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Li F, Hicks JW, Yu L, Desjardin L, Morrison L, Hadway J, Lee TY. Plasma radio-metabolite analysis of PET tracers for dynamic PET imaging: TLC and autoradiography. EJNMMI Res 2020; 10:141. [PMID: 33226509 PMCID: PMC7683627 DOI: 10.1186/s13550-020-00705-2] [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: 06/12/2020] [Accepted: 09/18/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In molecular imaging with dynamic PET, the binding and dissociation of a targeted tracer is characterized by kinetics modeling which requires the arterial concentration of the tracer to be measured accurately. Once in the body the radiolabeled parent tracer may be subjected to hydrolysis, demethylation/dealkylation and other biochemical processes, resulting in the production and accumulation of different metabolites in blood which can be labeled with the same PET radionuclide as the parent. Since these radio-metabolites cannot be distinguished by PET scanning from the parent tracer, their contribution to the arterial concentration curve has to be removed for the accurate estimation of kinetic parameters from kinetic analysis of dynamic PET. High-performance liquid chromatography has been used to separate and measure radio-metabolites in blood plasma; however, the method is labor intensive and remains a challenge to implement for each individual patient. The purpose of this study is to develop an alternate technique based on thin layer chromatography (TLC) and a sensitive commercial autoradiography system (Beaver, Ai4R, Nantes, France) to measure radio-metabolites in blood plasma of two targeted tracers-[18F]FAZA and [18F]FEPPA, for imaging hypoxia and inflammation, respectively. RESULTS Radioactivity as low as 17 Bq in 2 µL of pig's plasma can be detected on the TLC plate using autoradiography. Peaks corresponding to the parent tracer and radio-metabolites could be distinguished in the line profile through each sample (n = 8) in the autoradiographic image. Significant intersubject and intra-subject variability in radio-metabolites production could be observed with both tracers. For [18F]FEPPA, 50% of plasma activity was from radio-metabolites as early as 5-min post injection, while for [18F]FAZA, significant metabolites did not appear until 50-min post. Simulation study investigating the effect of radio-metabolite in the estimation of kinetic parameters indicated that 32-400% parameter error can result without radio-metabolites correction. CONCLUSION TLC coupled with autoradiography is a good alternative to high-performance liquid chromatography for radio-metabolite correction. The advantages of requiring only small blood samples (~ 100 μL) and of analyzing multiple samples simultaneously, make the method suitable for individual dynamic PET studies.
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Affiliation(s)
- Fiona Li
- Department of Medical Biophysics, The University of Western University, 1151 Richmond Street North, London, ON, N6A 3K7, Canada.,Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada.,Robarts Research Institute, London, ON, Canada
| | - Justin W Hicks
- Department of Medical Biophysics, The University of Western University, 1151 Richmond Street North, London, ON, N6A 3K7, Canada.,Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada
| | - Lihai Yu
- Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada
| | - Lise Desjardin
- Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada
| | - Laura Morrison
- Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada
| | - Jennifer Hadway
- Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada.,Robarts Research Institute, London, ON, Canada
| | - Ting-Yim Lee
- Department of Medical Biophysics, The University of Western University, 1151 Richmond Street North, London, ON, N6A 3K7, Canada. .,Lawson Health Research Institute, Grosvenor Campus, 268 Grosvenor Street, London, ON, N6A 4V2, Canada. .,Robarts Research Institute, London, ON, Canada.
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Ghosh KK, Padmanabhan P, Yang CT, Mishra S, Halldin C, Gulyás B. Dealing with PET radiometabolites. EJNMMI Res 2020; 10:109. [PMID: 32997213 PMCID: PMC7770856 DOI: 10.1186/s13550-020-00692-4] [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: 05/30/2020] [Accepted: 09/07/2020] [Indexed: 02/08/2023] Open
Abstract
Abstract Positron emission tomography (PET) offers the study of biochemical,
physiological, and pharmacological functions at a cellular and molecular level.
The performance of a PET study mostly depends on the used radiotracer of
interest. However, the development of a novel PET tracer is very difficult, as
it is required to fulfill a lot of important criteria. PET radiotracers usually
encounter different chemical modifications including redox reaction, hydrolysis,
decarboxylation, and various conjugation processes within living organisms. Due
to this biotransformation, different chemical entities are produced, and the
amount of the parent radiotracer is declined. Consequently, the signal measured
by the PET scanner indicates the entire amount of radioactivity deposited in the
tissue; however, it does not offer any indication about the chemical disposition
of the parent radiotracer itself. From a radiopharmaceutical perspective, it is
necessary to quantify the parent radiotracer’s fraction present in the tissue.
Hence, the identification of radiometabolites of the radiotracers is vital for
PET imaging. There are mainly two reasons for the chemical identification of PET
radiometabolites: firstly, to determine the amount of parent radiotracers in
plasma, and secondly, to rule out (if a radiometabolite enters the brain) or
correct any radiometabolite accumulation in peripheral tissue. Besides,
radiometabolite formations of the tracer might be of concern for the PET study,
as the radiometabolic products may display considerably contrasting distribution
patterns inside the body when compared with the radiotracer itself. Therefore,
necessary information is needed about these biochemical transformations to
understand the distribution of radioactivity throughout the body. Various
published review articles on PET radiometabolites mainly focus on the sample
preparation techniques and recently available technology to improve the
radiometabolite analysis process. This article essentially summarizes the
chemical and structural identity of the radiometabolites of various radiotracers
including [11C]PBB3,
[11C]flumazenil,
[18F]FEPE2I, [11C]PBR28,
[11C]MADAM, and
(+)[18F]flubatine. Besides, the importance of
radiometabolite analysis in PET imaging is also briefly summarized. Moreover,
this review also highlights how a slight chemical modification could reduce the
formation of radiometabolites, which could interfere with the results of PET
imaging. Graphical abstract ![]()
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Affiliation(s)
- Krishna Kanta Ghosh
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.
| | - Chang-Tong Yang
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Nuclear Medicine and Molecular Imaging, Radiological Sciences Division, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.,Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Sachin Mishra
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Christer Halldin
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore. .,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.
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Zhang L, Guo L, Shan X, Lin X, Gu T, Zhang J, Ge J, Li W, Ge H, Jiang Q, Ning X. An elegant nitroreductase responsive fluorescent probe for selective detection of pathogenic Listeria in vitro and in vivo. Talanta 2019; 198:472-479. [DOI: 10.1016/j.talanta.2019.02.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 12/24/2018] [Accepted: 02/04/2019] [Indexed: 01/24/2023]
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Moein MM, Nakao R, Amini N, Abdel-Rehim M, Schou M, Halldin C. Sample preparation techniques for radiometabolite analysis of positron emission tomography radioligands; trends, progress, limitations and future prospects. Trends Analyt Chem 2019. [DOI: 10.1016/j.trac.2018.10.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Nakao R, Amini N, Halldin C. Simultaneous Determination of Protein-Free and Total Positron Emission Tomography Radioligand Concentrations in Plasma Using High-Performance Frontal Analysis Followed by Mixed Micellar Liquid Chromatography: Application to [11C]PBR28 in Human Plasma. Anal Chem 2013; 85:8728-34. [DOI: 10.1021/ac401742v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ryuji Nakao
- Department
of Clinical Neuroscience, Center for Psychiatric
Research, Karolinska Institute, Stockholm, Sweden
| | - Nahid Amini
- Department
of Clinical Neuroscience, Center for Psychiatric
Research, Karolinska Institute, Stockholm, Sweden
| | - Christer Halldin
- Department
of Clinical Neuroscience, Center for Psychiatric
Research, Karolinska Institute, Stockholm, Sweden
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