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Singh MK, Dhull V, Vishwakarma M. Quality control performance evaluation of uMI550 digital PET-CT by utilising LYSO crystal natural radioactivity of 176Lu. Radiography (Lond) 2024; 30:1021-1025. [PMID: 38718694 DOI: 10.1016/j.radi.2024.04.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 04/15/2024] [Accepted: 04/22/2024] [Indexed: 07/03/2024]
Abstract
PURPOSE Quality Control (QC) of the Positron Emission Tomography-Computed Tomography (PET-CT) system must be performed prior to the PET-CT acquisition to ensure the reproducibility as per the manufacturer recommendation. In this study we have evaluated the performance of daily PET QC test by utilising lutetium yttrium oxyorthosilicate (LYSO) scintillation crystal natural radioactivity of 176Lu as a source of radiation to perform the PET uCare.iQC with uMI550 digital PET-CT system. This was also compared with existing radioactive external source-based QC test with other manufacturer PET-CT systems. METHOD This radioactive source free daily QC study was performed on uMI550 digital PET-CT system. The daily QC data report was captured and interpreted. This PET-CT system has unique feature that utilises the inherent property of LYSO crystal that is 176Lu with natural radioactivity abundance of 2.6%. The Lutetium-176 (176Lu) radioactivity is used to perform the daily QC in PET in place of external radioactive source of Germanium-68 (68Ge). This feature work automatically in preschedule manner to complete the daily QC at preset time in the morning and system get ready after the QC test. RESULTS Over 120 automatic PET daily uCare.iQC test were performed. The daily PET QC test was prescheduling setup for 6:00 am in every morning. No failure on daily QC test were observed. The QC parameters and system parameters consistency was observed. CONCLUSION It was concluded that the daily PET QC can be performed by utilising LYSO crystal inherent natural radioactivity of 176Lu as a source of radiation to perform the test as replacement of external 68Ge radioactive source. IMPLICATION FOR PRACTICE PET-CT daily QC by utilizing the 176Lu radioactivity of LYSO crystal results in reducing the radiation exposure to operation staff and reducing operational cost by elimination 68Ge shield source Phantom.
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Affiliation(s)
- M K Singh
- Medical Innovation Business, Medikabazaar, Technopolis Knowledge Park, Mumbai, 400093, India.
| | - V Dhull
- Department of Nuclear Medicine, MMU, Sadopur, Ambala, Haryana, 134007, India
| | - M Vishwakarma
- Medical Innovation Business, Medikabazaar, Technopolis Knowledge Park, Mumbai, 400093, India
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Nguyen HTM, Das N, Ricks M, Zhong X, Takematsu E, Wang Y, Ruvalcaba C, Mehadji B, Roncali E, Chan CKF, Pratx G. Ultrasensitive and multiplexed tracking of single cells using whole-body PET/CT. SCIENCE ADVANCES 2024; 10:eadk5747. [PMID: 38875333 PMCID: PMC11177933 DOI: 10.1126/sciadv.adk5747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 05/13/2024] [Indexed: 06/16/2024]
Abstract
In vivo molecular imaging tools are crucially important for elucidating how cells move through complex biological systems; however, achieving single-cell sensitivity over the entire body remains challenging. Here, we report a highly sensitive and multiplexed approach for tracking upward of 20 single cells simultaneously in the same subject using positron emission tomography (PET). The method relies on a statistical tracking algorithm (PEPT-EM) to achieve a sensitivity of 4 becquerel per cell and a streamlined workflow to reliably label single cells with over 50 becquerel per cell of 18F-fluorodeoxyglucose (FDG). To demonstrate the potential of the method, we tracked the fate of more than 70 melanoma cells after intracardiac injection and found they primarily arrested in the small capillaries of the pulmonary, musculoskeletal, and digestive organ systems. This study bolsters the evolving potential of PET in offering unmatched insights into the earliest phases of cell trafficking in physiological and pathological processes and in cell-based therapies.
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Affiliation(s)
- Hieu T. M. Nguyen
- School of Medicine, Department of Radiation Oncology and Medical Physics, Stanford University, Stanford, CA 94305, USA
| | - Neeladrisingha Das
- School of Medicine, Department of Radiation Oncology and Medical Physics, Stanford University, Stanford, CA 94305, USA
| | - Matthew Ricks
- School of Medicine, Department of Radiological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Xiaoxu Zhong
- School of Medicine, Department of Radiation Oncology and Medical Physics, Stanford University, Stanford, CA 94305, USA
| | - Eri Takematsu
- School of Medicine, Department of Surgery, Stanford University, Stanford, CA 94305, USA
| | - Yuting Wang
- School of Medicine, Department of Surgery, Stanford University, Stanford, CA 94305, USA
| | - Carlos Ruvalcaba
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Brahim Mehadji
- Department of Radiology, University of California, Davis, Davis, CA 95616, USA
| | - Emilie Roncali
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
- Department of Radiology, University of California, Davis, Davis, CA 95616, USA
| | - Charles K. F. Chan
- School of Medicine, Department of Surgery, Stanford University, Stanford, CA 94305, USA
| | - Guillem Pratx
- School of Medicine, Department of Radiation Oncology and Medical Physics, Stanford University, Stanford, CA 94305, USA
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Nguyen HT, Das N, Wang Y, Ruvalcaba C, Mehadji B, Roncali E, Chan CK, Pratx G. Efficient and multiplexed tracking of single cells using whole-body PET/CT. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.23.554536. [PMID: 37662335 PMCID: PMC10473747 DOI: 10.1101/2023.08.23.554536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
In vivo molecular imaging tools are crucially important for elucidating how cells move through complex biological systems, however, achieving single-cell sensitivity over the entire body remains challenging. Here, we report a highly sensitive and multiplexed approach for tracking upwards of 20 single cells simultaneously in the same subject using positron emission tomography (PET). The method relies on a new tracking algorithm (PEPT-EM) to push the cellular detection threshold to below 4 Bq/cell, and a streamlined workflow to reliably label single cells with over 50 Bq/cell of 18F-fluorodeoxyglucose (FDG). To demonstrate the potential of method, we tracked the fate of over 70 melanoma cells after intracardiac injection and found they primarily arrested in the small capillaries of the pulmonary, musculoskeletal, and digestive organ systems. This study bolsters the evolving potential of PET in offering unmatched insights into the earliest phases of cell trafficking in physiological and pathological processes and in cell-based therapies.
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Affiliation(s)
- Hieu T.M. Nguyen
- Stanford University, School of Medicine, Department of Radiation Oncology and Medical Physics
| | - Neeladrisingha Das
- Stanford University, School of Medicine, Department of Radiation Oncology and Medical Physics
| | - Yuting Wang
- Stanford University, School of Medicine, Department of Surgery
| | - Carlos Ruvalcaba
- University of California, Davis, Department of Biomedical Engineering
| | - Brahim Mehadji
- University of California, Davis, Department of Radiology
| | - Emilie Roncali
- University of California, Davis, Department of Biomedical Engineering
- University of California, Davis, Department of Radiology
| | | | - Guillem Pratx
- Stanford University, School of Medicine, Department of Radiation Oncology and Medical Physics
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Du J, Jones T. Technical opportunities and challenges in developing total-body PET scanners for mice and rats. EJNMMI Phys 2023; 10:2. [PMID: 36592266 PMCID: PMC9807733 DOI: 10.1186/s40658-022-00523-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 12/20/2022] [Indexed: 01/03/2023] Open
Abstract
Positron emission tomography (PET) is the most sensitive in vivo molecular imaging technique available. Small animal PET has been widely used in studying pharmaceutical biodistribution and disease progression over time by imaging a wide range of biological processes. However, it remains true that almost all small animal PET studies using mouse or rat as preclinical models are either limited by the spatial resolution or the sensitivity (especially for dynamic studies), or both, reducing the quantitative accuracy and quantitative precision of the results. Total-body small animal PET scanners, which have axial lengths longer than the nose-to-anus length of the mouse/rat and can provide high sensitivity across the entire body of mouse/rat, can realize new opportunities for small animal PET. This article aims to discuss the technical opportunities and challenges in developing total-body small animal PET scanners for mice and rats.
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Affiliation(s)
- Junwei Du
- grid.27860.3b0000 0004 1936 9684Department of Biomedical Engineering, University of California at Davis, Davis, CA 95616 USA
| | - Terry Jones
- grid.27860.3b0000 0004 1936 9684Department of Radiology, University of California at Davis, Davis, CA 95616 USA
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Kalaitzidis P, Gustafsson J, Hindorf C, Ljungberg M. Validation of a computational chain from PET Monte Carlo simulations to reconstructed images. Heliyon 2022; 8:e09316. [PMID: 35520630 PMCID: PMC9062260 DOI: 10.1016/j.heliyon.2022.e09316] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 12/25/2021] [Accepted: 04/19/2022] [Indexed: 01/21/2023] Open
Abstract
The study aimed to create a pipeline from Monte Carlo simulated projections of a Gate PET system to reconstructed images. The PET system was modelled after the GE Discovery MI (DMI) PET/CT, and the simulated projections were reconstructed with the stand-alone reconstruction software CASToR. Attenuation correction, normalisation calibration, random estimation, and scatter estimation for the simulations were computed with in-house programs. The pipeline was compared in both projection and image space with data acquired on a clinical DMI and reconstructed with GE's off-line PET reconstruction software (PET Toolbox) and CASToR. The simulated and measured data were compared for the number of prompt coincidences, scatter fraction, contrast recovery coefficient (CRC), signal-to-noise ratio (SNR), background variability, residual lung error, and image profiles. A slight discrepancy was noted in the projection space, but good agreements were generally achieved in image space between simulated and measured data. The CRC was found to be 81 % for Gate – CASToR, 84 % for GE – CASToR, and 84 % for GE - PET Toolbox for the largest sphere of the NEMA image quality (IQ) phantom, and the SNR was found to be 98 for Gate – CASToR, 91 for GE – CASToR, and 93 for GE – PET Toolbox. Profiles drawn over the spheres for the NEMA IQ phantom and the Data Spectrum (DS) phantom show a good match between measurement and simulation. The results indicate feasibility to utilise the pipeline as a tool for off-line simulation-based studies. A complete pipeline introduces possibilities to study the impact of single parameters in the whole chain from simulation to reconstructed images.
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Affiliation(s)
- Philip Kalaitzidis
- Medical Radiation Physics, Lund, Lund University, Lund, Sweden
- Corresponding author.
| | | | - Cecilia Hindorf
- Medical Radiation Physics, Lund, Lund University, Lund, Sweden
- Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Solna, Stockholm, Sweden
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Henry EC, Strugari M, Mawko G, Brewer K, Liu D, Gordon AC, Bryan JN, Maitz C, Karnia JJ, Abraham R, Kappadath SC, Syme A. Precision dosimetry in yttrium-90 radioembolization through CT imaging of radiopaque microspheres in a rabbit liver model. EJNMMI Phys 2022; 9:21. [PMID: 35312882 PMCID: PMC8938593 DOI: 10.1186/s40658-022-00447-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 03/02/2022] [Indexed: 12/24/2022] Open
Abstract
PURPOSE To perform precision dosimetry in yttrium-90 radioembolization through CT imaging of radiopaque microspheres in a rabbit liver model and to compare extracted dose metrics to those produced from conventional PET-based dosimetry. MATERIALS AND METHODS A CT calibration phantom was designed containing posts with nominal microsphere concentrations of 0.5 mg/mL, 5.0 mg/mL, and 25.0 mg/mL. The mean Hounsfield unit was extracted from the post volumes to generate a calibration curve to relate Hounsfield units to microsphere concentration. A nominal bolus of 40 mg of microspheres was administered to the livers of eight rabbits, followed by PET/CT imaging. A CT-based activity distribution was calculated through the application of the calibration curve to the CT liver volume. Post-treatment dosimetry was performed through the convolution of yttrium-90 dose-voxel kernels and the PET- and CT-based cumulated activity distributions. The mean dose to the liver in PET- and CT-based dose distributions was compared through linear regression, ANOVA, and Bland-Altman analysis. RESULTS A linear least-squares fit to the average Hounsfield unit and microsphere concentration data from the calibration phantom confirmed a strong correlation (r2 > 0.999) with a slope of 14.13 HU/mg/mL. A poor correlation was found between the mean dose derived from CT and PET (r2 = 0.374), while the ANOVA analysis revealed statistically significant differences (p < 10-12) between the MIRD-derived mean dose and the PET- and CT-derived mean dose. Bland-Altman analysis predicted an offset of 15.0 Gy between the mean dose in CT and PET. The dose within the liver was shown to be more heterogeneous in CT than in PET with an average coefficient of variation equal to 1.99 and 1.02, respectively. CONCLUSION The benefits of a CT-based approach to post-treatment dosimetry in yttrium-90 radioembolization include improved visualization of the dose distribution, reduced partial volume effects, a better representation of dose heterogeneity, and the mitigation of respiratory motion effects. Post-treatment CT imaging of radiopaque microspheres in yttrium-90 radioembolization provides the means to perform precision dosimetry and extract accurate dose metrics used to refine the understanding of the dose-response relationship, which could ultimately improve future patient outcomes.
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Affiliation(s)
- E Courtney Henry
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada.
| | - Matthew Strugari
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Biomedical Translational Imaging Centre, Halifax, NS, Canada
| | - George Mawko
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Department of Medical Physics, Nova Scotia Health Authority, Halifax, NS, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada
- Department of Diagnostic Radiology, Dalhousie University, Halifax, NS, Canada
| | - Kimberly Brewer
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Biomedical Translational Imaging Centre, Halifax, NS, Canada
- Department of Diagnostic Radiology, Dalhousie University, Halifax, NS, Canada
- Department of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
| | - David Liu
- School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Andrew C Gordon
- Department of Radiology, Northwestern University, Chicago, IL, USA
| | - Jeffrey N Bryan
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, USA
| | - Charles Maitz
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, USA
| | - James J Karnia
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, USA
| | - Robert Abraham
- Department of Diagnostic Radiology, Dalhousie University, Halifax, NS, Canada
- ABK Biomedical Inc., Halifax, NS, Canada
| | - S Cheenu Kappadath
- Department of Imaging Physics, University of Texas MD Anderson Cancer Centre, Houston, TX, USA
| | - Alasdair Syme
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada
- Department of Medical Physics, Nova Scotia Health Authority, Halifax, NS, Canada
- Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada
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Kang HG, Kim KJ, Kamada K, Yoshikawa A, Yoshida E, Nishikido F, Yamaya T. Optimization of GFAG crystal surface treatment for SiPM based TOF PET detector. Biomed Phys Eng Express 2022; 8. [PMID: 35180713 DOI: 10.1088/2057-1976/ac56c6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/18/2022] [Indexed: 11/12/2022]
Abstract
Coincidence timing resolution (CTR) is an important parameter in clinical positron emission tomography (PET) scanners to increase the signal-to-noise ratio of PET images by using time-of-flight (TOF) information. Lutetium (Lu) based scintillators are often used for TOF-PET systems. However, the self-radiation of Lu-based scintillators may influence the image quality for ultra-low activity PET imaging. Recently, a gadolinium fine aluminum gallate (Ce:GFAG) scintillation crystal that features a fast decay time (~55 ns) and no self-radiation was developed. The present study aimed at optimizing the GFAG crystal surface treatment to enhance both CTR and energy resolution (ER). The TOF-PET detector consisted of a GFAG crystal (3.0 × 3.0 × 20 mm3) and a SiPM with an effective area of 3.0 × 3.0 mm2. The timing and energy signals were extracted using a high-frequency SiPM readout circuit and then were digitized using a CAMAC DAQ system. The CTR and ER were evaluated with nine different crystal surface treatments such as partial saw-cut and chemical polishing and the 1-side saw-cut was the best choice among the treatments. The respective CTR and ER of 202±2 ps and 9.5±0.1% were obtained with the 1-side saw-cut; the other 5-side mechanically polished GFAG crystals had respective values which were 18 ps (9.0%) and 1.3% better than those of the all-side mechanically polished GFAG crystal. The chemically polished GFAG crystals also offered enhanced CTR and ER of about 17 ps (8.2%) and 2.1%, respectively, over the mechanically polished GFAG crystals.
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Affiliation(s)
- Han Gyu Kang
- Department of Nuclear Medicine Science, National Institutes for Quantum Science and technology, Imaging Physics Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba Japan, Chiba, Chiba, 263-8555, JAPAN
| | - Kyong Jin Kim
- Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980 8577, Japan, Sendai, Miyagi, 980-8577, JAPAN
| | - Kei Kamada
- New Industry Creation Hatchery Center, Tohoku University, 2-1-1, Katahira, Aoba-ku,, Sendai, JP, 980-8577, JAPAN
| | - Akira Yoshikawa
- Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980 8577, Japan, Sendai, Miyagi, 980-8577, JAPAN
| | - Eiji Yoshida
- Advanced Nuclear Medicine Science, National Institutes for Quantum Science and Technology (QST), 4-9-1 Anagawa, Inage-ku, Chiba, Japan, Chiba, 263-8555, JAPAN
| | - Fumihiko Nishikido
- National Institutes for Quantum and Technology, 4-9-1, Anagawa, Inage-ku, Chiba, Japan, Chiba, Chiba, 263-8555, JAPAN
| | - Taiga Yamaya
- National Institutes for Quantum and Radiological Science and Technology (QST), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, JAPAN, Chiba, 263-8555, JAPAN
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Omidvari N, Cheng L, Leung EK, Abdelhafez YG, Badawi RD, Ma T, Qi J, Cherry SR. Lutetium background radiation in total-body PET-A simulation study on opportunities and challenges in PET attenuation correction. FRONTIERS IN NUCLEAR MEDICINE (LAUSANNE, SWITZERLAND) 2022; 2:963067. [PMID: 36172601 PMCID: PMC9513593 DOI: 10.3389/fnume.2022.963067] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The current generation of total-body positron emission tomography (PET) scanners offer significant sensitivity increase with an extended axial imaging extent. With the large volume of lutetium-based scintillation crystals that are used as detector elements in these scanners, there is an increased flux of background radiation originating from 176Lu decay in the crystals and higher sensitivity for detecting it. Combined with the ability of scanning the entire body in a single bed position, this allows more effective utilization of the lutetium background as a transmission source for estimating 511 keV attenuation coefficients. In this study, utilization of the lutetium background radiation for attenuation correction in total-body PET was studied using Monte Carlo simulations of a 3D whole-body XCAT phantom in the uEXPLORER PET scanner, with particular focus on ultralow-dose PET scans that are now made possible with these scanners. Effects of an increased acceptance angle, reduced scan durations, and Compton scattering on PET quantification were studied. Furthermore, quantification accuracy of lutetium-based attenuation correction was compared for a 20-min scan of the whole body on the uEXPLORER, a one-meter-long, and a conventional 24-cm-long scanner. Quantification and lesion contrast were minimally affected in both long axial field-of-view scanners and in a whole-body 20-min scan, the mean bias in all analyzed organs of interest were within a ±10% range compared to ground-truth activity maps. Quantification was affected in certain organs, when scan duration was reduced to 5 min or a reduced acceptance angle of 17° was used. Analysis of the Compton scattered events suggests that implementing a scatter correction method for the transmission data will be required, and increasing the energy threshold from 250 keV to 290 keV can reduce the computational costs and data rates, with negligible effects on PET quantification. Finally, the current results can serve as groundwork for transferring lutetium-based attenuation correction into research and clinical practice.
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Affiliation(s)
- Negar Omidvari
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States,CORRESPONDENCE: Negar Omidvari,
| | - Li Cheng
- Department of Engineering Physics, Tsinghua University, Beijing, China
| | - Edwin K. Leung
- Department of Radiology, University of California, Davis, Davis, CA, United States,United Imaging Healthcare America Inc., Houston, TX, United States
| | - Yasser G. Abdelhafez
- Department of Radiology, University of California, Davis, Davis, CA, United States,Nuclear Medicine Unit, South Egypt Cancer Institute, Assiut University, Asyut, Egypt
| | - Ramsey D. Badawi
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States,Department of Radiology, University of California, Davis, Davis, CA, United States
| | - Tianyu Ma
- Department of Engineering Physics, Tsinghua University, Beijing, China
| | - Jinyi Qi
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
| | - Simon R. Cherry
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States,Department of Radiology, University of California, Davis, Davis, CA, United States
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Teimoorisichani M, Panin V, Rothfuss H, Sari H, Rominger A, Conti M. A CT-less approach to quantitative PET imaging using the LSO intrinsic radiation for long-axial FOV PET scanners. Med Phys 2021; 49:309-323. [PMID: 34818446 PMCID: PMC9299938 DOI: 10.1002/mp.15376] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 11/11/2022] Open
Abstract
Purpose Long‐axial field‐of‐view (FOV) positron emission tomography (PET) scanners have gained a lot of interest in the recent years. Such scanners provide increased sensitivity and enable unique imaging opportunities that were not previously feasible. Benefiting from the high sensitivity of a long‐axial FOV PET scanner, we studied a computed tomography (CT)–less reconstruction algorithm for the Siemens Biograph Vision Quadra with an axial FOV of 106 cm. Methods In this work, the background radiation from radioisotope lutetium‐176 in the scintillators was used to create an initial estimate of the attenuation maps. Then, joint activity and attenuation reconstruction algorithms were used to create an improved attenuation map of the object. The final attenuation maps were then used to reconstruct quantitative PET images, which were compared against CT‐based PET images. The proposed method was evaluated on data from three patients who underwent a flurodeoxyglucouse PET scan. Results Segmentation of the PET images of the three studied patients showed an average quantitative error of 6.5%–8.3% across all studied organs when using attenuation maps from maximum likelihood estimation of attenuation and activity and 5.3%–6.6% when using attenuation maps from maximum likelihood estimation of activity and attenuation correction coefficients. Conclusions Benefiting from the background radiation of lutetium‐based scintillators, a quantitative CT‐less PET imaging technique was evaluated in this work.
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Affiliation(s)
| | - Vladimir Panin
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
| | - Harold Rothfuss
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
| | - Hasan Sari
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.,Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Axel Rominger
- Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Maurizio Conti
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee, USA
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Ko K, Choi H, Yi Y, Kim W, Kim J, Hwang J, Ko E, Cho G. Discrete Convolution-Based Energy Spectrum Configuring Method for the Analysis of the Intrinsic Radiation of 176Lu. SENSORS 2021; 21:s21217040. [PMID: 34770347 PMCID: PMC8587293 DOI: 10.3390/s21217040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/15/2021] [Accepted: 10/21/2021] [Indexed: 11/16/2022]
Abstract
There has been considerable interest in inorganic scintillators based on lutetium due to their favorable physical properties. Despite their advantages, lutetium-based scintillators could face issues because of the natural occurring radioisotope of 176Lu that is contained in natural lutetium. In order to mitigate its potential shortcomings, previous works have studied to understand the energy spectrum of the intrinsic radiation of 176Lu (IRL). However, few studies have focused on the various principal types of photon interactions with matter; in other words, only the full-energy peak according to the photoelectric effect or internal conversion have been considered for understanding the energy spectrum of IRL. Thus, the approach we have used in this study considers other principal types of photon interactions by convoluting each energy spectrum with combinations for generating the spectrum of the intrinsic radiation of 176Lu. From the results, we confirm that the method provides good agreement with the experiment. A significant contribution of this study is the provision of a new approach to process energy spectra induced by mutually independent radiation interactions as a single spectrum.
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Affiliation(s)
- Kilyoung Ko
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Hyunwoong Choi
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Yongsun Yi
- Department of Nuclear Engineering, Khalifa University of Science Technology and Research, Abu Dhabi P.O. Box 127788, United Arab Emirates;
| | - Wonku Kim
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Junhyeok Kim
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Jisung Hwang
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Eunbie Ko
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
| | - Gyuseong Cho
- Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea; (K.K.); (H.C.); (W.K.); (J.K.); (J.H.); (E.K.)
- Correspondence:
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Hesse M, d'Abadie P, Lhommel R, Jamar F, Walrand S. Yttrium-90 TOF-PET-Based EUD Predicts Response Post Liver Radioembolizations Using Recommended Manufacturer FDG Reconstruction Parameters. Front Oncol 2021; 11:592529. [PMID: 34676157 PMCID: PMC8523947 DOI: 10.3389/fonc.2021.592529] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 09/07/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose Explaining why 90Y TOF-PET based equivalent uniform dose (EUD) using recommended manufacturer FDG reconstruction parameters has been shown to predict response. Methods The hot rods insert of a Jaszczak deluxe phantom was partially filled with a 2.65 GBq 90Y - 300ml DTPA water solution resulting in a 100 Gy mean absorbed dose in the 6 sectors. A two bed 20min/position acquisition was performed on a 550ps- and on a 320ps- TOF-PET/CT and reconstructed with recommended manufacturer FDG reconstruction parameters, without and with additional filtering. The whole procedure was repeated on both PET after adding 300ml of water (50Gy setup). The phantom was acquired again after decay by a factor of 10 (5Gy setup), but with 200min per bed position. For comparison, the phantom was also acquired with 18F activity corresponding to a clinical FDG whole body acquisition. Results The 100Gy-setup provided a hot rod sectors image almost as good as the 18F phantom. However, despite acquisition time compensation, the 5Gy-setup provides much lower quality imaging. TOF-PET based sectors EUDs for the three large rod sectors agreed with the actual EUDs computed with a radiosensitivity of 0.021Gy-1 well in the range observed in external beam radiotherapy (EBRT), i.e. 0.01-0.04Gy-1. This agreement explains the reunification of the dose-response relationships of the glass and resin spheres in HCC using the TOF-PET based EUD. Additional filtering reduced the EUDs agreement quality. Conclusions Recommended manufacturer FDG reconstruction parameters are suitable in TOF-PET post 90Y liver radioembolization for accurate tumour EUD computation. The present results rule out the use of low specific activity phantom studies to optimize reconstruction parameters.
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Affiliation(s)
- Michel Hesse
- Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium
| | - Philipe d'Abadie
- Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium
| | - Renaud Lhommel
- Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium
| | - Francois Jamar
- Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium
| | - Stephan Walrand
- Nuclear Medicine, Cliniques universitaires Saint-Luc, Brussels, Belgium
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Domínguez-Jiménez DY, Alva-Sánchez H. Energy spectra due to the intrinsic radiation of LYSO/LSO scintillators for a wide range of crystal sizes. Med Phys 2021; 48:1596-1607. [PMID: 33475160 DOI: 10.1002/mp.14729] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 10/22/2020] [Accepted: 12/21/2020] [Indexed: 01/02/2023] Open
Abstract
PURPOSE Most detectors in current positron emission tomography (PET) scanners and prototypes use lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) scintillators. The aim of this work is to provide a complete set of background energy spectra, due to the scintillator intrinsic radioactivity, for a wide range of crystal sizes. METHODS An analytical model, developed and validated in a previous work, was used to obtain the background energy spectra of square base cuboids of different dimensions. The model uses the photon absorption probabilities of the three gamma rays (88, 202, and 307 keV) emitted following the beta decay of 176 Lu to 176 Hf excited states. These probabilities were obtained for each crystal size considered in this work from Monte Carlo simulations using the PENELOPE code. The probabilities are then used to normalize and shift the beta spectrum to the corresponding energy value of the simultaneous detection of one, two, or three gamma rays in the scintillator. The simulated cuboids had side lengths of 5, 10, 20, 30, 40, 50, and 60 mm and crystal thickness T = 2.5, 5, 10, 15, and 20 mm. From these results a complete set of energy spectra, including intermediate dimensions, were obtained. In addition, LYSO and LSO were compared in terms of their analytical background energy spectra for two crystal sizes. The analytical spectra were convolved using a variable Gaussian kernel to account for the energy resolution of a typical detector. A parameterization of the photon absorption probabilities for each gamma ray energy as a function of the cuboid volume to surface area ratio was obtained. RESULTS A data set of L(Y)SO background energy spectra was obtained and is available for the reader as 2D histograms. The model accurately predicts the structure of the energy spectra including the relative peak and valley intensities. The data allow visualizing how the structure evolves with increasing crystal length and thickness. Lutetium yttrium oxyorthosilicate and LSO present very similar background energy spectra for the range of sizes studied in this work and therefore the data generated can be confidently used for both scintillator materials. The filtered spectra showed a variable shift in the main peaks, depending on crystal size, alerting that to achieve a correct detector calibration using the background spectrum is not straight forward and requires precise data analysis and measurements. In addition, we found that square base L(Y)SO cuboids with same volume to surface area ratio have background spectra with the same structure. CONCLUSIONS We present the energy spectra of L(Y)SO crystal of different sizes which will be very useful for industry and research groups developing and simulating detectors for positron imaging applications in terms of calibration, quality assurance, crystal maps, detector fine gain tuning, background reduction and other applications using the long-lived 176 Lu source. We analyzed the data produced in this work and found that crystal cuboids with equal volume to surface area ratio produce the same background energy spectra, a conclusion that simplifies its calculation and clarifies why the same energy spectrum is observed under different experimental setups.
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Affiliation(s)
| | - Héctor Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, Mexico City, 01000, Mexico
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Lara-Camacho VM, Hernández-Acevedo EM, Alva-Sánchez H, Murrieta-Rodríguez T, Martínez-Dávalos A, Moranchel M, Rodríguez-Villafuerte M. Experimental validation of the ANTS2 code for modelling optical photon transport in monolithic LYSO crystals. Phys Med 2021; 81:215-226. [PMID: 33482439 DOI: 10.1016/j.ejmp.2020.12.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/11/2020] [Accepted: 12/31/2020] [Indexed: 11/16/2022] Open
Abstract
In this work the scintillation energy spectra originating from the background radioactivity from polished monolithic lutetium yttrium oxyorthosilicate coupled to position-sensitive silicon photomultipliers (SiPM) was studied using the open source Monte Carlo simulation package ANTS2. Two crystal sizes, fully and partially covering the photosensor area, three surface crystal wrappings (black, specular or diffuse) and the full signal formation process in the photosensor were considered. The simulation results were validated with experimental data acquired under the same geometric and detector operating conditions. In all cases ANTS2 simulated spectra have very good agreement with experimental results, reproducing the expected shape, with correct onset and end at 88 and 1190 keV, respectively, as well as sharp edges at the reference energies of 88, 88 + 202, 88 + 307 and 88 + 202 + 307 keV. The normalized root-mean square error between simulated and measured spectra varied between 4.3% and 10.4%.
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Affiliation(s)
- Víctor Manuel Lara-Camacho
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, Ciudad de México 01000, Mexico; Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ciudad de México 07738, Mexico
| | | | - Héctor Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, Ciudad de México 01000, Mexico
| | - Tirso Murrieta-Rodríguez
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, Ciudad de México 01000, Mexico
| | - Arnulfo Martínez-Dávalos
- Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, Ciudad de México 01000, Mexico
| | - Mario Moranchel
- Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ciudad de México 07738, Mexico
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Wang Q, Mikhaylova E, Baikejiang R, Cherry SR. The reduction of 176Lu background in Lu-based PET scanners using optimized classification. ACTA ACUST UNITED AC 2020; 65:175016. [DOI: 10.1088/1361-6560/aba088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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15
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Enríquez-Mier-Y-Terán FE, Ortega-Galindo AS, Murrieta-Rodríguez T, Rodríguez-Villafuerte M, Martínez-Dávalos A, Alva-Sánchez H. Coincidence energy spectra due to the intrinsic radioactivity of LYSO scintillation crystals. EJNMMI Phys 2020; 7:21. [PMID: 32297045 PMCID: PMC7160222 DOI: 10.1186/s40658-020-00291-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 03/26/2020] [Indexed: 11/10/2022] Open
Abstract
Background Lutetium oxyorthosilicate or lutetium yttrium oxyorthosilicate (LYSO) scintillation crystals used in most current PET scanner detectors contain 176Lu, which decays by beta emission to excited states of 176Hf accompanied by the emission of prompt gamma rays or internal conversion electrons. This intrinsic radioactivity can be self-detected in singles mode as a constant background signal that has an energy spectrum whose structure has been explained previously. In this work, we studied the energy spectrum due to the intrinsic radioactivity of LYSO scintillation crystals of two opposing detectors working in coincidence mode. The investigation included experimental data, Monte Carlo simulations and an analytical model. Results The structure of the energy spectrum was completely understood and is the result of the self-detection of beta particles from 176Lu in one crystal and the detection of one or more prompt gamma rays detected in coincidence by the opposing crystal. The most probable coincidence detection involves the gamma rays of 202 and 307 keV, which result in two narrow photopeaks, superimposed on a continuous energy distribution due to the beta particle energy deposition. The relative intensities of the gamma ray peaks depend on crystal size and detector separation distance, as is explained by the analytical model and verified through the Monte Carlo simulations and experiments. Conclusions The analytical model used in this work accurately explains the general features of the coincidence energy spectrum due to the presence of 176Lu in the scintillation crystals, as observed experimentally and with Monte Carlo simulations. This work will be useful to those research studies aimed at using the intrinsic radioactivity of LYSO crystals for transmission scans and detector calibration in coincidence mode.
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Affiliation(s)
| | | | - Tirso Murrieta-Rodríguez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico
| | | | - Arnulfo Martínez-Dávalos
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico
| | - Héctor Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico.
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Zhu Z, Liu B, Cheng C, Chen H, Gu M, Chen L, Liu J, Ouyang X, Xu J, Zhang C. Convenient method for improving the light output of scintillators by using buffer layers coated with photonic crystals. OPTICS EXPRESS 2020; 28:11301-11308. [PMID: 32403644 DOI: 10.1364/oe.390677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 03/17/2020] [Indexed: 06/11/2023]
Abstract
The low light-extraction efficiency of scintillators is due to total internal reflection and has led to the extensive use of photonic crystals to improve the light output. However, in some applications, photonic crystals cannot be fabricated directly on scintillators. Here, we demonstrate a promising method to improve the light output of scintillators by using a buffer layer coated with photonic crystals and then fixed to the scintillator. Through both numerical simulations and experiments, we investigate how the refractive indexes of the buffer layer and photonic crystal affect the light output from scintillators. The experimental results indicate that the light output of (Lu,Y)2SiO5:Ce scintillators is enhanced 1.9 times by using a sapphire buffer layer coated with an array of polystyrene nanospheres. This method can be used to improve the detection efficiency of radiation-detection systems when photonic crystals cannot be fabricated directly on the scintillator.
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17
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Kunnen B, Beijst C, Lam MGEH, Viergever MA, de Jong HWAM. Comparison of the Biograph Vision and Biograph mCT for quantitative 90Y PET/CT imaging for radioembolisation. EJNMMI Phys 2020; 7:14. [PMID: 32130554 PMCID: PMC7056802 DOI: 10.1186/s40658-020-0283-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND New digital PET scanners with improved time of flight timing and extended axial field of view such as the Siemens Biograph Vision have come on the market and are expected to replace current generation photomultiplier tube (PMT)-based systems such as the Siemens Biograph mCT. These replacements warrant a direct comparison between the systems, so that a smooth transition in clinical practice and research is guaranteed, especially when quantitative values are used for dosimetry-based treatment guidance. The new generation digital PET scanners offer increased sensitivity. This could particularly benefit 90Y imaging, which tends to be very noisy owing to the small positron branching ratio and high random fraction of 90Y. This study aims to determine the ideal reconstruction settings for the digital Vision for quantitative 90Y imaging and to evaluate the image quality and quantification of the digital Vision in comparison with its predecessor, the PMT-based mCT, for 90Y imaging in radioembolisation procedures. METHODS The NEMA image quality phantom was scanned to determine the ideal reconstruction settings for the Vision. In addition, an anthropomorphic phantom was scanned with both the Vision and the mCT, mimicking a radioembolisation patient with lung, liver, tumour, and extrahepatic deposition inserts. Image quantification of the anthropomorphic phantom was assessed by the lung shunt fraction, the tumour to non-tumour ratio, the parenchymal dose, and the contrast to noise ratio of extrahepatic depositions. RESULTS For the Vision, a reconstruction with 3 iterations, 5 subsets, and no post-reconstruction filter is recommended for quantitative 90Y imaging, based on the convergence of the recovery coefficient. Comparing both systems showed that the noise level of the Vision is significantly lower than that of the mCT (background variability of 14% for the Vision and 25% for the mCT at 2.5·103 MBq for the 37 mm sphere size). For quantitative 90Y measures, such as needed in radioembolisation, both systems perform similarly. CONCLUSIONS We recommend to reconstruct 90Y images acquired on the Vision with 3 iterations, 5 subsets, and no post-reconstruction filter for quantitative imaging. The Vision provides a reduced noise level, but similar quantitative accuracy as compared with its predecessor the mCT.
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Affiliation(s)
- Britt Kunnen
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands.
- Image Sciences Institute, UMC Utrecht & University Utrecht, Heidelberglaan 100, CX 3584, Utrecht, the Netherlands.
| | - Casper Beijst
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
| | - Marnix G E H Lam
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
| | - Max A Viergever
- Image Sciences Institute, UMC Utrecht & University Utrecht, Heidelberglaan 100, CX 3584, Utrecht, the Netherlands
| | - Hugo W A M de Jong
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
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18
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García-Pérez P, España S. Simultaneous emission and attenuation reconstruction in time-of-flight PET using a reference object. EJNMMI Phys 2020; 7:3. [PMID: 31932984 PMCID: PMC6957598 DOI: 10.1186/s40658-020-0272-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/07/2020] [Indexed: 12/20/2022] Open
Abstract
Background Simultaneous reconstruction of emission and attenuation images in time-of-flight (TOF) positron emission tomography (PET) does not provide a unique solution. In this study, we propose to solve this limitation by including additional information given by a reference object with known attenuation placed outside the patient. Different configurations of the reference object were studied including geometry, material composition, and activity, and an optimal configuration was defined. In addition, this configuration was tested for different timing resolutions and noise levels. Results The proposed strategy was tested in 2D simulations obtained by forward projection of available PET/CT data and noise was included using Monte Carlo techniques. Obtained results suggest that the optimal configuration corresponds to a water cylinder inserted in the patient table and filled with activity. In that case, mean differences between reconstructed and true images were below 10%. However, better results can be obtained by increasing the activity of the reference object. Conclusion This study shows promising results that might allow to obtain an accurate attenuation map from pure TOF-PET data without prior knowledge obtained from CT, MRI, or transmission scans.
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Affiliation(s)
- Pablo García-Pérez
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, IdISSC, Ciudad Universitaria, 28040, Madrid, Spain
| | - Samuel España
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, IdISSC, Ciudad Universitaria, 28040, Madrid, Spain. .,Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain.
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Alva-Sánchez H, Zepeda-Barrios A, Díaz-Martínez VD, Murrieta-Rodríguez T, Martínez-Dávalos A, Rodríguez-Villafuerte M. Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals. Sci Rep 2018; 8:17310. [PMID: 30470826 PMCID: PMC6251911 DOI: 10.1038/s41598-018-35684-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 11/06/2018] [Indexed: 11/09/2022] Open
Abstract
Lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) are the scintillator materials most widely used today in PET detectors due to their convenient physical properties for the detection of 511 keV annihilation photons. Natural lutetium contains 2.6% of 176Lu which decays beta to excited states of 176Hf producing a constant background signal. Although previous works have studied the background activity from LSO/LYSO, the shape of the spectrum, resulting from β-particle and γ radiation self-detection, has not been fully explained. The present work examines the contribution of the different β-particle and γ-ray interactions to provide a fuller comprehension of this background spectrum and to explain the differences observed when using crystals of different sizes. To this purpose we have shifted the continuous β-particle energy spectrum of 176Lu from zero to the corresponding energy value for all combinations of the isomeric transitions of 176Hf (γ-rays/internal conversion). The area of each shifted β-spectrum was normalized to reflect the probability of occurrence. To account for the probability of the γ-rays escaping from the crystal, Monte Carlo simulations using PENELOPE were performed in which point-like sources of monoenergetic photons were generated, inside LYSO square base prisms (all 1 cm thick) of different sizes: 1.0 cm to 5.74 cm. The analytic distributions were convolved using a varying Gaussian function to account for the measured energy resolution. The calculated spectra were compared to those obtained experimentally using monolithic crystals of the same dimensions coupled to SiPM arrays. Our results are in very good agreement with the experiment, and even explain the differences observed due to crystal size. This work may prove useful to calibrate and assess detector performance, and to measure energy resolution at different energy values.
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Affiliation(s)
- H Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico.
| | - A Zepeda-Barrios
- Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - V D Díaz-Martínez
- Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510, Mexico City, Mexico
| | - T Murrieta-Rodríguez
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico
| | - A Martínez-Dávalos
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico
| | - M Rodríguez-Villafuerte
- Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, 01000, Mexico City, Mexico
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Ljungberg M, Sjogreen Gleisner K. 3-D Image-Based Dosimetry in Radionuclide Therapy. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2018. [DOI: 10.1109/trpms.2018.2860563] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Walrand S, Hesse M, Jamar F, Lhommel R. The origin and reduction of spurious extrahepatic counts observed in 90Y non-TOF PET imaging post radioembolization. Phys Med Biol 2018. [PMID: 29513273 DOI: 10.1088/1361-6560/aab4e9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Our literature survey revealed a physical effect unknown to the nuclear medicine community, i.e. internal bremsstrahlung emission, and also the existence of long energy resolution tails in crystal scintillation. None of these effects has ever been modelled in PET Monte Carlo (MC) simulations. This study investigates whether these two effects could be at the origin of two unexplained observations in 90Y imaging by PET: the increasing tails in the radial profile of true coincidences, and the presence of spurious extrahepatic counts post radioembolization in non-TOF PET and their absence in TOF PET. These spurious extrahepatic counts hamper the microsphere delivery check in liver radioembolization. An acquisition of a 32P vial was performed on a GSO PET system. This is the ideal setup to study the impact of bremsstrahlung x-rays on the true coincidence rate when no positron emission and no crystal radioactivity are present. A MC simulation of the acquisition was performed using Gate-Geant4. MC simulations of non-TOF PET and TOF-PET imaging of a synthetic 90Y human liver radioembolization phantom were also performed. Internal bremsstrahlung and long energy resolution tails inclusion in MC simulations quantitatively predict the increasing tails in the radial profile. In addition, internal bremsstrahlung explains the discrepancy previously observed in bremsstrahlung SPECT between the measure of the 90Y bremsstrahlung spectrum and its simulation with Gate-Geant4. However the spurious extrahepatic counts in non-TOF PET mainly result from the failure of conventional random correction methods in such low count rate studies and poor robustness versus emission-transmission inconsistency. A novel proposed random correction method succeeds in cleaning the spurious extrahepatic counts in non-TOF PET. Two physical effects not considered up to now in nuclear medicine were identified to be at the origin of the unusual 90Y true coincidences radial profile. TOF reconstruction removing of the spurious extrahepatic counts was theoretically explained by a better robustness against emission-transmission inconsistency. A novel random correction method was proposed to overcome the issue in non-TOF PET. Further studies are needed to assess the novel random correction method robustness.
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