1
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Wang X, Wang T, Fan X, Zhang Z, Wang Y, Li Z. A Molecular Toolbox of Positron Emission Tomography Tracers for General Anesthesia Mechanism Research. J Med Chem 2023; 66:6463-6497. [PMID: 37145921 DOI: 10.1021/acs.jmedchem.2c01965] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
With appropriate radiotracers, positron emission tomography (PET) allows direct or indirect monitoring of the spatial and temporal distribution of anesthetics, neurotransmitters, and biomarkers, making it an indispensable tool for studying the general anesthesia mechanism. In this Perspective, PET tracers that have been recruited in general anesthesia research are introduced in the following order: 1) 11C/18F-labeled anesthetics, i.e., PET tracers made from inhaled and intravenous anesthetics; 2) PET tracers targeting anesthesia-related receptors, e.g., neurotransmitters and voltage-gated ion channels; and 3) PET tracers for studying anesthesia-related neurophysiological effects and neurotoxicity. The radiosynthesis, pharmacodynamics, and pharmacokinetics of the above PET tracers are mainly discussed to provide a practical molecular toolbox for radiochemists, anesthesiologists, and those who are interested in general anesthesia.
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Affiliation(s)
- Xiaoxiao Wang
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Tao Wang
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Xiaowei Fan
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Zhao Zhang
- Department of Anesthesiology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yingwei Wang
- Department of Anesthesiology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Zijing Li
- Center for Molecular Imaging and Translational Medicine, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, Department of Laboratory Medicine, School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
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2
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Measurement of Protein Synthesis Rate in Rat by [11C]Leucine PET Imaging: Application to the TgF344-AD Model of Alzheimer’s Disease. Mol Imaging Biol 2022; 25:596-605. [PMID: 36538180 PMCID: PMC10172255 DOI: 10.1007/s11307-022-01796-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 12/03/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022]
Abstract
AbstractLong-term memory requires stable protein synthesis and is altered in Alzheimer’s disease (AD). This study aimed to implement a method to measure the cerebral protein synthesis rate (PSR) with [11C]leucine PET in vivo in rats and evaluate potential PSR alterations longitudinally (6, 12 and 18 months old) in the TgF344-AD rat model of AD. Wistar, wild-type (WT) and TgF344-AD rats (TG) were scanned for 60 min with [11C]leucine. Arterial blood activity was monitored online and with discrete whole blood and plasma samples by γ-counting in Wistar rats, WT (n = 4) and TG (n = 5). Unlabelled amino acids were measured in plasma. The sensitivity of [11C]leucine PET to measure alterations in PSR was assessed in Wistar rats by injection of PSR inhibitor anisomycin before PET acquisition. Anisomycin administration significantly reduced the net uptake rate constant (Kcplx) of [11C]leucine and PSR, proving the suitability of the method. For the longitudinal study, averaged population-based input functions were used to calculate PSR. We found a significant genotype effect on PSR (decrease in TG vs WT) only in the globus pallidus. This study suggests that [11C]leucine PET is sensitive enough to measure brain PSR in rat but that cross-sectional design with individual input function should be preferred.
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3
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Shegani A, Kealey S, Luzi F, Basagni F, Machado JDM, Ekici SD, Ferocino A, Gee AD, Bongarzone S. Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds. Chem Rev 2022; 123:105-229. [PMID: 36399832 PMCID: PMC9837829 DOI: 10.1021/acs.chemrev.2c00398] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.
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Affiliation(s)
- Antonio Shegani
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
| | - Steven Kealey
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
| | - Federico Luzi
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
| | - Filippo Basagni
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum−University of Bologna, via Belmeloro 6, 40126 Bologna, Italy
| | - Joana do Mar Machado
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
| | - Sevban Doğan Ekici
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom
| | - Alessandra Ferocino
- Institute
of Organic Synthesis and Photoreactivity, Italian National Research Council, via Piero Gobetti 101, 40129 Bologna, Italy
| | - Antony D. Gee
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom,A.G.: email,
| | - Salvatore Bongarzone
- School
of Biomedical Engineering & Imaging Sciences, King’s College London, King’s Health Partners, St Thomas’ Hospital, London SE1 7EH, United Kingdom,S.B.:
email,
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4
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Schmidt KC, Loutaev I, Burlin TV, Thurm A, Sheeler C, Smith CB. Decreased rates of cerebral protein synthesis in conscious young adults with fragile X syndrome demonstrated by L-[1- 11C]leucine PET. J Cereb Blood Flow Metab 2022; 42:1666-1675. [PMID: 35350914 PMCID: PMC9441731 DOI: 10.1177/0271678x221090997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. Fragile X mental retardation protein, a putative translation suppressor, is significantly reduced in FXS. The prevailing hypothesis is that rates of cerebral protein synthesis (rCPS) are increased by the absence of this regulatory protein. We have previously reported increased rCPS in the Fmr1 knockout mouse model of FXS. To address the hypothesis in human subjects, we measured rCPS in young men with FXS with L-[1-11C]leucine PET. In previous studies we had used sedation during imaging, and we did not find increases in rCPS as had been seen in the mouse model. Since mouse measurements were conducted in awake animals, we considered the possibility that sedation may have confounded our results. In the present study we used a modified and validated PET protocol that made it easier for participants with FXS to undergo the study awake. We compared rCPS in 10 fragile X participants and 16 healthy controls all studied while awake. Contrary to the prevailing hypothesis and findings in Fmr1 knockout mice, results indicate that rCPS in awake participants with FXS are decreased in whole brain and most brain regions by 13-21% compared to healthy controls.
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Affiliation(s)
- Kathleen C Schmidt
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Inna Loutaev
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Thomas V Burlin
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Audrey Thurm
- Neurodevelopmental and Behavioral Phenotyping Service, Office of the Clinical Director, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Carrie Sheeler
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Carolyn Beebe Smith
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
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5
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Takatani S, Tahara T, Tsuji M, Ozaki D, Shibata N, Hashizume Y, Suzuki M, Onoe H, Watanabe Y, Doi H. Synthesis of L-[5- 11 C]Leucine and L-α-[5- 11 C]Methylleucine via Pd 0 -mediated 11 C-Methylation and Microfluidic Hydrogenation: Potentiality of Leucine PET Probes for Tumor Imaging. ChemMedChem 2021; 16:3271-3279. [PMID: 34128324 DOI: 10.1002/cmdc.202100255] [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: 04/08/2021] [Indexed: 11/06/2022]
Abstract
The efficient synthesis of L-[5-11 C]leucine and L-α-[5-11 C]methylleucine has been investigated using a continuous two-step sequence of rapid reactions consisting of Pd0 -mediated 11 C-methylation and microfluidic hydrogenation. The synthesis of L-[5-11 C]leucine and L-α-[5-11 C]methylleucine was accomplished within 40 min with a decay-corrected radiochemical yield of 15-38 % based on [11 C]CH3 I, radiochemical purity of 95-99 %, and chemical purity of 95-99 %. The Pd impurities in the injectable solution measured using inductively coupled plasma mass spectrometry met the international criteria for human use. Positron emission tomography scanning after an intravenous injection of L-[5-11 C]leucine or L-α-[5-11 C]methyl leucine in A431 tumor-bearing mice was performed. As a result, L-α-[5-11 C]methylleucine was found to be a potentially useful probe for visualizing the tumor. Tissue distribution analysis showed that the accumulation value of L-α-[5-11 C]methylleucine in tumor tissue was high [12±3% injected dose/g tissue (%ID/g)].
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Affiliation(s)
- Shuhei Takatani
- Laboratory for Labeling Chemistry, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Tsuyoshi Tahara
- Laboratory for Biofunction Dynamics Imaging, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Mieko Tsuji
- Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Daiki Ozaki
- Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Nina Shibata
- Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Yoshinobu Hashizume
- RIKEN Program for Drug Discovery and Medical Technology Platforms, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Masaaki Suzuki
- Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,National Center for Geriatrics and Gerontology 35 Gengo, Morioka Obu, Aichi, 474-8511, Japan
| | - Hirotaka Onoe
- Human Brain Research Center, Graduate School of Medicine, Kyoto University, 54 Shogoin-kawahara-cho, Sakyo-ku, Kyoto, 606-8507, (Japan)
| | - Yasuyoshi Watanabe
- Laboratory for Pathophysiological and Health Science, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
| | - Hisashi Doi
- Laboratory for Labeling Chemistry, RIKEN Center for Biosystems Dynamics Research, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan.,Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo, 650-0047, Japan
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6
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Schmidt KC, Loutaev I, Quezado Z, Sheeler C, Smith CB. Regional rates of brain protein synthesis are unaltered in dexmedetomidine sedated young men with fragile X syndrome: A L-[1- 11C]leucine PET study. Neurobiol Dis 2020; 143:104978. [PMID: 32569795 PMCID: PMC7425798 DOI: 10.1016/j.nbd.2020.104978] [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: 04/20/2020] [Revised: 06/01/2020] [Accepted: 06/15/2020] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. Fragile X mental retardation protein (FMRP), a putative translation suppressor, is absent or significantly reduced in FXS. One prevailing hypothesis is that rates of protein synthesis are increased by the absence of this regulatory protein. In accord with this hypothesis, we have previously reported increased rates of cerebral protein synthesis (rCPS) in the Fmr1 knockout mouse model of FXS and others have reported similar effects in hippocampal slices. To address the hypothesis in human subjects, we applied the L[1-11C]leucine PET method to measure rCPS in adults with FXS and healthy controls. All subjects were males between the ages of 18 and 24 years and free of psychotropic medication. As most fragile X participants were not able to undergo the PET study awake, we used dexmedetomidine for sedation during the imaging studies. We found no differences between rCPS measured during dexmedetomidine-sedation and the awake state in ten healthy controls. In the comparison of rCPS in dexmedetomidine-sedated fragile X participants (n = 9) and healthy controls (n = 14) we found no statistically significant differences. Our results from in vivo measurements in human brain do not support the hypothesis that rCPS are elevated due to the absence of FMRP. This hypothesis is based on findings in animal models and in vitro measurements in human peripheral cells. The absence of a translation suppressor may produce a more complex response in pathways regulating translation than previously thought. We may need to revise our working hypotheses regarding FXS and our thinking about potential therapeutics.
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Affiliation(s)
- Kathleen C Schmidt
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, 10 Center Drive, Room 2D54, Bethesda, MD 20892-1298, United States of America
| | - Inna Loutaev
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, 10 Center Drive, Room 2D54, Bethesda, MD 20892-1298, United States of America
| | - Zenaide Quezado
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892-1512, United States of America
| | - Carrie Sheeler
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, 10 Center Drive, Room 2D54, Bethesda, MD 20892-1298, United States of America
| | - Carolyn Beebe Smith
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, 10 Center Drive, Room 2D54, Bethesda, MD 20892-1298, United States of America.
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7
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Tomasi G, Veronese M, Bertoldo A, Smith CB, Schmidt KC. Substitution of venous for arterial blood sampling in the determination of regional rates of cerebral protein synthesis with L-[1- 11C]leucine PET: A validation study. J Cereb Blood Flow Metab 2019; 39:1849-1863. [PMID: 29664322 PMCID: PMC6727135 DOI: 10.1177/0271678x18771242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We developed and validated a method to estimate input functions for determination of regional rates of cerebral protein synthesis (rCPS) with L-[1-11C]leucine PET without arterial sampling. The method is based on a population-derived input function (PDIF) approach, with venous samples for calibration. Population input functions were constructed from arterial blood data measured in 25 healthy 18-24-year-old males who underwent L-[1-11C]leucine PET scans while awake. To validate the approach, three additional groups of 18-27-year-old males underwent L-[1-11C]leucine PET scans with both arterial and venous blood sampling: 13 awake healthy volunteers, 10 sedated healthy volunteers, and 5 sedated subjects with fragile X syndrome. Rate constants of the L-[1-11C]leucine kinetic model were estimated voxel-wise with measured arterial input functions and with venous-calibrated PDIFs. Venous plasma leucine measurements were used with venous-calibrated PDIFs for rCPS computation. rCPS determined with PDIFs calibrated with 30-60 min venous samples had small errors (RMSE: 4-9%), and no statistically significant differences were found in any group when compared to rCPS determined with arterial input functions. We conclude that in young adult males, PDIFs calibrated with 30-60 min venous samples can be used in place of arterial input functions for determination of rCPS with L-[1-11C]leucine PET.
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Affiliation(s)
- Giampaolo Tomasi
- Section on Neuroadaptation & Protein
Metabolism, National Institute of Mental Health, Bethesda, MD, USA
| | - Mattia Veronese
- Department of Neuroimaging, IoPPN,
King’s College London, London, UK
| | | | - Carolyn B Smith
- Section on Neuroadaptation & Protein
Metabolism, National Institute of Mental Health, Bethesda, MD, USA
| | - Kathleen C Schmidt
- Section on Neuroadaptation & Protein
Metabolism, National Institute of Mental Health, Bethesda, MD, USA
- Kathleen C Schmidt, Section on
Neuroadaptation & Protein Metabolism, National Institute of Mental Health,
Bldg 10, Room 2D54, 10 Center Drive, Bethesda, MD 20892-1298, USA.
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8
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Tomasi G, Veronese M, Bertoldo A, Beebe Smith C, Schmidt KC. Effects of shortened scanning intervals on calculated regional rates of cerebral protein synthesis determined with the L-[1-11C]leucine PET method. PLoS One 2018; 13:e0195580. [PMID: 29659612 PMCID: PMC5901930 DOI: 10.1371/journal.pone.0195580] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 03/26/2018] [Indexed: 11/19/2022] Open
Abstract
To examine effects of scan duration on estimates of regional rates of cerebral protein synthesis (rCPS), we reanalyzed data from thirty-nine previously reported L-[1-11C]leucine PET studies. Subjects consisted of 12 healthy volunteers studied twice, awake and under propofol sedation, and 15 subjects with fragile X syndrome (FXS) studied once under propofol sedation. All scans were acquired on a high resolution scanner. We used a basis function method for voxelwise estimation of parameters of the kinetic model of L-[1-11C]leucine and rCPS over the interval beginning at the time of tracer injection and ending 30, 45, 60, 75 or 90 min later. For each study and scan interval, regional estimates in nine regions and whole brain were obtained by averaging voxelwise estimates over all voxels in the region. In all three groups rCPS was only slightly affected by scan interval length and was very stable between 60 and 90 min. Furthermore, statistical comparisons of rCPS between awake and sedated healthy volunteers provided almost identical results when they were based on 60 min scan data as when they were based on data from the full 90 min interval. Statistical comparisons between sedated healthy volunteers and sedated subjects with FXS also yielded almost identical results when based on 60 and 90 min scan intervals. We conclude that, under the conditions of our studies, scan duration can be shortened to 60 min without loss of precision.
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Affiliation(s)
- Giampaolo Tomasi
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, United States of America
| | - Mattia Veronese
- Department of Neuroimaging, IoPPN, King’s College London, London, United Kingdom
| | | | - Carolyn Beebe Smith
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, United States of America
| | - Kathleen C. Schmidt
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, United States of America
- * E-mail:
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9
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Xie F, Peng F. Radiopharmaceuticals for Assessment of Altered Metabolism and Biometal Fluxes in Brain Aging and Alzheimer's Disease with Positron Emission Tomography. J Alzheimers Dis 2018; 59:527-536. [PMID: 28671127 DOI: 10.3233/jad-170280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Aging is a risk factor for Alzheimer's disease (AD). There are changes of brain metabolism and biometal fluxes due to brain aging, which may play a role in pathogenesis of AD. Positron emission tomography (PET) is a versatile tool for tracking alteration of metabolism and biometal fluxes due to brain aging and AD. Age-dependent changes in cerebral glucose metabolism can be tracked with PET using 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG), a radiolabeled glucose analogue, as a radiotracer. Based on different patterns of altered cerebral glucose metabolism, 18F-FDG PET was clinically used for differential diagnosis of AD and Frontotemporal dementia (FTD). There are continued efforts to develop additional radiopharmaceuticals or radiotracers for assessment of age-dependent changes of various metabolic pathways and biometal fluxes due to brain aging and AD with PET. Elucidation of age-dependent changes of brain metabolism and altered biometal fluxes is not only significant for a better mechanistic understanding of brain aging and the pathophysiology of AD, but also significant for identification of new targets for the prevention, early diagnosis, and treatment of AD.
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Affiliation(s)
- Fang Xie
- Department of Radiology, and Advanced ImagingResearch Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Fangyu Peng
- Department of Radiology, and Advanced ImagingResearch Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
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10
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Veronese M, Bertoldo A, Tomasi G, Smith CB, Schmidt KC. Impact of tissue kinetic heterogeneity on PET quantification: case study with the L-[1- 11C]leucine PET method for cerebral protein synthesis rates. Sci Rep 2018; 8:931. [PMID: 29343731 PMCID: PMC5772379 DOI: 10.1038/s41598-017-18890-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 12/16/2017] [Indexed: 11/09/2022] Open
Abstract
Functional quantification with PET is generally based on modeling that assumes tissue regions are kinetically homogeneous. Even in regions sufficiently small to approach homogeneity, spillover due to resolution limitations of PET scanners may introduce heterogeneous kinetics into measured data. Herein we consider effects of kinetic heterogeneity at the smallest volume accessible, the single image voxel. We used L-[1-11C]leucine PET and compared rates of cerebral protein synthesis (rCPS) estimated voxelwise with methods that do (Spectral Analysis Iterative Filter, SAIF) and do not (Basis Function Method, BFM) allow for kinetic heterogeneity. In high resolution PET data with good counting statistics BFM produced estimates of rCPS comparable to SAIF, but at lower computational cost; thus the simpler, less costly method can be applied. With poorer counting statistics (lower injected radiotracer doses), BFM estimates were more biased. In data smoothed to simulate lower resolution PET, BFM produced estimates of rCPS 9-14% higher than SAIF, overestimation consistent with applying a homogeneous tissue model to kinetically heterogeneous data. Hence with lower resolution data it is necessary to account for kinetic heterogeneity in the analysis. Kinetic heterogeneity may impact analyses of other tracers and scanning protocols differently; assessments should be made on a case by case basis.
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Affiliation(s)
- Mattia Veronese
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, USA.,Department of Neuroimaging, IoPPN, King's college London, London, UK
| | - Alessandra Bertoldo
- Department of Information Engineering, University of Padova, Padova, Italy.,Padua Neuroscience Center, University of Padova, Padova, Italy
| | - Giampaolo Tomasi
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, USA
| | - Carolyn Beebe Smith
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, USA
| | - Kathleen C Schmidt
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland, USA.
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11
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Positron Emission Tomography: Basic Principles, New Applications, and Studies Under Anesthesia. Int Anesthesiol Clin 2016; 54:109-28. [PMID: 26655512 DOI: 10.1097/aia.0000000000000090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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12
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Qin M, Zeidler Z, Moulton K, Krych L, Xia Z, Smith CB. Endocannabinoid-mediated improvement on a test of aversive memory in a mouse model of fragile X syndrome. Behav Brain Res 2015; 291:164-171. [PMID: 25979787 DOI: 10.1016/j.bbr.2015.05.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 04/30/2015] [Accepted: 05/05/2015] [Indexed: 12/30/2022]
Abstract
Silencing the gene FMR1 in fragile X syndrome (FXS) with consequent loss of its protein product, FMRP, results in intellectual disability, hyperactivity, anxiety, seizure disorders, and autism-like behavior. In a mouse model (Fmr1 knockout (KO)) of FXS, a deficit in performance on the passive avoidance test of learning and memory is a robust phenotype. We report that drugs acting on the endocannabinoid (eCB) system can improve performance on this test. We present three lines of evidence: (1) Propofol (reported to inhibit fatty acid amide hydrolase (FAAH) activity) administered 30 min after training on the passive avoidance test improved performance in Fmr1 KO mice but had no effect on wild type (WT). FAAH catalyzes the metabolism of the eCB, anandamide, so its inhibition should result in increased anandamide levels. (2) The effect of propofol was blocked by prior administration of the cannabinoid receptor 1 antagonist AM-251. (3) Treatment with the FAAH inhibitor, URB-597, administered 30 min after training on the passive avoidance test also improved performance in Fmr1 KO mice but had no effect on WT. Our results indicate that the eCB system is involved in FXS and suggest that the eCB system is a promising target for treatment of FXS.
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Affiliation(s)
- Mei Qin
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA
| | - Zachary Zeidler
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA
| | - Kristen Moulton
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA
| | - Leland Krych
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA
| | - Zengyan Xia
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA
| | - Carolyn B Smith
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Bldg. 10, Rm. 2D54, Bethesda, MD 20892, USA.
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de Esch CE, Zeidler S, Willemsen R. Translational endpoints in fragile X syndrome. Neurosci Biobehav Rev 2014; 46 Pt 2:256-69. [DOI: 10.1016/j.neubiorev.2013.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/07/2013] [Accepted: 10/09/2013] [Indexed: 01/01/2023]
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Holland JP, Cumming P, Vasdev N. PET radiopharmaceuticals for probing enzymes in the brain. AMERICAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING 2013; 3:194-216. [PMID: 23638333 PMCID: PMC3627518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 03/07/2013] [Indexed: 06/02/2023]
Abstract
Biologically important processes in normal brain function and brain disease involve the action of various protein-based receptors, ion channels, transporters and enzymes. The ability to interrogate the location, abundance and activity of these entities in vivo using non-invasive molecular imaging can provide unprecedented information about the spatio-temporal dynamics of brain function. Indeed, positron emission tomography (PET) imaging is transforming our understanding of the central nervous system and brain disease. Great emphasis has historically been placed on developing radioligands for the non-invasive detection of neuroreceptors. In contrast, relatively few enzymes have been amenable to examination by PET imaging procedures based upon trapping or accumulation of enzymatic products, because only a subset of enzymes have sufficient catalytic rate to produce measureable accumulation within the practical time-limit of PET recordings. However, high affinity inhibitors are now serving as tracers for enzymes, particularly for measuring the abundance of enzymes mediating intracellular signal transduction in the brain, which offer a rich diversity of potential targets for drug discovery. The purpose of this review is to summarize well-known radiotracers for brain enzymes, and draw attention to recent developments in PET radiotracers for imaging signal transduction pathways in the brain. The review is organized by target class and focuses on structural chemistry of the best-established radiotracers identified in each class.
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Affiliation(s)
- Jason P Holland
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School55 Fruit St., White 427, Boston, MA 02114, USA
| | - Paul Cumming
- Department of Nuclear Medicine, Universitätsklinikum ErlangenUlmenweg 18, Erlangen, Germany, 91054
| | - Neil Vasdev
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School55 Fruit St., White 427, Boston, MA 02114, USA
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Altered cerebral protein synthesis in fragile X syndrome: studies in human subjects and knockout mice. J Cereb Blood Flow Metab 2013; 33:499-507. [PMID: 23299245 PMCID: PMC3618394 DOI: 10.1038/jcbfm.2012.205] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Dysregulated protein synthesis is thought to be a core phenotype of fragile X syndrome (FXS). In a mouse model (Fmr1 knockout (KO)) of FXS, rates of cerebral protein synthesis (rCPS) are increased in selective brain regions. We hypothesized that rCPS are also increased in FXS subjects. We measured rCPS with the L-[1-(11)C]leucine positron emission tomography (PET) method in whole brain and 10 regions in 15 FXS subjects who, because of their impairments, were studied under deep sedation with propofol. We compared results with those of 12 age-matched controls studied both awake and sedated. In controls, we found no differences in rCPS between awake and propofol sedation. Contrary to our hypothesis, FXS subjects under propofol sedation had reduced rCPS in whole brain, cerebellum, and cortex compared with sedated controls. To investigate whether propofol could have a disparate effect in FXS subjects masking usually elevated rCPS, we measured rCPS in C57Bl/6 wild-type (WT) and KO mice awake or under propofol sedation. Propofol decreased rCPS substantially in most regions examined in KO mice, but in WT mice caused few discrete changes. Propofol acts by decreasing neuronal activity either directly or by increasing inhibitory synaptic activity. Our results suggest that changes in synaptic signaling can correct increased rCPS in FXS.
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Hines CS, Fujita M, Zoghbi SS, Kim JS, Quezado Z, Herscovitch P, Miao N, Ferraris Araneta MD, Morse C, Pike VW, Labovsky J, Innis RB. Propofol decreases in vivo binding of 11C-PBR28 to translocator protein (18 kDa) in the human brain. J Nucl Med 2012; 54:64-9. [PMID: 23148296 DOI: 10.2967/jnumed.112.106872] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED The PET radioligand (11)C-PBR28 targets translocator protein (18 kDa) (TSPO) and is a potential marker of neuroimmune activation in vivo. Although several patient populations have been studied using (11)C-PBR28, no investigators have studied cognitively impaired patients who would require anesthesia for the PET procedure, nor have any reports investigated the effects that anesthesia may have on radioligand uptake. The purpose of this study was to determine whether the anesthetic propofol alters brain uptake of (11)C-PBR28 in healthy subjects. METHODS Ten healthy subjects (5 men; 5 women) each underwent 2 dynamic brain PET scans on the same day, first at baseline and then with intravenous propofol anesthesia. The subjects were injected with 680 ± 14 MBq (mean ± SD) of (11)C-PBR28 for each PET scan. Brain uptake was measured as total distribution volume (V(T)) using the Logan plot and metabolite-corrected arterial input function. RESULTS Propofol decreased V(T), which corrects for any alteration of metabolism of the radioligand, by about 26% (P = 0.011). In line with the decrease in V(T), brain time-activity curves showed decreases of about 20% despite a 13% increase in plasma area under the curve with propofol. Reduction of V(T) with propofol was observed across all brain regions, with no significant region X condition interaction (P = 0.40). CONCLUSION Propofol anesthesia reduces the V(T) of (11)C-PBR28 by about 26% in the brains of healthy human subjects. Given this finding, future studies will measure neuroimmune activation in the brains of autistic volunteers and their age and sex-matched healthy controls using propofol anesthesia. We recommend that future PET studies using (11)C-PBR28 and concomitant propofol anesthesia, as would be required in impaired populations, include a control arm to account for the effects of propofol on brain measurements of TSPO.
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Affiliation(s)
- Christina S Hines
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland 20892-1026, USA
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Use of spectral analysis with iterative filter for voxelwise determination of regional rates of cerebral protein synthesis with L-[1-11C]leucine PET. J Cereb Blood Flow Metab 2012; 32:1073-85. [PMID: 22395209 PMCID: PMC3367224 DOI: 10.1038/jcbfm.2012.27] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A spectral analysis approach was used to estimate kinetic parameters of the L-[1-(11)C]leucine positron emission tomography (PET) method and regional rates of cerebral protein synthesis (rCPS) on a voxel-by-voxel basis. Spectral analysis applies to both heterogeneous and homogeneous tissues; it does not require prior assumptions concerning number of tissue compartments. Parameters estimated with spectral analysis can be strongly affected by noise, but numerical filters improve estimation performance. Spectral analysis with iterative filter (SAIF) was originally developed to improve estimation of leucine kinetic parameters and rCPS in region-of-interest (ROI) data analyses. In the present study, we optimized SAIF for application at the voxel level. In measured L-[1-(11)C]leucine PET data, voxel-level SAIF parameter estimates averaged over all voxels within a ROI (mean voxel-SAIF) generally agreed well with corresponding estimates derived by applying the originally developed SAIF to ROI time-activity curves (ROI-SAIF). Region-of-interest-SAIF and mean voxel-SAIF estimates of rCPS were highly correlated. Simulations showed that mean voxel-SAIF rCPS estimates were less biased and less variable than ROI-SAIF estimates in the whole brain and cortex; biases were similar in white matter. We conclude that estimation of rCPS with SAIF is improved when the method is applied at voxel level than in ROI analysis.
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Bhakar AL, Dölen G, Bear MF. The pathophysiology of fragile X (and what it teaches us about synapses). Annu Rev Neurosci 2012; 35:417-43. [PMID: 22483044 DOI: 10.1146/annurev-neuro-060909-153138] [Citation(s) in RCA: 279] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Fragile X is the most common known inherited cause of intellectual disability and autism, and it typically results from transcriptional silencing of FMR1 and loss of the encoded protein, FMRP (fragile X mental retardation protein). FMRP is an mRNA-binding protein that functions at many synapses to inhibit local translation stimulated by metabotropic glutamate receptors (mGluRs) 1 and 5. Recent studies on the biology of FMRP and the signaling pathways downstream of mGluR1/5 have yielded deeper insight into how synaptic protein synthesis and plasticity are regulated by experience. This new knowledge has also suggested ways that altered signaling and synaptic function can be corrected in fragile X, and human clinical trials based on this information are under way.
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Affiliation(s)
- Asha L Bhakar
- Howard Hughes Medical Institute, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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The Assay of Enzyme Activity by Positron Emission Tomography. MOLECULAR IMAGING IN THE CLINICAL NEUROSCIENCES 2012. [DOI: 10.1007/7657_2012_53] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Veronese M, Bertoldo A, Bishu S, Unterman A, Tomasi G, Smith CB, Schmidt KC. A spectral analysis approach for determination of regional rates of cerebral protein synthesis with the L-[1-(11)C]leucine PET method. J Cereb Blood Flow Metab 2010; 30:1460-76. [PMID: 20197782 PMCID: PMC2907431 DOI: 10.1038/jcbfm.2010.26] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A spectral analysis approach was used to estimate kinetic model parameters of the L-[1-(11)C]leucine positron emission tomography (PET) method and regional rates of cerebral protein synthesis (rCPS) in predefined regions of interest (ROIs). Unlike analyses based on the assumption that tissue ROIs are kinetically homogeneous, spectral analysis allows for heterogeneity within a region. To improve estimation performance, a new approach was developed-spectral analysis with iterative filter (SAIF). In simulation SAIF produced low bias, low variance estimates of the influx rate constant for leucine (K(1)), blood volume fraction (V(b)), fraction of unlabeled leucine in the tissue precursor pool for protein synthesis derived from arterial plasma (lambda), and rCPS. Simulation of normal count rate studies showed that SAIF applied to ROI time-activity curves (TACs) performed comparably to the basis function method (BFM) applied to voxel TACs when voxelwise estimates were averaged over all voxels in the ROI. At low count rates, however, SAIF performed better. In measured L-[1-(11)C]leucine PET data, there was good agreement between ROI-based SAIF estimates and average voxelwise BFM estimates of K(1), V(b), lambda, and rCPS. We conclude that SAIF sufficiently addresses the problem of tissue heterogeneity in ROI data and provides a valid tool for estimation of rCPS, even in low count rate studies.
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Affiliation(s)
- Mattia Veronese
- Department of Information Engineering, University of Padova, Padova, Italy
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Voxel-based estimation of kinetic model parameters of the L-[1-(11)C]leucine PET method for determination of regional rates of cerebral protein synthesis: validation and comparison with region-of-interest-based methods. J Cereb Blood Flow Metab 2009; 29:1317-31. [PMID: 19436319 PMCID: PMC2818563 DOI: 10.1038/jcbfm.2009.52] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We adapted and validated a basis function method (BFM) to estimate at the voxel level parameters of the kinetic model of the L-[1-(11)C]leucine positron emission tomography (PET) method and regional rates of cerebral protein synthesis (rCPS). In simulation at noise levels typical of voxel data, BFM yielded low-bias estimates of rCPS; in measured data, BFM and nonlinear least-squares parameter estimates were in good agreement. We also examined whether there are advantages to using voxel-level estimates averaged over regions of interest (ROIs) in place of estimates obtained by directly fitting ROI time-activity curves (TACs). In both simulated and measured data, fits of ROI TACs were poor, likely because of tissue heterogeneity not taken into account in the kinetic model. In simulation, rCPS determined from fitting ROI TACs was substantially overestimated and BFM-estimated rCPS averaged over all voxels in an ROI was slightly underestimated. In measured data, rCPS determined by regional averaging of voxel estimates was lower than rCPS determined from ROI TACs, consistent with simulation. In both simulated and measured data, intersubject variability of BFM-estimated rCPS averaged over all voxels in a ROI was low. We conclude that voxelwise estimation is preferable to fitting ROI TACs using a homogeneous tissue model.
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