiology University of Otago Christchurch New Zealand
- European Organisation for Nuclear Research (CERN) Geneva Switzerland
- School of Physical and Chemical Sciences University of Canterbury Christchurch New Zealand
| | - Hugo Bouchard
- Département de physique Université de Montréal, Complexe des sciences 1375 Avenue Thérèse‐Lavoie‐Roux Montréal Québec H2V 0B3 Canada
- Centre de recherche du Centre hospitalier de l’Université de Montréal 900 Rue Saint‐Denis Montréal Québec H2X 3H8 Canada
- Département de radio‐oncologie Centre hospitalier de l’Université de Montréal (CHUM) 1051 rue Sanguinet Montréal Québec H2X 3E4 Canada
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17
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Fredette NR, Kavuri A, Das M. Multi-step material decomposition for spectral computed tomography. ACTA ACUST UNITED AC 2019; 64:145001. [DOI: 10.1088/1361-6560/ab2b0e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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18
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Leng S, Bruesewitz M, Tao S, Rajendran K, Halaweish AF, Campeau NG, Fletcher JG, McCollough CH. Photon-counting Detector CT: System Design and Clinical Applications of an Emerging Technology. Radiographics 2019; 39:729-743. [PMID: 31059394 PMCID: PMC6542627 DOI: 10.1148/rg.2019180115] [Citation(s) in RCA: 248] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 06/15/2018] [Accepted: 06/26/2018] [Indexed: 01/01/2023]
Abstract
Photon-counting detector (PCD) CT is an emerging technology that has shown tremendous progress in the last decade. Various types of PCD CT systems have been developed to investigate the benefits of this technology, which include reduced electronic noise, increased contrast-to-noise ratio with iodinated contrast material and radiation dose efficiency, reduced beam-hardening and metal artifacts, extremely high spatial resolution (33 line pairs per centimeter), simultaneous multienergy data acquisition, and the ability to image with and differentiate among multiple CT contrast agents. PCD technology is described and compared with conventional CT detector technology. With the use of a whole-body research PCD CT system as an example, PCD technology and its use for in vivo high-spatial-resolution multienergy CT imaging is discussed. The potential clinical applications, diagnostic benefits, and challenges associated with this technology are then discussed, and examples with phantom, animal, and patient studies are provided. ©RSNA, 2019.
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Affiliation(s)
- Shuai Leng
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Michael Bruesewitz
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Shengzhen Tao
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Kishore Rajendran
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Ahmed F. Halaweish
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Norbert G. Campeau
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Joel G. Fletcher
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
| | - Cynthia H. McCollough
- From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (S.L., M.B., S.T., K.R., N.G.C., J.G.F., C.H.M.); and Siemens Healthcare, Malvern, Pa (A.F.H.)
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19
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Vespucci S, Park CS, Torrico R, Das M. Robust Energy Calibration Technique for Photon Counting Spectral Detectors. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:968-978. [PMID: 30346280 DOI: 10.1109/tmi.2018.2875932] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This paper describes the implementation of a novel and robust threshold energy calibration method for photon counting detectors using polychromatic X-ray tubes. Methods often used for such energy calibration may require re-orientation of the detector or introduce calibration errors that are flux and acquisition time-dependent. Our newly proposed "differential intensity ratios" (DIR) method offers a practical and robust alternative to existing methods. We demonstrate this robustness against photon flux used in calibration, spectral errors such as pulse pile-up as well as the detector's inherent spectral resolution limits. The demonstrated significant insensitivity of the proposed DIR signature to detector spectral distortions and energy resolution is a key finding. The proposed DIR calibration method is demonstrated using Medipix3RX detectors with a CdTe sensor under varying flux conditions. A per pixel calibration using the DIR method has also been implemented to demonstrate an improvement over the global energy resolution of the PCD.
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20
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Persson M, Rajbhandary PL, Pelc NJ. A framework for performance characterization of energy-resolving photon-counting detectors. Med Phys 2018; 45:4897-4915. [PMID: 30191571 DOI: 10.1002/mp.13172] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 07/19/2018] [Accepted: 08/29/2018] [Indexed: 01/12/2023] Open
Abstract
PURPOSE Photon-counting, energy-resolving detectors are subject to intense research interest, and there is a need for a general framework for performance assessment of these detectors. The commonly used linear-systems theory framework, which measures detector performance in terms of noise-equivalent quanta (NEQ) and detective quantum efficiency (DQE) is widely used for characterizing conventional x-ray detectors but does not take energy-resolving capabilities into account. The purpose of this work is to extend this framework to encompass energy-resolving photon-counting detectors and elucidate how the imperfect energy response and other imperfections in real-world detectors affect imaging performance, both for feature detection and for material quantification tasks. METHOD We generalize NEQ and DQE to matrix-valued quantities as functions of spatial frequency, and show how these matrices can be calculated from simple Monte Carlo simulations. To demonstrate how the new metrics can be interpreted, we compute them for simplified models of fluorescence and Compton scatter in a photon-counting detector and for a Monte Carlo model of a CdTe detector with 0.5 × 0.5 mm 2 pixels. RESULTS Our results show that the ideal-linear-observer performance for any detection or material quantification task can be calculated from the proposed generalized NEQ and DQE metrics. We also demonstrate that the proposed NEQ metric is closely related to a generalized version of the Cramér-Rao lower bound commonly used for assessing material quantification performance. Off-diagonal elements in the NEQ and DQE matrices are shown to be related to loss of energy information due to imperfect energy resolution. The Monte Carlo model of the CdTe detector predicts a zero-frequency dose efficiency relative to an ideal detector of 0.86 and 0.65 for detecting water and bone, respectively. When the task instead is to quantify these materials, the corresponding values are 0.34 for water and 0.26 for bone. CONCLUSIONS We have developed a framework for assessing the performance of photon-counting energy-resolving detectors and shown that the matrix-valued NEQ and DQE metrics contain sufficient information for calculating the dose efficiency for both detection and quantification tasks, the task having any spatial and energy dependence. This framework will be beneficial for the development and optimization of photon-counting x-ray detectors.
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Affiliation(s)
- Mats Persson
- Departments of Bioengineering and Radiology, Stanford University, Stanford, CA, 94305, USA
| | - Paurakh L Rajbhandary
- Departments of Electrical Engineering and Radiology, Stanford University, Stanford, CA, 94305, USA
| | - Norbert J Pelc
- Departments of Bioengineering, Radiology and Electrical Engineering, Stanford University, Stanford, CA, 94305, USA
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21
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Willemink MJ, Persson M, Pourmorteza A, Pelc NJ, Fleischmann D. Photon-counting CT: Technical Principles and Clinical Prospects. Radiology 2018; 289:293-312. [PMID: 30179101 DOI: 10.1148/radiol.2018172656] [Citation(s) in RCA: 558] [Impact Index Per Article: 93.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Photon-counting CT is an emerging technology with the potential to dramatically change clinical CT. Photon-counting CT uses new energy-resolving x-ray detectors, with mechanisms that differ substantially from those of conventional energy-integrating detectors. Photon-counting CT detectors count the number of incoming photons and measure photon energy. This technique results in higher contrast-to-noise ratio, improved spatial resolution, and optimized spectral imaging. Photon-counting CT can reduce radiation exposure, reconstruct images at a higher resolution, correct beam-hardening artifacts, optimize the use of contrast agents, and create opportunities for quantitative imaging relative to current CT technology. In this review, the authors will explain the technical principles of photon-counting CT in nonmathematical terms for radiologists and clinicians. Following a general overview of the current status of photon-counting CT, they will explain potential clinical applications of this technology.
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Affiliation(s)
- Martin J Willemink
- From the Department of Radiology (M.J.W., M.P., N.J.P., D.F.) and Stanford Cardiovascular Institute (D.F.), Stanford University School of Medicine, 300 Pasteur Dr, S-072, Stanford, CA 94305-5105; Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (M.J.W.); Departments of Bioengineering (M.P., N.J.P.) and Electrical Engineering (N.J.P.), Stanford University, Stanford, Calif; Department of Radiology and Department of Imaging Sciences and Biomedical Informatics, Emory University School of Medicine, Atlanta, Ga (A.P.)
| | - Mats Persson
- From the Department of Radiology (M.J.W., M.P., N.J.P., D.F.) and Stanford Cardiovascular Institute (D.F.), Stanford University School of Medicine, 300 Pasteur Dr, S-072, Stanford, CA 94305-5105; Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (M.J.W.); Departments of Bioengineering (M.P., N.J.P.) and Electrical Engineering (N.J.P.), Stanford University, Stanford, Calif; Department of Radiology and Department of Imaging Sciences and Biomedical Informatics, Emory University School of Medicine, Atlanta, Ga (A.P.)
| | - Amir Pourmorteza
- From the Department of Radiology (M.J.W., M.P., N.J.P., D.F.) and Stanford Cardiovascular Institute (D.F.), Stanford University School of Medicine, 300 Pasteur Dr, S-072, Stanford, CA 94305-5105; Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (M.J.W.); Departments of Bioengineering (M.P., N.J.P.) and Electrical Engineering (N.J.P.), Stanford University, Stanford, Calif; Department of Radiology and Department of Imaging Sciences and Biomedical Informatics, Emory University School of Medicine, Atlanta, Ga (A.P.)
| | - Norbert J Pelc
- From the Department of Radiology (M.J.W., M.P., N.J.P., D.F.) and Stanford Cardiovascular Institute (D.F.), Stanford University School of Medicine, 300 Pasteur Dr, S-072, Stanford, CA 94305-5105; Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (M.J.W.); Departments of Bioengineering (M.P., N.J.P.) and Electrical Engineering (N.J.P.), Stanford University, Stanford, Calif; Department of Radiology and Department of Imaging Sciences and Biomedical Informatics, Emory University School of Medicine, Atlanta, Ga (A.P.)
| | - Dominik Fleischmann
- From the Department of Radiology (M.J.W., M.P., N.J.P., D.F.) and Stanford Cardiovascular Institute (D.F.), Stanford University School of Medicine, 300 Pasteur Dr, S-072, Stanford, CA 94305-5105; Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands (M.J.W.); Departments of Bioengineering (M.P., N.J.P.) and Electrical Engineering (N.J.P.), Stanford University, Stanford, Calif; Department of Radiology and Department of Imaging Sciences and Biomedical Informatics, Emory University School of Medicine, Atlanta, Ga (A.P.)
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22
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Li Q, Berman BP, Hagio T, Gavrielides MA, Zeng R, Sahiner B, Gong Q, Fang Y, Liu S, Petrick N. Coronary artery calcium quantification using contrast-enhanced dual-energy computed tomography scans in comparison with unenhanced single-energy scans. Phys Med Biol 2018; 63:175006. [PMID: 30101756 PMCID: PMC6183065 DOI: 10.1088/1361-6560/aad9be] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Extracting coronary artery calcium (CAC) scores from contrast-enhanced computed tomography (CT) images using dual-energy (DE) based material decomposition has been shown feasible, mainly through patient studies. However, the quantitative performance of such DE-based CAC scores, particularly per stenosis, is underexamined due to lack of reference standard and repeated scans. In this work we conducted a comprehensive quantitative comparative analysis of CAC scores obtained with DE and compare to conventional unenhanced single-energy (SE) CT scans through phantom studies. Synthetic vessels filled with iodinated blood mimicking material and containing calcium stenoses of different sizes and densities were scanned with a third generation dual-source CT scanner in a chest phantom using a DE coronary CT angiography protocol with three exposures/CTDIvol: auto-mAs/8 mGy (automatic exposure), 160 mAs/20 mGy and 260 mAs/34 mGy and 10 repeats. As a control, a set of vessel phantoms without iodine was scanned using a standard SE CAC score protocol (3 mGy). Calcium volume, mass and Agatston scores were estimated for each stenosis. For DE dataset, image-based three-material decomposition was applied to remove iodine before scoring. Performance of DE-based calcium scores were analyzed on a per-stenosis level and compared to SE-based scores. There was excellent correlation between the DE- and SE-based scores (correlation coefficient r: 0.92-0.98). Percent bias for the calcium volume and mass scores varied as a function of stenosis size and density for both modalities. Precision (coefficient of variation) improved with larger and denser stenoses for both DE- and SE-based calcium scores. DE-based scores (20 mGy and 34 mGy) provided comparable per-stenosis precision to SE-based (3 mGy). Our findings suggest that on a per-stenosis level, DE-based CAC scores from contrast-enhanced CT images can achieve comparable quantification performance to conventional SE-based scores. However, DE-based CAC scoring required more dose compared with SE for high per-stenosis precision so some caution is necessary with clinical DE-based CAC scoring.
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Affiliation(s)
- Qin Li
- US Food and Drug Administration, CDRH/OSEL/DIDSR, Silver Spring, MD, United States of America
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Measuring Identification and Quantification Errors in Spectral CT Material Decomposition. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8030467] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Discrimination Between Calcium Hydroxyapatite and Calcium Oxalate Using Multienergy Spectral Photon-Counting CT. AJR Am J Roentgenol 2017; 209:1088-1092. [DOI: 10.2214/ajr.17.18394] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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25
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Rajendran K, Leng S, Jorgensen SM, Abdurakhimova D, Ritman EL, McCollough CH. Detection of increased vasa vasorum in artery walls: Improving CT number accuracy using image deconvolution. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10132. [PMID: 28413240 DOI: 10.1117/12.2255676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Changes in arterial wall perfusion are an indicator of early atherosclerosis. This is characterized by an increased spatial density of vasa vasorum (VV), the micro-vessels that supply oxygen and nutrients to the arterial wall. Detection of increased VV during contrast-enhanced computed tomography (CT) imaging is limited due to contamination from blooming effect from the contrast-enhanced lumen. We report the application of an image deconvolution technique using a measured system point-spread function, on CT data obtained from a photon-counting CT system to reduce blooming and to improve the CT number accuracy of arterial wall, which enhances detection of increased VV. A phantom study was performed to assess the accuracy of the deconvolution technique. A porcine model was created with enhanced VV in one carotid artery; the other carotid artery served as a control. CT images at an energy range of 25-120 keV were reconstructed. CT numbers were measured for multiple locations in the carotid walls and for multiple time points, pre and post contrast injection. The mean CT number in the carotid wall was compared between the left (increased VV) and right (control) carotid arteries. Prior to deconvolution, results showed similar mean CT numbers in the left and right carotid wall due to the contamination from blooming effect, limiting the detection of increased VV in the left carotid artery. After deconvolution, the mean CT number difference between the left and right carotid arteries was substantially increased at all the time points, enabling detection of the increased VV in the artery wall.
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Affiliation(s)
- Kishore Rajendran
- Dept. of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, USA 55905
| | - Shuai Leng
- Dept. of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, USA 55905
| | - Steven M Jorgensen
- Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN, USA 55905
| | | | - Erik L Ritman
- Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street SW, Rochester, MN, USA 55905
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Abstract
Advances in cardiovascular computed tomography (CT) have resulted in an excellent ability to exclude coronary heart disease (CHD). Anatomical information, functional information, and spectral information can already be obtained with current CT technologies. Moreover, novel developments such as targeted nanoparticle contrast agents, photon-counting CT, and phase contrast CT will further enhance the diagnostic value of cardiovascular CT. This review provides an overview of current state of the art and future cardiovascular CT imaging.
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Faby S, Maier J, Sawall S, Simons D, Schlemmer HP, Lell M, Kachelrieß M. An efficient computational approach to model statistical correlations in photon counting x-ray detectors. Med Phys 2016; 43:3945. [DOI: 10.1118/1.4952726] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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Yang Q, Cong W, Xi Y, Wang G. Spectral X-Ray CT Image Reconstruction with a Combination of Energy-Integrating and Photon-Counting Detectors. PLoS One 2016; 11:e0155374. [PMID: 27171153 PMCID: PMC4865218 DOI: 10.1371/journal.pone.0155374] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 04/27/2016] [Indexed: 11/18/2022] Open
Abstract
The purpose of this paper is to develop an algorithm for hybrid spectral computed tomography (CT) which combines energy-integrating and photon-counting detectors. While the energy-integrating scan is global, the photon-counting scan can have a local field of view (FOV). The algorithm synthesizes both spectral data and energy-integrating data. Low rank and sparsity prior is used for spectral CT reconstruction. An initial estimation is obtained from the projection data based on physical principles of x-ray interaction with the matter, which provides a more accurate Taylor expansion than previous work and can guarantee the convergence of the algorithm. Numerical simulation with clinical CT images are performed. The proposed algorithm produces very good spectral features outside the FOV when no K-edge material exists. Exterior reconstruction of K-edge material can be partially achieved.
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Affiliation(s)
- Qingsong Yang
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
| | - Wenxiang Cong
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
| | - Yan Xi
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
| | - Ge Wang
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
- * E-mail:
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29
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Quantitative imaging of excised osteoarthritic cartilage using spectral CT. Eur Radiol 2016; 27:384-392. [DOI: 10.1007/s00330-016-4374-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 02/29/2016] [Accepted: 04/18/2016] [Indexed: 12/23/2022]
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30
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Lee JS, Kang DG, Jin SO, Kim I, Lee SY. Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior. SENSORS 2016; 16:s16040518. [PMID: 27077856 PMCID: PMC4851032 DOI: 10.3390/s16040518] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 03/22/2016] [Accepted: 04/06/2016] [Indexed: 01/18/2023]
Abstract
Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components.
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Affiliation(s)
- Jeong Seok Lee
- Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea.
- Department of Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi 17104, Korea.
| | - Dong-Goo Kang
- Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea.
| | - Seung Oh Jin
- Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea.
| | - Insoo Kim
- Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea.
| | - Soo Yeol Lee
- Department of Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi 17104, Korea.
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Danad I, Fayad ZA, Willemink MJ, Min JK. New Applications of Cardiac Computed Tomography: Dual-Energy, Spectral, and Molecular CT Imaging. JACC Cardiovasc Imaging 2016; 8:710-23. [PMID: 26068288 DOI: 10.1016/j.jcmg.2015.03.005] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/20/2015] [Accepted: 03/02/2015] [Indexed: 01/16/2023]
Abstract
Computed tomography (CT) has evolved into a powerful diagnostic tool, and it is impossible to imagine current clinical practice without CT imaging. Because of its widespread availability, ease of clinical application, superb sensitivity for the detection of coronary artery disease, and noninvasive nature, CT has become a valuable tool within the armamentarium of cardiologists. In the past few years, numerous technological advances in CT have occurred, including dual-energy CT, spectral CT, and CT-based molecular imaging. By harnessing the advances in technology, cardiac CT has advanced beyond the mere evaluation of coronary stenosis to an imaging tool that permits accurate plaque characterization, assessment of myocardial perfusion, and even probing of molecular processes that are involved in coronary atherosclerosis. Novel innovations in CT contrast agents and pre-clinical spectral CT devices have paved the way for CT-based molecular imaging.
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Affiliation(s)
- Ibrahim Danad
- Department of Radiology, Weill Cornell Medical College, Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital, New York, New York
| | - Zahi A Fayad
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Martin J Willemink
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York; Department of Radiology, University Medical Center, Utrecht, the Netherlands
| | - James K Min
- Department of Radiology, Weill Cornell Medical College, Dalio Institute of Cardiovascular Imaging, New York-Presbyterian Hospital, New York, New York.
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den Harder AM, Willemink MJ, de Jong PA, Schilham AMR, Rajiah P, Takx RAP, Leiner T. New horizons in cardiac CT. Clin Radiol 2016; 71:758-67. [PMID: 26932775 DOI: 10.1016/j.crad.2016.01.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 12/23/2015] [Accepted: 01/21/2016] [Indexed: 12/13/2022]
Abstract
Until recently, cardiovascular computed tomography angiography (CCTA) was associated with considerable radiation doses. The introduction of tube current modulation and automatic tube potential selection as well as high-pitch prospective ECG-triggering and iterative reconstruction offer the ability to decrease dose with approximately one order of magnitude, often to sub-millisievert dose levels. In parallel, advancements in computational technology have enabled the measurement of fractional flow reserve (FFR) from CCTA data (FFRCT). This technique shows potential to replace invasively measured FFR to select patients in need of coronary intervention. Furthermore, developments in scanner hardware have led to the introduction of dual-energy and photon-counting CT, which offer the possibility of material decomposition imaging. Dual-energy CT reduces beam hardening, which enables CCTA in patients with a high calcium burden and more robust myocardial CT perfusion imaging. Future-generation CT systems will be capable of counting individual X-ray photons. Photon-counting CT is promising and may result in a substantial further radiation dose reduction, vastly increased spatial resolution, and the introduction of a whole new class of contrast agents.
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Affiliation(s)
- A M den Harder
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands.
| | - M J Willemink
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands
| | - P A de Jong
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands
| | - A M R Schilham
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands
| | - P Rajiah
- Cardiothoracic Imaging Division, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, USA
| | - R A P Takx
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands
| | - T Leiner
- Department of Radiology, University Medical Center Utrecht, P.O. Box 85500, 3508GA Utrecht, The Netherlands
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Chen H, Xu C, Persson M, Danielsson M. Optimization of beam quality for photon-counting spectral computed tomography in head imaging: simulation study. J Med Imaging (Bellingham) 2015; 2:043504. [PMID: 26835495 DOI: 10.1117/1.jmi.2.4.043504] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 10/09/2015] [Indexed: 11/14/2022] Open
Abstract
Head computed tomography (CT) plays an important role in the comprehensive evaluation of acute stroke. Photon-counting spectral detectors, as promising candidates for use in the next generation of x-ray CT systems, allow for assigning more weight to low-energy x-rays that generally contain more contrast information. Most importantly, the spectral information can be utilized to decompose the original set of energy-selective images into several basis function images that are inherently free of beam-hardening artifacts, a potential advantage for further improving the diagnosis accuracy. We are developing a photon-counting spectral detector for CT applications. The purpose of this work is to determine the optimal beam quality for material decomposition in two head imaging cases: nonenhanced imaging and K-edge imaging. A cylindrical brain tissue of 16-cm diameter, coated by a 6-mm-thick bone layer and 2-mm-thick skin layer, was used as a head phantom. The imaging target was a 5-mm-thick blood vessel centered in the head phantom. In K-edge imaging, two contrast agents, iodine and gadolinium, with the same concentration ([Formula: see text]) were studied. Three parameters that affect beam quality were evaluated: kVp settings (50 to 130 kVp), filter materials ([Formula: see text] to 83), and filter thicknesses [0 to 2 half-value layer (HVL)]. The image qualities resulting from the varying x-ray beams were compared in terms of two figures of merit (FOMs): squared signal-difference-to-noise ratio normalized by brain dose ([Formula: see text]) and that normalized by skin dose ([Formula: see text]). For nonenhanced imaging, the results show that the use of the 120-kVp spectrum filtered by 2 HVL copper ([Formula: see text]) provides the best performance in both FOMs. When iodine is used in K-edge imaging, the optimal filter is 2 HVL iodine ([Formula: see text]) and the optimal kVps are 60 kVp in terms of [Formula: see text] and 75 kVp in terms of [Formula: see text]. A tradeoff of 65 kVp was proposed to lower the potential risk of skin injuries if a relatively long exposure time is necessarily performed in the iodinated imaging. In the case of gadolinium imaging, both SD and BD can be minimized at 120 kVp filtered with 2 HVL thulium ([Formula: see text]). The results also indicate that with the same concentration and their respective optimal spectrum, the values of [Formula: see text] and [Formula: see text] in gadolinium imaging are, respectively, around 3 and 10 times larger than those in iodine imaging. However, since gadolinium is used in much lower concentrations than iodine in the clinic, iodine may be a preferable candidate for K-edge imaging.
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Affiliation(s)
- Han Chen
- Royal Institute of Technology (KTH) , Department of Physics, Stockholm 106 91, Sweden
| | - Cheng Xu
- Royal Institute of Technology (KTH) , Department of Physics, Stockholm 106 91, Sweden
| | - Mats Persson
- Royal Institute of Technology (KTH) , Department of Physics, Stockholm 106 91, Sweden
| | - Mats Danielsson
- Royal Institute of Technology (KTH) , Department of Physics, Stockholm 106 91, Sweden
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35
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Li Z, Leng S, Yu L, Yu Z, McCollough CH. Image-based Material Decomposition with a General Volume Constraint for Photon-Counting CT. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2015; 9412. [PMID: 26229220 DOI: 10.1117/12.2082069] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Photon-counting CT (PCCT) potentially offers both improved dose efficiency and material decomposition capabilities relative to CT systems using energy integrating detectors. With respect to material decomposition, both projection-based and image-based methods have been proposed, most of which require accurate a priori information regarding the shape of the x-ray spectra and the response of the detectors. Additionally, projection-based methods require access to projection data. These data can be difficult to obtain, since spectra, detector response, and projection data formats are proprietary information. Further, some published image-based, 3-material decomposition methods require a volume conservation assumption, which is often violated in solutions. We have developed an image-based material decomposition method that can overcome those limitations. We introduced a general condition on volume constraint that does not require the volume to be conserved in a mixture. An empirical calibration can be performed with various concentrations of basis materials. The material decomposition method was applied to images acquired from a prototype whole-body PCCT scanner. The results showed good agreement between the estimation and known mass concentration values. Factors affecting the performance of material decomposition, such as energy threshold configuration and volume conservation constraint, were also investigated. Changes in accuracy of the mass concentration estimates were demonstrated for four different energy configurations and when volume conservation was assumed.
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Affiliation(s)
- Zhoubo Li
- Department of Biomedical Engineering and Physiology, Mayo Clinic College of Medicine, Rochester, MN 55905
| | - Shuai Leng
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | - Lifeng Yu
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | - Zhicong Yu
- Department of Radiology, Mayo Clinic, Rochester, MN 55905
| | - Cynthia H McCollough
- Department of Biomedical Engineering and Physiology, Mayo Clinic College of Medicine, Rochester, MN 55905 ; Department of Radiology, Mayo Clinic, Rochester, MN 55905
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36
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Shen L, Xing Y. Multienergy CT acquisition and reconstruction with a stepped tube potential scan. Med Phys 2014; 42:282-96. [DOI: 10.1118/1.4903756] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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Persson M, Huber B, Karlsson S, Liu X, Chen H, Xu C, Yveborg M, Bornefalk H, Danielsson M. Energy-resolved CT imaging with a photon-counting silicon-strip detector. Phys Med Biol 2014; 59:6709-27. [DOI: 10.1088/0022-3727/59/22/6709] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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38
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Koenig T, Zuber M, Hamann E, Cecilia A, Ballabriga R, Campbell M, Ruat M, Tlustos L, Fauler A, Fiederle M, Baumbach T. How spectroscopic x-ray imaging benefits from inter-pixel communication. Phys Med Biol 2014; 59:6195-213. [PMID: 25255737 DOI: 10.1088/0031-9155/59/20/6195] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Spectroscopic x-ray imaging based on pixellated semiconductor detectors can be sensitive to charge sharing and K-fluorescence, depending on the sensor material used, its thickness and the pixel pitch employed. As a consequence, spectroscopic resolution is partially lost. In this paper, we study a new detector ASIC, the Medipix3RX, that offers a novel feature called charge summing, which is established by making adjacent pixels communicate with each other. Consequently, single photon interactions resulting in multiple hits are almost completely avoided. We investigate this charge summing mode with respect to those of its imaging properties that are of interest in medical physics and benchmark them against the case without charge summing. In particular, we review its influence on spectroscopic resolution and find that the low energy bias normally present when recording energy spectra is dramatically reduced. Furthermore, we show that charge summing provides a modulation transfer function which is almost independent of the energy threshold setting, which is in contrast to approaches common so far. We demonstrate that this property is directly linked to the detective quantum efficiency, which is found to increase by a factor of three or more when the energy threshold approaches the photon energy and when using charge summing. As a consequence, the contrast-to-noise ratio is found to double at elevated threshold levels and the dynamic range increases for a given counter depth. All these effects are shown to lead to an improved ability to perform material discrimination in spectroscopic CT, using iodine and gadolinium contrast agents. Hence, when compared to conventional photon counting detectors, these benefits carry the potential of substantially reducing the imaging dose a patient is exposed to during diagnostic CT examinations.
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Affiliation(s)
- Thomas Koenig
- Karlsruhe Institute of Technology (KIT), Institute for Photon Science and Synchrotron Radiation (IPS) and ANKA Synchrotron Radiation Facility, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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Anderson NG, Butler AP. Clinical applications of spectral molecular imaging: potential and challenges. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 9:3-12. [PMID: 24470290 DOI: 10.1002/cmmi.1550] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 05/20/2013] [Accepted: 05/28/2013] [Indexed: 12/22/2022]
Abstract
Spectral molecular imaging is a new X-ray-based imaging technology providing highly specific 3D imaging at high spatial resolution that has the potential to measure disease activity and response to treatment noninvasively. The ability to identify and quantify components of tissue and biomarkers of disease activity derive from the properties of the photon-processing detector. Multiple narrow sections of the energy spectrum are sampled simultaneously, providing a range of energy dependent Hounsfield units. As each material has a specific measurable X-ray spectrum, spectroscopic imaging allows for multiple materials to be quantified and differentiated from each other simultaneously. The technology, currently in its infancy, is set to grow rapidly, much as magnetic resonance did. The critical clinical applications have not yet been established, but it is likely to play a major role in identifying and directing treatment for unstable atherosclerotic plaque, assessing activity and response to treatment of a range of inflammatory diseases, and monitoring biomarkers of cancer and its treatment. If combined with Positron-emission tomography (PET), spectral molecular imaging could have a far greater effective role in cancer diagnosis and treatment monitoring than PET-CT does at present. It is currently used for small animal and specimen imaging. There are many challenges to be overcome before spectral imaging can be introduced into clinical medicine - these include technological improvements to detector design, bonding to the semiconductor layer, image reconstruction and display software, identifying which biomarkers are of most relevance to the disease in question, and accelerating drug discovery enabled by the new capabilities provided by spectral imaging.
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Affiliation(s)
- Nigel G Anderson
- Academic Radiology and Centre for Bioengineering, University of Otago, Christchurch, New Zealand; Medical Imaging, Royal Hobart Hospital, Hobart, Australia
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Bennett JR, Opie AMT, Xu Q, Yu H, Walsh M, Butler A, Butler P, Cao G, Mohs A, Wang G. Hybrid spectral micro-CT: system design, implementation, and preliminary results. IEEE Trans Biomed Eng 2014; 61:246-53. [PMID: 23996533 DOI: 10.1109/tbme.2013.2279673] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Spectral CT has proven an important development in biomedical imaging, and there have been several publications in the past years demonstrating its merits in pre-clinical and clinical applications. In 2012, Xu reported that near-term implementation of spectral micro-CT could be enhanced by a hybrid architecture: a narrow-beam spectral “interior” imaging chain integrated with a traditional wide-beam “global” imaging chain. This hybrid integration coupled with compressive sensing (CS)-based interior tomography demonstrated promising results for improved contrast resolution, and decreased system cost and radiation dose. The motivation for the current study is implementation and evaluation of the hybrid architecture with a first-of-its-kind hybrid spectral micro-CT system. Preliminary results confirm improvements in both contrast and spatial resolution. This technology is shown to merit further investigation and potential application in future spectral CT scanner design.
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Alivov Y, Baturin P, Le HQ, Ducote J, Molloi S. Optimization of K-edge imaging for vulnerable plaques using gold nanoparticles and energy resolved photon counting detectors: a simulation study. Phys Med Biol 2013; 59:135-52. [PMID: 24334301 DOI: 10.1088/0031-9155/59/1/135] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We investigated the effect of different imaging parameters, such as dose, beam energy, energy resolution and the number of energy bins, on the image quality of K-edge spectral computed tomography (CT) of gold nanoparticles (GNP) accumulated in an atherosclerotic plaque. A maximum likelihood technique was employed to estimate the concentration of GNP, which served as a targeted intravenous contrast material intended to detect the degree of the plaque's inflammation. The simulation studies used a single-slice parallel beam CT geometry with an x-ray beam energy ranging between 50 and 140 kVp. The synthetic phantoms included small (3 cm in diameter) cylinder and chest (33 × 24 cm(2)) phantoms, where both phantoms contained tissue, calcium and gold. In the simulation studies, GNP quantification and background (calcium and tissue) suppression tasks were pursued. The x-ray detection sensor was represented by an energy resolved photon counting detector (e.g., CdZnTe) with adjustable energy bins. Both ideal and more realistic (12% full width at half maximum (FWHM) energy resolution) implementations of the photon counting detector were simulated. The simulations were performed for the CdZnTe detector with a pixel pitch of 0.5-1 mm, which corresponds to a performance without significant charge sharing and cross-talk effects. The Rose model was employed to estimate the minimum detectable concentration of GNPs. A figure of merit (FOM) was used to optimize the x-ray beam energy (kVp) to achieve the highest signal-to-noise ratio with respect to the patient dose. As a result, the successful identification of gold and background suppression was demonstrated. The highest FOM was observed at the 125 kVp x-ray beam energy. The minimum detectable GNP concentration was determined to be approximately 1.06 µmol mL(-1) (0.21 mg mL(-1)) for an ideal detector and about 2.5 µmol mL(-1) (0.49 mg mL(-1)) for a more realistic (12% FWHM) detector. The studies show the optimal imaging parameters at the lowest patient dose using an energy resolved photon counting detector to image GNP in an atherosclerotic plaque.
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Rink K, Oelfke U, Fiederle M, Zuber M, Koenig T. Investigating the feasibility of photon-counting K-edge imaging at high x-ray fluxes using nonlinearity corrections. Med Phys 2013; 40:101908. [DOI: 10.1118/1.4820535] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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