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Carroll L, Enger SA. M-TAG: A modular teaching-aid for Geant4. Heliyon 2023; 9:e20229. [PMID: 37810860 PMCID: PMC10556609 DOI: 10.1016/j.heliyon.2023.e20229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 10/10/2023] Open
Abstract
Geant4 is a versatile Monte Carlo radiation transport simulation toolkit with a steep learning curve. This work introduces a user-code called M-TAG (Modular Radiation Teaching-Aid for Geant4), built on top of Geant4. M-TAG is designed to help gradually introduce the Geant4 toolkit to new users. The goal of Geant4 is to record quantities from the simulated radiation as it is transported through geometries. M-TAG simplifies the inclusion of new geometric elements and detector components in the simulation by including new classes. M-TAG also provides basic validated examples for some common detector development tasks. Geant4 intercom modules, called messenger classes, manage these classes. To validate M-TAG, simulations were performed to calculate the range of positrons in water. One hundred million decays at the center of a water-filled sphere with a radius of 1 m were allowed for fluorine-18, carbon-11, oxygen-15 and gallium-68. These results were compared to literature values. An inexperienced Geant4 user was tasked with creating a simulation model for a plastic scintillator-based detector and conducting basic tests to assess the effectiveness of M-TAG as a teaching tool. The simulation involved calculating the dose to the detector's sensitive volume using a 2x2 cm planar monoenergetic photon source spanning energies from 20 to 100 keV. One billion particles were simulated twice: once with the actual detector geometry and once with the sensitive volume replaced by water. The validity of M-TAG was also verified by computing dose ratios and comparing them with mass-attenuation ratios obtained from NIST XCOM data sets. The mean positron travel distances were within the distribution of literature values. Simulated positron energy spectra means were within 1.8% of literature means. Simulated dose ratios agreed with literature values within uncertainties. We have developed and verified a modular Geant4 teaching aid called M-TAG. It was used to introduce a new user to Geant4, who used it to perform further validation simulations.
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Affiliation(s)
- Liam Carroll
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montreal, Quebec, Canada
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, QC, H3T 1E2, Canada
| | - Shirin A. Enger
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montreal, Quebec, Canada
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, QC, H3T 1E2, Canada
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Carroll L, Enger SA. Simulation of a novel, non-invasive radiation detector to measure the arterial input function for dynamic positron emission tomography. Med Phys 2023; 50:1647-1659. [PMID: 36250522 DOI: 10.1002/mp.16055] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 09/14/2022] [Accepted: 10/04/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dynamic positron emission tomography (dPET) is a nuclear medicine imaging technique providing functional images for organs of interest with applications in oncology, cardiology, and drug discovery. This technique requires the acquisition of the time-course arterial plasma activity concentration, called the arterial input function (AIF), which is conventionally acquired via arterial blood sampling. PURPOSE The aim of this study was to (A) optimize the geometry for a novel and cost efficient non-invasive detector called NID designed to measure the AIF for dPET scans through Monte Carlo simulations and (B) develop a clinical data analysis chain to successfully separate the arterial component of a simulated AIF signal from the venous component. METHODS The NID was optimized by using an in-house Geant4-based software package. The sensitive volume of the NID consists of a band of 10 cm long and 1 mm in diameter scintillating fibers placed over a wrist phantom. The phantom was simulated as a cylinder, 10 cm long and 6.413 cm in diameter comprised of polyethylene with two holes placed through it to simulate the patient's radial artery and vein. This phantom design was chosen to match the wrist phantom used in our previous proof of concept work. Two geometries were simulated with different arrangements of scintillating fibers. The first design used a single layer of 64 fibers. The second used two layers, an inner layer with 29 fibers and an outer layer with 30 fibers. Four positron emitting radioisotopes were simulated: 18 F, 11 C, 15 O, and 68 Ga with 100 million simulated decay events per run. The total and intrinsic efficiencies of both designs were calculated as well as the full width half maximum (FWHM) of the signal. In addition, contribution by the annihilation photons versus positrons to the signal was investigated. The results obtained from the two simulated detector models were compared. A clinical data analysis chain using an expectation maximization maximum likelihood algorithm was tested. This analysis chain will be used to separate arterial counts from the total signal. RESULTS The second NID design with two layers of scintillating fibers had a higher efficiency for all simulations with a maximum increase of 17% total efficiency for 11 C simulation. All simulations had a significant annihilation photon contribution. The signal for 18 F and 11 C was almost entirely due to photons. The clinical data analysis chain was within 1% of the true value for 434 out of 440 trials. Further experimental studies to validate these simulations will be required. CONCLUSIONS The design of the NID was optimized and its efficiency increased through Monte Carlo simulations. A clinical data analysis chain was successfully developed to separate the arterial component of an AIF signal from the venous component. The simulations show that the NID can be used to accurately measure the AIF non-invasively for dPET scans.
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Affiliation(s)
- Liam Carroll
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
| | - Shirin A Enger
- Medical Physics Unit, Department of Oncology, Faculty of Medicine, McGill University, Montréal, Quebec, Canada
- Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada
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The utilization of positron emission tomography in the evaluation of renal health and disease. Clin Transl Imaging 2021. [DOI: 10.1007/s40336-021-00469-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Abstract
Purpose
Positron emission tomography (PET) is a nuclear imaging technique that uses radiotracers to visualize metabolic processes of interest across different organs, to diagnose and manage diseases, and monitor therapeutic response. This systematic review aimed to characterize the value of PET for the assessment of renal metabolism and function in subjects with non-oncological metabolic disorders.
Methods
This review was conducted and reported in accordance with the PRISMA statement. Research articles reporting “kidney” or “renal” metabolism evaluated with PET imaging between 1980 and 2021 were systematically searched in Medline/PubMed, Science Direct, and the Cochrane Library. Search results were exported and stored in RefWorks, the duplicates were removed, and eligible studies were identified, evaluated, and summarized.
Results
Thirty reports met the inclusion criteria. The majority of the studies were prospective (73.33%, n = 22) in nature. The most utilized PET radiotracers were 15O-labeled radio water (H215O, n = 14) and 18F-fluorodeoxyglucose (18F-FDG, n = 8). Other radiotracers used in at least one study were 14(R,S)-(18)F-fluoro-6-thia-heptadecanoic acid (18F-FTHA), 18F-Sodium Fluoride (18F-NaF), 11C-acetate, 68-Gallium (68Ga), 13N-ammonia (13N-NH3), Rubidium-82 (82Rb), radiolabeled cationic ferritin (RadioCF), 11C‐para-aminobenzoic acid (11C-PABA), Gallium-68 pentixafor (68Ga-Pentixafor), 2-deoxy-2-F-fluoro-d-sorbitol (F-FDS) and 55Co-ethylene diamine tetra acetic acid (55Co-EDTA).
Conclusion
PET imaging provides an effective modality for evaluating a range of metabolic functions including glucose and fatty acid uptake, oxygen consumption and renal perfusion. Multiple positron emitting radiolabeled racers can be used for renal imaging in clinical settings. PET imaging thus holds the potential to improve the diagnosis of renal disorders, and to monitor disease progression and treatment response.
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Hess A, Nekolla SG, Meier M, Bengel FM, Thackeray JT. Accuracy of cardiac functional parameters measured from gated radionuclide myocardial perfusion imaging in mice. J Nucl Cardiol 2020; 27:1317-1327. [PMID: 31044402 DOI: 10.1007/s12350-019-01713-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 03/26/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND Quantitative cardiac contractile function assessment is the primary indicator of disease progression and therapeutic efficacy in small animals. Operator dependency is a major challenge with commonly used echocardiography. Simultaneous assessment of cardiac perfusion and function in nuclear scans would reduce burden on the animal and facilitate longitudinal studies. We evaluated the accuracy of contractile function measurements obtained from electrocardiogram-gated nuclear perfusion imaging compared with anatomic imaging. METHODS AND RESULTS In healthy C57Bl/6N mice (n = 11), 99mTc-sestamibi SPECT and 13N-ammonia PET underestimated left ventricular volumes (23 to 28%, P = 0.02) compared to matched anatomic images, though ejection fraction (LVEF) was comparable (%, SPECT: 73 ± 8 vs CMR: 72 ± 6, P = 0.1). At 1 week after myocardial infarction (n = 13), LV volumes were significantly lower in perfusion images compared to CMR and contrast CT (P = 0.003), and LVEF was modestly overestimated (%, SPECT: 37 ± 8, vs CMR: 27 ± 7, P = 0.003). Nuclear images exhibited good intra- and inter-reader agreement. Perfusion SPECT accurately calculated infarct size compared to histology (r = 0.95, P < 0.001). CONCLUSIONS Cardiac function can be calculated by gated nuclear perfusion imaging in healthy mice. After infarction, perfusion imaging overestimates LVEF, which should be considered for comparison to other modalities. Combined functional and infarct size analysis may optimize imaging protocols and reduce anaesthesia duration for longitudinal studies.
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Affiliation(s)
- Annika Hess
- Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - Stephan G Nekolla
- Department of Nuclear Medicine, Technical University of Munich, Munich, Germany
| | - Martin Meier
- Imaging Center of the Institute of Laboratory Animal Sciences, Hannover Medical School, Hannover, Germany
| | - Frank M Bengel
- Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - James T Thackeray
- Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
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Carroll L, Croteau E, Kertzscher G, Sarrhini O, Turgeon V, Lecomte R, Enger SA. Cross-validation of a non-invasive positron detector to measure the arterial input function for pharmacokinetic modelling in dynamic positron emission tomography. Phys Med 2020; 76:92-99. [PMID: 32623226 DOI: 10.1016/j.ejmp.2020.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/04/2020] [Accepted: 06/06/2020] [Indexed: 11/27/2022] Open
Abstract
Kinetic modeling of positron emission tomography (PET) data can assess index rate of uptake, metabolism and predict disease progression more accurately than conventional static PET. However, it requires knowledge of the time-course of the arterial blood radioactivity concentration, called the arterial input function (AIF). The gold standard to acquire the AIF is by invasive means. The purpose of this study was to validate a previously developed dual readout scintillating fiber-based non-invasive positron detector, hereinafter called non-invasive detector (NID), developed to determine the AIF for dynamic PET measured from the human radial artery. The NID consisted of a 3 m long plastic scintillating fiber with each end coupled to a 5 m long transmission fiber followed by a silicon photomultiplier. The scintillating fiber was enclosed inside the grooves of a plastic cylindrical shell. Two sets of experiments were performed to test the NID against a previously validated microfluidic positron detector. A closed-loop microfluidic system combined with a wrist phantom was used. During the first experiment, the three PET radioisotopes 18F, 11C and 68Ga were tested. After optimizing the detector, a second series of tests were performed using only 18F and 11C. The maximum pulse amplitude to electronic noise ratio was 52 obtained with 11C. Linear regressions showed a linear relation between the two detectors. These preliminary results show that the NID can accurately detect positrons from a patient's wrist and has the potential to non-invasively measure the AIF during a dynamic PET scan. The accuracy of these measurements needs to be determined.
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Affiliation(s)
- Liam Carroll
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Department of Biomedical Engineering, McGill University, Montreal, Quebec, Canada.
| | - Etienne Croteau
- Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | | | - Otman Sarrhini
- Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Vincent Turgeon
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Roger Lecomte
- Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Shirin A Enger
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Department of Biomedical Engineering, McGill University, Montreal, Quebec, Canada; Department of Oncology, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec H3H 2L9, Canada; Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
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Ferguson S, Jans HS, Wuest M, Riauka T, Wuest F. Comparison of scandium-44 g with other PET radionuclides in pre-clinical PET phantom imaging. EJNMMI Phys 2019; 6:23. [PMID: 31832809 PMCID: PMC6908536 DOI: 10.1186/s40658-019-0260-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 11/08/2019] [Indexed: 12/18/2022] Open
Abstract
PURPOSE The decay characteristics of radionuclides in PET studies can impact image reconstruction. 44gSc has been the topic of recent research due to potential theranostic applications and is a promising radiometal for PET imaging. In this study, the reconstructed images from phantom measurements with scandium in a small-animal PET scanner are compared with 18F and two prominent radiometals: 64Cu and 68Ga METHODS: Three phantoms filled with 18F, 64C, 68Ga, and 44gSc were imaged in the Siemens Inveon PET scanner. The NEMA image quality phantom was used to determine the recovery coefficients (RCs), spill-over ratios (SORs), and noise (%SD) under typical pre-clinical imaging conditions. Image contrast was determined using a Derenzo phantom, while the coincidence characteristics were investigated using an NEC phantom. Three reconstruction algorithms were used, namely filtered back projection (FBP), ordered subset expectation maximization (OSEM), and maximum a-posteriori (MAP). RESULTS Image quality parameters were measured for 18F, 64Cu, 68Ga, and 44gSc respectively; using FBP, the %SD are 5.65, 5.88, 7.28, and 7.70; the RCs for the 5-mm rod are 0.849, 1.01, 0.615, and 0.825; the SORs in water are 0.0473, 0.0595, 0.141, 0.0923; and the SORs in air are 0.0589, 0.0484, 0.0525, and 0.0509. The contrast measured in the 2.5-mm rods are 0.674, 0.637, 0.196, and 0.347. The NEC rate with 44gSc increased at a slower rate than 18F and 68Ga as a function of activity in the field of view. CONCLUSION 44gSc demonstrates intermediate behavior relative to 18F and 68Ga with regard to RC and contrast measurements. It is a promising radionuclide for preclinical imaging.
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Affiliation(s)
- Simon Ferguson
- Department of Oncology, University of Alberta, Edmonton, Canada.
| | - Hans-Sonke Jans
- Department of Oncology, University of Alberta, Edmonton, Canada
| | - Melinda Wuest
- Department of Oncology, University of Alberta, Edmonton, Canada
| | - Terence Riauka
- Department of Oncology, University of Alberta, Edmonton, Canada
| | - Frank Wuest
- Department of Oncology, University of Alberta, Edmonton, Canada
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Olde Heuvel J, de Wit-van der Veen BJ, Vyas KN, Tuch DS, Grootendorst MR, Stokkel MPM, Slump CH. Performance evaluation of Cerenkov luminescence imaging: a comparison of 68Ga with 18F. EJNMMI Phys 2019; 6:17. [PMID: 31650365 PMCID: PMC6813407 DOI: 10.1186/s40658-019-0255-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 09/27/2019] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Cerenkov Luminescence Imaging (CLI) is an emerging technology for intraoperative margin assessment. Previous research only evaluated radionuclide 18-Fluorine (18F); however, for future applications in prostate cancer, 68-Gallium (68Ga) seems more suitable, given its higher positron energy. Theoretical calculations predict that 68Ga should offer a higher signal-to-noise ratio than 18F; this is the first experimental confirmation. The aim of this study is to investigate the technical performance of CLI by comparing 68Ga to 18F. RESULTS The linearity of the system, detection limit, spatial resolution, and uniformity were determined with the LightPath imaging system. All experiments were conducted with clinically relevant activity levels in vitro, using dedicated phantoms. For both radionuclides, a linear relationship between the activity concentration and detected light yield was observed (R2 = 0.99). 68Ga showed approximately 22 times more detectable Cerenkov signal compared to 18F. The detectable activity concentration after a 120 s exposure time and 2 × 2 binning of 18F was 23.7 kBq/mL and 1.2 kBq/mL for 68Ga. The spatial resolution was 1.31 mm for 18F and 1.40 mm for 68Ga. The coefficient of variance of the uniformity phantom was 0.07 for the central field of view. CONCLUSION 68Ga was superior over 18F in terms of light yield and minimal detection limit. However, as could be expected, the resolution was 0.1 mm less for 68Ga. Given the clinical constraints of an acquisition time less than 120 s and a spatial resolution < 2 mm, CLI for intraoperative margin assessment using 68Ga could be feasible.
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Affiliation(s)
- J Olde Heuvel
- Department of Nuclear Medicine, Netherlands Cancer Institute, Amsterdam, The Netherlands. .,Robotics and Mechatronics , Technical Medical Centre, University of Twente, Enschede, The Netherlands.
| | | | - K N Vyas
- Lightpoint Medical Ltd, Misbourne Works, Waterside, Chesham, HP5 1PE, UK
| | - D S Tuch
- Lightpoint Medical Ltd, Misbourne Works, Waterside, Chesham, HP5 1PE, UK
| | - M R Grootendorst
- Lightpoint Medical Ltd, Misbourne Works, Waterside, Chesham, HP5 1PE, UK
| | - M P M Stokkel
- Department of Nuclear Medicine, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - C H Slump
- Robotics and Mechatronics , Technical Medical Centre, University of Twente, Enschede, The Netherlands
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Turgeon V, Kertzscher G, Carroll L, Hopewell R, Massarweh G, Enger SA. Characterization of scintillating fibers for use as positron detector in positron emission tomography. Phys Med 2019; 65:114-120. [PMID: 31450121 DOI: 10.1016/j.ejmp.2019.08.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 07/15/2019] [Accepted: 08/11/2019] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Manual and automatic blood sampling at different time intervals is considered the gold standard to determine the arterial input function (AIF) in dynamic positron emission tomography (PET). However, blood sampling is characterized by poor time resolution and is an invasive procedure. The aim of this study was to characterize the scintillating fibers used to develop a non-invasive positron detector. METHODS The detector consists of a scintillating fiber coupled at each end to transmission fiber-optic cables that are connected to photo multiplier tubes in a dual readout setup. The detector is designed to be wrapped around the wrist of the patient undergoing dynamic PET. The attenuation length and bending losses were measured with excitation from gamma radiation (137Cs) and ultraviolet (UV) light. The response to positron-emitting radio-tracers was evaluated with 18F and 11C. RESULTS The attenuation length for a 3.0 m and 1.5 m long scintillating fiber both coincides with the attenuation length given by the manufacturer when excited with the 137Cs source, but not with the UV source due to the differences in scintillation mechanisms. The bending losses are smaller than the measurement uncertainty for the 137Cs source irradiation, and increase when the bending radius decrease for the UV source irradiation. The signal-to-noise ratio for 18F and 11C solutions are 1.98 and 22.54 respectively. The measured decay constant of 11C agrees with its characteristic value. CONCLUSION The performed measurements in the dual readout configuration suggest that scintillating fibers may be suitable to determine the AIF non-invasively.
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Affiliation(s)
- Vincent Turgeon
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Jewish General Hospital, Montreal, Quebec, Canada.
| | | | - Liam Carroll
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada
| | - Robert Hopewell
- Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
| | - Gassan Massarweh
- Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada
| | - Shirin A Enger
- Medical Physics Unit, McGill University, Montreal, Quebec, Canada; Department of Oncology, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
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Yang J, Park D, Gullberg GT, Seo Y. Joint correction of attenuation and scatter in image space using deep convolutional neural networks for dedicated brain 18F-FDG PET. Phys Med Biol 2019; 64:075019. [PMID: 30743246 DOI: 10.1088/1361-6560/ab0606] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Dedicated brain positron emission tomography (PET) devices can provide higher-resolution images with much lower doses compared to conventional whole-body PET systems, which is important to support PET neuroimaging and particularly useful for the diagnosis of neurodegenerative diseases. However, when a dedicated brain PET scanner does not come with a combined CT or transmission source, there is no direct solution for accurate attenuation and scatter correction, both of which are critical for quantitative PET. To address this problem, we propose joint attenuation and scatter correction (ASC) in image space for non-corrected PET (PETNC) using deep convolutional neural networks (DCNNs). This approach is a one-step process, distinct from conventional methods that rely on generating attenuation maps first that are then applied to iterative scatter simulation in sinogram space. For training and validation, time-of-flight PET/MR scans and additional helical CTs were performed for 35 subjects (25/10 split for training and test dataset). A DCNN model was proposed and trained to convert PETNC to DCNN-based ASC PET (PETDCNN) directly in image space. For quantitative evaluation, uptake differences between PETDCNN and reference CT-based ASC PET (PETCT-ASC) were computed for 116 automated anatomical labels (AALs) across 10 test subjects (1160 regions in total). MR-based ASC PET (PETMR-ASC), a current clinical protocol in PET/MR imaging, was another reference for comparison. Statistical significance was assessed using a paired t test. The performance of PETDCNN was comparable to that of PETMR-ASC, in comparison to reference PETCT-ASC. The mean SUV differences (mean ± SD) from PETCT-ASC were 4.0% ± 15.4% (P < 0.001) and -4.2% ± 4.3% (P < 0.001) for PETDCNN and PETMR-ASC, respectively. The overall larger variation of PETDCNN (15.4%) was prone to the subject with the highest mean difference (48.5% ± 10.4%). The mean difference of PETDCNN excluding the subject was substantially improved to -0.8% ± 5.2% (P < 0.001), which was lower than that of PETMR-ASC (-5.07% ± 3.60%, P < 0.001). In conclusion, we demonstrated the feasibility of directly producing PET images corrected for attenuation and scatter using a DCNN (PETDCNN) from PETNC in image space without requiring conventional attenuation map generation and time-consuming scatter correction. Additionally, our DCNN-based method provides a possible alternative to MR-ASC for simultaneous PET/MRI.
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Affiliation(s)
- Jaewon Yang
- Physics Research Laboratory, Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States of America. UCSF Physics Research Laboratory, 185 Berry Street, Suite 350, San Francisco, CA 94143-0946, United States of America. Author to whom any correspondence should be addressed
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Price TW, Greenman J, Stasiuk GJ. Current advances in ligand design for inorganic positron emission tomography tracers 68Ga, 64Cu, 89Zr and 44Sc. Dalton Trans 2018; 45:15702-15724. [PMID: 26865360 DOI: 10.1039/c5dt04706d] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A key part of the development of metal based Positron Emission Tomography probes is the chelation of the radiometal. In this review the recent developments in the chelation of four positron emitting radiometals, 68Ga, 64Cu, 89Zr and 44Sc, are explored. The factors that effect the chelation of each radio metal and the ideal ligand system will be discussed with regards to high in vivo stability, complexation conditions, conjugation to targeting motifs and complexation kinetics. A series of cyclic, cross-bridged and acyclic ligands will be discussed, such as CP256 which forms stable complexes with 68Ga under mild conditions and PCB-TE2A which has been shown to form a highly stable complex with 64Cu. 89Zr and 44Sc have seen significant development in recent years with a number of chelates being applied to each metal - eight coordinate di-macrocyclic terephthalamide ligands were found to rapidly produce more stable complexes with 89Zr than the widely used DFO.
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Affiliation(s)
- Thomas W Price
- School of Biological, Biomedical and Environmental Sciences, The University of Hull, HU6 7RX, UK. and Positron Emission Tomography Research Centre, The University of Hull, HU6 7RX, UK
| | - John Greenman
- School of Biological, Biomedical and Environmental Sciences, The University of Hull, HU6 7RX, UK.
| | - Graeme J Stasiuk
- School of Biological, Biomedical and Environmental Sciences, The University of Hull, HU6 7RX, UK. and Positron Emission Tomography Research Centre, The University of Hull, HU6 7RX, UK
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12
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Jackson IM, Scott PJ, Thompson S. Clinical Applications of Radiolabeled Peptides for PET. Semin Nucl Med 2017; 47:493-523. [DOI: 10.1053/j.semnuclmed.2017.05.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Alva-Sánchez H, Quintana-Bautista C, Martínez-Dávalos A, Ávila-Rodríguez MA, Rodríguez-Villafuerte M. Positron range in tissue-equivalent materials: experimental microPET studies. Phys Med Biol 2016; 61:6307-21. [PMID: 27494279 DOI: 10.1088/0031-9155/61/17/6307] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this work an experimental investigation was carried out to study the effect that positron range has over positron emission tomography (PET) scans through measurements of the line spread function (LSF) in tissue-equivalent materials. Line-sources consisted of thin capillary tubes filled with (18)F, (13)N or (68)Ga water-solution inserted along the axis of symmetry of cylindrical phantoms constructed with the tissue-equivalent materials: lung (inhale and exhale), adipose tissue, solid water, trabecular and cortical bone. PET scans were performed with a commercial small-animal PET scanner and image reconstruction was carried out with filtered-backprojection. Line-source distributions were analyzed using radial profiles taken on axial slices from which the spatial resolution was determined through the full-width at half-maximum, tenth-maximum, twentieth-maximum and fiftieth-maximum. A double-Gaussian model of the LSFs was used to fit experimental data which can be incorporated into iterative reconstruction methods. In addition, the maximum activity concentration in the line-sources was determined from reconstructed images and compared to the known values for each case. The experimental data indicates that positron range in different materials has a strong effect on both spatial resolution and activity concentration quantification in PET scans. Consequently, extra care should be taken when computing standard-uptake values in PET scans, in particular when the radiopharmaceutical is taken up by different tissues in the body, and more even so with high-energy positron emitters.
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Affiliation(s)
- H Alva-Sánchez
- Instituto de Física, Universidad Nacional Autónoma de México, Mexico City, Mexico
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Fraile L, Herraiz J, Udías J, Cal-González J, Corzo P, España S, Herranz E, Pérez-Liva M, Picado E, Vicente E, Muñoz-Martín A, Vaquero J. Experimental validation of gallium production and isotope-dependent positron range correction in PET. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2016. [DOI: 10.1016/j.nima.2016.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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15
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System models for PET statistical iterative reconstruction: A review. Comput Med Imaging Graph 2016; 48:30-48. [DOI: 10.1016/j.compmedimag.2015.12.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 10/09/2015] [Accepted: 12/09/2015] [Indexed: 02/03/2023]
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16
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Cal-González J, Pérez-Liva M, Herraiz JL, Vaquero JJ, Desco M, Udías JM. Tissue-Dependent and Spatially-Variant Positron Range Correction in 3D PET. IEEE TRANSACTIONS ON MEDICAL IMAGING 2015; 34:2394-403. [PMID: 26011878 DOI: 10.1109/tmi.2015.2436711] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Positron range (PR) is a significant factor that limits PET image resolution, especially with some radionuclides currently used in clinical and preclinical studies such as (82)Rb, (124)I and (68)Ga. The use of an accurate model of the PR in the image reconstruction may minimize its impact on the image quality. Nevertheless, PR distributions are difficult to model, as they may be different at each voxel and direction, depending on the materials that the positron flies through. Several approximated methods have been proposed, considering only one or several propagating media without taking into account boundaries effects. In some regions, like lungs or trachea, these methods may not be accurate enough and yield artifacts. In this work, we present an efficient method to accurately incorporate spatially-variant PR corrections. The method is based on pre-computing voxel-dependent PR kernels using a CT or a manually segmented image, and a model of the dependence of the PR on each material derived from Monte Carlo simulations. The images are convoluted with these kernels in the forward-projection step of the iterative reconstruction algorithm. This implementation of the algorithm adds a modest overhead to the overall reconstruction time and it obtains artifact-free PR-corrected images, even when the activity is concentrated at tissue boundaries with extreme changes of density. We verified the method with the preclinical Argus PET/CT scanner, but it can be also applied to other scanners and improve the image quality in clinical PET studies using isotopes with large PR.
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Jødal L, Le Loirec C, Champion C. Positron range in PET imaging: non-conventional isotopes. Phys Med Biol 2014; 59:7419-34. [PMID: 25386999 DOI: 10.1088/0031-9155/59/23/7419] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In addition to conventional short-lived radionuclides, longer-lived isotopes are becoming increasingly important to positron emission tomography (PET). The longer half-life both allows for circumvention of the in-house production of radionuclides, and expands the spectrum of physiological processes amenable to PET imaging, including processes with prohibitively slow kinetics for investigation with short-lived radiotracers. However, many of these radionuclides emit 'high-energy' positrons and gamma rays which affect the spatial resolution and quantitative accuracy of PET images. The objective of the present work is to investigate the positron range distribution for some of these long-lived isotopes. Based on existing Monte Carlo simulations of positron interactions in water, the probability distribution of the line of response displacement have been empirically described by means of analytic displacement functions. Relevant distributions have been derived for the isotopes (22)Na, (52)Mn, (89)Zr, (45)Ti, (51)Mn, (94 m)Tc, (52 m)Mn, (38)K, (64)Cu, (86)Y, (124)I, and (120)I. It was found that the distribution functions previously found for a series of conventional isotopes (Jødal et al 2012 Phys. Med. Bio. 57 3931-43), were also applicable to these non-conventional isotopes, except that for (120)I, (124)I, (89)Zr, (52)Mn, and (64)Cu, parameters in the formulae were less well predicted by mean positron energy alone. Both conventional and non-conventional range distributions can be described by relatively simple analytic expressions. The results will be applicable to image-reconstruction software to improve the resolution.
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Affiliation(s)
- L Jødal
- Department of Nuclear Medicine, Aalborg University Hospital, Aalborg, Denmark
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Lu CC, Lin HH, Chuang KS, Dong SL, Wu J, Ni YC, Jan ML. Development and validation of a fast voxel-based dose evaluation system in nuclear medicine. Radiat Phys Chem Oxf Engl 1993 2014. [DOI: 10.1016/j.radphyschem.2014.01.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Shah NJ, Herzog H, Weirich C, Tellmann L, Kaffanke J, Caldeira L, Kops ER, Qaim SM, Coenen HH, Iida H. Effects of magnetic fields of up to 9.4 T on resolution and contrast of PET images as measured with an MR-BrainPET. PLoS One 2014; 9:e95250. [PMID: 24755872 PMCID: PMC3995683 DOI: 10.1371/journal.pone.0095250] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/25/2014] [Indexed: 11/18/2022] Open
Abstract
Simultaneous, hybrid MR-PET is expected to improve PET image resolution in the plane perpendicular to the static magnetic field of the scanner. Previous papers have reported this either by simulation or experiment with simple sources and detector arrangements. Here, we extend those studies using a realistic brain phantom in a recently installed MR-PET system comprising a 9.4 T MRI-scanner and an APD-based BrainPET insert in the magnet bore. Point and line sources and a 3D brain phantom were filled with 18F (low-energy positron emitter), 68Ga (medium energy positron emitter) or 120I, a non-standard positron emitter (high positron energies of up to 4.6 MeV). Using the BrainPET insert, emission scans of the phantoms were recorded at different positions inside and outside the magnet bore such that the magnetic field was 0 T, 3 T, 7 T or 9.4 T. Brain phantom images, with the 'grey matter' compartment filled with 18F, showed no obvious resolution improvement with increasing field. This is confirmed by practically unchanged transaxial FWHM and 'grey/white matter' ratio values between at 0T and 9.4T. Field-dependent improvements in the resolution and contrast of transaxial PET images were clearly evident when the brain phantom was filled with 68Ga or 120I. The grey/white matter ratio increased by 7.3% and 16.3%, respectively. The greater reduction of the FWTM compared to FWHM in 68Ga or 120I line-spread images was in agreement with the improved contrast of 68Ga or 120I images. Notwithstanding elongations seen in the z-direction of 68Ga or 120I point source images acquired in foam, brain phantom images show no comparable extension. Our experimental study confirms that integrated MR-PET delivers improved PET image resolution and contrast for medium- and high-energy positron emitters even though the positron range is reduced only in directions perpendicular to the magnetic field.
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Affiliation(s)
- N. Jon Shah
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
- Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany
| | - Hans Herzog
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Christoph Weirich
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Lutz Tellmann
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Joachim Kaffanke
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Liliana Caldeira
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Elena Rota Kops
- Institute of Neuroscience and Medicine, INM-4: Medical Imaging Physics, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Syed M. Qaim
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Heinz H. Coenen
- Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Hidehiro Iida
- Department of Investigative Radiology, National Cardiovascular Center Research Institute, Osaka, Japan
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Majo VJ, Milak MS, Prabhakaran J, Mali P, Savenkova L, Simpson NR, Mann JJ, Parsey RV, Dileep Kumar JS. Synthesis and in vivo evaluation of [(18)F]2-(4-(4-(2-(2-fluoroethoxy)phenyl)piperazin-1-yl)butyl)-4-methyl-1,2,4-triazine-3,5(2H,4H)-dione ([(18)F]FECUMI-101) as an imaging probe for 5-HT1A receptor agonist in nonhuman primates. Bioorg Med Chem 2013; 21:5598-604. [PMID: 23816046 PMCID: PMC3858174 DOI: 10.1016/j.bmc.2013.05.050] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/09/2013] [Accepted: 05/17/2013] [Indexed: 10/26/2022]
Abstract
The 5-HT1AR partial agonist PET radiotracer, [(11)C]CUMI-101, has advantages over an antagonist radiotracer as it binds preferentially to the high affinity state of the receptor and thereby provides more functionally meaningful information. The major drawback of C-11 tracers is the lack of cyclotron facility in many health care centers thereby limiting widespread clinical or research use. We identified the fluoroethyl derivative, 2-(4-(4-(2-(2-fluoroethoxy)phenyl)piperazin-1-yl)butyl)-4-methyl-1,2,4-triazine-3,5(2H,4H)dione (FECUMI-101) (Ki=0.1nM; Emax=77%; EC50=0.65nM) as a partial agonist 5-HT1AR ligand of the parent ligand CUMI-101. FECUMI-101 is radiolabeled with F-18 by O-fluoroethylation of the corresponding desmethyl analogue (1) with [(18)F]fluoroethyltosylate in DMSO in the presence of 1.6equiv of K2CO3 in 45±5% yield (EOS). PET shows [(18)F]FECUMI-101 binds specifically to 5-HT1AR enriched brain regions of baboon. The specificity of [(18)F]FECUMI-101 binding to 5-HT1AR was confirmed by challenge studies with the known 5-HT1AR ligand WAY100635. These findings indicate that [(18)F]FECUMI-101 can be a viable agonist ligand for the in vivo quantification of high affinity 5-HT1AR with PET.
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Affiliation(s)
- Vattoly J. Majo
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
| | - Matthew S. Milak
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York
| | - Jaya Prabhakaran
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
| | - Pratap Mali
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York
| | - Lyudmila Savenkova
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
| | - Norman R. Simpson
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York
| | - J. John Mann
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York
- Department of Radiology, Columbia University, New York, NY 10032
| | - Ramin V. Parsey
- Department of Psychiatry and Behavioral Science, Stony Brook University, New York
| | - J. S. Dileep Kumar
- Department of Psychiatry, Columbia University Medical Center, Columbia University, New York
- Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York
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Cal-González J, Herraiz JL, España S, Corzo PMG, Vaquero JJ, Desco M, Udias JM. Positron range estimations with PeneloPET. Phys Med Biol 2013; 58:5127-52. [PMID: 23835700 DOI: 10.1088/0031-9155/58/15/5127] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Technical advances towards high resolution PET imaging try to overcome the inherent physical limitations to spatial resolution. Positrons travel in tissue until they annihilate into the two gamma photons detected. This range is the main detector-independent contribution to PET imaging blurring. To a large extent, it can be remedied during image reconstruction if accurate estimates of positron range are available. However, the existing estimates differ, and the comparison with the scarce experimental data available is not conclusive. In this work we present positron annihilation distributions obtained from Monte Carlo simulations with the PeneloPET simulation toolkit, for several common PET isotopes ((18)F, (11)C, (13)N, (15)O, (68)Ga and (82)Rb) in different biological media (cortical bone, soft bone, skin, muscle striated, brain, water, adipose tissue and lung). We compare PeneloPET simulations against experimental data and other simulation results available in the literature. To this end the different positron range representations employed in the literature are related to each other by means of a new parameterization for positron range profiles. Our results are generally consistent with experiments and with most simulations previously reported with differences of less than 20% in the mean and maximum range values. From these results, we conclude that better experimental measurements are needed, especially to disentangle the effect of positronium formation in positron range. Finally, with the aid of PeneloPET, we confirm that scaling approaches can be used to obtain universal, material and isotope independent, positron range profiles, which would considerably simplify range correction.
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Affiliation(s)
- J Cal-González
- Grupo de Física Nuclear, Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Spain
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Cal-González J, Herraiz JL, España S, Corzo PMG, Vaquero JJ, Desco M, Udias JM. Positron range estimations with PeneloPET. Phys Med Biol 2013. [DOI: https://doi.org/10.1088/0031-9155/58/15/5127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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23
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Hicks RJ, Hofman MS. Is there still a role for SPECT-CT in oncology in the PET-CT era? Nat Rev Clin Oncol 2012; 9:712-20. [PMID: 23149896 DOI: 10.1038/nrclinonc.2012.188] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
For the evaluation of biological processes using radioisotopes, there are two competing technologies: single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Both are tomographic techniques that enable 3D localization and can be combined with CT for hybrid imaging. PET-CT has clear technical superiority including superior resolution, speed and quantitative capability. SPECT-CT currently has greater accessibility, lower cost and availability of a wider range of approved radiotracers. However, the past decade has seen dramatic growth in PET-CT with decreasing costs and development of an increasing array of PET tracers that can substitute existing SPECT applications. PET-CT is also changing the paradigm of imaging from lesion measurement to lesion characterization and target quantification, supporting a new era of personalized cancer therapy. The efficiency and cost savings associated with improved diagnosis and clinical decision-making provided by PET-CT make a cogent argument for it becoming the dominant molecular technique in oncology.
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Affiliation(s)
- Rodney J Hicks
- University of Melbourne, Departments of Medicine and Radiology, The Peter MacCallum Cancer Centre, 7 St Andrew's Place, Melbourne, VIC 3002, Australia.
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24
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Microfluidic reactor geometries for radiolysis reduction in radiopharmaceuticals. Appl Radiat Isot 2012; 70:1691-7. [PMID: 22750198 DOI: 10.1016/j.apradiso.2012.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 02/24/2012] [Accepted: 03/01/2012] [Indexed: 12/18/2022]
Abstract
Autoradiolysis describes the degradation of radioactively labeled compounds due to the activity of the labeled compounds themselves. It scales with activity concentration and is of importance for high activity and microfluidic PET tracer synthesis. This study shows that microfluidic devices can be shaped to reduce autoradiolysis by geometric exclusion of positron interaction. A model is developed and confirmed by demonstrating in-capillary storage of non-stabilized [(18)F]FDG (2-[(18)F]Fluoro-2-deoxy-d-glucose) at max. 23 GBq/ml while maintaining >90% radiochemical purity over 14 h.
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Cal-González J, Herraiz J, España S, Vicente E, Herranz E, Desco M, Vaquero J, Udías J. Study of CT-based positron range correction in high resolution 3D PET imaging. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2011. [DOI: 10.1016/j.nima.2010.12.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Lehnert W, Gregoire MC, Reilhac A, Meikle SR. Analytical positron range modelling in heterogeneous media for PET Monte Carlo simulation. Phys Med Biol 2011; 56:3313-35. [PMID: 21558591 DOI: 10.1088/0031-9155/56/11/009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Monte Carlo simulation codes that model positron interactions along their tortuous path are expected to be accurate but are usually slow. A simpler and potentially faster approach is to model positron range from analytical annihilation density distributions. The aims of this paper were to efficiently implement and validate such a method, with the addition of medium heterogeneity representing a further challenge. The analytical positron range model was evaluated by comparing annihilation density distributions with those produced by the Monte Carlo simulator GATE and by quantitatively analysing the final reconstructed images of Monte Carlo simulated data. In addition, the influence of positronium formation on positron range and hence on the performance of Monte Carlo simulation was investigated. The results demonstrate that 1D annihilation density distributions for different isotope-media combinations can be fitted with Gaussian functions and hence be described by simple look-up-tables of fitting coefficients. Together with the method developed for simulating positron range in heterogeneous media, this allows for efficient modelling of positron range in Monte Carlo simulation. The level of agreement of the analytical model with GATE depends somewhat on the simulated scanner and the particular research task, but appears to be suitable for lower energy positron emitters, such as (18)F or (11)C. No reliable conclusion about the influence of positronium formation on positron range and simulation accuracy could be drawn.
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Affiliation(s)
- Wencke Lehnert
- Discipline of Medical Radiation Sciences, Faculty of Health Sciences, University of Sydney, PO Box 170, Lidcombe NSW 1825, Australia.
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28
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Kemerink GJ, Visser MGW, Franssen R, Beijer E, Zamburlini M, Halders SGEA, Brans B, Mottaghy FM, Teule GJJ. Effect of the positron range of 18F, 68Ga and 124I on PET/CT in lung-equivalent materials. Eur J Nucl Med Mol Imaging 2011; 38:940-8. [PMID: 21287170 DOI: 10.1007/s00259-011-1732-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 01/04/2011] [Indexed: 11/28/2022]
Abstract
PURPOSE The aim of this study was to investigate the effect of positron range on visualization and quantification in (18)F, (68)Ga and (124)I positron emission tomography (PET)/CT of lung-like tissue. METHODS Different sources were measured in air, in lung-equivalent foams and in water, using a clinical PET/CT and a microPET system. Intensity profiles and curves with the cumulative number of annihilations were derived and numerically characterized. RESULTS (68)Ga and (124)I gave similar results. Their intensity profiles in lung-like foam had a peak similar to that for (18)F, and tails of very low intensity, but extending over distances of centimetres and containing a large fraction of all annihilations. For 90% recovery, volumes of interest with diameters up to 50 mm were required, and recovery within the 10% intensity isocontour was as low as 30%. In contrast, tailing was minor for (18)F. CONCLUSION Lung lesions containing (18)F, (68)Ga or (124)I will be visualized similarly, and at least as sharp as in soft tissue. Nevertheless, for quantification of (68)Ga and (124)I large volumes of interest are needed for complete activity recovery. For clinical studies containing noise and background, new quantification approaches may have to be developed.
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Affiliation(s)
- Gerrit J Kemerink
- Department of Nuclear Medicine, Maastricht University Medical Center, PO Box 5800, 6202 AZ Maastricht, The Netherlands.
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Brawley SJ, Armitage S, Beale J, Leslie DE, Williams AI, Laricchia G. Electron-like scattering of positronium. Science 2010; 330:789. [PMID: 21051631 DOI: 10.1126/science.1192322] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Positronium (Ps), a hydrogen-like atom composed of an electron and its antimatter partner, the positron, is formed in considerable quantities whenever positrons interact with matter. It has unexpectedly been found to scatter from a wide variety of atoms and molecules in a way very similar to that of a bare electron moving at the same velocity, despite Ps being neutral and twice the mass.
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Affiliation(s)
- S J Brawley
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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Alessio AM, Stearns CW, Tong S, Ross SG, Kohlmyer S, Ganin A, Kinahan PE. Application and evaluation of a measured spatially variant system model for PET image reconstruction. IEEE TRANSACTIONS ON MEDICAL IMAGING 2010; 29:938-49. [PMID: 20199927 PMCID: PMC2903538 DOI: 10.1109/tmi.2010.2040188] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Accurate system modeling in tomographic image reconstruction has been shown to reduce the spatial variance of resolution and improve quantitative accuracy. System modeling can be improved through analytic calculations, Monte Carlo simulations, and physical measurements. The purpose of this work is to improve clinical fully-3-D reconstruction without substantially increasing computation time. We present a practical method for measuring the detector blurring component of a whole-body positron emission tomography (PET) system to form an approximate system model for use with fully-3-D reconstruction. We employ Monte Carlo simulations to show that a non-collimated point source is acceptable for modeling the radial blurring present in a PET tomograph and we justify the use of a Na22 point source for collecting these measurements. We measure the system response on a whole-body scanner, simplify it to a 2-D function, and incorporate a parameterized version of this response into a modified fully-3-D OSEM algorithm. Empirical testing of the signal versus noise benefits reveal roughly a 15% improvement in spatial resolution and 10% improvement in contrast at matched image noise levels. Convergence analysis demonstrates improved resolution and contrast versus noise properties can be achieved with the proposed method with similar computation time as the conventional approach. Comparison of the measured spatially variant and invariant reconstruction revealed similar performance with conventional image metrics. Edge artifacts, which are a common artifact of resolution-modeled reconstruction methods, were less apparent in the spatially variant method than in the invariant method. With the proposed and other resolution-modeled reconstruction methods, edge artifacts need to be studied in more detail to determine the optimal tradeoff of resolution/contrast enhancement and edge fidelity.
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Affiliation(s)
- Adam M Alessio
- Department of Radiology, University of Washington Medical Center, Seattle, WA 98195, USA.
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Hasegawa T, Yoshida E, Shibuya K, Murayama H. Optical observation of energy loss distribution and practical range of positrons from a 18F water solution in a water-equivalent phantom. Med Phys 2009; 36:402-10. [PMID: 19291979 DOI: 10.1118/1.3054765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The energy loss distribution of beta+ particles is closely related to their maximum penetration depth distribution and annihilation point distribution. The latter is of practical importance for positron emission tomography. Experimental data related to the energy loss distribution are important for comprehensive validation of physics and simulation models of beta+ interactions. In this paper the authors present a new experimental approach that allows them to visually observe the beta+ energy loss distribution of a solution of nuclear medicine radioisotopes in a plastic scintillator using an optical camera. The authors also report a set of the first experimental results. A water solution of 18F was localized in a small hole in a plastic scintillator (BC430). Optical imaging of the scintillator yielded visual images of the energy loss distribution with a submillimeter resolution. The radial dependence in the energy distribution was quantitatively measured by analysis of the images, and exponential fitting parameters were obtained. The authors observed that the results of Monte Carlo simulation with EGS5 (version 1.0.2) and GEANT4 (version 4.9.01.p01) were consistent with those obtained experimentally. The results of the Monte Carlo simulation indicated that for a linear scale, the energy loss distribution in the scintillator was approximately the same as that in water, and the relative shape of the energy loss distribution was close to those of the maximum penetration depth distribution and annihilation point distribution. This paper also presents discussions about the further possibilities of this optical imaging approach. Thus, optical observation of the beta+ energy loss distribution in a scintillator is a promising technique for visual and quantitative experimental studies of beta+ emission from a solution of radioisotopes that are used in nuclear medicine.
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Affiliation(s)
- Tomoyuki Hasegawa
- Allied Health Sciences, Kitasato University, Kitasato 1-15-1, Sagamihara, Kanagawa 228-8555, Japan.
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Alessio A, MacDonald L. Spatially Variant Positron Range Modeling Derived from CT for PET Image Reconstruction. IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD. NUCLEAR SCIENCE SYMPOSIUM 2008; 2008:3637-3640. [PMID: 24839389 DOI: 10.1109/nssmic.2008.4774106] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The influence of a finite positron annihilation distance represents a fundamental limit to the spatial resolution of PET scanners. It is appreciated that this effect is a minor concern in whole-body F18 imaging, but it does represent an issue when imaging with higher energy isotopes such as N13 or Rb82. This effect is especially relevant for imaging tasks along tissue gradients such as the cardiac/lung boundary and diaphragm/lung boundary. This work presents a method to determine the positron range effect from a CT scan and to model this effect as shift-variant, anisotropic kernels. The positron annihilation distance across boundaries of tissues is represented with a simple model, which can be quickly derived from CT scans and applied in the reconstruction of PET images. The positron range compensation map is applied in a modified OSEM algorithm to simulated and measured data.
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Affiliation(s)
- Adam Alessio
- A. Alessio and L. MacDonald are with the Dept. of Radiology, University of Washington, Seattle, WA 98195 USA. (telephone: (206)543-2419, )
| | - Lawrence MacDonald
- A. Alessio and L. MacDonald are with the Dept. of Radiology, University of Washington, Seattle, WA 98195 USA. (telephone: (206)543-2419, )
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Lee K, Fox PT, Lancaster JL, Jerabek PA. A positron-probe system for arterial input function quantification for positron emission tomography in humans. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:064301. [PMID: 18601420 PMCID: PMC2678789 DOI: 10.1063/1.2936880] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Accepted: 05/03/2008] [Indexed: 05/26/2023]
Abstract
We developed an intra-arterial positron-probe (beta(+)-probe) system to measure the arterial time-activity concentration in humans for quantitative compartmental modeling of positron emission tomography studies. Performance was characterized in vitro, by using a uniform phantom to calculate dead time, linearity, and absolute detector sensitivity. In vitro evaluations in a uniform phantom showed a system dead time of 2.5 micros, linear regression between measured and true count rates with R(2)=0.999, and detector sensitivity of 6.9-7.0 counts/s kBq(-1) ml. These met or exceeded values of previously reported systems.
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Affiliation(s)
- Kihak Lee
- Research Imaging Center, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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