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Gunwhy ER, Hines CDG, Green C, Laitinen I, Tadimalla S, Hockings PD, Schütz G, Kenna JG, Sourbron S, Waterton JC. Assessment of hepatic transporter function in rats using dynamic gadoxetate-enhanced MRI: a reproducibility study. MAGMA (NEW YORK, N.Y.) 2024:10.1007/s10334-024-01192-5. [PMID: 39105950 DOI: 10.1007/s10334-024-01192-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 07/19/2024] [Accepted: 07/23/2024] [Indexed: 08/07/2024]
Abstract
OBJECTIVE Previous studies have revealed a substantial between-centre variability in DCE-MRI biomarkers of hepatocellular function in rats. This study aims to identify the main sources of variability by comparing data measured at different centres and field strengths, at different days in the same subjects, and over the course of several months in the same centre. MATERIALS AND METHODS 13 substudies were conducted across three facilities on two 4.7 T and two 7 T scanners using a 3D spoiled gradient echo acquisition. All substudies included 3-6 male Wistar-Han rats each, either scanned once with vehicle (n = 76) or twice with either vehicle (n = 19) or 10 mg/kg of rifampicin (n = 13) at follow-up. Absolute values, between-centre reproducibility, within-subject repeatability, detection limits, and effect sizes were derived for hepatocellular uptake rate (Ktrans) and biliary excretion rate (kbh). Sources of variability were identified using analysis of variance and stratification by centre, field strength, and time period. RESULTS Data showed significant differences between substudies of 31% for Ktrans (p = 0.013) and 43% for kbh (p < 0.001). Within-subject differences were substantially smaller for kbh (8%) but less so for Ktrans (25%). Rifampicin-induced inhibition was safely above the detection limits, with an effect size of 75 ± 3% in Ktrans and 67 ± 8% in kbh. Most of the variability in individual data was accounted for by between-subject (Ktrans = 23.5%; kbh = 42.5%) and between-centre (Ktrans = 44.9%; kbh = 50.9%) variability, substantially more than the between-day variation (Ktrans = 0.1%; kbh = 5.6%). Significant differences in kbh were found between field strengths at the same centre, between centres at the same field strength, and between repeat experiments over 2 months apart in the same centre. DISCUSSION Between-centre bias caused by factors such as hardware differences, subject preparations, and operator dependence is the main source of variability in DCE-MRI of liver function in rats, closely followed by biological between-subject differences. Future method development should focus on reducing these sources of error to minimise the sample sizes needed to detect more subtle levels of inhibition.
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Affiliation(s)
- Ebony R Gunwhy
- Division of Clinical Medicine, School of Medicine and Population Health, University of Sheffield, Polaris, 18 Claremont Crescent, Sheffield, S10 2TA, UK.
| | | | - Claudia Green
- MR & CT Contrast Media Research, Bayer AG, Berlin, Germany
| | - Iina Laitinen
- Antaros Medical, GoCo House, Mölndal, Sweden
- Sanofi-Aventis GmbH, Frankfurt, Germany
| | - Sirisha Tadimalla
- Institute of Medical Physics, University of Sydney, Sydney, Australia
| | - Paul D Hockings
- Antaros Medical, GoCo House, Mölndal, Sweden
- Chalmers University of Technology, Gothenburg, Sweden
| | - Gunnar Schütz
- MR & CT Contrast Media Research, Bayer AG, Berlin, Germany
| | | | - Steven Sourbron
- Division of Clinical Medicine, School of Medicine and Population Health, University of Sheffield, Polaris, 18 Claremont Crescent, Sheffield, S10 2TA, UK
| | - John C Waterton
- Bioxydyn Ltd, St. James Tower, Manchester, UK
- Centre for Imaging Sciences, Division of Informatics Imaging & Data Sciences, School of Health Sciences, Faculty of Biology Medicine & Health, University of Manchester, Manchester, UK
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Melillo N, Scotcher D, Kenna JG, Green C, Hines CDG, Laitinen I, Hockings PD, Ogungbenro K, Gunwhy ER, Sourbron S, Waterton JC, Schuetz G, Galetin A. Use of In Vivo Imaging and Physiologically-Based Kinetic Modelling to Predict Hepatic Transporter Mediated Drug-Drug Interactions in Rats. Pharmaceutics 2023; 15:896. [PMID: 36986758 PMCID: PMC10057977 DOI: 10.3390/pharmaceutics15030896] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/23/2023] [Accepted: 03/03/2023] [Indexed: 03/12/2023] Open
Abstract
Gadoxetate, a magnetic resonance imaging (MRI) contrast agent, is a substrate of organic-anion-transporting polypeptide 1B1 and multidrug resistance-associated protein 2. Six drugs, with varying degrees of transporter inhibition, were used to assess gadoxetate dynamic contrast enhanced MRI biomarkers for transporter inhibition in rats. Prospective prediction of changes in gadoxetate systemic and liver AUC (AUCR), resulting from transporter modulation, were performed by physiologically-based pharmacokinetic (PBPK) modelling. A tracer-kinetic model was used to estimate rate constants for hepatic uptake (khe), and biliary excretion (kbh). The observed median fold-decreases in gadoxetate liver AUC were 3.8- and 1.5-fold for ciclosporin and rifampicin, respectively. Ketoconazole unexpectedly decreased systemic and liver gadoxetate AUCs; the remaining drugs investigated (asunaprevir, bosentan, and pioglitazone) caused marginal changes. Ciclosporin decreased gadoxetate khe and kbh by 3.78 and 0.09 mL/min/mL, while decreases for rifampicin were 7.20 and 0.07 mL/min/mL, respectively. The relative decrease in khe (e.g., 96% for ciclosporin) was similar to PBPK-predicted inhibition of uptake (97-98%). PBPK modelling correctly predicted changes in gadoxetate systemic AUCR, whereas underprediction of decreases in liver AUCs was evident. The current study illustrates the modelling framework and integration of liver imaging data, PBPK, and tracer-kinetic models for prospective quantification of hepatic transporter-mediated DDI in humans.
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Affiliation(s)
- Nicola Melillo
- Centre for Applied Pharmacokinetic Research, Division of Pharmacy and Optometry, School of Health Science, The University of Manchester, Manchester M13 9PL, UK (D.S.)
- SystemsForecastingUK Ltd., Lancaster LA1 5DD, UK
| | - Daniel Scotcher
- Centre for Applied Pharmacokinetic Research, Division of Pharmacy and Optometry, School of Health Science, The University of Manchester, Manchester M13 9PL, UK (D.S.)
| | | | - Claudia Green
- MR & CT Contrast Media Research, Bayer AG, 13353 Berlin, Germany
| | | | - Iina Laitinen
- Sanofi-Aventis Deutschland GmbH, Bioimaging Germany, 65929 Frankfurt am Main, Germany
- Antaros Medical, 431 83 Mölndal, Sweden
| | - Paul D. Hockings
- Antaros Medical, 431 83 Mölndal, Sweden
- MedTech West, Chalmers University of Technology, 413 45 Gothenburg, Sweden
| | - Kayode Ogungbenro
- Centre for Applied Pharmacokinetic Research, Division of Pharmacy and Optometry, School of Health Science, The University of Manchester, Manchester M13 9PL, UK (D.S.)
| | - Ebony R. Gunwhy
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield S10 2TA, UK
| | - Steven Sourbron
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield S10 2TA, UK
| | - John C. Waterton
- Bioxydyn Ltd., Manchester M15 6SZ, UK
- Centre for Imaging Sciences, Division of Informatics Imaging & Data Sciences, School of Health Sciences, The University of Manchester, Manchester M13 9PL, UK
| | - Gunnar Schuetz
- MR & CT Contrast Media Research, Bayer AG, 13353 Berlin, Germany
| | - Aleksandra Galetin
- Centre for Applied Pharmacokinetic Research, Division of Pharmacy and Optometry, School of Health Science, The University of Manchester, Manchester M13 9PL, UK (D.S.)
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Kraiger M, Klein-Rodewald T, Rathkolb B, Calzada-Wack J, Sanz-Moreno A, Fuchs H, Wolf E, Gailus-Durner V, de Angelis MH. Monitoring longitudinal disease progression in a novel murine Kit tumor model using high-field MRI. Sci Rep 2022; 12:14608. [PMID: 36028522 PMCID: PMC9418174 DOI: 10.1038/s41598-022-17880-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/02/2022] [Indexed: 11/09/2022] Open
Abstract
Animal models are an indispensable platform used in various research disciplines, enabling, for example, studies of basic biological mechanisms, pathological processes and new therapeutic interventions. In this study, we applied magnetic resonance imaging (MRI) to characterize the clinical picture of a novel N-ethyl-N-nitrosourea-induced Kit-mutant mouse in vivo. Seven C3H KitN824K/WT mutant animals each of both sexes and their littermates were monitored every other month for a period of twelve months. MRI relaxometry data of hematopoietic bone marrow and splenic tissue as well as high-resolution images of the gastrointestinal organs were acquired. Compared with controls, the mutants showed a dynamic change in the shape and volume of the cecum and enlarged Peyer´s patches were identified throughout the entire study. Mammary tumors were observed in the majority of mutant females and were first detected at eight months of age. Using relaxation measurements, a substantial decrease in longitudinal relaxation times in hematopoietic tissue was detected in mutants at one year of age. In contrast, transverse relaxation time of splenic tissue showed no differences between genotypes, except in two mutant mice, one of which had leukemia and the other hemangioma. In this study, in vivo MRI was used for the first time to thoroughly characterize the evolution of systemic manifestations of a novel Kit-induced tumor model and to document the observable organ-specific disease cascade.
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Affiliation(s)
- Markus Kraiger
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
| | - Tanja Klein-Rodewald
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Birgit Rathkolb
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,German Center for Diabetes Research, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Julia Calzada-Wack
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Adrián Sanz-Moreno
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Helmut Fuchs
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Eckhard Wolf
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Valérie Gailus-Durner
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Martin Hrabě de Angelis
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,German Center for Diabetes Research, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,Chair of Experimental Genetics, TUM School of Life Sciences, Technische Universität München, Freising, Germany
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Feng L, Ma D, Liu F. Rapid MR relaxometry using deep learning: An overview of current techniques and emerging trends. NMR IN BIOMEDICINE 2022; 35:e4416. [PMID: 33063400 PMCID: PMC8046845 DOI: 10.1002/nbm.4416] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 08/25/2020] [Accepted: 09/09/2020] [Indexed: 05/08/2023]
Abstract
Quantitative mapping of MR tissue parameters such as the spin-lattice relaxation time (T1 ), the spin-spin relaxation time (T2 ), and the spin-lattice relaxation in the rotating frame (T1ρ ), referred to as MR relaxometry in general, has demonstrated improved assessment in a wide range of clinical applications. Compared with conventional contrast-weighted (eg T1 -, T2 -, or T1ρ -weighted) MRI, MR relaxometry provides increased sensitivity to pathologies and delivers important information that can be more specific to tissue composition and microenvironment. The rise of deep learning in the past several years has been revolutionizing many aspects of MRI research, including image reconstruction, image analysis, and disease diagnosis and prognosis. Although deep learning has also shown great potential for MR relaxometry and quantitative MRI in general, this research direction has been much less explored to date. The goal of this paper is to discuss the applications of deep learning for rapid MR relaxometry and to review emerging deep-learning-based techniques that can be applied to improve MR relaxometry in terms of imaging speed, image quality, and quantification robustness. The paper is comprised of an introduction and four more sections. Section 2 describes a summary of the imaging models of quantitative MR relaxometry. In Section 3, we review existing "classical" methods for accelerating MR relaxometry, including state-of-the-art spatiotemporal acceleration techniques, model-based reconstruction methods, and efficient parameter generation approaches. Section 4 then presents how deep learning can be used to improve MR relaxometry and how it is linked to conventional techniques. The final section concludes the review by discussing the promise and existing challenges of deep learning for rapid MR relaxometry and potential solutions to address these challenges.
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Affiliation(s)
- Li Feng
- Biomedical Engineering and Imaging Institute and Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Dan Ma
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Fang Liu
- Department of Radiology, Massachusetts General Hospital, Harvard University, Boston, Massachusetts
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Konjar Š, Pavšič M, Veldhoen M. Regulation of Oxygen Homeostasis at the Intestinal Epithelial Barrier Site. Int J Mol Sci 2021; 22:ijms22179170. [PMID: 34502078 PMCID: PMC8431628 DOI: 10.3390/ijms22179170] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 07/28/2021] [Accepted: 08/19/2021] [Indexed: 12/25/2022] Open
Abstract
The unique biology of the intestinal epithelial barrier is linked to a low baseline oxygen pressure (pO2), characterised by a high rate of metabolites circulating through the intestinal blood and the presence of a steep oxygen gradient across the epithelial surface. These characteristics require tight regulation of oxygen homeostasis, achieved in part by hypoxia-inducible factor (HIF)-dependent signalling. Furthermore, intestinal epithelial cells (IEC) possess metabolic identities that are reflected in changes in mitochondrial function. In recent years, it has become widely accepted that oxygen metabolism is key to homeostasis at the mucosae. In addition, the gut has a vast and diverse microbial population, the microbiota. Microbiome–gut communication represents a dynamic exchange of mediators produced by bacterial and intestinal metabolism. The microbiome contributes to the maintenance of the hypoxic environment, which is critical for nutrient absorption, intestinal barrier function, and innate and/or adaptive immune responses in the gastrointestinal tract. In this review, we focus on oxygen homeostasis at the epithelial barrier site, how it is regulated by hypoxia and the microbiome, and how oxygen homeostasis at the epithelium is regulated in health and disease.
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Affiliation(s)
- Špela Konjar
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia;
- Instituto de Medicina Molecular, João Lobo Antunes, Faculdade de Medicina de Lisboa, 1649-028 Lisbon, Portugal;
- Correspondence:
| | - Miha Pavšič
- Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia;
| | - Marc Veldhoen
- Instituto de Medicina Molecular, João Lobo Antunes, Faculdade de Medicina de Lisboa, 1649-028 Lisbon, Portugal;
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Garteiser P, Bane O, Doblas S, Friedli I, Hectors S, Pagé G, Van Beers BE, Waterton JC. Experimental Protocols for MRI Mapping of Renal T 1. Methods Mol Biol 2021; 2216:383-402. [PMID: 33476012 DOI: 10.1007/978-1-0716-0978-1_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
The water proton longitudinal relaxation time, T1, is a common and useful MR parameter in nephrology research. Here we provide three step-by-step T1-mapping protocols suitable for different types of nephrology research. Firstly, we provide a single-slice 2D saturation recovery protocol suitable for studies of global pathology, where whole-kidney coverage is unnecessary. Secondly, we provide an inversion recovery type imaging protocol that may be optimized for specific kidney disease applications. Finally, we also provide imaging protocol for small animal kidney imaging in a clinical scanner.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concept and experimental procedure.
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Affiliation(s)
- Philippe Garteiser
- Laboratory of Imaging Biomarkers, Centre de Recherche sur l'Inflammation, Inserm UMR 1149, Université de Paris and AP-HP, Paris, France
| | - Octavia Bane
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sabrina Doblas
- Laboratory of Imaging Biomarkers, Centre de Recherche sur l'Inflammation, Inserm UMR 1149, Université de Paris and AP-HP, Paris, France
| | - Iris Friedli
- Antaros Medical, BioVenture Hub, Mölndal, Sweden
| | - Stefanie Hectors
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Gwenaël Pagé
- Laboratory of Imaging Biomarkers, Centre de Recherche sur l'Inflammation, Inserm UMR 1149, Université de Paris and AP-HP, Paris, France
| | - Bernard E Van Beers
- Laboratory of Imaging Biomarkers, Centre de Recherche sur l'Inflammation, Inserm UMR 1149, Université de Paris and AP-HP, Paris, France
| | - John C Waterton
- Centre for Imaging Sciences, Division of Informatics Imaging & Data Sciences, School of Health Sciences, Faculty of Biology Medicine & Health, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, UK.
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Quantitative MRI: Defining repeatability, reproducibility and accuracy for prostate cancer imaging biomarker development. Magn Reson Imaging 2021; 77:169-179. [PMID: 33388362 DOI: 10.1016/j.mri.2020.12.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/25/2020] [Accepted: 12/29/2020] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Quantitative MRI (qMRI) parameters have been increasingly used to develop predictive models to accurately monitor treatment response in prostate cancer after radiotherapy. To reliably detect changes in signal due to treatment response, predictive models require qMRI parameters with high repeatability and reproducibility. The purpose of this study was to measure qMRI parameter uncertainties in both commercial and in-house developed phantoms to guide the development of robust predictive models for monitoring treatment response. MATERIALS AND METHODS ADC, T1, and R2* values were acquired across three 3 T scanners with a prostate-specific qMRI protocol using the NIST/ISMRM system phantom, RSNA/NIST diffusion phantom, and an in-house phantom. A B1 field map was acquired to correct for flip angle inhomogeneity in T1 maps. All sequences were repeated in each scan to assess within-session repeatability. Weekly scans were acquired on one scanner for three months with the in-house phantom. Between-session repeatability was measured with test-retest scans 6-months apart on all scanners with all phantoms. Accuracy, defined as percentage deviation from reference value for ADC and T1, was evaluated using the system and diffusion phantoms. Repeatability and reproducibility coefficients of variation (%CV) were calculated for all qMRI parameters on all phantoms. RESULTS Overall, repeatability CV of ADC was <2.40%, reproducibility CV was <3.98%, and accuracy ranged between -8.0% to 2.7% across all scanners. Applying B1 correction on T1 measurements significantly improved the repeatability and reproducibility (p<0.05) but increased error in accuracy (p<0.001). Repeatability and reproducibility of R2* was <4.5% and <7.3% respectively in the system phantom across all scanners. CONCLUSION Repeatability, reproducibility, and accuracy in qMRI parameters from a prostate-specific protocol was estimated using both commercial and in-house phantoms. Results from this work will be used to identify robust qMRI parameters for use in the development of predictive models to longitudinally monitor treatment response for prostate cancer in current and future clinical trials.
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Kapre R, Zhou J, Li X, Beckett L, Louie AY. A novel gamma GLM approach to MRI relaxometry comparisons. Magn Reson Med 2020; 84:1592-1604. [PMID: 32048764 PMCID: PMC7317199 DOI: 10.1002/mrm.28192] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 12/18/2019] [Accepted: 01/10/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE To demonstrate that constant coefficient of variation (CV), but nonconstant absolute variance in MRI relaxometry (T1 , T2 , R1 , R2 ) data leads to erroneous conclusions based on standard linear models such as ordinary least squares (OLS). We propose a gamma generalized linear model identity link (GGLM-ID) framework that factors the inherent CV into parameter estimates. We first examined the effects on calculations of contrast agent relaxivity before broadening to other applications such as analysis of variance (ANOVA) and liver iron content (LIC). METHODS Eight models including OLS and GGLM-ID were initially fit to data obtained on sulfated dextran iron oxide (SDIO) nanoparticles. Both a resampling simulation on the data as well as two separate Monte Carlo simulations (with and without concentration error) were performed to determine mean square error (MSE) and type I error rate. We then evaluated the performance of OLS/GGLM-ID on R1 repeatability and LIC data sets. RESULTS OLS had an MSE of 4-5× that of GGLM-ID as well as a type I error rate of 20-30%, whereas GGLM-ID was near the nominal 5% level in the relaxivity study. Only OLS found statistically significant effects of MRI facility on relaxivity in an R1 repeatability study, but no significant differences were found in a resampling, whereas GGLM was more consistent. GGLM-ID was also superior to OLS for modeling LIC. CONCLUSIONS OLS leads to erroneous conclusions when analyzing MRI relaxometry data. GGLM-ID factors in the inherent CV of an MRI experiment, leading to more reproducible conclusions.
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Affiliation(s)
- Rohan Kapre
- Department of Biomedical Engineering, University of California, Davis, CA.,Biostatistics Graduate Group, University of California, Davis, CA
| | - Junhan Zhou
- Chemistry Graduate Group, University of California, Davis, CA
| | - Xinzhe Li
- Department of Biomedical Engineering, University of California, Davis, CA
| | - Laurel Beckett
- Biostatistics Graduate Group, University of California, Davis, CA
| | - Angelique Y Louie
- Department of Biomedical Engineering, University of California, Davis, CA.,Chemistry Graduate Group, University of California, Davis, CA
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Vučković I, Nayfeh T, Mishra PK, Periyanan S, Sussman CR, Kline TL, Macura S. Influence of water based embedding media composition on the relaxation properties of fixed tissue. Magn Reson Imaging 2019; 67:7-17. [PMID: 31821849 DOI: 10.1016/j.mri.2019.11.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/30/2019] [Accepted: 11/21/2019] [Indexed: 10/25/2022]
Abstract
BACKGROUND In MRI of formalin-fixed tissue one of the problems is the dependence of tissue relaxation properties on formalin composition and composition of embedding medium (EM) used for scanning. In this study, we investigated molecular mechanisms by which the EM composition affects T2 relaxation directly and T1 relaxation indirectly. OBJECTIVE To identify principal components of formaldehyde based EM and the mechanism by which they affect relaxation properties of fixed tissue. METHODS We recorded high resolution 1H NMR spectra of common formalin fixatives at temperatures in the range of 5 °C to 45 °C. We also measured T1 and T2 relaxation times of various organs of formalin fixed (FF) zebrafish at 7 T at 21 °C and 31 °C in several EM with and without fixative or gadolinium contrast agents. RESULTS We showed that the major source of T2 variability is chemical exchange between protons from EM hydroxyls and water, mediated by the presence of phosphate ions. The exchange rate increases with temperature, formaldehyde concentration in EM and phosphate concentration in EM. Depending on which side of the coalescence the system resides, the temperature increase can lead to either shortening or prolongation of T2, or to no noticeable change at all when very close to the coalescence. Chemical exchange can be minimized by washing out from EM the fixative, the phosphate or both. CONCLUSION The dependence of T2 in fixed tissue on the fixative origin and composition described in prior literature could be attributed to the phosphate buffer accelerated chemical exchange among the fixative hydroxyls and the tissue water. More consistent results in the relaxation measurements could be obtained by stricter control of the fixative composition or by scanning fixed tissue in PBS without fixative.
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Affiliation(s)
- Ivan Vučković
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Tarek Nayfeh
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
| | - Prasanna K Mishra
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Caroline R Sussman
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA
| | - Timothy L Kline
- Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Slobodan Macura
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.
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