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Knopf P, Stowbur D, Hoffmann SHL, Hermann N, Maurer A, Bucher V, Poxleitner M, Tako B, Sonanini D, Krishnamachary B, Sinharay S, Fehrenbacher B, Gonzalez-Menendez I, Reckmann F, Bomze D, Flatz L, Kramer D, Schaller M, Forchhammer S, Bhujwalla ZM, Quintanilla-Martinez L, Schulze-Osthoff K, Pagel MD, Fransen MF, Röcken M, Martins AF, Pichler BJ, Ghoreschi K, Kneilling M. Acidosis-mediated increase in IFN-γ-induced PD-L1 expression on cancer cells as an immune escape mechanism in solid tumors. Mol Cancer 2023; 22:207. [PMID: 38102680 PMCID: PMC10722725 DOI: 10.1186/s12943-023-01900-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 11/12/2023] [Indexed: 12/17/2023] Open
Abstract
Immune checkpoint inhibitors have revolutionized cancer therapy, yet the efficacy of these treatments is often limited by the heterogeneous and hypoxic tumor microenvironment (TME) of solid tumors. In the TME, programmed death-ligand 1 (PD-L1) expression on cancer cells is mainly regulated by Interferon-gamma (IFN-γ), which induces T cell exhaustion and enables tumor immune evasion. In this study, we demonstrate that acidosis, a common characteristic of solid tumors, significantly increases IFN-γ-induced PD-L1 expression on aggressive cancer cells, thus promoting immune escape. Using preclinical models, we found that acidosis enhances the genomic expression and phosphorylation of signal transducer and activator of transcription 1 (STAT1), and the translation of STAT1 mRNA by eukaryotic initiation factor 4F (elF4F), resulting in an increased PD-L1 expression. We observed this effect in murine and human anti-PD-L1-responsive tumor cell lines, but not in anti-PD-L1-nonresponsive tumor cell lines. In vivo studies fully validated our in vitro findings and revealed that neutralizing the acidic extracellular tumor pH by sodium bicarbonate treatment suppresses IFN-γ-induced PD-L1 expression and promotes immune cell infiltration in responsive tumors and thus reduces tumor growth. However, this effect was not observed in anti-PD-L1-nonresponsive tumors. In vivo experiments in tumor-bearing IFN-γ-/- mice validated the dependency on immune cell-derived IFN-γ for acidosis-mediated cancer cell PD-L1 induction and tumor immune escape. Thus, acidosis and IFN-γ-induced elevation of PD-L1 expression on cancer cells represent a previously unknown immune escape mechanism that may serve as a novel biomarker for anti-PD-L1/PD-1 treatment response. These findings have important implications for the development of new strategies to enhance the efficacy of immunotherapy in cancer patients.
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Affiliation(s)
- Philipp Knopf
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Dimitri Stowbur
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
| | - Sabrina H L Hoffmann
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Natalie Hermann
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Andreas Maurer
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
| | - Valentina Bucher
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Marilena Poxleitner
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Bredi Tako
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - Dominik Sonanini
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
| | - Balaji Krishnamachary
- Division of Cancer Imaging Research, The Russell H Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sanhita Sinharay
- Department of Cancer Systems Imaging, MD Anderson Cancer Center, 1881 East Rd, Houston, TX, 77054, USA
| | | | - Irene Gonzalez-Menendez
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- Institute of Pathology and Neuropathology, Department of Pathology, Eberhard Karls University of Tübingen and Comprehensive Cancer Center, Tübingen University Hospital, Tübingen, Germany
| | - Felix Reckmann
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
| | - David Bomze
- Department of Dermatology, Tel-Aviv Medical Center, Tel-Aviv, Israel
| | - Lukas Flatz
- Department of Dermatology, Eberhard Karls University, Tübingen, Germany
| | - Daniela Kramer
- Interfaculty Institute of Biochemistry, Eberhard Karls University, Tübingen, Germany
| | - Martin Schaller
- Department of Dermatology, Eberhard Karls University, Tübingen, Germany
| | | | - Zaver M Bhujwalla
- Division of Cancer Imaging Research, The Russell H Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Leticia Quintanilla-Martinez
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- Institute of Pathology and Neuropathology, Department of Pathology, Eberhard Karls University of Tübingen and Comprehensive Cancer Center, Tübingen University Hospital, Tübingen, Germany
| | - Klaus Schulze-Osthoff
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- Interfaculty Institute of Biochemistry, Eberhard Karls University, Tübingen, Germany
- German Cancer Consortium (DKTK), partner site Tübingen, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - Mark D Pagel
- Department of Cancer Systems Imaging, MD Anderson Cancer Center, 1881 East Rd, Houston, TX, 77054, USA
| | - Marieke F Fransen
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center (LUMC), Leiden, Netherlands
| | - Martin Röcken
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- Department of Dermatology, Eberhard Karls University, Tübingen, Germany
- German Cancer Consortium (DKTK), partner site Tübingen, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - André F Martins
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- German Cancer Consortium (DKTK), partner site Tübingen, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - Bernd J Pichler
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany
- German Cancer Consortium (DKTK), partner site Tübingen, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - Kamran Ghoreschi
- Department of Dermatology, Venereology and Allergology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, 10117, Berlin, Germany
| | - Manfred Kneilling
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Tübingen, Germany.
- Cluster of Excellence iFIT (EXC 2180) "Image Guided and Functionally Instructed Tumor Therapies", Röntgenweg 13, 72076, Tübingen, Germany.
- Department of Dermatology, Eberhard Karls University, Tübingen, Germany.
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Li T, Cárdenas-Rodríguez J, Trakru PN, Pagel MD. A machine learning approach that measures pH using acidoCEST MRI of iopamidol. NMR IN BIOMEDICINE 2023; 36:e4986. [PMID: 37280721 PMCID: PMC10529789 DOI: 10.1002/nbm.4986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 05/16/2023] [Accepted: 05/17/2023] [Indexed: 06/08/2023]
Abstract
Tumor acidosis is an important biomarker for aggressive tumors, and extracellular pH (pHe) of the tumor microenvironment can be used to predict and evaluate tumor responses to chemotherapy and immunotherapy. AcidoCEST MRI measures tumor pHe by exploiting the pH-dependent chemical exchange saturation transfer (CEST) effect of iopamidol, an exogenous CT agent repurposed for CEST MRI. However, all pH fitting methodologies for acidoCEST MRI data have limitations. Herein we present results of the application of machine learning for extracting pH values from CEST Z-spectra of iopamidol. We acquired 36,000 experimental CEST spectra from 200 phantoms of iopamidol prepared at five concentrations, five T1 values, and eight pH values at five temperatures, acquired at six saturation powers and six saturation times. We also acquired T1 , T2 , B1 RF power, and B0 magnetic field strength supplementary MR information. These MR images were used to train and validate machine learning models for the tasks of pH classification and pH regression. Specifically, we tested the L1-penalized logistic regression classification (LRC) model and the random forest classification (RFC) model for classifying the CEST Z-spectra for thresholds at pH 6.5 and 7.0. Our results showed that both RFC and LRC were effective for pH classification, although the RFC model achieved higher predictive value, and improved the accuracy of classification accuracy with CEST Z-spectra with a more limited set of saturation frequencies. Furthermore, we used LASSO and random forest regression (RFR) models to explore pH regression, which showed that the RFR model achieved higher accuracy and precision for estimating pH across the entire pH range of 6.2-7.3, especially when using a more limited set of features. Based on these results, machine learning for analysis of acidoCEST MRI is promising for eventual in vivo determination of tumor pHe.
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Affiliation(s)
- Tianzhe Li
- The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- The University of Texas Health Science Center, Houston, Texas, USA
| | | | - Priya N. Trakru
- The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
- Rice University, Houston, Texas, USA
| | - Mark D. Pagel
- The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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Zhang Y, Zu T, Liu R, Zhou J. Acquisition sequences and reconstruction methods for fast chemical exchange saturation transfer imaging. NMR IN BIOMEDICINE 2023; 36:e4699. [PMID: 35067987 DOI: 10.1002/nbm.4699] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/02/2022] [Accepted: 01/17/2022] [Indexed: 05/23/2023]
Abstract
Chemical exchange saturation transfer (CEST) imaging is an emerging molecular magnetic resonance imaging (MRI) technique that has been developed and employed in numerous diseases. Based on the unique saturation transfer principle, a family of CEST-detectable biomolecules in vivo have been found capable of providing valuable diagnostic information. However, CEST MRI needs a relatively long scan time due to the common long saturation labeling module and typical acquisition of multiple frequency offsets and signal averages, limiting its widespread clinical applications. So far, a plethora of imaging schemes and techniques has been developed to accelerate CEST MRI. In this review, the key acquisition and reconstruction methods for fast CEST imaging are summarized from a practical and systematic point of view. The first acquisition sequence section describes the major development of saturation schemes, readout patterns, ultrafast z-spectroscopy, and saturation-editing techniques for rapid CEST imaging. The second reconstruction method section lists the important advances of parallel imaging, compressed sensing, sparsity in the z-spectrum, and algorithms beyond the Fourier transform for speeding up CEST MRI.
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Affiliation(s)
- Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Tao Zu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ruibin Liu
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jinyuan Zhou
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
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4
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Igarashi T, Kim H, Sun PZ. Detection of tissue pH with quantitative chemical exchange saturation transfer magnetic resonance imaging. NMR IN BIOMEDICINE 2023; 36:e4711. [PMID: 35141979 PMCID: PMC10249910 DOI: 10.1002/nbm.4711] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 02/03/2022] [Accepted: 02/05/2022] [Indexed: 05/12/2023]
Abstract
Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has emerged as a novel means for sensitive detection of dilute labile protons and chemical exchange rates. By sensitizing to pH-dependent chemical exchange, CEST MRI has shown promising results in monitoring tissue statuses such as pH changes in disorders like acute stroke, tumor, and acute kidney injury. This article briefly reviews the basic principles for CEST imaging and quantitative measures, from the simplistic asymmetry analysis to multipool Lorentzian decoupling and quasi-steady-state reconstruction. In particular, the advantages and limitations of commonly used quantitative approaches for CEST applications are discussed.
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Affiliation(s)
- Takahiro Igarashi
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA
| | - Hahnsung Kim
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA
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Saito S. [5. Advanced Imaging Technology-T1rho-CEST Imaging]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2022; 78:95-100. [PMID: 35046227 DOI: 10.6009/jjrt.780111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shigeyoshi Saito
- Laboratory of Advanced Imaging Technology, Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine.,Department of Advanced Medical Technology, National Cardiovascular and Cerebral Research Center
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6
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Kombala CJ, Kotrotsou A, Schuler FW, de la Cerda J, Ma JC, Zhang S, Pagel MD. Development of a Nanoscale Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agent That Measures pH. ACS NANO 2021; 15:20678-20688. [PMID: 34870957 DOI: 10.1021/acsnano.1c10107] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
AcidoCEST MRI can measure the extracellular pH (pHe) of the tumor microenvironment in mouse models of human cancers and in patients who have cancer. However, chemical exchange saturation transfer (CEST) is an insensitive magnetic resonance imaging (MRI) contrast mechanism, requiring a high concentration of small-molecule agent to be delivered to the tumor. Herein, we developed a nanoscale CEST agent that can measure pH using acidoCEST MRI, which may decrease the requirement for high delivery concentrations of agent. We also developed a monomer agent for comparison to the polymer. After optimizing CEST experimental conditions, we determined that the polymer agent could be used during acidoCEST MRI studies at 125-fold and 488-fold lower concentration than the monomer agent and iopamidol, respectively. We also determined that both agents can measure pH with negligible dependence on temperature. However, pH measurements with both agents were dependent on concentration, which may be due to concentration-dependent changes in hydrogen bonding and/or steric hindrance. We performed in vivo acidoCEST MRI studies using the three agents to study a xenograft MDA-MB-231 model of mammary carcinoma. The tumor pHe measurements were 6.33 ± 0.12, 6.70 ± 0.15, and 6.85 ± 0.15 units with iopamidol, the monomer agent, and polymer agent, respectively. The higher pHe measurements with the monomer and polymer agents were attributed to the concentration dependence of these agents. This study demonstrated that nanoscale agents have merit for CEST MRI studies, but consideration should be given to the dependence of CEST contrast on the concentration of these agents.
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Affiliation(s)
- Chathuri J Kombala
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - Aikaterini Kotrotsou
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - F William Schuler
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - Jorge de la Cerda
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - Jacqueline C Ma
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - Shu Zhang
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
| | - Mark D Pagel
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77054, United States
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Lombardi AF, Wong JH, High R, Ma Y, Jerban S, Tang Q, Du J, Frost P, Pagel MD, Chang EY. AcidoCEST MRI Evaluates the Bone Microenvironment in Multiple Myeloma. Mol Imaging Biol 2021; 23:865-873. [PMID: 33939066 PMCID: PMC8563482 DOI: 10.1007/s11307-021-01611-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 04/14/2021] [Accepted: 04/26/2021] [Indexed: 01/29/2023]
Abstract
PURPOSE Multiple myeloma (MM) is an incurable disease of malignant plasma cells in the bone marrow (BM). Adaptive responses to hypoxia may be an essential element in MM progression and drug resistance. This metabolic adaptation involves a decrease in extracellular pH (pHe), and it depends on the upregulation of glucose transporters (GLUTs) that is common in hypoxia and in cancer cells. CEST MRI is an imaging technique that assesses pHe indirectly by the exchange rate of magnetic saturation transfer between labile protons on a solute and water. Thus, this study aimed to determine the feasibility of acidoCEST MRI for pHe measurement using an orthotopic mouse model of MM compared with GLUT1 immunofluorescence staining as a reference. PROCEDURES Orthotopic BM engrafted MM xenografts were established in NSG/NOD mice using the human RPMI8226 myeloma cell line. AcidoCEST MRI was performed approximately 6 weeks after intravenous challenge, before and after intravenous administration of iopamidol. BM pHe values were generated via fitting the CEST spectrum with the Bloch-McConnell equations. Samples were decalcified, sectioned, and immunostained for GLUT1 expression. Pearson's correlation was used to assess the relationship between pHe and [H3O+] versus GLUT1 expression. RESULTS Ten mice underwent acidoCEST MRI followed by immunofluorescent histologic analysis. A strong negative correlation was seen between pHe versus GLUT1 expression (r = - 0.75, p < 0.001). After transformation of pH to [H3O+], a strong positive correlation between [H3O+] and GLUT1 expression was observed (r = 0.8, p < 0.001). CONCLUSIONS AcidoCEST MRI can measure the extracellular pH of bone marrow affected by multiple myeloma. In this MM orthotopic mouse model, pHe measured by acidoCEST MRI showed strong correlations with the metabolic phenotype of BM tumor assessed by immunofluorescent histological assessment of GLUT1 overexpression.
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Affiliation(s)
- Alecio F Lombardi
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Jonathan H Wong
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Rachel High
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Yajun Ma
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Saeed Jerban
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Qingbo Tang
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Jiang Du
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA
- Department of Radiology, University of California, San Diego, CA, USA
| | - Patrick Frost
- Research Service, Greater Los Angeles Veteran Administration Healthcare System, Los Angeles, CA, USA
- Department of Medicine, University of California, Los Angeles, CA, USA
| | - Mark D Pagel
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Eric Y Chang
- Research Service, VA San Diego Healthcare System, 3350 La Jolla Village Drive, CA, 92161, San Diego, USA.
- Department of Radiology, University of California, San Diego, CA, USA.
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Abstract
Magnetic resonance fingerprinting (MRF) is increasingly being used to evaluate brain development and differentiate normal and pathologic tissues in children. MRF can provide reliable and accurate intrinsic tissue properties, such as T1 and T2 relaxation times. MRF is a powerful tool in evaluating brain disease in pediatric population. MRF is a new quantitative MR imaging technique for rapid and simultaneous quantification of multiple tissue properties.
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Affiliation(s)
- Sheng-Che Hung
- Department of Radiology, School of Medicine, University of North Carolina at Chapel Hill, 2006 Old Clinic, CB#7510, 101 Manning Dr, Chapel Hill, NC 27599, USA; Biomedical Research Imaging Center, School of Medicine, University of North Carolina at Chapel Hill, 125 Mason Farm Road, Marsico Hall, suite 1200, Chapel Hill, NC 27599, USA
| | - Yong Chen
- Department of Radiology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Pew-Thian Yap
- Department of Radiology, School of Medicine, University of North Carolina at Chapel Hill, 2006 Old Clinic, CB#7510, 101 Manning Dr, Chapel Hill, NC 27599, USA; Biomedical Research Imaging Center, School of Medicine, University of North Carolina at Chapel Hill, 125 Mason Farm Road, Marsico Hall, suite 1200, Chapel Hill, NC 27599, USA
| | - Weili Lin
- Department of Radiology, School of Medicine, University of North Carolina at Chapel Hill, 2006 Old Clinic, CB#7510, 101 Manning Dr, Chapel Hill, NC 27599, USA; Biomedical Research Imaging Center, School of Medicine, University of North Carolina at Chapel Hill, 125 Mason Farm Road, Marsico Hall, suite 1200, Chapel Hill, NC 27599, USA.
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9
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Villano D, Romdhane F, Irrera P, Consolino L, Anemone A, Zaiss M, Dastrù W, Longo DL. A fast multislice sequence for 3D MRI-CEST pH imaging. Magn Reson Med 2020; 85:1335-1349. [PMID: 33031591 PMCID: PMC7756816 DOI: 10.1002/mrm.28516] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 07/30/2020] [Accepted: 08/22/2020] [Indexed: 12/13/2022]
Abstract
Purpose Chemical exchange saturation transfer MRI can provide accurate pH images, but the slow scan time (due to long saturation periods and multiple offsets sampling) reduce both the volume coverage and spatial resolution capability, hence the possibility to interrogate the heterogeneity in tumors and organs. To overcome these limitations, we propose a fast multislice CEST‐MRI sequence with high pH accuracy and spatial resolution. Methods The sequence first uses a long saturation pulse to induce the steady‐state CEST contrast and a second short saturation pulse repeated after each image acquisition to compensate for signal losses based on an uneven irradiation scheme combined with a single‐shot rapid acquisition with refocusing echoes readout. Sequence sensitivity and accuracy in measuring pH was optimized by simulation and assessed by in vitro studies in pH‐varying phantoms. In vivo validation was performed in two applications by acquiring multislice pH images covering the whole tumors and kidneys after iopamidol injection. Results Simulated and in vivo data showed comparable contrast efficiency and pH responsiveness by reducing saturation time. The experimental data from a homogeneous, pH‐varying, iopamidol‐containing phantom show that the sequence produced a uniform CEST contrast across slices and accurate values across slices in less than 10 minutes. In vivo measurements allowed us to quantify the 3D pH gradients of tumors and kidneys, with pH ranges comparable with the literature. Conclusion The proposed fast multislice CEST‐MRI sequence allows volumetric acquisitions with good pH sensitivity, accuracy, and spatial resolution for several in vivo pH imaging applications.
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Affiliation(s)
- Daisy Villano
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Feriel Romdhane
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.,National Engineering School of Tunis (ENIT), University al Manar, Tunis, Tunisia
| | - Pietro Irrera
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy.,Institute of Biostructures and Bioimaging, University of Campania "Luigi Vanvitelli," Italian National Research Council, Napoli, Italy
| | - Lorena Consolino
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Annasofia Anemone
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Moritz Zaiss
- Department of Neuroradiology, Friedrich-Alexander Universität Erlangen-Nürnberg, University Hospital Erlangen, Erlangen, Germany
| | - Walter Dastrù
- Molecular Imaging Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Dario Livio Longo
- Institute of Biostructures and Bioimaging, Italian National Research Council, Torino, Italy
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10
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Kwiatkowski G, Kozerke S. Accelerating CEST MRI in the mouse brain at 9.4 T by exploiting sparsity in the Z-spectrum domain. NMR IN BIOMEDICINE 2020; 33:e4360. [PMID: 32621367 DOI: 10.1002/nbm.4360] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 05/20/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
PURPOSE Chemical exchange saturation transfer (CEST) is an MR contrast modality offering an enhanced sensitivity for the detection of dilute metabolites with exchangeable protons. Quantitative analysis requires the acquisition of a number of images (usually between 20 and 50 RF offsets) per Z-spectrum, leading to long acquisition times of the order of 5-40 min in practice. In this work, we explore the possibility of employing sparsity in the Z-spectrum domain (irradiation offset dimension) to provide an accelerated acquisition scheme without compromising the quality of reconstructed CEST spectra. METHOD AND THEORY Ex vivo and in vivo data were acquired on an experimental, small animal 9.4 T system. Three different reconstruction methods were tested: k-Z SPARSE, k-Z SLR and k-Z principal component analysis (PCA) using retrospective undersampling with net acceleration factors R = 2, 3, 5. The quality of the reconstructed data was compared with respect to CEST spectra and full magnetization transfer ratio (MTR) asymmetry maps. RESULTS In both phantom and in vivo data, CEST spectra and the resulting MTR asymmetry maps were reconstructed without significant deterioration in data quality. For a low acceleration factor (R = 2, 3) all applied methods resulted in similar data quality, while for high acceleration factor (R = 5) only k-Z PCA and k-Z SLR could be used. Loss in spatial resolution was observed in reconstruction with k-Z PCA for all acceleration factors. An example of prospective undersampling with acceleration factor R = 3 and k-Z PCA reconstruction demonstrates improved CEST maps when compared with fully sampled data acquisition with either three times longer scan duration or threefold prolonged acquisition window per frequency offset. CONCLUSION The acquisition time of CEST spectra can be significantly accelerated by exploiting the sparsity of the Z-domain. For prospective and retrospective analysis using k-Z PCA, an acceleration factor of up to R = 3 can be used without significant loss in data quality.
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Affiliation(s)
- Grzegorz Kwiatkowski
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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11
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Goldenberg JM, Berthusen AJ, Cárdenas-Rodríguez J, Pagel MD. Differentiation of Myositis-Induced Models of Bacterial Infection and Inflammation with T 2-Weighted, CEST, and DCE-MRI. ACTA ACUST UNITED AC 2020; 5:283-291. [PMID: 31572789 PMCID: PMC6752290 DOI: 10.18383/j.tom.2019.00009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We used T2 relaxation, chemical exchange saturation transfer (CEST), and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to assess whether bacterial infection can be differentiated from inflammation in a myositis-induced mouse model. We measured the T2 relaxation time constants, %CEST at 5 saturation frequencies, and area under the curve (AUC) from DCE-MRI after maltose injection from infected, inflamed, and normal muscle tissue models. We applied principal component analysis (PCA) to reduce dimensionality of entire CEST spectra and DCE signal evolutions, which were analyzed using standard classification methods. We extracted features from dimensional reduction as predictors for machine learning classifier algorithms. Normal, inflamed, and infected tissues were evaluated with H&E and gram-staining histological studies, and bacterial-burden studies. The T2 relaxation time constants and AUC of DCE-MRI after injection of maltose differentiated infected, inflamed, and normal tissues. %CEST amplitudes at −1.6 and −3.5 ppm differentiated infected tissues from other tissues, but these did not differentiate inflamed tissue from normal tissue. %CEST amplitudes at 3.5, 3.0, and 2.5 ppm, AUC of DCE-MRI for shorter time periods, and relative Ktrans and kep values from DCE-MRI could not differentiate tissues. PCA and machine learning of CEST-MRI and DCE-MRI did not improve tissue classifications relative to traditional analysis methods. Similarly, PCA and machine learning did not further improve tissue classifications relative to T2 MRI. Therefore, future MRI studies of infection models should focus on T2-weighted MRI and analysis of T2 relaxation times.
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Affiliation(s)
- Joshua M Goldenberg
- Department of Pharmaceutical Sciences, University of Arizona, Tucson, AZ.,Department of Genitourinary Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
| | | | | | - Mark D Pagel
- Department of Cancer Systems Imaging, The University of Texas MD Anderson Cancer Center, Houston, TX
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12
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Saito S, Tanoue M, Ohki A, Takahashi Y. [19. Application of Chemical Exchange Saturation Transfer Imaging Using Ultra-high Filed MRI]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2019; 75:1194-1199. [PMID: 31631114 DOI: 10.6009/jjrt.2019_jsrt_75.10.1194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shigeyoshi Saito
- Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine.,Department of Biomedical Imaging, National Cardiovascular and Cerebral Research Center
| | - Minori Tanoue
- Department of Clinical Radiology Service, Kyoto University Hospital
| | - Akiko Ohki
- Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine.,Department of Biomedical Imaging, National Cardiovascular and Cerebral Research Center
| | - Yusuke Takahashi
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine
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13
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Sun PZ. Development of intravoxel inhomogeneity correction for chemical exchange saturation transfer spectral imaging: a high-resolution field map-based deconvolution algorithm for magnetic field inhomogeneity correction. Magn Reson Med 2019; 83:1348-1355. [PMID: 31628765 DOI: 10.1002/mrm.28015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 12/12/2022]
Abstract
PURPOSE CEST MRI is sensitive to dilute proteins/peptides and microenvironmental properties yet susceptible to magnetic field inhomogeneity. We aimed to develop a high-resolution field map-based CEST intravoxel inhomogeneity correction (CIVIC) algorithm for CEST Z-spectral imaging. METHODS The proposed CIVIC approach treats the intravoxel inhomogeneity as a point spread function and applies the deconvolution algorithm to reconstruct the original Z-spectrum. We simulated the effect of B0 field inhomogeneity on CEST measurement and tested the efficacy of the proposed CIVIC algorithm. We also performed CEST MRI on a dual-pH Creatine-gel phantom under varied field homogeneity conditions and compared the CEST MRI contrast-to-noise ratio from the raw Z-spectrum, water saturation shift referencing, and the proposed CIVIC methods. RESULTS The numerical simulation showed that the CIVIC algorithm remains effective even in the case of symmetric field dispersion with a 0 mean shift. The experimental results confirmed that the proposed CIVIC method substantially improves the CEST MRI contrast-to-noise ratio under different field homogeneity conditions. CONCLUSION Our study established a new intravoxel B0 inhomogeneity correction algorithm, promising to facilitate CEST spectral imaging in challenging experimental conditions.
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Affiliation(s)
- Phillip Zhe Sun
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia.,Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia
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14
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Lindeman LR, Jones KM, High RA, Howison CM, Shubitz LF, Pagel MD. Differentiating lung cancer and infection based on measurements of extracellular pH with acidoCEST MRI. Sci Rep 2019; 9:13002. [PMID: 31506562 PMCID: PMC6736855 DOI: 10.1038/s41598-019-49514-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/27/2019] [Indexed: 01/17/2023] Open
Abstract
Lung cancer diagnosis via imaging may be confounded by the presence of indolent infectious nodules in imaging studies. This issue is pervasive in the southwestern US where coccidioidomycosis (Valley Fever) is endemic. AcidoCEST MRI is a noninvasive imaging method that quantifies the extracellular pH (pHe) of tissues in vivo, allowing tumor acidosis to be used as a diagnostic biomarker. Using murine models of lung adenocarcinoma and coccidoidomycosis, we found that average lesion pHe differed significantly between tumors and granulomas. Our study shows that acidoCEST MRI is a promising tool for improving the specificity of lung cancer diagnosis.
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Affiliation(s)
- Leila R Lindeman
- Cancer Biology Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ, USA
| | - Kyle M Jones
- Bioengineering Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ, USA
| | - Rachel A High
- Cancer Biology Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ, USA
| | | | - Lisa F Shubitz
- Valley Fever Center for Excellence, University of Arizona, Tucson, AZ, USA
| | - Mark D Pagel
- Department of Cancer Systems Imaging, MD Anderson Cancer Center, Houston, TX, USA.
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15
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Zhang Y, Heo HY, Jiang S, Zhou J, Bottomley PA. Fast 3D chemical exchange saturation transfer imaging with variably-accelerated sensitivity encoding (vSENSE). Magn Reson Med 2019; 82:2046-2061. [PMID: 31264278 DOI: 10.1002/mrm.27881] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 05/31/2019] [Accepted: 06/02/2019] [Indexed: 12/20/2022]
Abstract
PURPOSE To extend the variably-accelerated sensitivity encoding (vSENSE) method from 2D to 3D for fast chemical exchange saturation transfer (CEST) imaging, and prospectively implement it for clinical MRI. METHODS The CEST scans were acquired from 7 normal volunteers and 15 brain tumor patients using a 3T clinical scanner. The 2D and 3D "artifact suppression" (AS) vSENSE algorithms were applied to generate sensitivity maps from a first scan acquired with conventional SENSE-accelerated 2D and 3D CEST data. The AS sensitivity maps were then applied to reconstruct the other CEST frames at higher acceleration factors. Both retrospective and prospective acceleration in phase-encoding and slice-encoding dimensions were implemented. RESULTS Applying the 2D AS vSENSE algorithm to a 2-fold undersampled 3.5-ppm CEST frame halved the scan time of conventional SENSE, while generating essentially identical reconstruction errors (p ≈ 1.0). The 3D AS vSENSE algorithm permitted prospective acceleration by up to 8-fold, in total, from phase-encoding and slice-encoding directions for individual source CEST images, and an overall speed-up in scan time of 5-fold. The resulting vSENSE-accelerated amide proton transfer-weighted images agreed with conventional 2-fold-accelerated SENSE CEST results in brain tumor patients and healthy volunteers. Importantly, the vSENSE method eliminated unfolding artifacts in the slice-encoding direction that compromised conventional SENSE CEST scans. CONCLUSION The vSENSE method can be extended to 3D CEST imaging to provide higher acceleration factors than conventional SENSE without compromising accuracy.
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Affiliation(s)
- Yi Zhang
- Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.,Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Hye-Young Heo
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Paul A Bottomley
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
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16
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Cai J, Wu J, Guo C, Cai S, Cai C. Ultrafast multi-slice chemical exchange saturation transfer imaging scheme based on segmented spatiotemporal encoding. Magn Reson Imaging 2019; 60:122-129. [PMID: 30953697 DOI: 10.1016/j.mri.2019.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 03/29/2019] [Accepted: 04/02/2019] [Indexed: 12/25/2022]
Abstract
Chemical exchange saturation transfer (CEST) imaging is an important magnetic resonance molecular imaging technology. However, long acquisition time limits its clinical application, especially when multi-slice CEST imaging is needed. Though single-shot EPI can be used to accelerate CEST imaging, images are often distorted under inhomogeneous magnetic fields. In this work, we propose a new method called CEST-SeSPEN for ultrafast multi-slice CEST imaging based on segmented spatiotemporally encoded (SeSPEN) MRI. Experiments were performed on creatine phantom and hen egg. The results show that CEST-SeSPEN can provide good CEST contrast images. Its acquisition time is much shorter than other multi-slice CEST methods currently available. It may be used in challenging situation where high temporal resolution and robustness to field inhomogeneity are vital.
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Affiliation(s)
- Jizhou Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jian Wu
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Chenlu Guo
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.
| | - Congbo Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.
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17
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Preliminary Results that Assess Metformin Treatment in a Preclinical Model of Pancreatic Cancer Using Simultaneous [ 18F]FDG PET and acidoCEST MRI. Mol Imaging Biol 2019; 20:575-583. [PMID: 29374343 DOI: 10.1007/s11307-018-1164-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
PURPOSE We sought to determine if the synergy between evaluations of glucose uptake in tumors and extracellular tumor acidosis measured with simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) can improve longitudinal evaluations of the response to metformin treatment. PROCEDURES A standard 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET protocol that evaluates glucose uptake in tumors, and a standard acidoCEST MRI protocol that measures extracellular pH (pHe) in tumors, were simultaneously performed to assess eight vehicle-treated (control) mice and eight metformin-treated mice 1 day before treatment, 1 day after initiating daily treatment with metformin, and 7 days after initiating treatment. Longitudinal changes in SUVmax and extracellular pH (pHe) were evaluated for each treatment group, and differences in SUVmax and pHe between metformin-treated and control groups were also evaluated. RESULTS MRI acquisition protocols had little effect on the PET count rate, and the PET instrumentation had little effect on image contrast during acidoCEST MRI, verifying that [18F]FDG PET and acidoCEST MRI can be performed simultaneously. The average SUVmax of the tumor model had a significant decrease after 7 days of treatment with metformin, as expected. The average tumor pHe decreased after 7 days of metformin treatment, which reflected the inhibition of the consumption of cytosolic lactic acid caused by metformin. However, the average SUVmax of the tumor model was not significantly different between the metformin-treated and control groups after 7 days of treatment, and average pHe was also not significantly different between these groups. For comparison, the combination of average SUVmax and pHe measurements significantly differed between the treatment group and control group on Day 7. CONCLUSIONS [18F]FDG PET and acidoCEST MRI studies can be performed simultaneously. The synergistic combination of assessing glucose uptake and tumor acidosis can improve differentiation of a drug-treated group from a control group during drug treatment of a tumor model.
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18
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Sinharay S, Randtke EA, Howison CM, Ignatenko NA, Pagel MD. Detection of Enzyme Activity and Inhibition during Studies in Solution, In Vitro and In Vivo with CatalyCEST MRI. Mol Imaging Biol 2019; 20:240-248. [PMID: 28726131 DOI: 10.1007/s11307-017-1092-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
PURPOSE The detection of enzyme activities and evaluation of enzyme inhibitors have been challenging with magnetic resonance imaging (MRI). To address this need, we have developed a diamagnetic, nonmetallic contrast agent and a protocol known as catalyCEST MRI that uses chemical exchange saturation transfer (CEST) to detect enzyme activity as well as enzyme inhibition. PROCEDURES We synthesized a diamagnetic MRI contrast agent that has enzyme responsive and enzyme unresponsive CEST signals. We tested the ability of this agent to detect the activity of kallikrein 6 (KLK6) in biochemical solutions, in vitro and in vivo, with and without a KLK6 inhibitor. RESULTS The agent detected KLK6 activity in solution and also detected KLK6 inhibition by antithrombin III. KLK6 activity was detected during in vitro studies with HCT116 colon cancer cells, relative to the detection of almost no activity in a KLK6-knockdown HCT116 cell line and HCT116 cells treated with antithrombin III inhibitor. Finally, strong enzyme activity was detected within an in vivo HCT116 tumor model, while lower enzyme activity was detected in a KLK6 knockdown tumor model and in the HCT116 tumor model treated with antithrombin III inhibitor. In all cases, comparisons of the enzyme responsive and enzyme unresponsive CEST signals were critical for the detection of enzyme activity. CONCLUSIONS This study has established that catalyCEST MRI with an exogenous diaCEST agent can evaluate enzyme activity and inhibition in solution, in vitro and in vivo.
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Affiliation(s)
- Sanhita Sinharay
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Edward A Randtke
- Department of Medical Imaging, University of Arizona, 1515 N. Campbell Avenue, Tucson, AZ, 84724-5024, USA
| | - Christine M Howison
- Department of Medical Imaging, University of Arizona, 1515 N. Campbell Avenue, Tucson, AZ, 84724-5024, USA
| | - Natalia A Ignatenko
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ, USA.,University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA
| | - Mark D Pagel
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA. .,Department of Medical Imaging, University of Arizona, 1515 N. Campbell Avenue, Tucson, AZ, 84724-5024, USA. .,University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA. .,Department of Cancer Systems Imaging, MD Anderson Cancer Center, 1881 East Road, Houston, TX, 77054, USA.
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19
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Goldenberg JM, Cárdenas-Rodríguez J, Pagel MD. Machine learning improves classification of preclinical models of pancreatic cancer with chemical exchange saturation transfer MRI. Magn Reson Med 2019; 81:594-601. [PMID: 30277270 PMCID: PMC6258293 DOI: 10.1002/mrm.27439] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/08/2018] [Accepted: 06/09/2018] [Indexed: 11/06/2022]
Abstract
PURPOSE We sought to assess whether machine learning-based classification approaches can improve the classification of pancreatic tumor models relative to more simplistic analysis methods, using T1 relaxation, CEST, and DCE MRI. METHODS The T1 relaxation time constants, % CEST at five saturation frequencies, and vascular permeability constants from DCE MRI were measured from Hs 766 T, MIA PaCa-2, and SU.86.86 pancreatic tumor models. We used each of these measurements as predictors for machine learning classifier algorithms. We also used principal component analysis to reduce the dimensionality of entire CEST spectra and DCE signal evolutions, which were then analyzed using classification methods. RESULTS The T1 relaxation time constants, % CEST amplitudes at specific saturation frequencies, and the relative Ktrans and kep values from DCE MRI could not classify all three tumor types. However, the area under the curve from DCE signal evolutions could classify each tumor type. Principal component analysis was used to analyze the entire CEST spectrum and DCE signal evolutions, which predicted the correct tumor model with 87.5% and 85.1% accuracy, respectively. CONCLUSIONS Machine learning applied to the entire CEST spectrum improved the classification of the three tumor models, relative to classifications that used % CEST values at single saturation frequencies. A similar improvement was not attained with machine learning applied to T1 relaxation times or DCE signal evolutions, relative to more simplistic analysis methods.
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Affiliation(s)
- Joshua M. Goldenberg
- Department of Pharmaceutical Sciences, University of Arizona, Tucson, AZ
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, TX
| | | | - Mark D. Pagel
- Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, TX
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20
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Simegn GL, Van der Kouwe AJW, Robertson FC, Meintjes EM, Alhamud A. Real-time simultaneous shim and motion measurement and correction in glycoCEST MRI using double volumetric navigators (DvNavs). Magn Reson Med 2018; 81:2600-2613. [PMID: 30506877 DOI: 10.1002/mrm.27597] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/13/2018] [Accepted: 10/16/2018] [Indexed: 11/11/2022]
Abstract
PURPOSE CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequencies. The resulting extended scan time makes CEST susceptible to subject motion, which introduces field inhomogeneity, shifting offset frequencies and causing distortions in CEST spectra that resemble true CEST effects. This is a particular problem for molecules that resonate close to water, such as hydroxyl group in glycogen. To address this, a technique for real-time measurement and correction of motion and field inhomogeneity is proposed. METHODS A CEST sequence was modified to include double volumetric navigators (DvNavs) for real-time simultaneous motion and shim correction. Phantom tests were conducted to investigate the effects of motion and shim changes on CEST quantification and to validate the accuracy of DvNav motion and shim estimates. To evaluate DvNav shim and motion correction in vivo, acquisitions including 5 experimental conditions were performed in the calf muscle of 2 volunteers. RESULTS Phantom data show that DvNav-CEST accurately estimates frequency and linear gradient changes because of motion and corrects resulting image distortions. In addition, DvNav-CEST improves CEST quantification in vivo in the presence of motion. CONCLUSION The proposed technique allows for real-time simultaneous motion and shim correction with no additional scanning time, enabling accurate CEST quantification even in the presence of motion and field inhomogeneity.
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Affiliation(s)
- Gizeaddis L Simegn
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Cape Town, South Africa
| | - Andre J W Van der Kouwe
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Athinoula A. Martinos Center for Biomedical Imaging/MGH, Charlestown, Massachusetts.,Department of Radiology, Harvard Medical School, Boston, Massachusetts
| | - Frances C Robertson
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Cape Universities Body Imaging Centre (CUBIC-UCT), Cape Town, South Africa
| | - Ernesta M Meintjes
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Cape Universities Body Imaging Centre (CUBIC-UCT), Cape Town, South Africa
| | - Ali Alhamud
- UCT Medical Imaging Research Unit, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Cape Town, South Africa.,Cape Universities Body Imaging Centre (CUBIC-UCT), Cape Town, South Africa
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21
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Lindeman LR, Randtke EA, High RA, Jones KM, Howison CM, Pagel MD. A comparison of exogenous and endogenous CEST MRI methods for evaluating in vivo pH. Magn Reson Med 2018; 79:2766-2772. [PMID: 29024066 PMCID: PMC5821269 DOI: 10.1002/mrm.26924] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 08/24/2017] [Accepted: 08/27/2017] [Indexed: 12/24/2022]
Abstract
PURPOSE Extracellular pH (pHe) is an important biomarker for cancer cell metabolism. Acido-chemical exchange saturation transfer (CEST) MRI uses the contrast agent iopamidol to create spatial maps of pHe. Measurements of amide proton transfer exchange rates (kex ) from endogenous CEST MRI were compared to pHe measurements by exogenous acido-CEST MRI to determine whether endogenous kex could be used as a proxy for pHe measurements. METHODS Spatial maps of pHe and kex were obtained using exogenous acidoCEST MRI and an endogenous CEST MRI analyzed with the omega plot method, respectively, to evaluate mouse kidney, a flank tumor model, and a spontaneous lung tumor model. The pHe and kex results were evaluated using pixelwise comparisons. RESULTS The kex values obtained from endogenous CEST measurements did not correlate with the pHe results from exogenous CEST measurements. The kex measurements were limited to fewer pixels and had a limited dynamic range relative to pHe measurements. CONCLUSION Measurements of kex with endogenous CEST MRI cannot substitute for pHe measurements with acidoCEST MRI. Whereas endogenous CEST MRI may still have good utility for evaluating some specific pathologies, exogenous acido-CEST MRI is more appropriate when evaluating pathologies based on pHe values. Magn Reson Med 79:2766-2772, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Leila R. Lindeman
- Cancer Biology Graduate Interdisciplinary Program, University of Arizona Cancer Center, Tucson, AZ, USA
| | - Edward A. Randtke
- Department of Medical Imaging, University of Arizona, Tucson, AZ, USA
| | - Rachel A. High
- Cancer Biology Graduate Interdisciplinary Program, University of Arizona Cancer Center, Tucson, AZ, USA
| | - Kyle M. Jones
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA
| | | | - Mark D. Pagel
- Cancer Biology Graduate Interdisciplinary Program, University of Arizona Cancer Center, Tucson, AZ, USA
- Department of Medical Imaging, University of Arizona, Tucson, AZ, USA
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA
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22
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Jones KM, Stuehm CA, Hsu CC, Kuo PH, Pagel MD, Randtke EA. Imaging Lung Cancer by Using Chemical Exchange Saturation Transfer MRI With Retrospective Respiration Gating. Tomography 2018; 3:201-210. [PMID: 29479563 PMCID: PMC5823523 DOI: 10.18383/j.tom.2017.00017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Performing chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) in lung tissue is difficult because of motion artifacts. We, therefore, developed a CEST MRI acquisition and analysis method that performs retrospective respiration gating. Our method used an acquisition scheme with a short 200-millisecond saturation pulse that can accommodate the timing of the breathing cycle, and with saturation applied at frequencies in 0.03-ppm intervals. The Fourier transform of each image was used to calculate the difference in phase angle between adjacent pixels in the longitudinal direction of the respiratory motion. Additional digital filtering techniques were used to evaluate the breathing cycle, which was used to construct CEST spectra from images during quiescent periods. Results from CEST MRI with and without respiration gating analysis were used to evaluate the asymmetry of the magnetization transfer ratio (MTRasym), a measure of CEST, for an egg white phantom that underwent cyclic motion, in the liver of healthy patients, as well as liver and tumor tissues of patients diagnosed with lung cancer. Retrospective respiration gating analysis produced more precise measurements in all cases with significant motion compared with nongated analysis methods. Finally, a preliminary clinical study with the same respiration-gated CEST MRI method showed a large increase in MTRasym after radiation therapy, a small increase or decrease in MTRasym after chemotherapy, and mixed results with combined chemoradiation therapy. Therefore, our retrospective respiration-gated method can improve CEST MRI evaluations of tumors and organs that are affected by respiratory motion.
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Affiliation(s)
- Kyle M Jones
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ
| | - Carol A Stuehm
- Department of Medical Imaging, University of Arizona, Tucson, AZ.,University of Arizona Cancer Center, University of Arizona, Tucson, AZ
| | - Charles C Hsu
- Department of Radiation Oncology, University of Arizona, Tucson, AZ
| | - Phillip H Kuo
- Department of Medical Imaging, University of Arizona, Tucson, AZ.,University of Arizona Cancer Center, University of Arizona, Tucson, AZ
| | - Mark D Pagel
- Department of Medical Imaging, University of Arizona, Tucson, AZ.,University of Arizona Cancer Center, University of Arizona, Tucson, AZ
| | - Edward A Randtke
- Department of Medical Imaging, University of Arizona, Tucson, AZ.,University of Arizona Cancer Center, University of Arizona, Tucson, AZ
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Sinharay S, Howison CM, Baker AF, Pagel MD. Detecting in vivo urokinase plasminogen activator activity with a catalyCEST MRI contrast agent. NMR IN BIOMEDICINE 2017; 30:10.1002/nbm.3721. [PMID: 28370884 PMCID: PMC5704996 DOI: 10.1002/nbm.3721] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 02/04/2017] [Accepted: 02/06/2017] [Indexed: 05/22/2023]
Abstract
Urokinase plasminogen activator (uPA) promotes tumor invasion and metastasis. The monitoring of uPA activity using molecular imaging may have prognostic value and be predictive for response to anti-cancer therapies. However, the detection of in vivo enzyme activity with molecular imaging remains a challenge. To address this problem, we designed a nonmetallic contrast agent, GR-4Am-SA, that can be detected with chemical exchange saturation transfer (CEST) MRI. This agent has a peptide that is cleaved by uPA, which causes a CEST signal at 5.0 ppm to decrease, and also has a salicylic acid moiety that can produce a CEST signal at 9.5 ppm, which is largely unresponsive to enzyme activity. The two CEST signals were used to determine a reaction coordinate, representing the extent of enzyme-catalyzed cleavage of the GR-4Am-SA agent during an experimental study. Initial biochemical studies showed that GR-4Am-SA could detect uPA activity in reducing conditions. Subsequently, we used our catalyCEST MRI protocol with the agent to detect the uPA catalysis of GR-4Am-SA in a flank xenograft model of Capan-2 pancreatic cancer. The results showed an average reaction coordinate of 80% ± 8%, which was strongly dependent on the CEST signal at 5.0 ppm. The relative independence of the reaction coordinate on the CEST signal at 9.5 ppm showed that the detection of enzyme activity was largely independent of the concentration of GR-4Am-SA within the tumor tissue. These results demonstrated the advantages of a single CEST agent with biomarker-responsive and unresponsive signals for reliably assessing enzyme activity during in vivo cancer studies.
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Affiliation(s)
- Sanhita Sinharay
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ
| | | | - Amanda F. Baker
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ
| | - Mark D. Pagel
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ
- Department of Medical Imaging, University of Arizona, Tucson, AZ
- Corresponding Author: Mark D. Pagel, University of Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724-5024, Tel: (520)-404-7049, Fax: (520)-626-0395,
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24
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In Vitro and In Vivo Assessment of Nonionic Iodinated Radiographic Molecules as Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Tumor Perfusion Agents. Invest Radiol 2016; 51:155-62. [PMID: 26460826 DOI: 10.1097/rli.0000000000000217] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The aim of this study was to evaluate 4 nonionic x-ray iodinated contrast agents (CAs), commonly used in radiographic procedures, as novel chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) agents by assessing their in vitro exchange properties and preliminary in vivo use as tumor enhancing agents. MATERIALS AND METHODS The CEST properties, as function of pH (range, 5.5-7.9) and of radio frequency conditions (irradiation field strength range of 1-9 μT and time of 1-9 seconds), have been determined at 7 T and 310 K for 4 x-ray CAs commonly used in clinical settings, namely, iomeprol, iohexol, ioversol, and iodixanol. Their in vivo properties have been investigated upon intravenous injection in a murine HER2+ breast tumor model (n = 4 mice for each CA) using both computed tomography (CT) and MRI modalities. RESULTS The prototropic exchange rates measured for the 4 investigated iodinated molecules showed strong pH dependence with base catalyzed exchange rate that was faster for monomeric compounds (20-4000 Hz in the pH range of 5.5-7.9). Computed tomography quantification showed marked (up to 2 mg I/mL concentration) and prolonged accumulation (up to 30 minutes postinjection) inside tumor regions. Among the 4 agents we tested, iohexol and ioversol display good CEST contrast properties at 7 T, and in vivo results confirmed strong and prolonged contrast enhancement of the tumors, with elevated extravasation fractions (74%-91%). A strong and significant correlation was found between CT and CEST-MRI tumor-enhanced images (R = 0.70, P < 0.01). CONCLUSIONS The obtained results demonstrate that iohexol and ioversol, 2 commonly used radiographic compounds, can be used as MRI perfusion agents, particularly useful when serial images acquisitions are needed to complement CT information.
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25
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Randtke EA, Granados JC, Howison CM, Pagel MD, Cárdenas-Rodríguez J. Multislice CEST MRI improves the spatial assessment of tumor pH. Magn Reson Med 2016; 78:97-106. [PMID: 27465207 DOI: 10.1002/mrm.26348] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/25/2016] [Accepted: 06/28/2016] [Indexed: 12/19/2022]
Abstract
PURPOSE Multislice maps of extracellular pH (pHe) are needed to interrogate the heterogeneities of tumors and normal organs. To address this need, we have developed a multislice chemical exchange saturation transfer (CEST) MRI acquisition method with a CEST spectrum-fitting method that measures in vivo pHe over a range of 6.3 to 7.4. METHODS The phase offset multiplanar (POMP) method was adapted for CEST fast imaging with steady-state free precession (FISP) MRI to acquire multiple image slices with a single CEST saturation pulse. The Bloch-McConnell equations were modified to include pH based on a calibration of pH and chemical exchange rate for the contrast agent iopamidol. These equations were used to estimate the pixel-wise pHe values throughout the multislice acidoCEST MR images of the tumor, kidney, bladder, and other tissues of a MDA-MB-231 tumor model. RESULTS Multislice acidoCEST MRI successfully mapped a gradient of pHe from 6.73 to 6.81 units from the tumor core to rim, and also mapped a gradient of pHe 6.56 to 6.97 across the mouse kidney. The bladder was found to be pHe 6.3. CONCLUSION AcidoCEST MRI with POMP acquisition and Bloch-McConnel analysis can map pHe in multiple imaging slices through the tumor, kidney, and bladder. This multislice evaluation facilitates assessments of spatial heterogeneity of tissue pHe. Magn Reson Med 78:97-106, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Edward A Randtke
- Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA
| | - Jeffry C Granados
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA
| | | | - Mark D Pagel
- Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA
| | - Julio Cárdenas-Rodríguez
- Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.,Department of Biomedical Engineering, University of Arizona, Tucson, Arizona, USA
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26
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Zhang Y, Heo HY, Lee DH, Jiang S, Zhao X, Bottomley PA, Zhou J. Chemical exchange saturation transfer (CEST) imaging with fast variably-accelerated sensitivity encoding (vSENSE). Magn Reson Med 2016; 77:2225-2238. [PMID: 27364631 DOI: 10.1002/mrm.26307] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/21/2016] [Accepted: 05/22/2016] [Indexed: 12/12/2022]
Abstract
PURPOSE The widespread clinical use of chemical exchange saturation transfer (CEST) imaging is hampered by relatively long scan times due to its requirement that multiple saturation-offset image frames be acquired. Here, a novel variably-accelerated sensitivity encoding (vSENSE) method is proposed that provides faster CEST acquisition than conventional SENSE. THEORY AND METHODS The vSENSE method fully samples one CEST saturation frame, then undersamples the other frames variably. The fully-sampled frame, in conjunction with newly proposed incoherence absorption and artifact suppression strategies, improves the accuracy of sensitivity maps and permits higher acceleration factors for the other undersampled frames than regular SENSE. vSENSE is validated in a phantom, a normal volunteer and eight brain tumor patients at 3 Tesla. RESULTS vSENSE with an acceleration factor of four generated a 3-6 times smaller error on average than conventional SENSE (P ≤ 0.02), with acceleration factors of 2-4, as compared with full k-space reconstruction. vSENSE permitted four-fold acceleration for amide proton transfer-weighted images, while regular SENSE could only provide a factor of two. When conventional SENSE is used with vSENSE's variable undersampling pattern, erroneous (∼9%) z-spectra result. CONCLUSION The vSENSE method enabled twice the acceleration and generated more accurate images than conventional SENSE. Magn Reson Med 77:2225-2238, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Yi Zhang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Hye-Young Heo
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Dong-Hoon Lee
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Shanshan Jiang
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Xuna Zhao
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Paul A Bottomley
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Jinyuan Zhou
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.,F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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27
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Jiang W, Zhou IY, Wen L, Zhou X, Sun PZ. A theoretical analysis of chemical exchange saturation transfer echo planar imaging (CEST-EPI) steady state solution and the CEST sensitivity efficiency-based optimization approach. CONTRAST MEDIA & MOLECULAR IMAGING 2016; 11:415-423. [PMID: 27312932 DOI: 10.1002/cmmi.1699] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 04/27/2016] [Accepted: 05/02/2016] [Indexed: 11/11/2022]
Abstract
Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute labile protons and microenvironmental properties, augmenting routine relaxation-based MRI. Recent developments of quantitative CEST (qCEST) analysis such as omega plots and RF-power based ratiometric calculation have extended our ability to elucidate the underlying CEST system beyond the simplistic apparent CEST measurement. CEST MRI strongly varies with experimental factors, including the RF irradiation level and duration as well as repetition time and flip angle. In addition, the CEST MRI effect is typically small, and experimental optimization strategies have to be carefully evaluated in order to enhance the CEST imaging sensitivity. Although routine CEST MRI has been optimized largely based on maximizing the magnitude of the CEST effect, the CEST signal-to-noise (SNR) efficiency provides a more suitable optimization index, particularly when the scan time is constrained. Herein, we derive an analytical solution of the CEST effect that takes into account key experimental parameters including repetition time, imaging flip angle and RF irradiation level, and solve its SNR efficiency. The solution expedites CEST imaging sensitivity calculation, substantially faster than the Bloch-McConnell equation-based numerical simulation approach. In addition, the analytical solution-based SNR formula enables the exhaustive optimization of CEST MRI, which simultaneously predicts multiple optimal parameters such as repetition time, flip angle and RF saturation level based on the chemical shift and exchange rate. The sensitivity efficiency-based optimization approach could simplify and guide imaging of CEST agents, including glycogen, glucose, creatine, gamma-aminobutyric acid and glutamate. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Weiping Jiang
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Lingyi Wen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Xin Zhou
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China.
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA. .,Department of Radiology, University of Illinois at Chicago, IL, USA.
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28
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Sinharay S, Randtke EA, Jones KM, Howison CM, Chambers SK, Kobayashi H, Pagel MD. Noninvasive detection of enzyme activity in tumor models of human ovarian cancer using catalyCEST MRI. Magn Reson Med 2016; 77:2005-2014. [PMID: 27221386 DOI: 10.1002/mrm.26278] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 04/25/2016] [Accepted: 04/25/2016] [Indexed: 12/17/2022]
Abstract
PURPOSE We proposed to detect the in vivo enzyme activity of γ-glutamyl transferase (GGT) within mouse models of human ovarian cancers using catalyCEST MRI with a diamagnetic CEST agent. METHODS A CEST-FISP MRI protocol and a diamagnetic CEST agent were developed to detect GGT enzyme activity in biochemical solution. A quantitative Michaelis-Menten enzyme kinetics study was performed to confirm that catalyCEST MRI can measure enzyme activity. In vivo catalyCEST MRI studies generated pixel-wise activity maps of GGT activities. Ex vivo fluorescence imaging was performed for validation. RESULTS CatalyCEST MRI selectively detected two CEST signals from a single CEST agent, whereby one CEST signal was responsive to GGT enzyme activity and the other CEST signal was an unresponsive control signal. The comparison of these CEST signals facilitated in vivo catalyCEST MRI studies that detected high GGT activity in OVCAR-8 tumors, low GGT activity in OVCAR-3 tumors, and low or no GGT activity in muscle tissues. CONCLUSION CatalyCEST MRI with a diamagnetic CEST agent can detect the level of GGT enzyme activity within in vivo tumor models of human ovarian cancers. Magn Reson Med 77:2005-2014, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Sanhita Sinharay
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA
| | - Edward A Randtke
- Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA
| | - Kyle M Jones
- Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson, Arizona, USA
| | | | - Setsuko K Chambers
- Department of Obstetrics and Gynecology, University of Arizona, Tucson, Arizona, USA.,University of Arizona Cancer Center, University of Arizona, Tucson, Arizona, USA
| | - Hisataka Kobayashi
- Laboratory of Molecular Theranostics, National Cancer Institute, NIH, Bethesda, Maryland, USA
| | - Mark D Pagel
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA.,Department of Medical Imaging, University of Arizona, Tucson, Arizona, USA.,University of Arizona Cancer Center, University of Arizona, Tucson, Arizona, USA
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29
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Sinharay S, Fernández-Cuervo G, Acfalle JP, Pagel MD. Detection of Sulfatase Enzyme Activity with a CatalyCEST MRI Contrast Agent. Chemistry 2016; 22:6491-5. [PMID: 26956002 PMCID: PMC4877021 DOI: 10.1002/chem.201600685] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Indexed: 01/07/2023]
Abstract
A chemical exchange saturation transfer (CEST) MRI contrast agent has been developed that detects sulfatase enzyme activity. The agent produces a CEST signal at δ=5.0 ppm before enzyme activity, and a second CEST signal appears at δ=9.0 ppm after the enzyme cleaves a sulfate group from the agent. The comparison of the two signals improved detection of sulfatase activity.
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Affiliation(s)
- Sanhita Sinharay
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | | | - Jasmine P Acfalle
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Mark D Pagel
- Department of Medical Imaging, University of Arizona, 1515 N. Campbell Ave., Tucson, AZ, USA.
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30
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Sun PZ, Xiao G, Zhou IY, Guo Y, Wu R. A method for accurate pH mapping with chemical exchange saturation transfer (CEST) MRI. CONTRAST MEDIA & MOLECULAR IMAGING 2016; 11:195-202. [PMID: 26689424 PMCID: PMC4892969 DOI: 10.1002/cmmi.1680] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 10/04/2015] [Accepted: 11/24/2015] [Indexed: 02/05/2023]
Abstract
Chemical exchange saturation transfer (CEST) MRI holds enormous promise for imaging pH. Whereas the routine CEST-weighted MRI contrast is complex and susceptible to confounding factors such as labile proton ratio, chemical shift, bulk water relaxation and RF saturation, ratiometric CEST imaging simplifies pH determination. However, the conventional ratiometric CEST (RCEST) MRI approach is limited to CEST agents with multiple exchangeable groups. To address this limitation, RF power-based ratiometric CEST (PRCEST) imaging has been proposed that ratios CEST effects obtained under different RF power levels. Nevertheless, due to concomitant RF saturation (spillover) effect, the recently proposed PRCEST imaging is somewhat dependent on parameters including bulk water relaxation time and chemical shift. Herein we hypothesized that RF power-based ratiometric analysis of RF spillover effect-corrected inverse CEST asymmetry (PRICEST) provides enhanced pH measurement. The postulation was verified numerically, and validated experimentally using an in vitro phantom. Briefly, our study showed that the difference between MRI-determined pH (pHMRI ) and electrode-measured pH being 0.12 ± 0.13 and 0.04 ± 0.03 for PRCEST and PRICEST imaging, respectively, and the newly proposed PRICEST imaging provides significantly more accurate pH determination than PRCEST imaging (P < 0.01, Wilcoxon signed-rank test). Notably, the exchange rate shows dominantly base-catalysed relationship with pH, independent of creatine concentration (P > 0.10, Analysis of Covariance). In addition, the derived labile proton ratio linearly scales with creatine concentration (P < 0.01, Pearson Regression). To summarize, PRICEST MRI provides concentration-independent pH imaging, augmenting prior quantitative CEST methods for accurate pH mapping. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
- Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of
Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA,
USA
- Corresponding Authors: Prof. Phillip Zhe Sun
(), Athinoula A. Martinos Center
for Biomedical Imaging, Department of Radiology, MGH and Harvard Medical School,
Rm 2301, 149 13 Street, Charlestown, MA 02129, Phone: 617-726-4060,
Fax: 617-726-7422; Prof. Renhua Wu (), Department
of Radiology, 2 Affiliated Hospital of Shantou University Medical
College, Shantou 515041, Guangdong, China, Tel: (86) 0754-88915674
| | - Gang Xiao
- Department of Math and Applied Mathematics, Hanshan Normal
University, Chaozhou, China
- Department of Radiology, 2 Affiliated Hospital of
Shantou University Medical College, Shantou, China
| | - Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of
Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA,
USA
| | - Yingkun Guo
- Athinoula A. Martinos Center for Biomedical Imaging, Department of
Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA,
USA
| | - Renhua Wu
- Department of Radiology, 2 Affiliated Hospital of
Shantou University Medical College, Shantou, China
- Corresponding Authors: Prof. Phillip Zhe Sun
(), Athinoula A. Martinos Center
for Biomedical Imaging, Department of Radiology, MGH and Harvard Medical School,
Rm 2301, 149 13 Street, Charlestown, MA 02129, Phone: 617-726-4060,
Fax: 617-726-7422; Prof. Renhua Wu (), Department
of Radiology, 2 Affiliated Hospital of Shantou University Medical
College, Shantou 515041, Guangdong, China, Tel: (86) 0754-88915674
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31
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Liu Z, Dimitrov IE, Lenkinski RE, Hajibeigi A, Vinogradov E. UCEPR: Ultrafast localized CEST-spectroscopy with PRESS in phantoms and in vivo. Magn Reson Med 2016; 75:1875-85. [PMID: 26033357 PMCID: PMC4663188 DOI: 10.1002/mrm.25780] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 04/02/2015] [Accepted: 04/27/2015] [Indexed: 11/10/2022]
Abstract
PURPOSE Chemical exchange saturation transfer (CEST) is a contrast mechanism enhancing low-concentration molecules through saturation transfer from their exchangeable protons to bulk water. Often many scans are acquired to form a Z-spectrum, making the CEST method time-consuming. Here, an ultrafast localized CEST-spectroscopy with PRESS (UCEPR) is proposed to obtain the entire Z-spectrum of a voxel using only two scans, significantly accelerating CEST. THEORY AND METHODS The approach combines ultrafast nonlocalized CEST spectroscopy with localization using PRESS. A field gradient is applied concurrently with the saturation pulse producing simultaneous saturation of all Z-spectrum frequencies that are also spatially encoded. A readout gradient during data acquisition resolves the spatial dependence of the CEST responses into frequency. UCEPR was tested on a 3T scanner both in phantoms and in vivo. RESULTS In phantoms, a fast Z-spectroscopy acquisition of multiple pH-variant iopamidol samples was achieved with four- to seven-fold acceleration as compared to the conventional CEST methods. In vivo, amide proton transfer (APT) in white matter of healthy human brain was measured rapidly in 48 s and with high frequency resolution (≤ 0.2 ppm). CONCLUSION Compared with conventional CEST methods, UCEPR has the advantage of rapidly acquiring high-resolution Z-spectra. Potential in vivo applications include ultrafast localized Z-spectroscopy, quantitative, or dynamic CEST studies.
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Affiliation(s)
- Zheng Liu
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, USA
| | - Ivan E. Dimitrov
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Philips Medical Systems, Highland Heights, Ohio, USA
| | - Robert E. Lenkinski
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Asghar Hajibeigi
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Elena Vinogradov
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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32
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Huang J, Zhang M, Lu J, Cai C, Chen L, Cai S. A fast chemical exchange saturation transfer imaging scheme based on single-shot spatiotemporal encoding. Magn Reson Med 2016; 77:1786-1796. [PMID: 27120691 DOI: 10.1002/mrm.26258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/30/2016] [Accepted: 04/01/2016] [Indexed: 01/31/2023]
Abstract
PURPOSE To design a new approach that can not only keep the spatial and temporal resolution but also have better built-in immunity to magnetic field inhomogeneity and chemical shift effects than the single-shot echo planar imaging (EPI) for chemical exchange saturation transfer (CEST) MRI. METHOD The single-shot spatiotemporally encoded (SPEN) MRI sequence was combined with a continuous wave saturation pulse for fast CEST MRI (CEST-SPEN MRI). The resulting images were super-resolved reconstructed by a hybrid method that solves the l1 norm minimization together with total variation (TV) regularization. Partial Lorentzian fitting was used to analyze the subsequent Z-spectra. RESULTS Experimental results of a creatine phantom and in vivo tumor rat brains show that CEST-SPEN MRI has good capability in providing CEST-based and NOE-based contrast images. CONCLUSIONS Compared with CEST-EPI, CEST-SPEN MRI has better immunity to magnetic field inhomogeneity and provides better contrast images within identical acquisition time, especially under an identical inhomogeneous field. Magn Reson Med 77:1786-1796, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Jianpan Huang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Miao Zhang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jianhua Lu
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China.,Meizhouwan Vocational Technology College, Putian, China
| | - Congbo Cai
- Department of Communication Engineering, Xiamen University, Xiamen, China
| | - Lin Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
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33
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Daryaei I, Randtke EA, Pagel MD. A biomarker-responsive T 2ex MRI contrast agent. Magn Reson Med 2016; 77:1665-1670. [PMID: 27090199 DOI: 10.1002/mrm.26250] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/08/2016] [Accepted: 03/29/2016] [Indexed: 11/11/2022]
Abstract
PURPOSE This study investigated a fundamentally new type of responsive MRI contrast agent for molecular imaging that alters T2 exchange (T2ex ) properties after interacting with a molecular biomarker. METHODS The contrast agent Tm-DO3A-oAA was treated with nitric oxide (NO) and O2 . The R1 and R2 relaxation rates of the reactant and product were measured with respect to concentration, temperature, and pH. Chemical exchange saturation transfer (CEST) spectra of the reactant and product were acquired using a 7 Tesla (T) MRI scanner and analyzed to estimate the chemical exchange rates and r2ex relaxivities. RESULTS The reaction of Tm-DO3A-oAA with NO and O2 caused a 6.4-fold increase in the r2 relaxivity of the agent, whereas r1 relaxivity remained unchanged, which demonstrated that Tm-DO3A-oAA is a responsive T2ex agent. The effects of pH and temperature on the r2 relaxivities of the reactant and product supported the conclusion that the product's benzimidazole ligand caused the agent to have a fast chemical exchange rate relative to the slow exchange rate of the reactant's ortho-aminoanilide ligand. CONCLUSIONS T2ex MRI contrast agents are a new type of responsive agent that have good detection sensitivity and specificity for detecting a biomarker, which can serve as a new tool for molecular imaging. Magn Reson Med 77:1665-1670, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Iman Daryaei
- Department of Chemistry and Biochemistry, University of Arizona
| | | | - Mark D Pagel
- Department of Chemistry and Biochemistry, University of Arizona.,Department of Medical Imaging, University of Arizona
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34
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Fernández-Cuervo G, Sinharay S, Pagel MD. A CatalyCEST MRI Contrast Agent that Can Simultaneously Detect Two Enzyme Activities. Chembiochem 2016; 17:383-7. [PMID: 26693680 PMCID: PMC4814164 DOI: 10.1002/cbic.201500586] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Indexed: 12/28/2022]
Abstract
The simultaneous detection of multiple enzyme activities can improve the specificity of disease diagnoses. We therefore synthesized and characterized a diamagnetic chemical exchange saturation transfer (CEST) MRI contrast agent that can simultaneously detect two enzyme activities. Sulfatase and esterase enzymes cleave the ligands of the CEST agent, releasing salicylic acid that can be detected with CEST MRI. Importantly, both enzymes are required to activate the agent to produce a CEST MRI contrast, and the CEST agent was stable without enzyme treatment. These results established that this diamagnetic CEST MRI contrast agent is a platform technology with a modular design that can be potentially exploited to detect other combinations of enzyme activities, which can expand the armamentarium of contrast agents for molecular imaging.
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Affiliation(s)
- Gabriela Fernández-Cuervo
- Department of Pharmaceutical Sciences, University of Arizona, 1515 N. Campbell Ave., Tucson, AZ, 85724, USA
| | - Sanhita Sinharay
- Department of Chemistry and Biochemistry, University of Arizona, 1515 N. Campbell Ave., Tucson, AZ, 85724, USA
| | - Mark D Pagel
- Department of Medical Imaging, University of Arizona, 1515 N. Campbell Ave., Tucson, AZ, 85724, USA.
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Moon BF, Jones KM, Chen LQ, Liu P, Randtke EA, Howison CM, Pagel MD. A comparison of iopromide and iopamidol, two acidoCEST MRI contrast media that measure tumor extracellular pH. CONTRAST MEDIA & MOLECULAR IMAGING 2015; 10:446-55. [PMID: 26108564 PMCID: PMC4691225 DOI: 10.1002/cmmi.1647] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2014] [Revised: 01/30/2015] [Accepted: 04/20/2015] [Indexed: 11/09/2022]
Abstract
Acidosis within tumor and kidney tissues has previously been quantitatively measured using a molecular imaging technique known as acidoCEST MRI. The previous studies used iopromide and iopamidol, two iodinated contrast agents that are approved for clinical CT diagnoses and have been repurposed for acidoCEST MRI studies. We aimed to compare the performance of the two agents for measuring pH by optimizing image acquisition conditions, correlating pH with a ratio of CEST effects from an agent, and evaluating the effects of concentration, endogenous T1 relaxation time and temperature on the pH-CEST ratio correlation for each agent. These results showed that the two agents had similar performance characteristics, although iopromide produced a pH measurement with a higher dynamic range while iopamidol produced a more precise pH measurement. We then compared the performance of the two agents to measure in vivo extracellular pH (pHe) within xenograft tumor models of Raji lymphoma and MCF-7 breast cancer. Our results showed that the pHe values measured with each agent were not significantly different. Also, iopromide consistently measured a greater region of the tumor relative to iopamidol in both tumor models. Therefore, an iodinated contrast agent for acidoCEST MRI should be selected based on the measurement properties needed for a specific biomedical study and the pharmacokinetic properties of a specific tumor model.
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Affiliation(s)
- Brianna F. Moon
- Department of Biomedical Engineering, University of Arizona, Tucson AZ
| | - Kyle M. Jones
- Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson AZ
| | - Liu Qi Chen
- Department of Chemistry & Biochemistry, University of Arizona, Tucson AZ
| | - Peilu Liu
- Department of Chemistry & Biochemistry, University of Arizona, Tucson AZ
| | - Edward A. Randtke
- Department of Biomedical Engineering, University of Arizona, Tucson AZ
| | | | - Mark D. Pagel
- Department of Biomedical Engineering, University of Arizona, Tucson AZ
- Department of Chemistry & Biochemistry, University of Arizona, Tucson AZ
- Department of Medical Imaging, University of Arizona, Tucson AZ
- University of Arizona Cancer Center, University of Arizona, Tucson AZ
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Yoo B, Sheth VR, Howison CM, Douglas MJK, Pineda CT, Maine EA, Baker AF, Pagel MD. Detection of in vivo enzyme activity with CatalyCEST MRI. Magn Reson Med 2015; 71:1221-30. [PMID: 23640714 DOI: 10.1002/mrm.24763] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE CatalyCEST MRI compares the detection of an enzyme-responsive chemical exchange saturation transfer (CEST) agent with the detection of an unresponsive "control" CEST agent that accounts for other conditions that influence CEST. The purpose of this study was to investigate the feasibility of in vivo catalyCEST MRI. METHODS CEST agents that were responsive and unresponsive to the activity of urokinase plasminogen activator were shown to have negligible interaction with each other. A CEST-fast imaging with steady state precession (FISP) MRI protocol was used to acquire MR CEST spectroscopic images with a Capan-2 pancreatic tumor model after intravenous injection of the CEST agents. A function of (super)-Lorentzian line shapes was fit to CEST spectra of a region-of-interest that represented the tumor. RESULTS The CEST effects from each agent showed the same initial uptake into tumor tissues, indicating that both agents had the same pharmacokinetic transport rates. Starting 5 min after injection, CEST from the enzyme-responsive agent disappeared more quickly than CEST from the unresponsive agent, indicating that the enzyme responsive agent was being catalyzed by urokinase plasminogen activator, while both agents also experienced net pharmacokinetic washout from the tumor. CONCLUSION CatalyCEST MRI demonstrates that dynamic tracking of enzyme-responsive and unresponsive CEST agents during the same in vivo MRI study is feasible.
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Affiliation(s)
- Byunghee Yoo
- MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Xiao G, Sun PZ, Wu R. Fast simulation and optimization of pulse-train chemical exchange saturation transfer (CEST) imaging. Phys Med Biol 2015; 60:4719-30. [PMID: 26020414 DOI: 10.1088/0031-9155/60/12/4719] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chemical exchange saturation transfer (CEST) MRI has been increasingly applied to detect dilute solutes and physicochemical properties, with promising in vivo applications. Whereas CEST imaging has been implemented with continuous wave (CW) radio-frequency irradiation on preclinical scanners, pulse-train irradiation is often chosen on clinical systems. Therefore, it is necessary to optimize pulse-train CEST imaging, particularly important for translational studies. Because conventional Bloch-McConnell formulas are not in the form of homogeneous differential equations, the routine simulation approach simulates the evolving magnetization step by step, which is time consuming. Herein we developed a computationally efficient numerical solution using matrix iterative analysis of homogeneous Bloch-McConnell equations. The proposed algorithm requires simulation of pulse-train CEST MRI magnetization within one irradiation repeat, with 99% computation time reduction from that of conventional approach under typical experimental conditions. The proposed solution enables determination of labile proton ratio and exchange rate from pulse-train CEST MRI experiment, within 5% from those determined from quantitative CW-CEST MRI. In addition, the structural similarity index analysis shows that the dependence of CEST contrast on saturation pulse flip angle and duration between simulation and experiment was 0.98 ± 0.01, indicating that the proposed simulation algorithm permits fast optimization and quantification of pulse-train CEST MRI.
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Affiliation(s)
- Gang Xiao
- Department of Mathematics and Statistics, Hanshan Normal University, Guangdong, People's Republic of China
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Wu R, Xiao G, Zhou IY, Ran C, Sun PZ. Quantitative chemical exchange saturation transfer (qCEST) MRI - omega plot analysis of RF-spillover-corrected inverse CEST ratio asymmetry for simultaneous determination of labile proton ratio and exchange rate. NMR IN BIOMEDICINE 2015; 28:376-83. [PMID: 25615718 PMCID: PMC4339459 DOI: 10.1002/nbm.3257] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/04/2014] [Accepted: 12/16/2014] [Indexed: 02/05/2023]
Abstract
Chemical exchange saturation transfer (CEST) MRI is sensitive to labile proton concentration and exchange rate, thus allowing measurement of dilute CEST agent and microenvironmental properties. However, CEST measurement depends not only on the CEST agent properties but also on the experimental conditions. Quantitative CEST (qCEST) analysis has been proposed to address the limitation of the commonly used simplistic CEST-weighted calculation. Recent research has shown that the concomitant direct RF saturation (spillover) effect can be corrected using an inverse CEST ratio calculation. We postulated that a simplified qCEST analysis is feasible with omega plot analysis of the inverse CEST asymmetry calculation. Specifically, simulations showed that the numerically derived labile proton ratio and exchange rate were in good agreement with input values. In addition, the qCEST analysis was confirmed experimentally in a phantom with concurrent variation in CEST agent concentration and pH. Also, we demonstrated that the derived labile proton ratio increased linearly with creatine concentration (P < 0.01) while the pH-dependent exchange rate followed a dominantly base-catalyzed exchange relationship (P < 0.01). In summary, our study verified that a simplified qCEST analysis can simultaneously determine labile proton ratio and exchange rate in a relatively complex in vitro CEST system.
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Affiliation(s)
- Renhua Wu
- Department of Radiology, 2 Affiliated Hospital of Shantou University Medical College, Shantou, China
| | - Gang Xiao
- Department of Radiology, 2 Affiliated Hospital of Shantou University Medical College, Shantou, China
- Department of Mathematics and Statistics, Hanshan Normal University, Chaozhou, China
| | - Iris Yuwen Zhou
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Chongzhao Ran
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
- Corresponding Authors: Dr. Phillip Zhe Sun (), Biomarker and Metabolism Imaging Lab, Martinos Center for Biomedical Imaging, MGH and Harvard Medical School, Rm 2301, 149 13 Street, Charlestown, MA 02129, USA, Tel: 617-726-4060, Fax: 617-726-7422
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Gao Y, Chen Y, Ma D, Jiang Y, Herrmann KA, Vincent JA, Dell KM, Drumm ML, Brady-Kalnay SM, Griswold MA, Flask CA, Lu L. Preclinical MR fingerprinting (MRF) at 7 T: effective quantitative imaging for rodent disease models. NMR IN BIOMEDICINE 2015; 28:384-394. [PMID: 25639694 PMCID: PMC4396690 DOI: 10.1002/nbm.3262] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 12/18/2014] [Accepted: 12/22/2014] [Indexed: 05/29/2023]
Abstract
High-field preclinical MRI scanners are now commonly used to quantitatively assess disease status and the efficacy of novel therapies in a wide variety of rodent models. Unfortunately, conventional MRI methods are highly susceptible to respiratory and cardiac motion artifacts resulting in potentially inaccurate and misleading data. We have developed an initial preclinical 7.0-T MRI implementation of the highly novel MR fingerprinting (MRF) methodology which has been described previously for clinical imaging applications. The MRF technology combines a priori variation in the MRI acquisition parameters with dictionary-based matching of acquired signal evolution profiles to simultaneously generate quantitative maps of T1 and T2 relaxation times and proton density. This preclinical MRF acquisition was constructed from a fast imaging with steady-state free precession (FISP) MRI pulse sequence to acquire 600 MRF images with both evolving T1 and T2 weighting in approximately 30 min. This initial high-field preclinical MRF investigation demonstrated reproducible and differentiated estimates of in vitro phantoms with different relaxation times. In vivo preclinical MRF results in mouse kidneys and brain tumor models demonstrated an inherent resistance to respiratory motion artifacts as well as sensitivity to known pathology. These results suggest that MRF methodology may offer the opportunity for the quantification of numerous MRI parameters for a wide variety of preclinical imaging applications.
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Affiliation(s)
- Ying Gao
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Yong Chen
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
| | - Dan Ma
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Yun Jiang
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Kelsey A. Herrmann
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Jason A. Vincent
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106
| | - Katherine M. Dell
- CWRU Center for the Study of Kidney Disease and Biology, MetroHealth Campus, Case Western Reserve University, Cleveland, OH 44109
- Pediatric Institute, Cleveland Clinic Foundation, Cleveland, OH 44106
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
| | - Mitchell L. Drumm
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106
| | - Susann M. Brady-Kalnay
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Mark A. Griswold
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
| | - Chris A. Flask
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
| | - Lan Lu
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Urology, Case Western Reserve University, Cleveland, OH 44106
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Kim J, Wu Y, Guo Y, Zheng H, Sun PZ. A review of optimization and quantification techniques for chemical exchange saturation transfer MRI toward sensitive in vivo imaging. CONTRAST MEDIA & MOLECULAR IMAGING 2015; 10:163-178. [PMID: 25641791 DOI: 10.1002/cmmi.1628] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 08/26/2014] [Accepted: 09/10/2014] [Indexed: 01/10/2023]
Abstract
Chemical exchange saturation transfer (CEST) MRI is a versatile imaging method that probes the chemical exchange between bulk water and exchangeable protons. CEST imaging indirectly detects dilute labile protons via bulk water signal changes following selective saturation of exchangeable protons, which offers substantial sensitivity enhancement and has sparked numerous biomedical applications. Over the past decade, CEST imaging techniques have rapidly evolved owing to contributions from multiple domains, including the development of CEST mathematical models, innovative contrast agent designs, sensitive data acquisition schemes, efficient field inhomogeneity correction algorithms, and quantitative CEST (qCEST) analysis. The CEST system that underlies the apparent CEST-weighted effect, however, is complex. The experimentally measurable CEST effect depends not only on parameters such as CEST agent concentration, pH and temperature, but also on relaxation rate, magnetic field strength and more importantly, experimental parameters including repetition time, RF irradiation amplitude and scheme, and image readout. Thorough understanding of the underlying CEST system using qCEST analysis may augment the diagnostic capability of conventional imaging. In this review, we provide a concise explanation of CEST acquisition methods and processing algorithms, including their advantages and limitations, for optimization and quantification of CEST MRI experiments.
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Affiliation(s)
- Jinsuh Kim
- Department of Radiology, University of Iowa, Iowa City, IA, USA
| | - Yin Wu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.,Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Yingkun Guo
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
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Song X, Xu J, Xia S, Yadav NN, Lal B, Laterra J, Bulte JWM, van Zijl PCM, McMahon MT. Multi-echo length and offset VARied saturation (MeLOVARS) method for improved CEST imaging. Magn Reson Med 2014; 73:488-96. [PMID: 25516490 DOI: 10.1002/mrm.25567] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/14/2014] [Accepted: 11/14/2014] [Indexed: 12/15/2022]
Abstract
PURPOSE The aim of this study was to develop a technique for rapid collection of chemical exchange saturation transfer images with the saturation varied to modulate signal loss transfer and enhance contrast. METHODS Multi-echo Length and Offset VARied Saturation (MeLOVARS) divides the saturation pulse of length Tsat into N = 3-8 submodules, each consisting of a saturation pulse with length of Tsat /N (∼0.3-1 s), one or more low flip-angle gradient-echo readout(s) and a flip back pulse. This results in N readouts with increasing saturation time from Tsat /N to Tsat without extra scan time. RESULTS For phantoms, eight images with Tsat incremented every 0.5 s from 0.5-4 s were collected simultaneously using MeLOVARS, which allows rapid determination of exchange rates for agent protons. For live mice bearing glioblastomas, the Z-spectra for five different Tsat values from 0.5 to 2.5 s were acquired in a time normally used for one Tsat . With the additional Tsat -dependence information, LOVARS phase maps were produced with a more clearly defined tumor boundary and an estimated 4.3-fold enhanced contrast-to-noise ratio (CNR). We also show that enhancing CNR is achievable by simply averaging the collected images or transforming them using the principal component analysis. CONCLUSIONS MeLOVARS enables collection of multiple saturation-time-weighted images without extra time, producing a LOVARS phase map with increased CNR.
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Affiliation(s)
- Xiaolei Song
- Division of MR Research, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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Sun PZ, Wang Y, Dai Z, Xiao G, Wu R. Quantitative chemical exchange saturation transfer (qCEST) MRI--RF spillover effect-corrected omega plot for simultaneous determination of labile proton fraction ratio and exchange rate. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 9:268-75. [PMID: 24706610 DOI: 10.1002/cmmi.1569] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/28/2013] [Accepted: 08/11/2013] [Indexed: 12/20/2022]
Abstract
Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute proteins and peptides as well as microenvironmental properties. However, the complexity of the CEST MRI effect, which varies with the labile proton content, exchange rate and experimental conditions, underscores the need for developing quantitative CEST (qCEST) analysis. Towards this goal, it has been shown that omega plot is capable of quantifying paramagnetic CEST MRI. However, the use of the omega plot is somewhat limited for diamagnetic CEST (DIACEST) MRI because it is more susceptible to direct radio frequency (RF) saturation (spillover) owing to the relatively small chemical shift. Recently, it has been found that, for dilute DIACEST agents that undergo slow to intermediate chemical exchange, the spillover effect varies little with the labile proton ratio and exchange rate. Therefore, we postulated that the omega plot analysis can be improved if RF spillover effect could be estimated and taken into account. Specifically, simulation showed that both labile proton ratio and exchange rate derived using the spillover effect-corrected omega plot were in good agreement with simulated values. In addition, the modified omega plot was confirmed experimentally, and we showed that the derived labile proton ratio increased linearly with creatine concentration (p < 0.01), with little difference in their exchange rate (p = 0.32). In summary, our study extends the conventional omega plot for quantitative analysis of DIACEST MRI.
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Affiliation(s)
- Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129, USA
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Magnetization transfer prepared gradient echo MRI for CEST imaging. PLoS One 2014; 9:e112219. [PMID: 25384020 PMCID: PMC4226502 DOI: 10.1371/journal.pone.0112219] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 10/10/2014] [Indexed: 11/20/2022] Open
Abstract
Chemical exchange saturation transfer (CEST) is an emerging MRI contrast mechanism that is capable of noninvasively imaging dilute CEST agents and local properties such as pH and temperature, augmenting the routine MRI methods. However, the routine CEST MRI includes a long RF saturation pulse followed by fast image readout, which is associated with high specific absorption rate and limited spatial resolution. In addition, echo planar imaging (EPI)-based fast image readout is prone to image distortion, particularly severe at high field. To address these limitations, we evaluated magnetization transfer (MT) prepared gradient echo (GRE) MRI for CEST imaging. We proved the feasibility using numerical simulations and experiments in vitro and in vivo. Then we optimized the sequence by serially evaluating the effects of the number of saturation steps, MT saturation power (B1), GRE readout flip angle (FA), and repetition time (TR) upon the CEST MRI, and further demonstrated the endogenous amide proton CEST imaging in rats brains (n = 5) that underwent permanent middle cerebral artery occlusion. The CEST images can identify ischemic lesions in the first 3 hours after occlusion. In summary, our study demonstrated that the readily available MT-prepared GRE MRI, if optimized, is CEST-sensitive and remains promising for translational CEST imaging.
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Chen LQ, Howison CM, Jeffery JJ, Robey IF, Kuo PH, Pagel MD. Evaluations of extracellular pH within in vivo tumors using acidoCEST MRI. Magn Reson Med 2014; 72:1408-17. [PMID: 24281951 PMCID: PMC4033731 DOI: 10.1002/mrm.25053] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 10/26/2013] [Accepted: 10/28/2013] [Indexed: 11/07/2022]
Abstract
PURPOSE A practical, noninvasive method is needed to measure the extracellular pH (pHe) within in vivo tumors to longitudinally monitor tumor acidosis. We have optimized a biomedical imaging method, termed acidoCEST MRI, to provide noninvasive assessments of tumor pHe in preclinical models of mammary carcinoma. METHODS A CEST-FISP MRI method was optimized to detect the chemical exchange saturation transfer (CEST) of two amide protons of a clinically approved CT contrast agent, iopromide. The ratio of the two CEST effects was used to measure pH. Routes of administration of iopromide were evaluated to ensure sufficient delivery of the agent to the tumor. The optimized acidoCEST MRI method was then used to evaluate the change in tumor pHe following alkalinizing bicarbonate treatment. RESULTS The acidoCEST MRI protocol measured pH between 6.2 and 7.2 pH units. Greater delivery of iopromide was shown to improve the precision of the measurement of tumor pHe, but the agent did not influence the tumor pHe. AcidoCEST MRI was used to longitudinally monitor the effect of bicarbonate treatment on the pHe of tumors and bladders. CONCLUSION This study demonstrates that an optimized acidoCEST MRI method is a practical, noninvasive method for assessing changes in tumor acidosis.
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Affiliation(s)
- Liu Qi Chen
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | | | - Justin J. Jeffery
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA
| | - Ian F. Robey
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA
- Department of Medicine, University of Arizona, Tucson, AZ, USA
| | - Phillip H. Kuo
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA
- Department of Medical Imaging, University of Arizona, Tucson, AZ, USA
| | - Mark D. Pagel
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA
- University of Arizona Cancer Center, University of Arizona, Tucson, AZ, USA
- Department of Medical Imaging, University of Arizona, Tucson, AZ, USA
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Gao Y, Goodnough CL, Erokwu BO, Farr GW, Darrah R, Lu L, Dell KM, Yu X, Flask CA. Arterial spin labeling-fast imaging with steady-state free precession (ASL-FISP): a rapid and quantitative perfusion technique for high-field MRI. NMR IN BIOMEDICINE 2014; 27:996-1004. [PMID: 24891124 PMCID: PMC4110188 DOI: 10.1002/nbm.3143] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/28/2014] [Accepted: 04/30/2014] [Indexed: 05/03/2023]
Abstract
Arterial spin labeling (ASL) is a valuable non-contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either echo-planar imaging (EPI) or true fast imaging with steady-state free precession (true FISP) readouts, which are prone to off-resonance artifacts on high-field MRI scanners. We have developed a rapid ASL-FISP MRI acquisition for high-field preclinical MRI scanners providing perfusion-weighted images with little or no artifacts in less than 2 s. In this initial implementation, a flow-sensitive alternating inversion recovery (FAIR) ASL preparation was combined with a rapid, centrically encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 and 9.4 T (249 ± 38 and 241 ± 17 mL/min/100 g, respectively). The utility of this method was further demonstrated in the detection of significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL-FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high-field MRI scanners with minimal image artifacts.
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Affiliation(s)
- Ying Gao
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Candida L. Goodnough
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | | | - George W. Farr
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
- Aeromics, LLC, Cleveland, OH 44106
| | - Rebecca Darrah
- Frances Payne Bolton School of Nursing, Case Western Reserve University, Cleveland, OH 44106
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH 44106
| | - Lan Lu
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Urology, Case Western Reserve University, Cleveland, OH 44106
| | - Katherine M. Dell
- CWRU Center for the Study of Kidney Disease and Biology, MetroHealth Campus, Case Western Reserve University, Cleveland, OH 44109
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
| | - Xin Yu
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106
| | - Chris A. Flask
- Department of Radiology, Case Western Reserve University, Cleveland, OH 44106
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
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Lu L, Donnola SB, Koontz M, Griswold MA, Duerk JL, Flask CA. Lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA) MRI. Magn Reson Med 2014; 73:711-7. [PMID: 24639034 DOI: 10.1002/mrm.25177] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 01/21/2014] [Accepted: 01/21/2014] [Indexed: 12/22/2022]
Abstract
PURPOSE The Dixon techniques provide uniform water-fat separation but require multiple image sets, which extend the overall acquisition time. Here, an alternative rapid single acquisition method, lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), was introduced. METHODS The LEENA method utilized a fast imaging with steady-state free precession sequence to obtain a single k-space dataset in which successive k-space lines are acquired to allow the fat magnetization to precess 180°. The LEENA data were then unghosted using either image-domain (LEENA-S) or k-space domain (LEENA-G) parallel imaging techniques to reconstruct water-only and fat-only images. An off-resonance correction technique was incorporated to improve the uniformity of the water-fat separation. RESULTS Uniform water-fat separation was achieved for both the LEENA-S and LEENA-G methods for phantom and human body and leg imaging applications at 1.5T and 3T. The resultant water and fat images were qualitatively similar to conventional 2-point Dixon and fat-suppressed images. CONCLUSION The LEENA-S and LEENA-G methods provide uniform water and fat images from a single MRI acquisition. These straightforward methods can be adapted to 1.5T and 3T clinical MRI scanners and provide comparable fat/water separation with conventional 2-point Dixon and fat-suppression techniques.
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Affiliation(s)
- Lan Lu
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA; Department of Urology, Case Western Reserve University, Cleveland, Ohio, USA
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Sun PZ, Wang Y, Lu J. Sensitivity-enhanced chemical exchange saturation transfer (CEST) MRI with least squares optimization of Carr Purcell Meiboom Gill multi-echo echo planar imaging. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 9:177-81. [PMID: 24523063 PMCID: PMC3957332 DOI: 10.1002/cmmi.1546] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 03/05/2013] [Accepted: 05/02/2013] [Indexed: 11/07/2022]
Abstract
Chemical exchange saturation transfer (CEST) imaging is a novel MRI technique that is sensitive to biomolecules, local pH and temperature, and offers considerable advantages for in vivo applications. However, the magnitude of CEST effect for dilute CEST agents undergoing slow or intermediate chemical exchange is typically small, requiring the use of signal averaging to enhance its sensitivity. Given that T2 -induced signal loss can be normalized by asymmetry analysis, the magnitude of CEST effect is independent of echo time. Therefore, CEST MRI with multi-echo echo planar imaging (EPI) readout should yield the same CEST effect as conventional single echo acquisition. Importantly, CEST multi-echo (CESTme) EPI images can be averaged to enhance CEST MRI sensitivity. The goal of this study was to validate CESTme EPI using a creatine-agarose gel CEST phantom with similar T2 as biological tissue. Using least-squares optimization, we found that the sensitivity of CESTme sequence was significantly higher than that obtained by conventional single echo CEST-EPI acquisition. Specifically, signal-to-noise ratio and contrast-to-noise ratio from the proposed CESTme EPI were approximately equivalent to that obtained by doubling the number of signal averages of the standard single echo CEST MRI sequence. In summary, our results demonstrated CESTme EPI for sensitivity-enhanced CEST imaging.
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Affiliation(s)
- Phillip Zhe Sun
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School
| | - Yu Wang
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School
- Department of Radiology, Xuanwu Hospital and Capital Medical University
| | - Jie Lu
- Department of Radiology, Xuanwu Hospital and Capital Medical University
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Liu G, Qin Q, Chan KW, Li Y, Bulte JW, McMahon MT, van Zijl PC, Gilad AA. Non-invasive temperature mapping using temperature-responsive water saturation shift referencing (T-WASSR) MRI. NMR IN BIOMEDICINE 2014; 27:320-31. [PMID: 24395616 PMCID: PMC3989428 DOI: 10.1002/nbm.3066] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 11/25/2013] [Accepted: 11/26/2013] [Indexed: 05/12/2023]
Abstract
We present a non-invasive MRI approach for assessing the water proton resonance frequency (PRF) shifts associated with changes in temperature. This method is based on water saturation shift referencing (WASSR), a method first developed for assessing B0 field inhomogeneity. Temperature-induced water PRF shifts were determined by estimating the frequency of the minimum intensity of the water direct saturation spectrum at each temperature using Lorentzian line-shape fitting. The change in temperature was then calculated from the difference in water PRF shifts between temperatures. Optimal acquisition parameters were first estimated using simulations and later confirmed experimentally. Results in vitro and in vivo showed that the temperature changes measured using the temperature-responsive WASSR (T-WASSR) were in good agreement with those obtained with MR spectroscopy or phase-mapping-based water PRF measurement methods,. In addition, the feasibility of temperature mapping in fat-containing tissue is demonstrated in vitro. In conclusion, the T-WASSR approach provides an alternative for non-invasive temperature mapping by MRI, especially suitable for temperature measurements in fat-containing tissues.
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Affiliation(s)
- Guanshu Liu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
- CORRESPONDING AUTHOR: Guanshu Liu, Ph.D. 707 N. Broadway, Baltimore, MD 21205 Phone (office): 443-923-9500, Fax: 410-614-3147
| | - Qin Qin
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
| | - Kannie W.Y. Chan
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering
| | - Yuguo Li
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
| | - Jeff W.M. Bulte
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
- Department of Chemical & Biomolecular Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michael T. McMahon
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
| | - Peter C.M. van Zijl
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
| | - Assaf A. Gilad
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland
- The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering
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Dorazio SJ, Olatunde AO, Tsitovich PB, Morrow JR. Comparison of divalent transition metal ion paraCEST MRI contrast agents. J Biol Inorg Chem 2014; 19:191-205. [PMID: 24253281 PMCID: PMC3946895 DOI: 10.1007/s00775-013-1059-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/28/2013] [Indexed: 01/06/2023]
Abstract
Transition-metal-ion-based paramagnetic chemical exchange saturation transfer (paraCEST) agents are a promising new class of compounds for magnetic resonance imaging (MRI) contrast. Members in this class of compounds include paramagnetic complexes of Fe(II), Co(II), and Ni(II). The development of the coordination chemistry for these paraCEST agents is presented with an emphasis on the choice of the azamacrocycle backbone and pendent groups with the goals of controlling the oxidation state, spin state, and stability of the complexes. Chemical exchange saturation transfer spectra and images are compared for different macrocyclic complexes containing amide or heterocyclic pendent groups. The potential of paraCEST agents that function as pH- and redox-activated MRI probes is discussed.
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Affiliation(s)
- Sarina J. Dorazio
- Department of Chemistry, University at Buffalo, Amherst, New York, 14260 USA
| | - Abiola O. Olatunde
- Department of Chemistry, University at Buffalo, Amherst, New York, 14260 USA
| | - Pavel B. Tsitovich
- Department of Chemistry, University at Buffalo, Amherst, New York, 14260 USA
| | - Janet R. Morrow
- Department of Chemistry, University at Buffalo, Amherst, New York, 14260 USA
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