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Lee SH, Griffiths JR. How and Why Are Cancers Acidic? Carbonic Anhydrase IX and the Homeostatic Control of Tumour Extracellular pH. Cancers (Basel) 2020; 12:cancers12061616. [PMID: 32570870 PMCID: PMC7352839 DOI: 10.3390/cancers12061616] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/13/2020] [Accepted: 06/15/2020] [Indexed: 12/11/2022] Open
Abstract
The acidic tumour microenvironment is now recognized as a tumour phenotype that drives cancer somatic evolution and disease progression, causing cancer cells to become more invasive and to metastasise. This property of solid tumours reflects a complex interplay between cellular carbon metabolism and acid removal that is mediated by cell membrane carbonic anhydrases and various transport proteins, interstitial fluid buffering, and abnormal tumour-associated vessels. In the past two decades, a convergence of advances in the experimental and mathematical modelling of human cancers, as well as non-invasive pH-imaging techniques, has yielded new insights into the physiological mechanisms that govern tumour extracellular pH (pHe). In this review, we examine the mechanisms by which solid tumours maintain a low pHe, with a focus on carbonic anhydrase IX (CAIX), a cancer-associated cell surface enzyme. We also review the accumulating evidence that suggest a role for CAIX as a biological pH-stat by which solid tumours stabilize their pHe. Finally, we highlight the prospects for the clinical translation of CAIX-targeted therapies in oncology.
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Affiliation(s)
- Shen-Han Lee
- Department of Otorhinolaryngology, Hospital Sultanah Bahiyah, Jalan Langgar, Alor Setar 05460, Kedah, Malaysia
- Correspondence:
| | - John R. Griffiths
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK;
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Toramatsu C, Mohammadi A, Wakizaka H, Seki C, Nishikido F, Sato S, Kanno I, Takahashi M, Karasawa K, Hirano Y, Yamaya T. Biological washout modelling for in-beam PET: rabbit brain irradiation by 11C and 15O ion beams. Phys Med Biol 2020; 65:105011. [PMID: 32235057 DOI: 10.1088/1361-6560/ab8532] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Positron emission tomography (PET) has been used for dose verification in charged particle therapy. The causes of washout of positron emitters by physiological functions should be clarified for accurate dose verification. In this study, we visualized the distribution of irradiated radioactive beams, 11C and 15O beams, in the rabbit whole-body using our original depth-of-interaction (DOI)-PET prototype to add basic data for biological washout effect correction. Time activity curves of the irradiated field and organs were measured immediately after the irradiations. All data were corrected for physical decay before further analysis. We also collected expired gas of the rabbit during beam irradiation and the energy spectrum was measured with a germanium detector. Irradiated radioactive beams into the brain were distributed to the whole body due to the biological washout process, and the implanted 11C and 15O ions were concentrated in the regions which had high blood volume. The 11C-labelled 11CO2 was detected in expired gas under the 11C beam irradiation, while no significant signal was detected under the 15O beam irradiation as a form of C15O2. Results suggested that the implanted 11C ions form molecules that diffuse out to the whole body by undergoing perfusion, then, they are incorporated into the blood-gas exchange in the respiratory system. This study provides basic data for modelling of the biological washout effect.
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Affiliation(s)
- Chie Toramatsu
- Department of Radiation Oncology, Tokyo Women's University School of Medicine, Tokyo, Japan. National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
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3
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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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4
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Spatiotemporal pH Heterogeneity as a Promoter of Cancer Progression and Therapeutic Resistance. Cancers (Basel) 2019; 11:cancers11071026. [PMID: 31330859 PMCID: PMC6678451 DOI: 10.3390/cancers11071026] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 12/15/2022] Open
Abstract
Dysregulation of pH in solid tumors is a hallmark of cancer. In recent years, the role of altered pH heterogeneity in space, between benign and aggressive tissues, between individual cancer cells, and between subcellular compartments, has been steadily elucidated. Changes in temporal pH-related processes on both fast and slow time scales, including altered kinetics of bicarbonate-CO2 exchange and its effects on pH buffering and gradual, progressive changes driven by changes in metabolism, are further implicated in phenotypic changes observed in cancers. These discoveries have been driven by advances in imaging technologies. This review provides an overview of intra- and extracellular pH alterations in time and space reflected in cancer cells, as well as the available technology to study pH spatiotemporal heterogeneity.
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5
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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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6
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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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Korenchan DE, Flavell RR, Baligand C, Sriram R, Neumann K, Sukumar S, VanBrocklin H, Vigneron DB, Wilson DM, Kurhanewicz J. Dynamic nuclear polarization of biocompatible (13)C-enriched carbonates for in vivo pH imaging. Chem Commun (Camb) 2016; 52:3030-3. [PMID: 26792559 PMCID: PMC4864526 DOI: 10.1039/c5cc09724j] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A hyperpolarization technique using carbonate precursors of biocompatible molecules was found to yield high concentrations of hyperpolarized (13)C bicarbonate in solution. This approach enabled large signal gains for low-toxicity hyperpolarized (13)C pH imaging in a phantom and in vivo in a murine model of prostate cancer.
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Affiliation(s)
- D E Korenchan
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, California, USA. and Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - R R Flavell
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - C Baligand
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - R Sriram
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - K Neumann
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - S Sukumar
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - H VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - D B Vigneron
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, California, USA. and Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - D M Wilson
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
| | - J Kurhanewicz
- UC Berkeley-UCSF Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, California, USA. and Department of Radiology and Biomedical Imaging, University of California, San Francisco, California, USA.
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8
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Hirano Y, Takuwa H, Yoshida E, Nishikido F, Nakajima Y, Wakizaka H, Yamaya T. Washout rate in rat brain irradiated by a11C beam after acetazolamide loading using a small single-ring OpenPET prototype. Phys Med Biol 2016; 61:1875-87. [PMID: 26863938 DOI: 10.1088/0031-9155/61/5/1875] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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9
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Ghosh RK, Kadlecek SJ, Pourfathi M, Rizi RR. Efficient production of hyperpolarized bicarbonate by chemical reaction on a DNP precursor to measure pH. Magn Reson Med 2014; 74:1406-13. [PMID: 25393101 DOI: 10.1002/mrm.25530] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 10/24/2014] [Accepted: 10/26/2014] [Indexed: 01/09/2023]
Abstract
PURPOSE To produce hyperpolarized bicarbonate indirectly via chemical reaction from a hyperpolarized precursor and utilize it for the simultaneous regional measurement of metabolism and pH. METHODS Alpha keto carboxylic acids are first hyperpolarized by dissolution dynamic nuclear polarization (DNP). These precursor molecules are rapidly reacted with hydrogen peroxide (H2O2) to decarboxylate the species, resulting in new target molecules. Unreacted H2O2 is removed from the system by reaction with sulfite. Interrogation of the ratio of dissolved carbon dioxide (CO2) to bicarbonate can be used to determine pH. RESULTS Conversion of hyperpolarized alpha keto acids to bicarbonate and CO2 results in a minimal loss of the spin order. The reaction can be conducted to completion within seconds and preserves the nuclear spin polarization. CONCLUSION Through a rapid chemical reaction, we can conserve the nuclear spin order of a DNP precursor to generate multiple hyperpolarized bioprobes otherwise unamenable to polarization. This indirect technique for the production of hyperpolarized agents can be applied to different precursor compounds to generate additional novel probes.
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Affiliation(s)
- Rajat K Ghosh
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Stephen J Kadlecek
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mehrdad Pourfathi
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Rahim R Rizi
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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10
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Hirano Y, Kinouchi S, Ikoma Y, Yoshida E, Wakizaka H, Ito H, Yamaya T. Compartmental analysis of washout effect in rat brain: in-beam OpenPET measurement using a11C beam. Phys Med Biol 2013; 58:8281-94. [DOI: 10.1088/0031-9155/58/23/8281] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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11
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Fernández S, Dematteis S, Giglio J, Cerecetto H, Rey A. Synthesis, in vitro and in vivo characterization of two novel 68Ga-labelled 5-nitroimidazole derivatives as potential agents for imaging hypoxia. Nucl Med Biol 2013; 40:273-9. [DOI: 10.1016/j.nucmedbio.2012.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 10/29/2012] [Accepted: 11/01/2012] [Indexed: 10/27/2022]
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12
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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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Gallagher FA, Kettunen MI, Brindle KM. Imaging pH with hyperpolarized 13C. NMR IN BIOMEDICINE 2011; 24:1006-1015. [PMID: 21812047 DOI: 10.1002/nbm.1742] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 03/23/2011] [Accepted: 04/05/2011] [Indexed: 05/31/2023]
Abstract
pH is a fundamental physiological parameter that is tightly controlled by endogenous buffers. The acid-base balance is altered in many disease states, such as inflammation, ischemia and cancer. Despite the importance of pH, there are currently no routine methods for imaging the spatial distribution of pH in humans. The enormous gain in sensitivity afforded by dynamic nuclear polarization (DNP) has provided a novel way in which to image tissue pH using MR, which has the potential to be translated into the clinic. This review explores the advantages and disadvantages of current pH imaging techniques and how they compare with DNP-based approaches for the measurement and imaging of pH with hyperpolarized (13)C. Intravenous injection of hyperpolarized (13)C-labeled bicarbonate results in the rapid production of hyperpolarized (13)CO(2) in the reaction catalyzed by carbonic anhydrase. As this reaction is close to equilibrium in the body and is pH dependent, the ratio of the (13)C signal intensities from H(13)CO(3)(-) and (13)CO(2), measured using MRS, can be used to calculate pH in vivo. The application of this technique to a murine tumor model demonstrated that it measured predominantly extracellular pH and could be mapped in the animal using spectroscopic imaging techniques. A second approach has been to use the production of hyperpolarized (13)CO(2) from hyperpolarized [1-(13)C]pyruvate to measure predominantly intracellular pH. In tissues with a high aerobic capacity, such as the heart, the hyperpolarized [1-(13)C]pyruvate undergoes rapid oxidative decarboxylation, catalyzed by intramitochondrial pyruvate dehydrogenase. Provided that there is sufficient carbonic anhydrase present to catalyze the rapid equilibration of the hyperpolarized (13)C label between CO(2) and bicarbonate, the ratio of their resonance intensities may again be used to estimate pH, which, in this case, is predominantly intracellular. As both pyruvate and bicarbonate are endogenous molecules they have the potential to image tissue pH in the clinic.
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Affiliation(s)
- Ferdia A Gallagher
- Cancer Research UK Cambridge Research Institute, Li Ka Shing Centre, and Department of Biochemistry, University of Cambridge, Cambridge, UK.
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Abstract
Molecular imaging allows for the remote, noninvasive sensing and measurement of cellular and molecular processes in living subjects. Drawing upon a variety of modalities, molecular imaging provides a window into the biology of cancer from the subcellular level to the patient undergoing a new, experimental therapy. As signal transduction cascades and protein interaction networks become clarified, an increasing number of relevant targets for cancer therapy--and imaging--become available. Although conventional imaging is already critical to the management of patients with cancer, molecular imaging will provide even more relevant information, such as early detection of changes with therapy, identification of patient-specific cellular and metabolic abnormalities, and the disposition of therapeutic, gene-tagged cells throughout the body--all of which will have a considerable impact on morbidity and mortality. This overview discusses molecular imaging in oncology, providing examples from a variety of modalities, with an emphasis on emerging techniques for translational imaging.
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Affiliation(s)
- Luke J Higgins
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
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15
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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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16
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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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17
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Bishu S, Schmidt KC, Burlin TV, Channing MA, Horowitz L, Huang T, Liu ZH, Qin M, Vuong BK, Unterman AJ, Xia Z, Zametkin A, Herscovitch P, Quezado Z, Smith CB. Propofol anesthesia does not alter regional rates of cerebral protein synthesis measured with L-[1-(11)C]leucine and PET in healthy male subjects. J Cereb Blood Flow Metab 2009; 29:1035-47. [PMID: 19223912 PMCID: PMC3150740 DOI: 10.1038/jcbfm.2009.7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We report regional rates of cerebral protein synthesis (rCPS) in 10 healthy young males, each studied under two conditions: awake and anesthetized with propofol. We used the quantitative L-[1-(11)C]leucine positron emission tomography (PET) method to measure rCPS. The method accounts for the fraction (lambda) of unlabeled leucine in the precursor pool for protein synthesis that is derived from arterial plasma; the remainder comes from proteolysis of tissue proteins. Across 18 regions and whole brain, mean differences in rCPS between studies ranged from -5% to 5% and were within the variability of rCPS in awake studies (coefficient of variation range: 7% to 14%). Similarly, differences in lambda (range: 1% to 4%) were typically within the variability of lambda (coefficient of variation range: 3% to 6%). Intersubject variances and patterns of regional variation were also similar under both conditions. In propofol-anesthetized subjects, rCPS varied regionally from 0.98+/-0.12 to 2.39+/-0.23 nmol g(-1) min(-1) in the corona radiata and in the cerebellum, respectively. Our data indicate that the values, variances, and patterns of regional variation in rCPS and lambda measured by the L-[1-(11)C]leucine PET method are not significantly altered by anesthesia with propofol.
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Affiliation(s)
- Shrinivas Bishu
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland 20892-1298, USA.
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18
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Bishu S, Schmidt KC, Burlin T, Channing M, Conant S, Huang T, Liu ZH, Qin M, Unterman A, Xia Z, Zametkin A, Herscovitch P, Smith CB. Regional rates of cerebral protein synthesis measured with L-[1-11C]leucine and PET in conscious, young adult men: normal values, variability, and reproducibility. J Cereb Blood Flow Metab 2008; 28:1502-13. [PMID: 18493259 PMCID: PMC2775471 DOI: 10.1038/jcbfm.2008.43] [Citation(s) in RCA: 30] [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
We report regional rates of cerebral protein synthesis (rCPS) measured with the fully quantitative L-[1-(11)C]leucine positron emission tomography (PET) method. The method accounts for the fraction (lambda) of unlabeled amino acids in the precursor pool for protein synthesis derived from arterial plasma; the remainder (1-lambda) comes from tissue proteolysis. We determined rCPS and lambda in 18 regions and whole brain in 10 healthy men (21 to 24 years). Subjects underwent two 90-min dynamic PET studies with arterial blood sampling at least 2 weeks apart. Rates of cerebral protein synthesis varied regionally and ranged from 0.97+/-0.70 to 2.25+/-0.20 nmol/g per min. Values of rCPS were in good agreement between the two PET studies. Mean differences in rCPS between studies ranged from 9% in cortical regions to 15% in white matter. The lambda value was comparatively more uniform across regions, ranging from 0.63+/-0.03 to 0.79+/-0.02. Mean differences in lambda between studies were 2% to 8%. Intersubject variability in rCPS was on average 6% in cortical areas, 9% in subcortical regions, and 12% in white matter; intersubject variability in lambda was 2% to 8%. Our data indicate that in human subjects low variance and highly reproducible measures of rCPS can be made with the L-[1-(11)C]leucine PET method.
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Affiliation(s)
- Shrinivas Bishu
- Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-1298, USA.
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19
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Smith CB, Schmidt KC, Bishu S, Channing MA, Bacon J, Burlin TV, Qin M, Liu ZH, Xia Z, Huang T, Vuong BK, Herscovitch P. Use of acute hyperphenylalaninemia in rhesus monkeys to examine sensitivity and stability of the L-[1-11C]leucine method for measurement of regional rates of cerebral protein synthesis with PET. J Cereb Blood Flow Metab 2008; 28:1388-98. [PMID: 18431402 PMCID: PMC2531290 DOI: 10.1038/jcbfm.2008.27] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have previously shown by direct comparison with autoradiographic and biochemical measurements that the L-[1-(11)C]leucine positron emission tomography method provides accurate determinations of regional rates of cerebral protein synthesis (rCPS) and the fraction (lambda) of unlabeled leucine in the precursor pool for protein synthesis derived from arterial plasma. In this study, we examine sensitivity of the method to detect changes in lambda and stability of the method to measure rCPS in the face of these changes. We studied four isoflurane-anesthetized monkeys dynamically scanned with the high resolution research tomograph under control and mild hyperphenylalaninemic conditions. Hyperphenylalaninemia was produced by an infusion of phenylalanine that increased plasma phenylalanine concentrations three- to five-fold. In phenylalanine-infused monkeys, plasma leucine concentrations remained relatively constant, but values of lambda were statistically significantly decreased by 11% to 15%; rCPS was unaffected. Effects on lambda are consistent with competitive inhibition of leucine transport by increased plasma phenylalanine. The effect on lambda shows that competition for the transporter results in a reduction in the fraction of leucine in the precursor pool for protein synthesis coming from plasma. Even under these hyperphenylalaninemic conditions, rCPS remains unchanged due to the compensating increased contribution of leucine from protein degradation to the precursor pool.
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Affiliation(s)
- Carolyn B Smith
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, Bethesda, Maryland 20892-1298, USA.
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20
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Smith CB, Schmidt KC, Qin M, Burlin TV, Cook MP, Kang J, Saunders RC, Bacher JD, Carson RE, Channing MA, Eckelman WC, Herscovitch P, Laverman P, Vuong BK. Measurement of regional rates of cerebral protein synthesis with L-[1-11C]leucine and PET with correction for recycling of tissue amino acids: II. Validation in rhesus monkeys. J Cereb Blood Flow Metab 2005; 25:629-40. [PMID: 15703697 DOI: 10.1038/sj.jcbfm.9600066] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The confounding effect of recycling of amino acids derived from tissue protein breakdown into the precursor pool for protein synthesis has been an obstacle to adapting in vivo methods for determination of regional rates of cerebral protein synthesis (rCPS) to positron emission tomography (PET). We used a kinetic modeling approach to estimate lambda, the fraction of the precursor pool for protein synthesis derived from arterial plasma, and to measure rCPS in three anesthetized adult monkeys dynamically scanned after a bolus injection of L-[1-11C]leucine. In the same animals, lambda was directly measured in a steady-state terminal experiment, and values showed excellent agreement with those estimated in the PET studies. In three additional monkeys rCPS was determined with the quantitative autoradiographic L-[1-14C]leucine method. In whole brain and cerebellum, rates of protein synthesis determined with the autoradiographic method were in excellent agreement with those determined with PET, and regional values were in good agreement when differences in spatial resolution of the two methods were taken into account. Low intrasubject variability was found on repeated PET studies. Our results in anesthetized monkey indicate that, by using a kinetic modeling approach to correct for recycling of tissue amino acids, quantitatively accurate and reproducible measurement of rCPS is possible with L-[1-11C]leucine and PET.
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Affiliation(s)
- Carolyn Beebe Smith
- Unit on Neuroadaptation and Protein Metabolism, Laboratory of Cerebral Metabolism, National Institute of Mental Health, Bethesda, Maryland 20892-4030, USA.
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21
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Wells JM, Mankoff DA, Muzi M, O'Sullivan F, Eary JF, Spence AM, Krohn KA. Kinetic Analysis of 2-[11C]Thymidine PET Imaging Studies of Malignant Brain Tumors: Compartmental Model Investigation and Mathematical Analysis. Mol Imaging 2002; 1:151-9. [PMID: 12920853 DOI: 10.1162/15353500200202112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
2-[11C]Thymidine (TdR), a PET tracer for cellular proliferation, may be advantageous for monitoring brain tumor progression and response to therapy. We previously described and validated a five-compartment model for thymidine incorporation into DNA in somatic tissues, but the effect of the blood–brain barrier on the transport of TdR and its metabolites necessitated further validation before it could be applied to brain tumors. Methods: We investigated the behavior of the model under conditions experienced in the normal brain and brain tumors, performed sensitivity and identifiability analysis to determine the ability of the model to estimate the model parameters, and conducted simulations to determine whether it can distinguish between thymidine transport and retention. Results: Sensitivity and identifiability analysis suggested that the non-CO2 metabolite parameters could be fixed without significantly affecting thymidine parameter estimation. Simulations showed that K1t and KTdR could be estimated accurately ( r = .97 and .98 for estimated vs. true parameters) with standard errors < 15%. The model was able to separate increased transport from increased retention associated with tumor proliferation. Conclusion: Our model adequately describes normal brain and brain tumor kinetics for thymidine and its metabolites, and it can provide an estimate of the rate of cellular proliferation in brain tumors.
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22
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Evans SM, Bergeron M, Ferriero DM, Sharp FR, Hermeking H, Kitsis RN, Geenen DL, Bialik S, Lord EM, Koch CJ. Imaging hypoxia in diseased tissues. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 428:595-603. [PMID: 9500104 DOI: 10.1007/978-1-4615-5399-1_84] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- S M Evans
- Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, USA
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23
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Chang MC, Arai T, Freed LM, Wakabayashi S, Channing MA, Dunn BB, Der MG, Bell JM, Sasaki T, Herscovitch P, Eckelman WC, Rapoport SI. Brain incorporation of [1-11C]arachidonate in normocapnic and hypercapnic monkeys, measured with positron emission tomography. Brain Res 1997; 755:74-83. [PMID: 9163542 DOI: 10.1016/s0006-8993(97)00088-7] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Positron emission tomography (PET) was used to determine brain incorporation coefficients k* of [1-11C]arachidonate in isoflurane-anesthetized rhesus monkeys, as well as cerebral blood flow (CBF) using [15O]water. Intravenously injected [1-11C]arachidonate disappeared from plasma with a half-life of 1.1 min, whereas brain radioactivity reached a steady-state by 10 min. Mean values of k* were the same whether calculated by a single-time point method at 20 min after injection began, or by least-squares fitting of an equation for total brain radioactivity to data at all time points. k* equalled 1.1-1.2 x 10(-4) ml x s(-1) x g(-1) in gray matter and was unaffected by a 2.6-fold increase in CBF caused by hypercapnia. These results indicate that brain incorporation of [1-11C]arachidonate can be quantified in the primate using PET, and that incorporation is flow-independent.
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Affiliation(s)
- M C Chang
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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24
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Nunn A, Linder K, Strauss HW. Nitroimidazoles and imaging hypoxia. EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1995; 22:265-80. [PMID: 7789400 DOI: 10.1007/bf01081524] [Citation(s) in RCA: 271] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Decreased tissue oxygen tension is a component of many diseases. Although hypoxia can be secondary to a low inspired pO2 or a variety of lung disorders, the commonest cause is ischemia due to an oxygen demand greater than the local oxygen supply. In tumors, low tissue pO2 is often observed, most often due to a blood supply inadequate to meet the tumor's demands. Hypoxic tumor tissue is associated with increased resistance to therapy. In the heart tissue hypoxia is often observed in persistent low-flow states, such as hibernating myocardium. In patients with stroke, hypoxia has been associated with the penumbral region, where an intervention could preserve function. Despite the potential importance of oxygen levels in tissue, difficulty in making this measurement in vivo has limited its role in clinical decision making. A class of compounds known to undergo different intracellular metabolism depending on the availability of oxygen in tissue, the nitroimidazoles, have been advocated for imaging hypoxic tissue. When a nitroimidazole enters a viable cell the molecule undergoes a single electron reduction, to form a potentially reactive species. In the presence of normal oxygen levels the molecule is immediately reoxidized. This futile shuttling takes place for some time, before the molecule diffuses out of the cell. In hypoxic tissue the low oxygen concentration is not able to effectively compete to reoxidize the molecule and further reduction appears to take place, culminating in the association of the reduced nitroimidazole with various intracellular components. The association is not irreversible, since these agents clear from hypoxic tissue over time. Initial development of nitroimidazoles for in vivo imaging used radiohalogenated derivatives of misonidazole, such as fluoromisonidazole, some of which have recently been employed in patients. Two major problems with fluoromisonidazole are its relatively low concentration within the lesion and the need to wait several hours to permit clearance of the agent from the normoxic background tissue (contrast between lesion and background typically < 2:1 at about 90 min after injection). Even with high-resolution positron emission tomographic imaging, this combination of circumstances makes successful evaluation of hypoxic lesions a challenge.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- A Nunn
- Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, N.J., USA
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25
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Rosenthal M, Sick TJ. Brain oxygenation: monitoring techniques and insights into brain function and survival. ACTA ACUST UNITED AC 1989. [DOI: 10.1016/s0950-3501(89)80023-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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26
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Senda M, Alpert NM, Mackay BC, Buxton RB, Correia JA, Weise SB, Ackerman RH, Dorer D, Buonanno FS. Evaluation of the 11CO2 positron emission tomographic method for measuring brain pH. II. Quantitative pH mapping in patients with ischemic cerebrovascular diseases. J Cereb Blood Flow Metab 1989; 9:859-73. [PMID: 2511212 DOI: 10.1038/jcbfm.1989.120] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A practical method has been developed that, using 11CO2 and positron emission tomography (PET), computes and maps (a) "effective pH" (pHt), a weighted average of intra- and extracellular pH, and (b) "clearance" (K1), product of blood flow and 11CO2 extraction. This method, together with measurements of cerebral blood flow (CBF) and oxygen extraction fraction (OEF), was applied to 12 patients with cerebral ischemia or stroke. The regional K1 was positively correlated with CBF (n = +0.78). The k1/CBF ratio, representing the extraction fraction ratio of 11CO2 to H2 15O, was negatively correlated with CBF (r = -0.54), suggesting that 11CO2 extraction decreases as flow increases. In five acute stroke patients within 2 days of onset, the injured cortex had lower CBF (20.6 ml/min/100 g), higher OEF (78.1%), and lower pHt (6.96) than the contralateral cortex (CBF = 41.4 ml/min/100 g, OEF = 53.3%, pHt = 7.00), suggesting intracellular acidosis with intact cell membranes. In three stroke patients 5-8 days after onset, the injured cortex had higher CBF (60.9 ml/min/100 g), lower OEF (32.0%), and higher pHt (7.12) than the contralateral cortex (CBF = 45.3 ml/min/100 g, OEF = 58.0%, pHt = 7.06), which suggested an increase in extracellular volume compartment reflecting loss of cell membrane integrity. This method provides information on the regional tissue acid-base status and cell membrane integrity, which may be prognostic of tissue viability.
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Affiliation(s)
- M Senda
- Department of Radiology, Massachusetts General Hospital, Boston 02114
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