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Tunissen SAM, Oostveen LJ, Moriakov N, Teuwen J, Michielsen K, Smit EJ, Sechopoulos I. Development, validation, and simplification of a scanner-specific CT simulator. Med Phys 2024; 51:2081-2095. [PMID: 37656009 PMCID: PMC10904672 DOI: 10.1002/mp.16679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 07/13/2023] [Accepted: 07/13/2023] [Indexed: 09/02/2023] Open
Abstract
BACKGROUND Simulated computed tomography (CT) images allow for knowledge of the underlying ground truth and for easy variation of imaging conditions, making them ideal for testing and optimization of new applications or algorithms. However, simulating all processes that affect CT images can result in simulations that are demanding in terms of processing time and computer memory. Therefore, it is of interest to determine how much the simulation can be simplified while still achieving realistic results. PURPOSE To develop a scanner-specific CT simulation using physics-based simulations for the position-dependent effects and shift-invariant image corruption methods for the detector effects. And to investigate the impact on image realism of introducing simplifications in the simulation process that lead to faster and less memory-demanding simulations. METHODS To make the simulator realistic and scanner-specific, the spatial resolution and noise characteristics, and the exposure-to-detector output relationship of a clinical CT system were determined. The simulator includes a finite focal spot size, raytracing of the digital phantom, gantry rotation during projection acquisition, and finite detector element size. Previously published spectral models were used to model the spectrum for the given tube voltage. The integrated energy at each element of the detector was calculated using the Beer-Lambert law. The resulting angular projections were subsequently corrupted by the detector modulation transfer function (MTF), and by addition of noise according to the noise power spectrum (NPS) and signal mean-variance relationship, which were measured for different scanner settings. The simulated sinograms were reconstructed on the clinical CT system and compared to real CT images in terms of CT numbers, noise magnitude using the standard deviation, noise frequency content using the NPS, and spatial resolution using the MTF throughout the field of view (FOV). The CT numbers were validated using a multi-energy CT phantom, the noise magnitude and frequency were validated with a water phantom, and the spatial resolution was validated with a tungsten wire. These metrics were compared at multiple scanner settings, and locations in the FOV. Once validated, the simulation was simplified by reducing the level of subsampling of the focal spot area, rotation and of detector pixel size, and the changes in MTFs were analyzed. RESULTS The average relative errors for spatial resolution within and across image slices, noise magnitude, and noise frequency content within and across slices were 3.4%, 3.3%, 4.9%, 3.9%, and 6.2%, respectively. The average absolute difference in CT numbers was 10.2 HU and the maximum was 22.5 HU. The simulation simplification showed that all subsampling can be avoided, except for angular, while the error in frequency at 10% MTF would be maximum 16.3%. CONCLUSION The simulation of a scanner-specific CT allows for the generation of realistic CT images by combining physics-based simulations for the position-dependent effects and image-corruption methods for the shift-invariant ones. Together with the available ground truth of the digital phantom, it results in a useful tool to perform quantitative analysis of reconstruction or post-processing algorithms. Some simulation simplifications allow for reduced time and computer power requirements with minimal loss of realism.
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Affiliation(s)
| | - Luuk J. Oostveen
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
| | - Nikita Moriakov
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Jonas Teuwen
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
- AI for Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Koen Michielsen
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
| | - Ewoud J. Smit
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
| | - Ioannis Sechopoulos
- Department of Medical Imaging, Radboudumc, Nijmegen, The Netherlands
- Dutch Expert Centre for Screening (LRCB), Nijmegen, The Netherlands
- Technical Medicine Centre, University of Twente, Enschede, The Netherlands
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Murayama K, Smit EJ, Prokop M, Ikeda Y, Fujii K, Nakahara I, Hanamatsu S, Katada K, Ohno Y, Toyama H. A Bayesian estimation method for cerebral blood flow measurement by area-detector CT perfusion imaging. Neuroradiology 2023; 65:65-75. [PMID: 35851924 DOI: 10.1007/s00234-022-03013-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 07/06/2022] [Indexed: 01/10/2023]
Abstract
PURPOSE Bayesian estimation with advanced noise reduction (BEANR) in CT perfusion (CTP) could deliver more reliable cerebral blood flow (CBF) measurements than the commonly used reformulated singular value decomposition (rSVD). We compared the efficacy of CBF measurement by CTP using BEANR and rSVD, evaluating both relative to N-isopropyl-p-[(123) I]- iodoamphetamine (123I-IMP) single-photon emission computed tomography (SPECT) as a reference standard, in patients with cerebrovascular disease. METHODS Thirty-one patients with suspected cerebrovascular disease underwent both CTP on a 320 detector-row CT system and SPECT. We applied rSVD and BEANR in the ischemic and contralateral regions to create CBF maps and calculate CBF ratios from the ischemic side to the healthy contralateral side (CBF index). The analysis involved comparing the CBF index between CTP methods and SPECT using Pearson's correlation and limits of agreement determined with Bland-Altman analyses, before comparing the mean difference in the CBF index between each CTP method and SPECT using the Wilcoxon matched pairs signed-rank test. RESULTS The CBF indices of BEANR and 123I-IMP SPECT were significantly and positively correlated (r = 0.55, p < 0.0001), but there was no significant correlation between the rSVD method and SPECT (r = 0.15, p > 0.05). BEANR produced smaller limits of agreement for CBF than rSVD. The mean difference in the CBF index between BEANR and SPECT differed significantly from that between rSVD and SPECT (p < 0.001). CONCLUSIONS BEANR has a better potential utility for CBF measurement in CTP than rSVD compared to SPECT in patients with cerebrovascular disease.
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Affiliation(s)
- Kazuhiro Murayama
- Department of Radiology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan.
| | - Ewoud J Smit
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA, Nijmegen, The Netherlands
| | - Mathias Prokop
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein Zuid 10, 6525 GA, Nijmegen, The Netherlands
| | - Yoshihiro Ikeda
- Canon Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, 325-8550, Japan
| | - Kenji Fujii
- Canon Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, 325-8550, Japan
| | - Ichiro Nakahara
- Department of Comprehensive Strokology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan
| | - Satomu Hanamatsu
- Department of Radiology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan
| | - Kazuhiro Katada
- Department of Radiology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan
| | - Yoshiharu Ohno
- Department of Radiology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan
| | - Hiroshi Toyama
- Department of Radiology, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake-Cho Toyoake, Aichi, 470-1101, Japan
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Perik TH, van Genugten EAJ, Aarntzen EHJG, Smit EJ, Huisman HJ, Hermans JJ. Quantitative CT perfusion imaging in patients with pancreatic cancer: a systematic review. Abdom Radiol (NY) 2022; 47:3101-3117. [PMID: 34223961 PMCID: PMC9388409 DOI: 10.1007/s00261-021-03190-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 01/18/2023]
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related death with a 5-year survival rate of 10%. Quantitative CT perfusion (CTP) can provide additional diagnostic information compared to the limited accuracy of the current standard, contrast-enhanced CT (CECT). This systematic review evaluates CTP for diagnosis, grading, and treatment assessment of PDAC. The secondary goal is to provide an overview of scan protocols and perfusion models used for CTP in PDAC. The search strategy combined synonyms for 'CTP' and 'PDAC.' Pubmed, Embase, and Web of Science were systematically searched from January 2000 to December 2020 for studies using CTP to evaluate PDAC. The risk of bias was assessed using QUADAS-2. 607 abstracts were screened, of which 29 were selected for full-text eligibility. 21 studies were included in the final analysis with a total of 760 patients. All studies comparing PDAC with non-tumorous parenchyma found significant CTP-based differences in blood flow (BF) and blood volume (BV). Two studies found significant differences between pathological grades. Two other studies showed that BF could predict neoadjuvant treatment response. A wide variety in kinetic models and acquisition protocol was found among included studies. Quantitative CTP shows a potential benefit in PDAC diagnosis and can serve as a tool for pathological grading and treatment assessment; however, clinical evidence is still limited. To improve clinical use, standardized acquisition and reconstruction parameters are necessary for interchangeability of the perfusion parameters.
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Affiliation(s)
- T H Perik
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - E A J van Genugten
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - E H J G Aarntzen
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - E J Smit
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - H J Huisman
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - J J Hermans
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Oostveen LJ, Meijer FJA, de Lange F, Smit EJ, Pegge SA, Steens SCA, van Amerongen MJ, Prokop M, Sechopoulos I. Deep learning-based reconstruction may improve non-contrast cerebral CT imaging compared to other current reconstruction algorithms. Eur Radiol 2021; 31:5498-5506. [PMID: 33693996 PMCID: PMC8270865 DOI: 10.1007/s00330-020-07668-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 11/24/2020] [Accepted: 12/22/2020] [Indexed: 11/30/2022]
Abstract
Objectives To evaluate image quality and reconstruction times of a commercial deep learning reconstruction algorithm (DLR) compared to hybrid-iterative reconstruction (Hybrid-IR) and model-based iterative reconstruction (MBIR) algorithms for cerebral non-contrast CT (NCCT). Methods Cerebral NCCT acquisitions of 50 consecutive patients were reconstructed using DLR, Hybrid-IR and MBIR with a clinical CT system. Image quality, in terms of six subjective characteristics (noise, sharpness, grey-white matter differentiation, artefacts, natural appearance and overall image quality), was scored by five observers. As objective metrics of image quality, the noise magnitude and signal-difference-to-noise ratio (SDNR) of the grey and white matter were calculated. Mean values for the image quality characteristics scored by the observers were estimated using a general linear model to account for multiple readers. The estimated means for the reconstruction methods were pairwise compared. Calculated measures were compared using paired t tests. Results For all image quality characteristics, DLR images were scored significantly higher than MBIR images. Compared to Hybrid-IR, perceived noise and grey-white matter differentiation were better with DLR, while no difference was detected for other image quality characteristics. Noise magnitude was lower for DLR compared to Hybrid-IR and MBIR (5.6, 6.4 and 6.2, respectively) and SDNR higher (2.4, 1.9 and 2.0, respectively). Reconstruction times were 27 s, 44 s and 176 s for Hybrid-IR, DLR and MBIR respectively. Conclusions With a slight increase in reconstruction time, DLR results in lower noise and improved tissue differentiation compared to Hybrid-IR. Image quality of MBIR is significantly lower compared to DLR with much longer reconstruction times. Key Points • Deep learning reconstruction of cerebral non-contrast CT results in lower noise and improved tissue differentiation compared to hybrid-iterative reconstruction. • Deep learning reconstruction of cerebral non-contrast CT results in better image quality in all aspects evaluated compared to model-based iterative reconstruction. • Deep learning reconstruction only needs a slight increase in reconstruction time compared to hybrid-iterative reconstruction, while model-based iterative reconstruction requires considerably longer processing time. Supplementary Information The online version contains supplementary material available at 10.1007/s00330-020-07668-x.
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Affiliation(s)
- Luuk J Oostveen
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands.
| | - Frederick J A Meijer
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Frank de Lange
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Ewoud J Smit
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Sjoert A Pegge
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Stefan C A Steens
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Martin J van Amerongen
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Mathias Prokop
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
| | - Ioannis Sechopoulos
- Department of Medical Imaging, Radboud University Medical Center, P.O. Box 9101 (route 766), 6500 HB, Nijmegen, The Netherlands
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Tsuneta S, Oyama-Manabe N, Kameda H, Harada T, Kato F, Smit EJ, Prokop M, Kudo K. Improvement of image quality on low-dose dynamic myocardial perfusion computed tomography with a novel 4-dimensional similarity filter. Medicine (Baltimore) 2020; 99:e20804. [PMID: 32590765 PMCID: PMC7328929 DOI: 10.1097/md.0000000000020804] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
The aim of this study was to evaluate the effect of a novel 4-dimensional similarity filter (4DSF) on quantitative and qualitative parameters of low-dose dynamic myocardial computed tomography perfusion (CTP) images.In this retrospective study, medical records of 32 patients with suspected or known coronary artery disease who underwent dynamic myocardial CTP at 80 kV were included. The 4DSF reduces noise by averaging voxels that have similar dynamic behavior after adaptive iterative dose reduction 3D (AIDR3D) and deformable image registration were applied. Qualitative (artefact, contour sharpness, and myocardial homogeneity [1 = poor; 2 = intermediate; 3 = good]) and quantitative measurement (standard deviation [SD] and signal-to-noise ratio [SNR]) were compared between the 4DSF and AIDR3D. Contrast-to-noise ratio (CNR) between ischemic and normal remote myocardium was also assessed using myocardial perfusion magnetic resonance imaging as the reference standard in seven patients.The 4DSF was successfully applied to all the images. Improvement in subjective image quality yielded by 4DSF was higher than that yielded by AIDR3D (homogeneity, 1.0 [3 vs 2]; artefact, 1.5 [3 vs 1.5]; P < .001) in all patients. The 4DSF significantly decreased the SD by 59% (AIDR3D vs 4DSF: 33.5 ± 0.4 vs 13.8 ± 0.4, P < .001), increased the SNR by 134% (AIDR3D vs 4DSF: 4.4 ± 0.2 vs 10.3 ± 0.2, P < .001), and increased the CNR by 131% (AIDR3D vs 4DSF: 1.6 ± 0.2 vs 3.7 ± 0.2, P < .001).The 4DSF improved the qualitative and quantitative parameters of low-dose dynamic myocardial CTP images.
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Affiliation(s)
- Satonori Tsuneta
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido
- Department of Diagnostic Imaging, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido
| | - Noriko Oyama-Manabe
- Department of Radiology, Saitama Medical Center, Jichi Medical University, Saitama-shi, Saitama
| | - Hiroyuki Kameda
- Department of Dental Radiology, Hokkaido University Graduate School of Dental Medicine, Sapporo, Hokkaido, Japan
| | - Taisuke Harada
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido
| | - Fumi Kato
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido
| | - Ewoud J. Smit
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mathias Prokop
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Kohsuke Kudo
- Department of Diagnostic Imaging, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido
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Oei MTH, Meijer FJA, Mordang JJ, Smit EJ, Idema AJS, Goraj BM, Laue HOA, Prokop M, Manniesing R. Observer variability of reference tissue selection for relativecerebral blood volume measurements in glioma patients. Eur Radiol 2018; 28:3902-3911. [PMID: 29572637 PMCID: PMC6096614 DOI: 10.1007/s00330-018-5353-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/27/2017] [Accepted: 01/23/2018] [Indexed: 11/05/2022]
Abstract
Objectives To assess observer variability of different reference tissues used for relative CBV (rCBV) measurements in DSC-MRI of glioma patients. Methods In this retrospective study, three observers measured rCBV in DSC-MR images of 44 glioma patients on two occasions. rCBV is calculated by the CBV in the tumour hotspot/the CBV of a reference tissue at the contralateral side for normalization. One observer annotated the tumour hotspot that was kept constant for all measurements. All observers annotated eight reference tissues of normal white and grey matter. Observer variability was evaluated using the intraclass correlation coefficient (ICC), coefficient of variation (CV) and Bland-Altman analyses. Results For intra-observer, the ICC ranged from 0.50–0.97 (fair–excellent) for all reference tissues. The CV ranged from 5.1–22.1 % for all reference tissues and observers. For inter-observer, the ICC for all pairwise observer combinations ranged from 0.44–0.92 (poor–excellent). The CV ranged from 8.1–31.1 %. Centrum semiovale was the only reference tissue that showed excellent intra- and inter-observer agreement (ICC>0.85) and lowest CVs (<12.5 %). Bland-Altman analyses showed that mean differences for centrum semiovale were close to zero. Conclusion Selecting contralateral centrum semiovale as reference tissue for rCBV provides the lowest observer variability. Key Points • Reference tissue selection for rCBV measurements adds variability to rCBV measurements. • rCBV measurements vary depending on the choice of reference tissue. • Observer variability of reference tissue selection varies between poor and excellent. • Centrum semiovale as reference tissue for rCBV provides the lowest observer variability.
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Affiliation(s)
- Marcel T H Oei
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Frederick J A Meijer
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Jan-Jurre Mordang
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ewoud J Smit
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Albert J S Idema
- Department of Neurosurgery, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Bozena M Goraj
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | | | - Mathias Prokop
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Rashindra Manniesing
- Department of Radiology and Nuclear Medicine, Radboudumc, Geert Grooteplein 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Oei MTH, Meijer FJA, van der Woude WJ, Smit EJ, van Ginneken B, Prokop M, Manniesing R. Interleaving cerebral CT perfusion with neck CT angiography part I. Proof of concept and accuracy of cerebral perfusion values. Eur Radiol 2016; 27:2649-2656. [PMID: 27718078 PMCID: PMC5409805 DOI: 10.1007/s00330-016-4577-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 07/27/2016] [Accepted: 08/22/2016] [Indexed: 11/27/2022]
Abstract
Objectives We present a novel One-Step-Stroke protocol for wide-detector CT scanners that interleaves cerebral CTP with volumetric neck CTA (vCTA). We evaluate whether the resulting time gap in CTP affects the accuracy of CTP values. Methods Cerebral CTP maps were retrospectively obtained from 20 patients with suspicion of acute ischemic stroke and served as the reference standard. To simulate a 4 s gap for interleaving CTP with vCTA, we eliminated one acquisition at various time points of CTP starting from the bolus-arrival-time(BAT). Optimal timing of the vCTA was evaluated. At the time point with least errors, we evaluated elimination of a second time point (6 s gap). Results Mean absolute percentage errors of all perfusion values remained below 10 % in all patients when eliminating any one time point in the CTP sequence starting from the BAT. Acquiring the vCTA 2 s after reaching a threshold of 70HU resulted in the lowest errors (mean <3.0 %). Eliminating a second time point still resulted in mean errors <3.5 %. CBF/CBV showed no significant differences in perfusion values except MTT. However, the percentage errors were always below 10 % compared to the original protocol. Conclusion Interleaving cerebral CTP with neck CTA is feasible with minor effects on the perfusion values. Key Points • Removing a single CTP acquisition has minor effects on calculated perfusion values • Calculated perfusion values errors depend on timing of skipping a CTP acquisition • Qualitative evaluation of CTP was not influenced by removing two time points • Neck CTA is optimally timed in the upslope of arterial enhancement Electronic supplementary material The online version of this article (doi:10.1007/s00330-016-4577-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Marcel T H Oei
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Frederick J A Meijer
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Willem-Jan van der Woude
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ewoud J Smit
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Bram van Ginneken
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Mathias Prokop
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Rashindra Manniesing
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Oei MTH, Meijer FJA, van der Woude WJ, Smit EJ, van Ginneken B, Manniesing R, Prokop M. Interleaving cerebral CT perfusion with neck CT angiography. Part II: clinical implementation and image quality. Eur Radiol 2016; 27:2411-2418. [PMID: 27651144 PMCID: PMC5408041 DOI: 10.1007/s00330-016-4592-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 08/23/2016] [Accepted: 08/29/2016] [Indexed: 12/28/2022]
Abstract
Objectives Feasibility evaluation of the One-Step Stroke Protocol, which is an interleaved cerebral computed tomography perfusion (CTP) and neck volumetric computed tomography angiography (vCTA) scanning technique using wide-detector computed tomography, and to assess the image quality of vCTA. Methods Twenty patients with suspicion of acute ischaemic stroke were prospectively scanned and evaluated with a head and neck CTA and with the One-Step Stroke Protocol. Arterial enhancement and contrast-to-noise ratio (CNR) in the carotid arteries was assessed. Three observers scored artefacts and image quality of the cervical arteries. The total z-coverage was evaluated. Results Mean enhancement in the carotid bifurcation was rated higher in the vCTA (595 ± 164 HU) than CTA (441 ± 117 HU). CNR was rated higher in vCTA. Image quality scores showed no significant difference in the region of the carotid bifurcation between vCTA and CTA. Lower neck image quality scores were slightly lower for vCTA due to artefacts, although not rated as diagnostically relevant. In ten patients, the origin of the left common carotid artery was missed by 1.6 ± 0.8 cm. Mean patient height was 1.8 ± 0.09 m. Carotid bifurcation and origin of vertebral arteries were covered in all patients. Conclusions The One-Step Stroke Protocol is feasible with good diagnostic image quality of vCTA, although full z-coverage is limited in tall patients. Key Points • Interleaving cerebral CTP with neck CTA (One-Step Stroke Protocol) is feasible • Diagnostic quality of One-Step Stroke Protocol neck CTA is similar to conventional CTA • One-Step Stroke Protocol neck CTA suffers from streak artefacts in the lower neck • A limitation of One-Step Stroke Protocol CTA is lack of coverage in tall patients • Precise planning of One-Step Stroke Protocol neck CTA is necessary in tall patients Electronic supplementary material The online version of this article (doi:10.1007/s00330-016-4592-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Marcel T H Oei
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Frederick J A Meijer
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Willem-Jan van der Woude
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ewoud J Smit
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Bram van Ginneken
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Rashindra Manniesing
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Mathias Prokop
- Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Smit EJ, Vonken EJ, Meijer FJA, Dankbaar JW, Horsch AD, van Ginneken B, Velthuis B, van der Schaaf I, Prokop M. Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study. AJNR Am J Neuroradiol 2015; 36:1834-8. [PMID: 26113070 DOI: 10.3174/ajnr.a4376] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 02/22/2015] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted. MATERIALS AND METHODS Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics. RESULTS We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76). CONCLUSIONS Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.
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Affiliation(s)
- E J Smit
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands Department of Radiology (E.J.S., F.J.A.M, B.v.G., M.P.), Radboud University Medical Center Nijmegen, Nijmegen, the Netherlands.
| | - E-J Vonken
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - F J A Meijer
- Department of Radiology (E.J.S., F.J.A.M, B.v.G., M.P.), Radboud University Medical Center Nijmegen, Nijmegen, the Netherlands
| | - J W Dankbaar
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - A D Horsch
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - B van Ginneken
- Department of Radiology (E.J.S., F.J.A.M, B.v.G., M.P.), Radboud University Medical Center Nijmegen, Nijmegen, the Netherlands
| | - B Velthuis
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - I van der Schaaf
- From the Department of Radiology (E.J.S., E.-j.V., J.W.D., A.D.H., B.V., I.v.d.S.), University Medical Center Utrecht, Utrecht, the Netherlands
| | - M Prokop
- Department of Radiology (E.J.S., F.J.A.M, B.v.G., M.P.), Radboud University Medical Center Nijmegen, Nijmegen, the Netherlands
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Abstract
CT angiography is a widely used technique for the noninvasive evaluation of neurovascular pathology. Because CTA is a snapshot of arterial contrast enhancement, information on flow dynamics is limited. Dynamic CTA techniques, also referred to as 4D-CTA, have become available for clinical practice in recent years. This article provides a description of 4D-CTA techniques and a review of the available literature on the application of 4D-CTA for the evaluation of intracranial vascular malformations and hemorrhagic and ischemic stroke. Most of the research performed to date consists of observational cohort studies or descriptive case series. These studies show that intracranial vascular malformations can be adequately depicted and classified by 4D-CTA, with DSA as the reference standard. In ischemic stroke, 4D-CTA better estimates thrombus burden and the presence of collateral vessels than conventional CTA. In intracranial hemorrhage, 4D-CTA improves the detection of the "spot" sign, which represents active ongoing bleeding.
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Affiliation(s)
- H G J Kortman
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - E J Smit
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - M T H Oei
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - R Manniesing
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - M Prokop
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands
| | - F J A Meijer
- From the Department of Radiology and Nuclear Medicine, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
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11
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van den Boom R, Manniesing R, Oei MTH, van der Woude WJ, Smit EJ, Laue HOA, van Ginneken B, Prokop M. A 4D digital phantom for patient-specific simulation of brain CT perfusion protocols. Med Phys 2014; 41:071907. [DOI: 10.1118/1.4881520] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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12
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Riordan AJ, Bennink E, Dankbaar JW, Viergever MA, Velthuis BK, Smit EJ, de Jong HWAM. Comparison of partial volume effects in arterial and venous contrast curves in CT brain perfusion imaging. PLoS One 2014; 9:e97586. [PMID: 24858308 PMCID: PMC4032231 DOI: 10.1371/journal.pone.0097586] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 04/21/2014] [Indexed: 11/29/2022] Open
Abstract
Purpose In brain CT perfusion (CTP), the arterial contrast bolus is scaled to have the same area under the curve (AUC) as the venous outflow to correct for partial volume effects (PVE). This scaling is based on the assumption that large veins are unaffected by PVE. Measurement of the internal carotid artery (ICA), usually unaffected by PVE due to its large diameter, may avoid the need for partial volume correction. The aims of this work are to examine i) the assumptions behind PVE correction and ii) the potential of selecting the ICA obviating correction for PVE. Methods The AUC of the ICA and sagittal sinus were measured in CTP datasets from 52 patients. The AUCs were determined by i) using commercial CTP software based on a Gaussian curve-fitting to the time attenuation curve, and ii) by simple integration of the time attenuation curve over a time interval. In addition, frames acquired up to 3 minutes after first bolus passage were used to examine the ratio of arterial and venous enhancement. The impact of selecting the ICA without PVE correction was illustrated by reporting cerebral blood volume (CBV) measurements. Results In 49 of 52 patients, the AUC of the ICA was significantly larger than that of the sagittal sinus (p = 0.017). Measured after the first pass bolus, contrast enhancement remained 50% higher in the ICA just after the first pass bolus, and 30% higher 3 minutes later. CBV measurements were significantly lowered when the ICA was used without PVE correction. Conclusions Contradicting the assumptions underlying PVE correction, contrast in the ICA was significantly higher than in the sagittal sinus, even 3 minutes after the first pass of the contrast bolus. PVE correction might lead to overestimation of CBV if the CBV is calculated using the AUC of the time attenuation curves.
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Affiliation(s)
- Alan J. Riordan
- Department of Radiology, University Medical Centre, Utrecht, The Netherlands
- * E-mail:
| | - Edwin Bennink
- Department of Radiology, University Medical Centre, Utrecht, The Netherlands
| | - Jan Willem Dankbaar
- Department of Radiology, University Medical Centre, Utrecht, The Netherlands
| | - Max A. Viergever
- Department of Radiology, University Medical Centre, Utrecht, The Netherlands
| | | | - Ewoud J. Smit
- Department of Radiology, University Medical Centre, Utrecht, The Netherlands
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13
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Niesten JM, van der Schaaf IC, van der Graaf Y, Kappelle LJ, Biessels GJ, Horsch AD, Dankbaar JW, Luitse MJA, van Seeters T, Smit EJ, Mali WPTM, Velthuis BK. Predictive value of thrombus attenuation on thin-slice non-contrast CT for persistent occlusion after intravenous thrombolysis. Cerebrovasc Dis 2014; 37:116-22. [PMID: 24435107 DOI: 10.1159/000357420] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 11/19/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In stroke erythrocyte-rich thrombi are more sensitive to intravenous thrombolysis with recombinant tissue plasminogen activator (IV-rtPA) and have higher density on non-contrast CT (NCCT). We investigated the relationship between thrombus density and recanalization and whether persistent occlusions can be predicted by Hounsfield unit (HU) measurements. METHODS In 88 IV-rtPA-treated patients with intracranial ICA or MCA occluding thrombus and follow-up imaging, thrombus and contralateral vessel attenuation measurements were performed on thin-slice NCCT. Mean absolute and relative HU were compared between patients with persistent occlusion (modified Thrombolysis in Cerebral Infarction system, grade 0/1/2a) and recanalization (grade 2b/3). Univariate and multivariate (adjusted for stroke subtype, clot burden score, occlusion site and time to thrombolysis) odds ratios for persistent occlusion were calculated. Additional prognostic value for persistent occlusion was estimated by adding HU measurements to the area under the curve (AUC) of known determinants and calculating optimal cut-off values. RESULTS Patients with persistent occlusion (n = 19) had significant lower mean HU (absolute 52.2 ± 9.5, relative 1.29 ± 0.20) compared to recanalization (absolute 63.1 ± 10.7, relative 1.54 ± 0.23, both p < 0.0001). Odds ratios for persistent occlusion were 3.1 (95% confidence interval, CI 1.6-6.0) univariate and 3.1 (95% CI 1.7-5.7) multivariate per 10 absolute HU decrease and 3.2 (95% CI 1.6-6.5) univariate and 4.1 (95% CI 1.8-9.1) multivariate per 0.20 relative HU decrease. Attenuation measurements significantly increased the AUC (0.67) of the known determinants to 0.84 (absolute HU) and 0.86 (relative HU). Cut-off values of <56.5 absolute HU and <1.38 relative HU showed optimal predictive values for persistent occlusion. CONCLUSIONS Thrombus density is related to recanalization rate. Lower absolute and relative HU are independently related to persistent occlusion and HU measurements significantly increase discriminative performances of known recanalization determinants.
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Affiliation(s)
- J M Niesten
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
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Smit EJ, Vonken EJ, van Seeters T, Dankbaar JW, van der Schaaf IC, Kappelle LJ, van Ginneken B, Velthuis BK, Prokop M. Timing-invariant imaging of collateral vessels in acute ischemic stroke. Stroke 2013; 44:2194-9. [PMID: 23760216 DOI: 10.1161/strokeaha.111.000675] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Although collateral vessels have been shown to be an important prognostic factor in acute ischemic stroke, patients with lack of collaterals on standard imaging techniques may still have good clinical outcome. We postulate that in these cases collateral vessels are present though not visible on standard imaging techniques that are based on a single time frame. METHODS This study included 40 consecutive patients with acute ischemic stroke with a large-vessel occlusion. Standard computed tomography angiography (CTA, single time frame) and CT perfusion (multiple time frames) were obtained at admission and timing-invariant (TI)-CTA was created from the CT perfusion data. Clinical outcome data (modified Rankin Scale) were assessed at 3-month follow-up. Four experienced observers independently assessed collateral status twice on both standard CTA and TI-CTA in an independent, blinded, randomized manner. Collateral status was rated as good if ≥50% and poor if <50% of collaterals were present compared with the contralateral hemisphere. RESULTS Collateral status was rated higher on TI-CTA (good in 84%) compared with standard CTA (good in 49%; P<0.001). Thirty-one percent of patients with poor collateral status on standard CTA still had good clinical outcome. All of those patients, however, showed good collaterals on TI-CTA. All cases with poor collateral status rated on TI-CTA had poor clinical outcome. CONCLUSIONS Collateral vessels may not always be visible on standard single time-frame CTA because of delayed contrast arrival. Future prognostic studies in acute stroke should consider delay-insensitive techniques, such as TI-CTA, instead of standard single time-frame imaging, such as standard CTA.
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Affiliation(s)
- Ewoud J Smit
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
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15
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van der Kolk AG, Hendrikse J, Brundel M, Biessels GJ, Smit EJ, Visser F, Luijten PR, Zwanenburg JJM. Multi-sequence whole-brain intracranial vessel wall imaging at 7.0 tesla. Eur Radiol 2013; 23:2996-3004. [DOI: 10.1007/s00330-013-2905-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 04/05/2013] [Accepted: 04/17/2013] [Indexed: 11/27/2022]
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16
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Mendrik AM, Vonken EPA, de Kort GAP, van Ginneken B, Smit EJ, Viergever MA, Prokop M. Improved arterial visualization in cerebral CT perfusion-derived arteriograms compared with standard CT angiography: a visual assessment study. AJNR Am J Neuroradiol 2012; 33:2171-7. [PMID: 22627803 DOI: 10.3174/ajnr.a3118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND AND PURPOSE Invasive cerebral DSA has largely been replaced by CTA, which is noninvasive but has a compromised arterial view due to superimposed bone and veins. The purpose of this study was to evaluate whether arterial visualization in CTPa is superior to standard CTA, which would eliminate the need for an additional CTA scan to assess arterial diseases and therefore reduce radiation dose. MATERIALS AND METHODS In this study, we included 24 patients with subarachnoid hemorrhage for whom CTA and CTP were available. Arterial quality and presence of superimposed veins and bone in CTPa were compared with CTA and scored by 2 radiologists by using a VAS (0%-100%). Average VAS scores were determined and VAS scores per patient were converted to a 10-point NRS. Arterial visualization was considered to be improved when the highest rate (NRS 10, VAS > 90%) was scored for arterial quality, and the lowest rate (NRS 1, VAS < 10%), for the presence of superimposed veins and bone. A sign test with continuity correction was used to test whether the number of cases with these rates was significant. RESULTS Average VAS scores in the proximal area were 94% (arterial quality), 4% (presence of bone), and 7% (presence of veins). In this area, the sign test showed that a significant number of cases scored NRS 10 for arterial quality (P < .02) and NRS 1 for the presence of superimposed veins and bone (P < .01). CONCLUSIONS Cerebral CTPa shows improved arterial visualization in the proximal area compared with CTA, with similar arterial quality but no superimposed bone and veins.
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Affiliation(s)
- A M Mendrik
- Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
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17
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Mets OM, Smit EJ, Mohamed Hoesein FAA, Gietema HA, Bokkers RPH, Attrach M, van Amelsvoort-van de Vorst S, Scholten ET, Buckens CFM, Oudkerk M, Lammers JWJ, Prokop M, de Jong PA. Visual versus automated evaluation of chest computed tomography for the presence of chronic obstructive pulmonary disease. PLoS One 2012; 7:e42227. [PMID: 22848747 PMCID: PMC3407100 DOI: 10.1371/journal.pone.0042227] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 07/02/2012] [Indexed: 11/18/2022] Open
Abstract
Background Incidental CT findings may provide an opportunity for early detection of chronic obstructive pulmonary disease (COPD), which may prove important in CT-based lung cancer screening setting. We aimed to determine the diagnostic performance of human observers to visually evaluate COPD presence on CT images, in comparison to automated evaluation using quantitative CT measures. Methods This study was approved by the Dutch Ministry of Health and the institutional review board. All participants provided written informed consent. We studied 266 heavy smokers enrolled in a lung cancer screening trial. All subjects underwent volumetric inspiratory and expiratory chest computed tomography (CT). Pulmonary function testing was used as the reference standard for COPD. We evaluated the diagnostic performance of eight observers and one automated model based on quantitative CT measures. Results The prevalence of COPD in the study population was 44% (118/266), of whom 62% (73/118) had mild disease. The diagnostic accuracy was 74.1% in the automated evaluation, and ranged between 58.3% and 74.3% for the visual evaluation of CT images. The positive predictive value was 74.3% in the automated evaluation, and ranged between 52.9% and 74.7% for the visual evaluation. Interobserver variation was substantial, even within the subgroup of experienced observers. Agreement within observers yielded kappa values between 0.28 and 0.68, regardless of the level of expertise. The agreement between the observers and the automated CT model showed kappa values of 0.12–0.35. Conclusions Visual evaluation of COPD presence on chest CT images provides at best modest accuracy and is associated with substantial interobserver variation. Automated evaluation of COPD subjects using quantitative CT measures appears superior to visual evaluation by human observers.
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Affiliation(s)
- Onno M Mets
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
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Smit EJ, Vonken EJ, van der Schaaf IC, Mendrik AM, Dankbaar JW, Horsch AD, van Seeters T, van Ginneken B, Prokop M. Timing-Invariant Reconstruction for Deriving High-Quality CT Angiographic Data from Cerebral CT Perfusion Data. Radiology 2012; 263:216-25. [DOI: 10.1148/radiol.11111068] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Mendrik AM, Vonken EJ, van Ginneken B, de Jong HW, Riordan A, van Seeters T, Smit EJ, Viergever MA, Prokop M. TIPS bilateral noise reduction in 4D CT perfusion scans produces high-quality cerebral blood flow maps. Phys Med Biol 2011; 56:3857-72. [PMID: 21654042 DOI: 10.1088/0031-9155/56/13/008] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cerebral computed tomography perfusion (CTP) scans are acquired to detect areas of abnormal perfusion in patients with cerebrovascular diseases. These 4D CTP scans consist of multiple sequential 3D CT scans over time. Therefore, to reduce radiation exposure to the patient, the amount of x-ray radiation that can be used per sequential scan is limited, which results in a high level of noise. To detect areas of abnormal perfusion, perfusion parameters are derived from the CTP data, such as the cerebral blood flow (CBF). Algorithms to determine perfusion parameters, especially singular value decomposition, are very sensitive to noise. Therefore, noise reduction is an important preprocessing step for CTP analysis. In this paper, we propose a time-intensity profile similarity (TIPS) bilateral filter to reduce noise in 4D CTP scans, while preserving the time-intensity profiles (fourth dimension) that are essential for determining the perfusion parameters. The proposed TIPS bilateral filter is compared to standard Gaussian filtering, and 4D and 3D (applied separately to each sequential scan) bilateral filtering on both phantom and patient data. Results on the phantom data show that the TIPS bilateral filter is best able to approach the ground truth (noise-free phantom), compared to the other filtering methods (lowest root mean square error). An observer study is performed using CBF maps derived from fifteen CTP scans of acute stroke patients filtered with standard Gaussian, 3D, 4D and TIPS bilateral filtering. These CBF maps were blindly presented to two observers that indicated which map they preferred for (1) gray/white matter differentiation, (2) detectability of infarcted area and (3) overall image quality. Based on these results, the TIPS bilateral filter ranked best and its CBF maps were scored to have the best overall image quality in 100% of the cases by both observers. Furthermore, quantitative CBF and cerebral blood volume values in both the phantom and the patient data showed that the TIPS bilateral filter resulted in realistic mean values with a smaller standard deviation than the other evaluated filters and higher contrast-to-noise ratios. Therefore, applying the proposed TIPS bilateral filtering method to 4D CTP data produces higher quality CBF maps than applying the standard Gaussian, 3D bilateral or 4D bilateral filter. Furthermore, the TIPS bilateral filter is computationally faster than both the 3D and 4D bilateral filters.
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Affiliation(s)
- Adriënne M Mendrik
- Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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Riordan AJ, Prokop M, Viergever MA, Dankbaar JW, Smit EJ, de Jong HWAM. Validation of CT brain perfusion methods using a realistic dynamic head phantom. Med Phys 2011; 38:3212-21. [DOI: 10.1118/1.3592639] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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21
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Jayasuriya AN, Itzhaki RF, Wozniak MA, Patel R, Smit EJ, Noone R, Gilleran G, Taylor S, White DJ. Apolipoprotein E- 4 and recurrent genital herpes in individuals co-infected with herpes simplex virus type 2 and HIV. Sex Transm Infect 2008; 84:516-7. [DOI: 10.1136/sti.2008.032367] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Abstract
The gamma-evaluation method is a tool by which dose distributions can be compared in a quantitative manner combining dose-difference and distance-to-agreement criteria. Since its introduction, the gamma evaluation has been used in many studies and is on the verge of becoming the preferred dose distribution comparison method, particularly for intensity-modulated radiation therapy (IMRT) verification. One major disadvantage, however, is its long computation time, which especially applies to the comparison of three-dimensional (3D) dose distributions. We present a fast algorithm for a full 3D gamma evaluation at high resolution. Both the reference and evaluated dose distributions are first resampled on the same grid. For each point of the reference dose distribution, the algorithm searches for the best point of agreement according to the gamma method in the evaluated dose distribution, which can be done at a subvoxel resolution. Speed, computer memory efficiency, and high spatial resolution are achieved by searching around each reference point with increasing distance in a sphere, which has a radius of a chosen maximum search distance and is interpolated "on-the-fly" at a chosen sample step size. The smaller the sample step size and the larger the differences between the dose distributions, the longer the gamma evaluation takes. With decreasing sample step size, statistical measures of the 3D gamma distribution converge. Two clinical examples were investigated using 3% of the prescribed dose as dose-difference and 0.3 cm as distance-to-agreement criteria. For 0.2 cm grid spacing, the change in gamma indices was negligible below a sample step size of 0.02 cm. Comparing the full 3D gamma evaluation and slice-by-slice 2D gamma evaluations ("2.5D") for these clinical examples, the gamma indices improved by searching in full 3D space, with the average gamma index decreasing by at least 8%.
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Affiliation(s)
- Markus Wendling
- Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Affiliation(s)
- E J Smit
- HPA Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK.
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Mphahlele MJ, Moloto MJ, Burnett RJ, Smit EJ, Jensch S, van der Merwe CF, Webber L. Frequent detection of high viraemia in HBeAg-negative South African carriers. S Afr Med J 2001; 91:231-2. [PMID: 11291421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
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van der Ryst E, Cloete K, van Heerden A, Smit EJ, Williams MM. Hepatitis D virus--how prevalent? S Afr Med J 1997; 87:1387; author reply 1388. [PMID: 9472257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Abstract
This study analysed the effects of reaming and intramedullary nailing and thoracic injury related to development of ARDS and multi-organ failure in multiply injured patients. Sixty patients were entered into a retrospective follow-up study. Twenty-one patients with thoracic injury and femoral shaft fracture, treated by intramedullary nailing, were compared with 17 patients with a femoral shaft fracture without thoracic injury, and with 22 patients without femoral shaft fracture but with major thoracic injury. The incidence of ARDS, multiple organ failure (MOF) and the mortality rate in the groups was analysed, using chi 2 and Fisher exact tests. No significant differences in age, sex and ISS existed between the groups. There were no statistically significant differences with regard to the incidence of developing ARDS (P > 0.5), MOF (P > 0.5) and mortality rate (P > 0.2) after injury. The results of this study suggest that reaming of the femoral shaft as part of an intramedullary nailing procedure is not a major cause in developing ARDS and MOF in patients with femoral shaft fractures and thoracic injury. Conventional intramedullary nailing can be considered as a safe procedure in femoral shaft fractures in multiply injured patients, as well as in the presence of major thoracic injury.
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Affiliation(s)
- W J van der Made
- Department of General Surgery and Traumatology, Leiden University Hospital, Netherlands
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Smit EJ, Van Wyk PW, vd Westhuizen JP, Kock JL. An extended QBASIC program for the normalization and computation of whole-cell protein profiles and the application to clinically important Candida species. J Med Vet Mycol 1990; 28:303-15. [PMID: 2269910 DOI: 10.1080/02681219080000391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The computer program described enables a rapid calculation of relative molecular masses of proteins from different yeasts and microbial pathogens, by interpolation from a molecular weight calibration curve that comprises stepwise linear regression between the protein bands produced by the internal standards. A similarity matrix can then be produced, taking into account variations between calculated molecular masses caused by small differences in bandwidths and/or positions of specific protein bands. This program has been applied to different Candida species and the similarity data obtained further analysed numerically utilizing CLUSTAN II on a SPERRY 1100 multi-processor.
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Affiliation(s)
- E J Smit
- Department of Dermatology, Medical Faculty, University of the Orange Free State, Bloemfontein, Republic of South Africa
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Smit EJ, Kock JL, van der Westhuizen JP, Britz TJ. Taxonomic relationships of Cryptococcus and Tremella based on fatty acid composition and other phenotypic characters. J Gen Microbiol 1988; 134:2849-55. [PMID: 3254938 DOI: 10.1099/00221287-134-10-2849] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The cellular long-chain fatty acids present in 33 strains, representing 15 species of Cryptococcus, and 4 species of Tremella, were determined by gas chromatography. According to the relative amounts of fatty acid methyl esters, the Cryptococcus species studied were divided into four main groups. Possible relationships between species representing the two genera are presented in a new model, where cellular long-chain fatty acid compositions and other phenotypic characteristics are included.
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Affiliation(s)
- E J Smit
- Department of Dermatology, Medical Faculty, University of the Orange Free State, Bloemfontein, Republic of South Africa
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