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Hu T, Li B, Yang J, Zhang B, Fang L, Liu Y, Xiao P, Xie Q. Application of geometric shape-based CT field-of-view extension algorithms in an all-digital positron emission tomography/computed tomography system. Med Phys 2024; 51:1034-1046. [PMID: 38103259 DOI: 10.1002/mp.16888] [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: 07/13/2023] [Revised: 10/30/2023] [Accepted: 11/14/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Computed tomography (CT)-based positron emission tomography (PET) attenuation correction (AC) is a commonly used method in PET AC. However, the CT truncation caused by the subject's limbs outside the CT field-of-view (FOV) leads to errors in PET AC. PURPOSE In order to enhance the quantitative accuracy of PET imaging in the all-digital DigitMI 930 PET/CT system, we assessed the impact of FOV truncation on its image quality and investigated the effectiveness of geometric shape-based FOV extension algorithms in this system. METHODS We implemented two geometric shape-based FOV extension algorithms. By setting the data from different numbers of detector channels on either side of the sinogram to zero, we simulated various levels of truncation. Specific regions of interest (ROI) were selected, and the mean values of these ROIs were calculated to visually compare the differences between truncated CT, CT extended using the FOV extension algorithms, and the original CT. Furthermore, we conducted statistical analyses on the mean and standard deviation of residual maps between truncated/extended CT and the original CT at different levels of truncation. Subsequently, similar data processing was applied to PET images corrected using original CT and those corrected using simulated truncated and extended CT images. This allowed us to evaluate the influence of FOV truncation on the images produced by the DigitMI 930 PET/CT system and assess the effectiveness of the FOV extension algorithms. RESULTS Truncation caused bright artifacts at the CT FOV edge and a slight increase in pixel values within the FOV. When using truncated CT data for PET AC, the PET activity outside the CT FOV decreased, while the extension algorithm effectively reduced these effects. Patient data showed that the activity within the CT FOV decreased by 60% in the truncated image compared to the base image, but this number could be reduced to at least 17.3% after extension. CONCLUSION The two geometric shape-based algorithms effectively eliminate CT truncation artifacts and restore the true distribution of CT shape and PET emission data outside the FOV in the all-digital DigitMI 930 PET/CT system. These two algorithms can be used as basic solutions for CT FOV extension in all-digital PET/CT systems.
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Affiliation(s)
- Tianjiao Hu
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, China
| | - Bingxuan Li
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
| | - Jigang Yang
- Nuclear Medicine Department, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Bo Zhang
- Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Fang
- Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, China
| | - Yuqing Liu
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
| | - Peng Xiao
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
- Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, China
| | - Qingguo Xie
- Department of Electronic Engineering and Information Science, University of Science and Technology of China, Hefei, China
- Institute of Artificial Intelligence, Hefei Comprehensive National Science Center, Hefei, China
- Biomedical Engineering Department, Huazhong University of Science and Technology, Wuhan, China
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Shiri I, Salimi Y, Hervier E, Pezzoni A, Sanaat A, Mostafaei S, Rahmim A, Mainta I, Zaidi H. Artificial Intelligence-Driven Single-Shot PET Image Artifact Detection and Disentanglement: Toward Routine Clinical Image Quality Assurance. Clin Nucl Med 2023; 48:1035-1046. [PMID: 37883015 PMCID: PMC10662584 DOI: 10.1097/rlu.0000000000004912] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 08/22/2023] [Indexed: 10/27/2023]
Abstract
PURPOSE Medical imaging artifacts compromise image quality and quantitative analysis and might confound interpretation and misguide clinical decision-making. The present work envisions and demonstrates a new paradigm PET image Quality Assurance NETwork (PET-QA-NET) in which various image artifacts are detected and disentangled from images without prior knowledge of a standard of reference or ground truth for routine PET image quality assurance. METHODS The network was trained and evaluated using training/validation/testing data sets consisting of 669/100/100 artifact-free oncological 18 F-FDG PET/CT images and subsequently fine-tuned and evaluated on 384 (20% for fine-tuning) scans from 8 different PET centers. The developed DL model was quantitatively assessed using various image quality metrics calculated for 22 volumes of interest defined on each scan. In addition, 200 additional 18 F-FDG PET/CT scans (this time with artifacts), generated using both CT-based attenuation and scatter correction (routine PET) and PET-QA-NET, were blindly evaluated by 2 nuclear medicine physicians for the presence of artifacts, diagnostic confidence, image quality, and the number of lesions detected in different body regions. RESULTS Across the volumes of interest of 100 patients, SUV MAE values of 0.13 ± 0.04, 0.24 ± 0.1, and 0.21 ± 0.06 were reached for SUV mean , SUV max , and SUV peak , respectively (no statistically significant difference). Qualitative assessment showed a general trend of improved image quality and diagnostic confidence and reduced image artifacts for PET-QA-NET compared with routine CT-based attenuation and scatter correction. CONCLUSION We developed a highly effective and reliable quality assurance tool that can be embedded routinely to detect and correct for 18 F-FDG PET image artifacts in clinical setting with notably improved PET image quality and quantitative capabilities.
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Affiliation(s)
- Isaac Shiri
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
- Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yazdan Salimi
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
| | - Elsa Hervier
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
| | - Agathe Pezzoni
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
| | - Amirhossein Sanaat
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
| | - Shayan Mostafaei
- Division of Clinical Geriatrics, Department of Neurobiology, Care Sciences and Society
- Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
| | - Arman Rahmim
- Departments of Radiology and Physics, University of British Columbia
- Department of Integrative Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada
| | - Ismini Mainta
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
| | - Habib Zaidi
- From the Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva
- Geneva University Neuro 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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Hu Y, Liu G, Yu H, Gu J, Shi H. Diagnostic performance of total-body 18F-FDG PET/CT with fast 2-min acquisition for liver tumours: comparison with conventional PET/CT. Eur J Nucl Med Mol Imaging 2022; 49:3538-3546. [PMID: 35344063 DOI: 10.1007/s00259-022-05772-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 03/19/2022] [Indexed: 12/29/2022]
Abstract
PURPOSE To comparatively evaluate the diagnostic performances of total-body 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (18F-FDG PET/CT) with fast 2-min acquisition and conventional PET/CT in liver cancer patients. METHODS This study included 156 patients with liver tumours. Seventy-eight patients underwent total-body PET/CT. PET raw data were reconstructed using acquisition durations of 2 min (G2) and 15 min (G15). Another 78 patients with liver lesions (control patients) underwent conventional uMI780 PET/CT (G780). All patients were evaluated based on TNM staging. The maximum tumour standardized uptake value (tumour SUVmax), mean normal liver SUV (SUVmean), and tumour SUVmax-to-liver SUVmean ratio (TLR) were determined for all patients. G15 data were used as the reference in the lesion detectability analysis. The diagnostic performances of PET/CT in terms of visual parameters and of PET in terms of semi-quantitative parameters such as SUVmax and TLR were evaluated. Receiver operating characteristics (ROC) curve analysis of SUVmax and TLR at G2 was performed. Pathologic findings of surgical specimens served as the gold standard for all patients. RESULTS The lesions found in G15 were also noted in G2; three lymph nodes were missed in G2. However, no significant difference was found in the TNM stage among G2, G15, and G780. For benign and malignant lesions, the liver SUVmean in G2 and G15 was higher than that in G780 (all P < 0.05). The tumour SUVmax and TLR in G2 were equivalent to those in G15 and G780 regardless of whether the lesions were benign or malignant. ROC curve analysis (SUVmax cutoff: 4.34, TLR cutoff: 1.34) demonstrated that G2 also had good sensitivity in detecting liver cancer. CONCLUSION The diagnostic performance of total-body PET/CT in G2 was comparable to that in G15 among liver cancer patients. Further, the diagnostic efficiency of total-body PET/CT imaging with fast 2-min acquisition and conventional PET/CT was similar.
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Affiliation(s)
- Yan Hu
- Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Rd, Shanghai, 200032, China.,Nuclear Medicine Institute of Fudan University, Shanghai, 200032, China.,Shanghai Institute of Medical Imaging, Shanghai, 200032, China
| | - Guobing Liu
- Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Rd, Shanghai, 200032, China.,Nuclear Medicine Institute of Fudan University, Shanghai, 200032, China.,Shanghai Institute of Medical Imaging, Shanghai, 200032, China
| | - Haojun Yu
- Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Rd, Shanghai, 200032, China.,Nuclear Medicine Institute of Fudan University, Shanghai, 200032, China.,Shanghai Institute of Medical Imaging, Shanghai, 200032, China
| | - Jianying Gu
- Department of Plastic Surgery, Zhongshan Hospital, Fudan University, 180 Fenglin Rd, Shanghai, 200032, China.
| | - Hongcheng Shi
- Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Rd, Shanghai, 200032, China. .,Nuclear Medicine Institute of Fudan University, Shanghai, 200032, China. .,Shanghai Institute of Medical Imaging, Shanghai, 200032, China.
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Lindemann ME, Gratz M, Blumhagen JO, Jakoby B, Quick HH. MR-based truncation correction using an advanced HUGE method to improve attenuation correction in PET/MR imaging of obese patients. Med Phys 2022; 49:865-877. [PMID: 35014697 DOI: 10.1002/mp.15446] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 12/08/2021] [Accepted: 12/18/2021] [Indexed: 10/19/2022] Open
Abstract
PURPOSE Truncation artifacts in the periphery of the magnetic resonance (MR) field-of-view (FOV) and thus, in the MR-based attenuation correction (AC) map, may hamper accurate positron emission tomography (PET) quantification in whole-body PET/MR, which is especially problematic in patients with obesity with overall large body dimensions. Therefore, an advanced truncation correction (TC) method to extend the conventional MR FOV is needed. METHODS The extent of MR-based AC-map truncations in obese patients was determined in a data set including n = 10 patients that underwent whole-body PET/MR exams. Patient inclusion criteria were defined as BMI > 30 kg/m2 and body weight > 100 kg. Truncations in PET/MR patients with obesity were quantified comparing the MR-based AC-map volume to segmented non-AC PET data, serving as the reference body volume without truncations to demonstrate the need of improved TC. The new method implemented in this study, termed "advanced HUGE", was modified and extended from the original HUGE method by Blumhagen et al. in order to provide improved TC across the entire axial MR FOV and to unlock new clinical applications of PET/MR. Advanced HUGE was then systematically tested in PET/MR NEMA phantom measurements. Relative differences between computed tomography (CT) AC PET data of the phantom setup (reference) and MR-based Dixon AC, respectively Dixon + advanced HUGE AC, were calculated. The applicability of the method for advanced TC was then demonstrated in first MR-based measurements in healthy volunteers. RESULTS It was found that the MR-based AC maps of obese patients often reveal truncations in anterior-posterior direction. Especially the abdominal region could benefit from improved TC, where maximal relative differences in the AC-map volume up to -17 % were calculated. Applying advanced HUGE to improve the MR-based AC in PET/MR, PET quantification errors in the large-volume phantom setup could be considerably reduced from average -18.6 % (Dixon AC) to 4.6 % compared to the CT AC reference. Volunteer measurements demonstrate that formerly missing AC-map volume in the Dixon-VIBE AC-map could be added due to advanced HUGE in anterior-posterior direction and thus, potentially improves AC in PET/MR. CONCLUSIONS The advanced HUGE method for truncation correction considerably reduces truncations in anterior-posterior direction demonstrated in phantom measurements and healthy volunteers and thus, further improves MR-based AC in PET/MR imaging. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Maike E Lindemann
- High-Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Marcel Gratz
- High-Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.,Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
| | | | | | - Harald H Quick
- High-Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany.,Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
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Hybrid System: PET/CT. Nucl Med Mol Imaging 2022. [DOI: 10.1016/b978-0-12-822960-6.00103-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Accurate Transmission-Less Attenuation Correction Method for Amyloid-β Brain PET Using Deep Neural Network. ELECTRONICS 2021. [DOI: 10.3390/electronics10151836] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The lack of physically measured attenuation maps (μ-maps) for attenuation and scatter correction is an important technical challenge in brain-dedicated stand-alone positron emission tomography (PET) scanners. The accuracy of the calculated attenuation correction is limited by the nonuniformity of tissue composition due to pathologic conditions and the complex structure of facial bones. The aim of this study is to develop an accurate transmission-less attenuation correction method for amyloid-β (Aβ) brain PET studies. We investigated the validity of a deep convolutional neural network trained to produce a CT-derived μ-map (μ-CT) from simultaneously reconstructed activity and attenuation maps using the MLAA (maximum likelihood reconstruction of activity and attenuation) algorithm for Aβ brain PET. The performance of three different structures of U-net models (2D, 2.5D, and 3D) were compared. The U-net models generated less noisy and more uniform μ-maps than MLAA μ-maps. Among the three different U-net models, the patch-based 3D U-net model reduced noise and cross-talk artifacts more effectively. The Dice similarity coefficients between the μ-map generated using 3D U-net and μ-CT in bone and air segments were 0.83 and 0.67. All three U-net models showed better voxel-wise correlation of the μ-maps compared to MLAA. The patch-based 3D U-net model was the best. While the uptake value of MLAA yielded a high percentage error of 20% or more, the uptake value of 3D U-nets yielded the lowest percentage error within 5%. The proposed deep learning approach that requires no transmission data, anatomic image, or atlas/template for PET attenuation correction remarkably enhanced the quantitative accuracy of the simultaneously estimated MLAA μ-maps from Aβ brain PET.
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Abstract
PET/CT has become a preferred imaging modality over PET-only scanners in clinical practice. However, along with the significant improvement in diagnostic accuracy and patient throughput, pitfalls on PET/CT are reported as well. This review provides a general overview on the potential influence of the limitations with respect to PET/CT instrumentation and artifacts associated with the modality integration on the image appearance and quantitative accuracy of PET. Approaches proposed in literature to address the limitations or minimize the artifacts are discussed as well as their current challenges for clinical applications. Although the CT component can play an important role in assisting clinical diagnosis, we concentrate on the imaging scenarios where CT is used to provide auxiliary information for attenuation compensation and scatter correction in PET.
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Affiliation(s)
- Yu-Jung Tsai
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT
| | - Chi Liu
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT; Department of Biomedical Engineering, Yale University, New Haven, CT.
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8
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Lee JS. A Review of Deep-Learning-Based Approaches for Attenuation Correction in Positron Emission Tomography. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3009269] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Miyaji N, Miwa K, Motegi K, Yamashita K, Terauchi T, Onoguchi M. Patient arm position during quantitative bone single-photon emission computed tomography/computed tomography acquisition can affect image quality and quantitative accuracy: a phantom study. Nucl Med Commun 2021; 42:267-275. [PMID: 33323866 DOI: 10.1097/mnm.0000000000001338] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE The present study used a phantom to determine the effects of various arm positions on bone SPECT/computed tomography (CT) images and the optimal arm position to acquire good-quality and quantitatively accurate images. MATERIALS AND METHODS We designed a phantom study of five simulated arm positions that are assumed during SPECT image acquisition. All SPECT data were acquired during a total of 120 projections of 10 and 100 s/view over 360° in a non-circular mode and reconstructed using Flash 3D (Siemens Healthineers). We evaluated contrast (QH,17 mm), image noise (NB,17 mm), contrast-to-noise ratios (QNRs), and visual scores according to the guidelines for bone SPECT acquisition protocols published by the Japanese Society of Nuclear Medicine Technology. The SUVmean, SUVmax, and SUVpeak were calculated and quantitative errors were evaluated using the recovery coefficient (RC) and the root means square error (RMSE). RESULTS The spatial resolution of SPECT images was better when the arms were down than raised with simulated shoulder disorders. Raised arms with shoulder disorders significantly increased the NB,17 mm and decreased the QH,17 mm, and the QNR in each image differed over a range from 2.2 to 5.2. The visual score was >1.5 with the arms down, raised normally, and raised with moderate shoulder disorders. The SUVmax and SUVpeak were overestimated compared with 100-min data for all images, whereas SUVmean was underestimated. Raised arms with a shoulder disorder decreased RCmax, and RCmean and RCpeak suppressed differences among arm positions. In addition, RMSE with the arms down and raised normally were close to that for 100-min data. CONCLUSION Bone SPECT images with good quality and quantitative accuracy can be acquired with patients holding their arms down by their sides. This will help patients with shoulder pain who have difficulties raising their arms.
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Affiliation(s)
- Noriaki Miyaji
- Department of Nuclear Medicine, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo
- Department of Quantum Medical Technology, Institute of Medical Pharmaceutical and Health Sciences, Kanazawa University, Ishikawa
| | - Kenta Miwa
- Department of Radiological Sciences, School of Health Science, International University of Health and Welfare, Tochigi, Japan
| | - Kazuki Motegi
- Department of Nuclear Medicine, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo
| | - Kosuke Yamashita
- Department of Nuclear Medicine, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo
| | - Takashi Terauchi
- Department of Nuclear Medicine, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo
| | - Masahisa Onoguchi
- Department of Quantum Medical Technology, Institute of Medical Pharmaceutical and Health Sciences, Kanazawa University, Ishikawa
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Sarikaya I, Sarikaya A. PET/CT Image Artifacts Caused by the Arms. J Nucl Med Technol 2020; 49:19-22. [PMID: 32709674 DOI: 10.2967/jnmt.120.248641] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 06/17/2020] [Indexed: 11/16/2022] Open
Abstract
PET/CT images are usually obtained in the arms-up position in patients with no head and neck pathology and in the arms-down position to image the head and neck area. The arms usually cause artifacts regardless of up or down positioning. These artifacts include beam hardening, scatter, truncation, and cold areas (cold artifacts) in obese or large patients; motion artifacts; implanted-metal-object artifacts; and artifacts related to radiotracer extravasation at the injection site. In this review article, we will discuss the mechanisms of these artifacts and suggest solutions to reduce or eliminate them, such as reviewing the non-attenuation-corrected PET images, performing extended-field-of-view reconstruction, not applying scatter correction, and using software to correct beam-hardening, scatter, and truncation artifacts. We will present various PET/CT images before and after corrections for such artifacts.
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Affiliation(s)
- Ismet Sarikaya
- Department of Nuclear Medicine, Kuwait University Faculty of Medicine, Safat, Kuwait; and
| | - Ali Sarikaya
- Department of Nuclear Medicine, Trakya University Faculty of Medicine, Edirne, Turkey
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Beheshti M, Manafi-Farid R, Rezaee A, Langsteger W. PET/CT and PET/MRI, Normal Variations, and Artifacts. Clin Nucl Med 2020. [DOI: 10.1007/978-3-030-39457-8_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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12
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Kuttner S, Lassen ML, Øen SK, Sundset R, Beyer T, Eikenes L. Quantitative PET/MR imaging of lung cancer in the presence of artifacts in the MR-based attenuation correction maps. Acta Radiol 2020; 61:11-20. [PMID: 31091969 DOI: 10.1177/0284185119848118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Background Positron emission tomography (PET)/magnetic resonance (MR) imaging may become increasingly important for assessing tumor therapy response. A prerequisite for quantitative PET/MR imaging is reliable and repeatable MR-based attenuation correction (AC). Purpose To investigate the frequency and test–retest reproducibility of artifacts in MR-AC maps in a lung cancer patient cohort and to study the impact of artifact corrections on PET-based tumor quantification. Material and Methods Twenty-five lung cancer patients underwent single-day, test–retest, 18F-fluorodeoxyglucose (FDG) PET/MR imaging. The acquired MR-AC maps were inspected for truncation, susceptibility, and tissue inversion artifacts. An anatomy-based bone template and a PET-based estimation of truncated arms were employed, while susceptibility artifacts were corrected manually. We report the frequencies of artifacts and the relative difference (RD) on standardized uptake value (SUV) based quantification in PET images reconstructed with the corrected AC maps. Results Truncation artifacts were found in all 50 acquisitions (100%), while susceptibility and tissue inversion artifacts were observed in six (12%) and 26 (52%) of the scans, respectively. The RD in lung tumor SUV was < 5% from bone and truncation corrections, while up to 20% RD was introduced after susceptibility artifact correction, with large inconsistencies between test–retest scans. Conclusion The absence of bone and truncation artifacts have limited effect on the PET quantification of lung lesions. In contrast, susceptibility artifacts caused significant and inconsistent underestimations of the lung tumor SUVs, between test–retest scans. This may have clinical implications for patients undergoing serial imaging for tumor therapy response assessment.
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Affiliation(s)
- Samuel Kuttner
- Nuclear Medicine and Radiation Biology Research Group, Department of Clinical Medicine, University of Tromsø - The Arctic University of Norway, Norway
- The PET Imaging Center, University Hospital of North Norway, Norway
| | - Martin Lyngby Lassen
- QIMP Team, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria
- Cedars-Sinai Medical Center, Los Angeles, California
| | - Silje Kjærnes Øen
- Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Norway
| | - Rune Sundset
- Nuclear Medicine and Radiation Biology Research Group, Department of Clinical Medicine, University of Tromsø - The Arctic University of Norway, Norway
- The PET Imaging Center, University Hospital of North Norway, Norway
| | - Thomas Beyer
- QIMP Team, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria
| | - Live Eikenes
- Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Norway
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Brady SL, Shulkin BL. Dose optimization: a review of CT imaging for PET attenuation correction. Clin Transl Imaging 2017. [DOI: 10.1007/s40336-017-0232-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Fursevich DM, LiMarzi GM, O'Dell MC, Hernandez MA, Sensakovic WF. Bariatric CT Imaging: Challenges and Solutions. Radiographics 2016; 36:1076-86. [PMID: 27232505 DOI: 10.1148/rg.2016150198] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The obesity epidemic in the adult and pediatric populations affects all aspects of health care, including diagnostic imaging. With the increasing prevalence of obese and morbidly obese patients, bariatric computed tomographic (CT) imaging is becoming common in day-to-day radiology practice, and a basic understanding of the unique problems that bariatric patients pose to the imaging community is crucial in any setting. Because larger patients may not fit into conventional scanners, having a CT scanner with an adequate table load limit, a large gantry aperture, a large scan field of view, and a high-power generator is a prerequisite for bariatric imaging. Iterative reconstruction methods, high tube current, and high tube voltage can reduce the image noise that is frequently seen in bariatric CT images. Truncation artifacts, cropping artifacts, and ring artifacts frequently complicate the interpretation of CT images of larger patients. If recognized, these artifacts can be easily reduced by using the proper CT equipment, scan acquisition parameters, and postprocessing options. Lastly, because of complex contrast material dynamics, contrast material-enhanced studies of bariatric patients require special attention. Understanding how the rate of injection, the scan timing, and the total mass of iodine affect vascular and parenchymal enhancement will help to optimize contrast-enhanced studies in the bariatric population. This article familiarizes the reader with the challenges that are frequently encountered at CT imaging of bariatric patients, beginning with equipment selection and ending with a review of the most commonly encountered obesity-related artifacts and the technical considerations in the acquisition of contrast-enhanced images. (©)RSNA, 2016.
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Affiliation(s)
- Dzmitry M Fursevich
- From the Department of Diagnostic Radiology, Florida Hospital, 601 E Rollins St, Orlando, FL 32803
| | - Gary M LiMarzi
- From the Department of Diagnostic Radiology, Florida Hospital, 601 E Rollins St, Orlando, FL 32803
| | - Matthew C O'Dell
- From the Department of Diagnostic Radiology, Florida Hospital, 601 E Rollins St, Orlando, FL 32803
| | - Manuel A Hernandez
- From the Department of Diagnostic Radiology, Florida Hospital, 601 E Rollins St, Orlando, FL 32803
| | - William F Sensakovic
- From the Department of Diagnostic Radiology, Florida Hospital, 601 E Rollins St, Orlando, FL 32803
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Abstract
Accurate reporting of combined PET/CT imaging requires a thorough understanding of the normal and variant physiological distribution of tracers as well as common incidental findings and technical artifacts. We describe these pitfalls and artifacts, what action may help to mitigate them in clinical practice, and what further action may be appropriate. This review presents these in a region-based approach, in order to closely mimic clinical practice, and focuses on technical artifacts followed by a description of two commonly used oncologic tracers: FDG and choline.
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Affiliation(s)
| | - Paul John Schleyer
- St Thomas' PET Imaging Centre, Guys and St Thomas NHS Trust and Kings College London, London, UK
| | - Gary John Cook
- St Thomas' PET Imaging Centre, Guys and St Thomas NHS Trust and Kings College London, London, UK
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16
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Evaluation of scatter limitation correction: a new method of correcting photopenic artifacts caused by patient motion during whole-body PET/CT imaging. Nucl Med Commun 2015; 37:147-54. [PMID: 26440565 DOI: 10.1097/mnm.0000000000000403] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Overcorrection of scatter caused by patient motion during whole-body PET/computed tomography (CT) imaging can induce the appearance of photopenic artifacts in the PET images. The present study aimed to quantify the accuracy of scatter limitation correction (SLC) for eliminating photopenic artifacts. METHODS This study analyzed photopenic artifacts in (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT images acquired from 12 patients and from a National Electrical Manufacturers Association phantom with two peripheral plastic bottles that simulated the human body and arms, respectively. The phantom comprised a sphere (diameter, 10 or 37 mm) containing fluorine-18 solutions with target-to-background ratios of 2, 4, and 8. The plastic bottles were moved 10 cm posteriorly between CT and PET acquisitions. All PET data were reconstructed using model-based scatter correction (SC), no scatter correction (NSC), and SLC, and the presence or absence of artifacts on the PET images was visually evaluated. The SC and SLC images were also semiquantitatively evaluated using standardized uptake values (SUVs). RESULTS Photopenic artifacts were not recognizable in any NSC and SLC image from all 12 patients in the clinical study. The SUVmax of mismatched SLC PET/CT images were almost equal to those of matched SC and SLC PET/CT images. Applying NSC and SLC substantially eliminated the photopenic artifacts on SC PET images in the phantom study. SLC improved the activity concentration of the sphere for all target-to-background ratios. The highest %errors of the 10 and 37-mm spheres were 93.3 and 58.3%, respectively, for mismatched SC, and 73.2 and 22.0%, respectively, for mismatched SLC. CONCLUSION Photopenic artifacts caused by SC error induced by CT and PET image misalignment were corrected using SLC, indicating that this method is useful and practical for clinical qualitative and quantitative PET/CT assessment.
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Ren L, Chen Y, Zhang Y, Giles W, Jin J, Yin FF. Scatter Reduction and Correction for Dual-Source Cone-Beam CT Using Prepatient Grids. Technol Cancer Res Treat 2015; 15:416-27. [PMID: 26009495 DOI: 10.1177/1533034615587615] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2015] [Accepted: 04/25/2015] [Indexed: 11/16/2022] Open
Abstract
PURPOSE Scatter significantly limits the application of the dual-source cone-beam computed tomography by inducing scatter artifacts and degrading contrast-to-noise ratio, Hounsfield-unit accuracy, and image uniformity. Although our previously developed interleaved acquisition mode addressed the cross scatter between the 2 X-ray sources, it doubles the scanning time and doesn't address the forward scatter issue. This study aims to develop a prepatient grid system to address both forward scatter and cross scatter in the dual-source cone-beam computed tomography. METHODS Grids attached to both X-ray sources provide physical scatter reduction during the image acquisition. Image data were measured in the unblocked region, while both forward scatter and cross scatter were measured in the blocked region of the projection for postscan scatter correction. Complementary projections were acquired with grids at complementary locations and were merged to form complete projections for reconstruction. Experiments were conducted with different phantom sizes, grid blocking ratios, image acquisition modes, and reconstruction algorithms to investigate their effects on the scatter reduction and correction. The image quality improvement by the prepatient grids was evaluated both qualitatively through the artifact reduction and quantitatively through contrast-to-noise ratio, Hounsfield-unit accuracy, and uniformity using a CATphan 504 phantom. RESULTS Scatter artifacts were reduced by scatter reduction and were removed by scatter correction method. Contrast-to-noise ratio, Hounsfield-unit accuracy, and image uniformity were improved substantially. The simultaneous acquisition mode achieved comparable contrast-to-noise ratio as the interleaved and sequential modes after scatter reduction and correction. Higher grid blocking ratio and smaller phantom size led to higher contrast-to-noise ratio for the simultaneous mode. The iterative reconstruction with total variation regularization was more effective than the Feldkamp, Davis, and Kress method in reducing noise caused by the scatter correction to enhance contrast-to-noise ratio. CONCLUSION The prepatient grid system is effective in removing the scatter effects in the simultaneous acquisition mode of the dual-source cone-beam computed tomography, which is useful for scanning time reduction or dual energy imaging.
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Affiliation(s)
- Lei Ren
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA Medical Physics Graduate Program, Duke University, Durham, NC, USA
| | - Yingxuan Chen
- Medical Physics Graduate Program, Duke University, Durham, NC, USA
| | - You Zhang
- Medical Physics Graduate Program, Duke University, Durham, NC, USA
| | - William Giles
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
| | - Jianyue Jin
- Department of Radiation Oncology, Georgia Regents University, Augusta, GA, USA
| | - Fang-Fang Yin
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA Medical Physics Graduate Program, Duke University, Durham, NC, USA
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Sopena Novales P, Plancha Mansanet M, Martinez Carsi C, Sopena Monforte R. Medicina nuclear y radiofármacos. RADIOLOGIA 2014; 56 Suppl 1:29-37. [DOI: 10.1016/j.rx.2014.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 06/18/2014] [Accepted: 07/02/2014] [Indexed: 11/25/2022]
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Schramm G, Langner J, Hofheinz F, Petr J, Lougovski A, Beuthien-Baumann B, Platzek I, van den Hoff J. Influence and compensation of truncation artifacts in MR-based attenuation correction in PET/MR. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:2056-2063. [PMID: 24186268 DOI: 10.1109/tmi.2013.2272660] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
UNLABELLED The goal of this article is to quantify the influence of truncation artifacts in the magnetic resonance (MR)-based attenuation map (MRMap) on reconstructed positron emission tomography (PET) image volumes and to propose a new method for minimizing this influence. METHODS PET data sets of 20 patients investigated in a Philips Ingenuity PET/MR were reconstructed with and without applying two different methods for truncation compensation (TC1 vendor-provided, TC2 newly developed). In this patient group, the extent of truncation artifacts and quality of the truncation compensation (TC) was assessed visually in the MRMaps. In three additional patients MRMaps generated by algorithm TC2 could be compared to the ground truth of transmission-based attenuation maps obtained with a Siemens ECAT HR(+) scanner. The influence of truncation on regional SUVs in lesions, other hot structures (bladder, kidney, myocardium) and the arms was assessed in suitable volume of interests (VOI). RESULTS Truncation compensated MRMaps exhibited residual artifacts in the arms in 16 patients for algorithm TC1 and to a lesser extent in eight patients for algorithm TC2. Compared to the transmission-based attenuation maps algorithm TC2 slightly overestimated the size of the truncated arms by 0.3 cm in the radial direction. Without truncation compensation, VOIs located in the trunk showed an average SUVmax underestimation of less than 5.4% relative to the results obtained with TC2. Inside the patients' arms underestimations up to 46.5% were found. CONCLUSION In the trunk, standardized uptake values (SUV) underestimations due to truncation artifacts in the MRMap are rather small. Inside the arms, severe SUV underestimations can occur. Therefore, reliable TC is mandatory and can be achieved by applying the newly developed algorithm TC2 which has yielded promising results so far. Implementation of the proposed method is straightforward and should be easily adaptable to other PET/MR systems.
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Kangai Y, Onishi H, Sanai H, Mimura H, Yanagimoto S. [Impact of the standardized uptake value on the body trunk with truncation error of μ-map in the positron emission tomography/computed tomography: phantom studies]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2013; 69:178-83. [PMID: 23448836 DOI: 10.6009/jjrt.2013_jsrt_69.2.178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE The aim of this study was evaluate to impact of standardized uptake value (SUV) on the body trunk with truncation error of μ-map for CT attenuation correction (CTAC) in whole-body 2-deoxy-2-[(18)F] fluoro-D-glucose ((18)F-FDG)-positron emission tomography (PET)/CT with use of anthropomorphic phantom. METHODS We used body phantom (2.5 MBq/l) including simulated tumor targets (11.25 MBq/l) and arm phantom. The CT scan was used with a field of view (FOV) of 50 cm. The μ-maps were created by assuming a state of the arm protruding from the FOV (Pmap). A 3D-PET scan with an emission time of 20 min was performed. The PET images were then reconstructed with CTAC, and with and without scatter correction. We evaluated the relationship to Pmap size and the count of simulated tumors and background (B.G.) in PET images which reconstructed the use of each Pmap, respectively. RESULTS The count of simulated tumor (large) with scatter correction was decreased to 1.3% (Pmap: 15 mm) and 8.8% (Pmap: 35 mm). Then, the count severe reduction was 86.9% in Pmap of 65 mm. The same trend was shown by simulated tumor (middle, small) and B.G. The count of the simulated tumor (large) without scatter correction decreased to 1.3% (Pmap: 15 mm), 6.4% (Pmap: 35 mm) and 13.1% (Pmap: 65 mm). CONCLUSION Truncation error by μ-map for CTAC in whole-body (18)F-PET/CT caused a decrease of the SUV on the body trunk used for attenuation and scatter correction in the PET images.
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Affiliation(s)
- Yoshiharu Kangai
- Department of Radiology, Kawasaki Medical School Hospital, Japan
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Keereman V, Mollet P, Berker Y, Schulz V, Vandenberghe S. Challenges and current methods for attenuation correction in PET/MR. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2012; 26:81-98. [PMID: 22875599 DOI: 10.1007/s10334-012-0334-7] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 07/17/2012] [Accepted: 07/18/2012] [Indexed: 11/25/2022]
Affiliation(s)
- Vincent Keereman
- MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, De Pintelaan 185, 9000 Ghent, Belgium.
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Kalemis A, Delattre BMA, Heinzer S. Sequential whole-body PET/MR scanner: concept, clinical use, and optimisation after two years in the clinic. The manufacturer’s perspective. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2012; 26:5-23. [DOI: 10.1007/s10334-012-0330-y] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 07/10/2012] [Accepted: 07/11/2012] [Indexed: 01/08/2023]
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Frey EC, Humm JL, Ljungberg M. Accuracy and precision of radioactivity quantification in nuclear medicine images. Semin Nucl Med 2012; 42:208-18. [PMID: 22475429 PMCID: PMC3586419 DOI: 10.1053/j.semnuclmed.2011.11.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The ability to reliably quantify activity in nuclear medicine has a number of increasingly important applications. Dosimetry for targeted therapy treatment planning or for approval of new imaging agents requires accurate estimation of the activity in organs, tumors, or voxels at several imaging time points. Another important application is the use of quantitative metrics derived from images, such as the standard uptake value commonly used in positron emission tomography (PET), to diagnose and follow treatment of tumors. These measures require quantification of organ or tumor activities in nuclear medicine images. However, there are a number of physical, patient, and technical factors that limit the quantitative reliability of nuclear medicine images. There have been a large number of improvements in instrumentation, including the development of hybrid single-photon emission computed tomography/computed tomography and PET/computed tomography systems, and reconstruction methods, including the use of statistical iterative reconstruction methods, which have substantially improved the ability to obtain reliable quantitative information from planar, single-photon emission computed tomography, and PET images.
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Affiliation(s)
- Eric C. Frey
- Russell H. Morgan Department of Radiology and Radiological Science Johns Hopkins University, Baltimore, Maryland
| | - John L. Humm
- Memorial Sloan-Kettering Cancer Center, New York
| | - Michael Ljungberg
- Department of Medical Radiation Physics, Clinical Sciences, Lund, Lund University, Lund, Sweden
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Lodge MA, Mhlanga JC, Cho SY, Wahl RL. Effect of patient arm motion in whole-body PET/CT. J Nucl Med 2011; 52:1891-7. [PMID: 22080444 DOI: 10.2967/jnumed.111.093583] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Arm motion during whole-body PET/CT acquisition is not uncommon and can give rise to striking cold artifacts on PET images. We investigated the mechanisms that underlie these artifacts and proposed a potential solution. METHODS A phantom experiment based on 5 clinical cases of suspected arm motion was designed. The experiment involved a central 20-cm-diameter (68)Ge/(68)Ga cylinder simulating the neck and 2 peripheral 10-cm-diameter (18)F cylinders simulating arms. After motion-free CT and PET on a whole-body PET/CT system, the position of the arms was altered so as to introduce different amounts of misalignment. Twenty sequential PET scans were acquired in this position, alternating between 2-dimensional (2D) and 3-dimensional (3D) acquisition, as the (18)F decayed. Decay of (18)F in the arms, while the activity in the (68)Ge/(68)Ga cylinder remained approximately constant, allowed the relative impact of scatter and attenuation-correction errors to be determined. RESULTS Image artifacts were largely confined to the local region of motion in 2D but extended throughout the affected slices in 3D, where they manifested as a striking underestimation of radiotracer concentration that became more significant with increasing misalignment. For 3D, scatter-correction error depended on activity in the arms, but for typical activity concentrations scatter-correction error was more significant than attenuation-correction error. 3D image reconstruction without scatter correction substantially eliminated these artifacts in both phantom and patient images. CONCLUSION Reconstruction artifacts due to patient arm motion can be substantial and should be recognized because they can affect both qualitative and quantitative assessment of PET.
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Affiliation(s)
- Martin A Lodge
- Division of Nuclear Medicine, Russell H Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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Delso G, Martinez-Möller A, Bundschuh RA, Nekolla SG, Ziegler SI. The effect of limited MR field of view in MR/PET attenuation correction. Med Phys 2010; 37:2804-12. [DOI: 10.1118/1.3431576] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Hofmann M, Pichler B, Schölkopf B, Beyer T. Towards quantitative PET/MRI: a review of MR-based attenuation correction techniques. Eur J Nucl Med Mol Imaging 2009; 36 Suppl 1:S93-104. [PMID: 19104810 DOI: 10.1007/s00259-008-1007-7] [Citation(s) in RCA: 232] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Positron emission tomography (PET) is a fully quantitative technology for imaging metabolic pathways and dynamic processes in vivo. Attenuation correction of raw PET data is a prerequisite for quantification and is typically based on separate transmission measurements. In PET/CT attenuation correction, however, is performed routinely based on the available CT transmission data. OBJECTIVE Recently, combined PET/magnetic resonance (MR) has been proposed as a viable alternative to PET/CT. Current concepts of PET/MRI do not include CT-like transmission sources and, therefore, alternative methods of PET attenuation correction must be found. This article reviews existing approaches to MR-based attenuation correction (MR-AC). Most groups have proposed MR-AC algorithms for brain PET studies and more recently also for torso PET/MR imaging. Most MR-AC strategies require the use of complementary MR and transmission images, or morphology templates generated from transmission images. We review and discuss these algorithms and point out challenges for using MR-AC in clinical routine. DISCUSSION MR-AC is work-in-progress with potentially promising results from a template-based approach applicable to both brain and torso imaging. While efforts are ongoing in making clinically viable MR-AC fully automatic, further studies are required to realize the potential benefits of MR-based motion compensation and partial volume correction of the PET data.
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Affiliation(s)
- Matthias Hofmann
- Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076, Tuebingen, Germany.
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Abstract
PET/CT is an effective tool for the diagnosis, staging and restaging of cancer patients. It combines the complementary information of functional PET images and anatomical CT images in one imaging session. Conventional stand-alone PET has been replaced by PET/CT for improved patient comfort, patient throughput, and most importantly the proven clinical outcome of PET/CT over that of PET and that of separate PET and CT. There are over two thousand PET/CT scanners installed worldwide since 2001. Oncology is the main application for PET/CT. Fluorine-18 deoxyglucose is the choice of radiopharmaceutical in PET for imaging the glucose uptake in tissues, correlated with an increased rate of glycolysis in many tumor cells. New molecular targeted agents are being developed to improve the accuracy of targeting different disease states and assessing therapeutic response. Over 50% of cancer patients receive radiation therapy (RT) in the course of their disease treatment. Clinical data have demonstrated that the information provided by PET/CT often changes patient management of the patient and/or modifies the RT plan from conventional CT simulation. The application of PET/CT in RT is growing and will become increasingly important. Continuing improvement of PET/CT instrumentation will also make it easier for radiation oncologists to integrate PET/CT in RT. The purpose of this article is to provide a review of the current PET/CT technology, to project the future development of PET and CT for PET/CT, and to discuss some issues in adopting PET/CT in RT and potential improvements in PET/CT simulation of the thorax in radiation therapy.
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Affiliation(s)
- Tinsu Pan
- Department of Imaging Physics, M. D. Anderson Cancer Center, The University of Texas, Houston, Texas 77030, USA.
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Abstract
Molecular imaging using high-resolution PET instrumentation has a pivotal role in basic and clinical research. The development of optimized detection geometries combined with high-performance detector technologies and compact designs of PET tomographs has become the goal of active research groups in academic and corporate settings. More recently, the introduction of dual-modality PET/CT imaging systems in clinical environments has revolutionized the practice of diagnostic imaging. This article discusses recent advances in PET instrumentation and the advantages and challenges of multimodality imaging systems including PET/MR. Future opportunities and the challenges facing the adoption of multimodality imaging instrumentation and its role in biomedical research are also addressed.
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Affiliation(s)
- Habib Zaidi
- Department of Radiology and Medical Informatics, Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva, Switzerland.
| | - Abass Alavi
- Department of Radiology, Division of Nuclear Medicine, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
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Abstract
Molecular imaging using PET has evolved from a vigorous academic field into the clinical arena. Considerable advances have been made in the design of high-resolution standalone PET and combined PET/CT units dedicated to clinical whole-body scanning. Likewise, much worthwhile research focused on the development of quantitative imaging protocols incorporating accurate data correction techniques and sophisticated image reconstruction algorithms. Since its inception, photon attenuation in biological tissues has been identified as the most important physical degrading factor affecting PET image quality and quantitative accuracy. Various strategies have been devised to determine an accurate attenuation map to enable correction for nonlinear photon attenuation in whole-body PET studies. This article presents the physical and methodological basis of photon attenuation and summarizes state-of-the-art developments in algorithms used to derive the attenuation map aiming at accurate attenuation compensation of PET data. Future prospects, research trends, and challenges are identified, and directions for future research are discussed.
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Affiliation(s)
- Habib Zaidi
- Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva 4, Switzerland.
| | | | - Abass Alavi
- Division of Nuclear Medicine, Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
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Kennedy JA, Israel O, Frenkel A, Bar-Shalom R, Azhari H. The reduction of artifacts due to metal hip implants in CT-attenuation corrected PET images from hybrid PET/CT scanners. Med Biol Eng Comput 2007; 45:553-62. [PMID: 17520306 DOI: 10.1007/s11517-007-0188-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2006] [Accepted: 04/28/2007] [Indexed: 11/28/2022]
Abstract
CT beam hardening artifacts near metal hip implants may erroneously enhance or diminish radiotracer uptake following CT attenuation correction (AC) of PET images. An artifact reduction algorithm (ARA) was developed to reduce metal artifacts in CT-based AC-PET. The algorithm employed a Bayes classifier to identify beam-hardening artifacts, followed by a partial correction of the attenuation map. ARA was implemented on phantom and patient 18F-FDG studies using a clinical PET/CT scanner. In phantom studies ARA successfully removed two artifacts of erroneously elevated uptake near a stainless steel hip prosthesis which were depicted in the standard CT-AC PET. ARA has also identified two targets absent on the scanner PET images. Target-to-background ratios were 1.5-3 times higher for ARA-PET than scanner images. In a patient study, metal artifacts were of lower intensity in ARA-PET as compared to standard images. Potentially, ARA may improve detectability of small lesions located near metal hip implants.
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Affiliation(s)
- John A Kennedy
- Faculty of Biomedical Engineering, Technion Israel Institute of Technology, 32000, Haifa, Israel
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Zaidi H. Optimisation of whole-body PET/CT scanning protocols. Biomed Imaging Interv J 2007; 3:e36. [PMID: 21614277 PMCID: PMC3097669 DOI: 10.2349/biij.3.2.e36] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Accepted: 04/05/2007] [Indexed: 11/17/2022] Open
Abstract
Positron emission tomography (PET) has become one of the major tools for the in vivo localisation of positron-emitting tracers and now is performed routinely using (18)F-fluorodeoxyglucose (FDG) to answer important clinical questions including those in cardiology, neurology, psychiatry, and oncology. The latter application contributed largely to the wide acceptance of this imaging modality and its use in clinical diagnosis, staging, restaging, and assessment of tumour response to treatment. Dual-modality PET/CT systems have been operational for almost a decade since their inception. The complementarity between anatomic (CT) and functional or metabolic (PET) information provided in a "one-stop shop" has been the driving force of this technology. Although combined anato-metabolic imaging is an obvious choice, the way to perform imaging is still an open issue. The tracers or combinations of tracers to be used, how the imaging should be done, when contrast-enhanced CT should be performed, what are the optimal acquisition and processing protocols, are all unanswered questions. Moreover, each data acquisition-processing combination may need to be independently optimised and validated. This paper briefly reviews the basic principles of dual-modality imaging and addresses some of the practical issues involved in optimising PET/CT scanning protocols in a clinical environment.
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Affiliation(s)
- H Zaidi
- Division of Nuclear Medicine, Geneva University Hospital, Geneva, Switzerland
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Pettinato C, Nanni C, Farsad M, Castellucci P, Sarnelli A, Civollani S, Franchi R, Fanti S, Marengo M, Bergamini C. Artefacts of PET/CT images. Biomed Imaging Interv J 2006; 2:e60. [PMID: 21614340 PMCID: PMC3097808 DOI: 10.2349/biij.2.4.e60] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 11/08/2006] [Accepted: 12/24/2006] [Indexed: 11/30/2022] Open
Abstract
Positron emission tomography (PET) is a non-invasive imaging modality, which is clinically widely used both for diagnosis and accessing therapy response in oncology, cardiology and neurology.Fusing PET and CT images in a single dataset would be useful for physicians who could read the functional and the anatomical aspects of a disease in a single shot.The use of fusion software has been replaced in the last few years by integrated PET/CT systems, which combine a PET and a CT scanner in the same gantry. CT images have the double function to correct PET images for attenuation and can fuse with PET for a better visualization and localization of lesions. The use of CT for attenuation correction yields several advantages in terms of accuracy and patient comfort, but can also introduce several artefacts on PET-corrected images.PET/CT image artefacts are due primarily to metallic implants, respiratory motion, use of contrast media and image truncation. This paper reviews different types artefacts and their correction methods.PET/CT improves image quality and image accuracy. However, to avoid possible pitfalls the simultaneous display of both Computed Tomography Attenuation Corrected (CTAC) and non corrected PET images, side by side with CT images is strongly recommended.
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Affiliation(s)
- C Pettinato
- Health Physics Department, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - C Nanni
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - M Farsad
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - P Castellucci
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - A Sarnelli
- Health Physics Department, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - S Civollani
- Health Physics Department, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - R Franchi
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - S Fanti
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - M Marengo
- Nuclear Medicine Division, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
| | - C Bergamini
- Health Physics Department, Azienda Ospedaliero Universitaria S. Orsola Malpighi, Bologna, Italy
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Abstract
Over the past six years, PET/CT has spread rapidly and replaced conventional PET. Although PET/CT is a combination of PET for functional information and CT for morphological information, their combination is synergistic. PET/CT fusion images result in higher diagnostic accuracy with fewer equivocal findings. This results in a greater impact on cancer diagnosis. With attenuation correction performed by the CT component, PET/CT can provide higher quality images over shorter examination times than conventional PET. As with all modalities, PET/CT has several characteristic artifacts such as misregistration due to respiration, overattenuation correction due to metals, etc. Awareness of these pitfalls will help the imaging physician use PET/CT effectively in daily practice.
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