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Dudysheva N, Mauconduit F, Abdeddaim R, Gapais PF, Hosseinnezhadian S, Dubois M, Amadon A, Boulant N, Hertz-Pannier L, Vignaud A. The restricted SAR protocol: A method to assess MRI coil prototypes in an unconditionally safe manner. Magn Reson Med 2024; 91:1723-1734. [PMID: 38084471 DOI: 10.1002/mrm.29962] [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: 07/25/2023] [Revised: 10/24/2023] [Accepted: 11/17/2023] [Indexed: 02/03/2024]
Abstract
PURPOSE Testing an RF coil prototype on subjects involves laborious verifications to ensure its safety. In particular, it requires preliminary electromagnetic simulations and their validations on phantoms to accurately predict the specific absorption rate (SAR). For coil design validation with a simpler safety procedure, the restricted SAR (rS) mode is proposed, enabling representative first experiments in vivo. The goal of the developed approach is to accelerate the transition of a custom coil system from prototype to clinical use. METHODS The restricted specific absorption rate (SAR) (rS) mode imposes a radical limitation on the transmitted RF power based on a worst-case scenario of local RF power absorption. The limitations used are independent of the SAR spatial distribution, making this approach unconditionally safe. The developed rS protocol contains the sequences required for coil evaluation and satisfies the imposed rS conditions. It provides a quantitative characterization of the coil transmission and reception profiles and a qualitative evaluation of the anatomical images. Protocol validation was performed on commercial and pre-industrial prototype coils on a small cohort of healthy volunteers. RESULTS The proposed rS protocol enables coil evaluation within an acquisition time compatible with common clinical protocol duration. The total time of all evaluation steps does not exceed 17 min. At the same time, the global SAR remains 100 times less than the International Electrotechnical Commission safety limit for played sequences. CONCLUSION The rS protocol allows characterizing and comparing coil prototypes on volunteers without extensive electromagnetic calculations and phantom validations in an unconditionally safe way.
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Affiliation(s)
- Natalia Dudysheva
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
- Multiwave Imaging, Marseille, France
| | - Franck Mauconduit
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Redha Abdeddaim
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Institut Marseille Imaging, Marseille, France
| | | | | | | | - Alexis Amadon
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Nicolas Boulant
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Lucie Hertz-Pannier
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Alexandre Vignaud
- Paris-Saclay University, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
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2
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Zhang T, Zhao Y, Jin W, Li Y, Guo R, Ke Z, Luo J, Li Y, Liang ZP. B 1 mapping using pre-learned subspaces for quantitative brain imaging. Magn Reson Med 2023; 90:2089-2101. [PMID: 37345702 DOI: 10.1002/mrm.29764] [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] [Received: 04/06/2023] [Revised: 05/24/2023] [Accepted: 05/30/2023] [Indexed: 06/23/2023]
Abstract
PURPOSE To develop a machine learning-based method for estimation of both transmitter and receiver B1 fields desired for correction of the B1 inhomogeneity effects in quantitative brain imaging. THEORY AND METHODS A subspace model-based machine learning method was proposed for estimation of B1t and B1r fields. Probabilistic subspace models were used to capture scan-dependent variations in the B1 fields; the subspace basis and coefficient distributions were learned from pre-scanned training data. Estimation of the B1 fields for new experimental data was achieved by solving a linear optimization problem with prior distribution constraints. We evaluated the performance of the proposed method for B1 inhomogeneity correction in quantitative brain imaging scenarios, including T1 and proton density (PD) mapping from variable-flip-angle spoiled gradient-echo (SPGR) data as well as neurometabolic mapping from MRSI data, using phantom, healthy subject and brain tumor patient data. RESULTS In both phantom and healthy subject data, the proposed method produced high-quality B1 maps. B1 correction on SPGR data using the estimated B1 maps produced significantly improved T1 and PD maps. In brain tumor patients, the proposed method produced more accurate and robust B1 estimation and correction results than conventional methods. The B1 maps were also applied to MRSI data from tumor patients and produced improved neurometabolite maps, with better separation between pathological and normal tissues. CONCLUSION This work presents a novel method to estimate B1 variations using probabilistic subspace models and machine learning. The proposed method may make correction of B1 inhomogeneity effects more robust in practical applications.
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Affiliation(s)
- Tianxiao Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Yibo Zhao
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Wen Jin
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Yudu Li
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Rong Guo
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Siemens Medical Solutions USA, Inc., Urbana, Illinois, USA
| | - Ziwen Ke
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Jie Luo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Yao Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhi-Pei Liang
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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3
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Nöth U, Shrestha M, Deichmann R. B 1 mapping using an EPI-based double angle approach: A practical guide for correcting slice profile and B 0 distortion effects. Magn Reson Med 2023; 90:103-116. [PMID: 36912496 DOI: 10.1002/mrm.29632] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 02/01/2023] [Accepted: 02/20/2023] [Indexed: 03/14/2023]
Abstract
PURPOSE Aim of this study was to develop a reliable B1 mapping method for brain imaging based on vendor MR sequences available on clinical scanners. Correction procedures for B0 distortions and slice profile imperfections are proposed, together with a phantom experiment for deriving the approximate time-bandwidth-product (TBP) of the excitation pulse, which is usually not known for vendor sequences. METHODS The double angle method was used, acquiring two gradient echo echo-planar imaging data sets with different excitation angles. A correction factor C (B1 , TBP, B0 ) was derived from simulations for converting double angle method signal quotients into bias-free B1 maps. In vitro and in vivo tests compare results with reference B1 maps based on an established in-house sequence. RESULTS The simulation shows that C has a negligible B1 dependence, allowing for a polynomial approximation of C (TBP, B0 ). Signal quotients measured in a phantom experiment with known TBP reconfirm the simulation results. In vitro and in vivo B1 maps based on the proposed method, assuming TBP = 5.8 as derived from a phantom experiment, match closely the reference B1 maps. Analysis without B0 correction shows marked deviations in areas of distorted B0 , highlighting the importance of this correction. CONCLUSION Double angle method-based B1 mapping was set up for vendor gradient echo-echo-planar imaging sequences, using a correction procedure for slice profile imperfections and B0 distortions. This will help to set up quantitative MRI studies on clinical scanners with release sequences, as the method does not require knowledge of the exact RF-pulse profiles or the use of in-house sequences.
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Affiliation(s)
- Ulrike Nöth
- Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Manoj Shrestha
- Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Ralf Deichmann
- Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt am Main, Germany
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4
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Glasser MF, Coalson TS, Harms MP, Xu J, Baum GL, Autio JA, Auerbach EJ, Greve DN, Yacoub E, Van Essen DC, Bock NA, Hayashi T. Empirical transmit field bias correction of T1w/T2w myelin maps. Neuroimage 2022; 258:119360. [PMID: 35697132 PMCID: PMC9483036 DOI: 10.1016/j.neuroimage.2022.119360] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 06/01/2022] [Accepted: 06/04/2022] [Indexed: 12/30/2022] Open
Abstract
T1-weighted divided by T2-weighted (T1w/T2w) myelin maps were initially developed for neuroanatomical analyses such as identifying cortical areas, but they are increasingly used in statistical comparisons across individuals and groups with other variables of interest. Existing T1w/T2w myelin maps contain radiofrequency transmit field (B1+) biases, which may be correlated with these variables of interest, leading to potentially spurious results. Here we propose two empirical methods for correcting these transmit field biases using either explicit measures of the transmit field or alternatively a 'pseudo-transmit' approach that is highly correlated with the transmit field at 3T. We find that the resulting corrected T1w/T2w myelin maps are both better neuroanatomical measures (e.g., for use in cross-species comparisons), and more appropriate for statistical comparisons of relative T1w/T2w differences across individuals and groups (e.g., sex, age, or body-mass-index) within a consistently acquired study at 3T. We recommend that investigators who use the T1w/T2w approach for mapping cortical myelin use these B1+ transmit field corrected myelin maps going forward.
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Affiliation(s)
| | | | - Michael P Harms
- Psychiatry, Washington University Medical School, St. Louis, MO, United States
| | - Junqian Xu
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States; Departments of Radiology and Psychiatry, Baylor College of Medicine, Houston, TX, United States
| | - Graham L Baum
- Department of Psychology, Harvard University, Cambridge, MA, United States
| | - Joonas A Autio
- RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Edward J Auerbach
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | - Douglas N Greve
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Essa Yacoub
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
| | | | - Nicholas A Bock
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada
| | - Takuya Hayashi
- RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
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5
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Zhu D, Schär M, Qin Q. Ultrafast B1 mapping with RF-prepared 3D FLASH acquisition: Correcting the bias due to T 1 -induced k-space filtering effect. Magn Reson Med 2022; 88:757-769. [PMID: 35381114 PMCID: PMC9232926 DOI: 10.1002/mrm.29247] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 03/06/2022] [Accepted: 03/07/2022] [Indexed: 01/25/2023]
Abstract
Purpose The traditional radiofrequency (RF)‐prepared B1 mapping technique consists of one scan with an RF preparation module for flip angle‐encoding and a second scan without this module for normalizing. To reduce the T1‐induced k‐space filtering effect, this method is limited to 2D FLASH acquisition with a two‐parameter method. A novel 3D RF‐prepared three‐parameter method for ultrafast B1‐mapping is proposed to correct the T1‐induced quantification bias. Theory The point spread function analysis of FLASH shows that the prepared longitudinal magnetization before the FLASH acquisition and the image signal obeys a linear (not proportional) relationship. The intercept of the linear function causes the quantification bias and can be captured by a third saturated scan. Methods Using the 2D double‐angle method (DAM) as the reference, a 3D RF‐prepared three‐parameter protocol with 9 s duration was compared with the two‐parameter method, as well as the saturated DAM (SDAM) method, the dual refocusing echo acquisition mode (DREAM) method, and the actual flip‐angle imaging (AFI) method, for B1 mapping of brain, breast, and abdomen with different orientations and shim settings at 3T. Results The 3D RF‐prepared three‐parameter method with complex‐subtraction delivered consistently lower RMS error, error mean, error standard deviation, and higher concordance correlation coefficients values than the two‐parameter method, the three‐parameter method with magnitude‐subtraction, the multi‐slice DREAM and the 3D AFI, and were close to the results of 2D or multi‐slice SDAM. Conclusion The proposed ultrafast 3D RF‐prepared three‐parameter method with complex‐subtraction was demonstrated with high accuracy for B1 mapping of brain, breast, and abdomen.
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Affiliation(s)
- Dan Zhu
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.,The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael Schär
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Qin Qin
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.,The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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6
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Delgado PR, Kuehne A, Aravina M, Millward JM, Vázquez A, Starke L, Waiczies H, Pohlmann A, Niendorf T, Waiczies S. B 1 inhomogeneity correction of RARE MRI at low SNR: Quantitative in vivo 19 F MRI of mouse neuroinflammation with a cryogenically-cooled transceive surface radiofrequency probe. Magn Reson Med 2021; 87:1952-1970. [PMID: 34812528 DOI: 10.1002/mrm.29094] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/03/2021] [Accepted: 11/04/2021] [Indexed: 12/26/2022]
Abstract
PURPOSE Low SNR in fluorine-19 (19 F) MRI benefits from cryogenically-cooled transceive surface RF probes (CRPs), but strong B1 inhomogeneities hinder quantification. Rapid acquisition with refocused echoes (RARE) is an SNR-efficient method for MRI of neuroinflammation with perfluorinated compounds but lacks an analytical signal intensity equation to retrospectively correct B1 inhomogeneity. Here, a workflow was proposed and validated to correct and quantify 19 F-MR signals from the inflamed mouse brain using a 19 F-CRP. METHODS In vivo 19 F-MR images were acquired in a neuroinflammation mouse model with a quadrature 19 F-CRP using an imaging setup including 3D-printed components to acquire co-localized anatomical and 19 F images. Model-based corrections were validated on a uniform 19 F phantom and in the neuroinflammatory model. Corrected 19 F-MR images were benchmarked against reference images and overlaid on in vivo 1 H-MR images. Computed concentration uncertainty maps using Monte Carlo simulations served as a measure of performance of the B1 corrections. RESULTS Our study reports on the first quantitative in vivo 19 F-MR images of an inflamed mouse brain using a 19 F-CRP, including in vivo T1 calculations for 19 F-nanoparticles during pathology and B1 corrections for 19 F-signal quantification. Model-based corrections markedly improved 19 F-signal quantification from errors > 50% to < 10% in a uniform phantom (p < 0.001). Concentration uncertainty maps ex vivo and in vivo yielded uncertainties that were generally < 25%. Monte Carlo simulations prescribed SNR ≥ 10.1 to reduce uncertainties < 10%, and SNR ≥ 4.25 to achieve uncertainties < 25%. CONCLUSION Our model-based correction method facilitated 19 F signal quantification in the inflamed mouse brain when using the SNR-boosting 19 F-CRP technology, paving the way for future low-SNR 19 F-MRI applications in vivo.
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Affiliation(s)
- Paula Ramos Delgado
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany.,Experimental and Clinical Research Center, a cooperation between the Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association and the Charité-Universitätsmedizin Berlin, Berlin, Germany
| | | | - Mariya Aravina
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany
| | - Jason M Millward
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany
| | | | - Ludger Starke
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany
| | | | - Andreas Pohlmann
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany
| | - Thoralf Niendorf
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany.,Experimental and Clinical Research Center, a cooperation between the Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association and the Charité-Universitätsmedizin Berlin, Berlin, Germany.,MRI.TOOLS, Berlin, Germany
| | - Sonia Waiczies
- Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin Ultrahigh Field Facility, Berlin, Germany
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7
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Keenan KE, Gimbutas Z, Dienstfrey A, Stupic KF, Boss MA, Russek SE, Chenevert TL, Prasad PV, Guo J, Reddick WE, Cecil KM, Shukla-Dave A, Aramburu Nunez D, Shridhar Konar A, Liu MZ, Jambawalikar SR, Schwartz LH, Zheng J, Hu P, Jackson EF. Multi-site, multi-platform comparison of MRI T1 measurement using the system phantom. PLoS One 2021; 16:e0252966. [PMID: 34191819 PMCID: PMC8244851 DOI: 10.1371/journal.pone.0252966] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 05/26/2021] [Indexed: 11/19/2022] Open
Abstract
Recent innovations in quantitative magnetic resonance imaging (MRI) measurement methods have led to improvements in accuracy, repeatability, and acquisition speed, and have prompted renewed interest to reevaluate the medical value of quantitative T1. The purpose of this study was to determine the bias and reproducibility of T1 measurements in a variety of MRI systems with an eye toward assessing the feasibility of applying diagnostic threshold T1 measurement across multiple clinical sites. We used the International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) system phantom to assess variations of T1 measurements, using a slow, reference standard inversion recovery sequence and a rapid, commonly-available variable flip angle sequence, across MRI systems at 1.5 tesla (T) (two vendors, with number of MRI systems n = 9) and 3 T (three vendors, n = 18). We compared the T1 measurements from inversion recovery and variable flip angle scans to ISMRM/NIST phantom reference values using Analysis of Variance (ANOVA) to test for statistical differences between T1 measurements grouped according to MRI scanner manufacturers and/or static field strengths. The inversion recovery method had minor over- and under-estimations compared to the NMR-measured T1 values at both 1.5 T and 3 T. Variable flip angle measurements had substantially greater deviations from the NMR-measured T1 values than the inversion recovery measurements. At 3 T, the measured variable flip angle T1 for one vendor is significantly different than the other two vendors for most of the samples throughout the clinically relevant range of T1. There was no consistent pattern of discrepancy between vendors. We suggest establishing rigorous quality control procedures for validating quantitative MRI methods to promote confidence and stability in associated measurement techniques and to enable translation of diagnostic threshold from the research center to the entire clinical community.
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Affiliation(s)
- Kathryn E. Keenan
- National Institute of Standards and Technology, Boulder, Colorado, United State of America
- * E-mail:
| | - Zydrunas Gimbutas
- National Institute of Standards and Technology, Boulder, Colorado, United State of America
| | - Andrew Dienstfrey
- National Institute of Standards and Technology, Boulder, Colorado, United State of America
| | - Karl F. Stupic
- National Institute of Standards and Technology, Boulder, Colorado, United State of America
| | - Michael A. Boss
- American College of Radiology, Center for Research and Innovation, Philadelphia, Pennsylvania, United State of America
| | - Stephen E. Russek
- National Institute of Standards and Technology, Boulder, Colorado, United State of America
| | | | - P. V. Prasad
- NorthShore University Health System, Evanston, Illinois, United State of America
| | - Junyu Guo
- St. Jude Children’s Research Hospital, Memphis, Tennessee, United State of America
| | - Wilburn E. Reddick
- St. Jude Children’s Research Hospital, Memphis, Tennessee, United State of America
| | - Kim M. Cecil
- Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine Cincinnati, Ohio, United State of America
| | - Amita Shukla-Dave
- Memorial Sloan Kettering Cancer Center, New York, New York, United State of America
| | - David Aramburu Nunez
- Memorial Sloan Kettering Cancer Center, New York, New York, United State of America
| | | | - Michael Z. Liu
- Columbia University Medical Center, New York, New York, United State of America
| | | | | | - Jie Zheng
- Washington University in St. Louis, St. Louis, Missouri, United State of America
| | - Peng Hu
- University of California, Los Angeles, California, United State of America
| | - Edward F. Jackson
- University of Wisconsin, Madison, Wisconsin, United State of America
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8
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Maggioni MB, Krämer M, Reichenbach JR. Optimized gradient spoiling of UTE VFA-AFI sequences for robust T 1 estimation with B 1-field correction. Magn Reson Imaging 2021; 82:1-8. [PMID: 34147596 DOI: 10.1016/j.mri.2021.06.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 05/21/2021] [Accepted: 06/15/2021] [Indexed: 10/21/2022]
Abstract
Quantifying T1 relaxation times is a challenge because inhomogeneities of the B1 field have to be corrected to obtain proper values. It is a particular challenge in tissues with short T2⁎ values, for which conventional MRI techniques do not provide sufficient signal. Recently, a B1-field correction technique called AFI (Actual Flip angle Imaging) has been introduced that can be combined with UTE (ultra-short echo-time) sequences, which have much shorter echo times compared to conventional MRI techniques, allowing quantification of signal in short T2⁎ tissues. A disadvantage of AFI is that it requires very long relaxation delays between repetitions to minimize the influence of imperfect spoiling of transverse magnetization on signal behavior. In this work, we propose a novel spoiling scheme for the AFI sequence that efficiently provides accurate B1 correction maps with strongly reduced acquisition time. We validated the method with both phantom and preliminary in vivo results.
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Affiliation(s)
- Marta B Maggioni
- Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.
| | - Martin Krämer
- Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany
| | - Jürgen R Reichenbach
- Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.
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9
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Hays CC, Zlatar ZZ, Meloy MJ, Osuna J, Liu TT, Galasko DR, Wierenga CE. Anterior Cingulate Structure and Perfusion is Associated with Cerebrospinal Fluid Tau among Cognitively Normal Older Adult APOEɛ4 Carriers. J Alzheimers Dis 2021; 73:87-101. [PMID: 31743999 DOI: 10.3233/jad-190504] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Evidence suggests the ɛ4 allele of the apolipoprotein E (APOE) gene may accelerate an age-related process of cortical thickening and cerebral blood flow (CBF) reduction in the anterior cingulate cortex (ACC). Although the neural basis of this association remains unclear, evidence suggests it might reflect early neurodegenerative processes. However, to date, associations between cerebrospinal fluid (CSF) biomarkers of neurodegeneration, such as CSF tau, and APOE-related alterations in ACC cortical thickness (CTH) and CBF have yet to be explored. The current study explored the interaction of CSF tau and APOE genotype (ɛ4+, ɛ4-) on FreeSurfer-derived CTH and arterial spin labeling MRI-measured resting CBF in the ACC (caudal ACC [cACC] and rostral ACC [rACC]) among a sample of 45 cognitively normal older adults. Secondary analyses also examined associations between APOE, CTH/CBF, and cognitive performance. In the cACC, higher CSF tau was associated with higher CTH and lower CBF in ɛ4+, whereas these relationships were not evident in ɛ4-. In the rACC, higher CSF tau was associated with higher CTH for both ɛ4+ and ɛ4-, and with lower CBF only in ɛ4+. Significant interactions of CSF tau and APOE on CTH/CBF were not observed in two posterior reference regions implicated in Alzheimer's disease. Secondary analyses revealed a negative relationship between cACC CTH and executive functioning in ɛ4+ and a positive relationship in ɛ4-. Findings suggest the presence of an ɛ4-related pattern of increased CTH and reduced CBF in the ACC that is associated with biomarkers of neurodegeneration and subtle decrements in cognition.
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Affiliation(s)
- Chelsea C Hays
- VA San Diego Healthcare System, San Diego, CA, USA.,SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA
| | - Zvinka Z Zlatar
- Department of Psychiatry, UC San Diego, La Jolla, CA, USA.,SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA
| | - M J Meloy
- VA San Diego Healthcare System, San Diego, CA, USA
| | - Jessica Osuna
- VA San Diego Healthcare System, San Diego, CA, USA.,Department of Psychiatry, UC San Diego, La Jolla, CA, USA
| | - Thomas T Liu
- Department of Radiology, UC San Diego, La Jolla, CA, USA
| | - Douglas R Galasko
- VA San Diego Healthcare System, San Diego, CA, USA.,Department of Neurosciences, UC San Diego, La Jolla, CA, USA
| | - Christina E Wierenga
- VA San Diego Healthcare System, San Diego, CA, USA.,Department of Psychiatry, UC San Diego, La Jolla, CA, USA.,SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA
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10
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Hays CC, Zlatar ZZ, Meloy MJ, Bondi MW, Gilbert PE, Liu T, Helm JL, Wierenga CE. Interaction of APOE, cerebral blood flow, and cortical thickness in the entorhinal cortex predicts memory decline. Brain Imaging Behav 2021; 14:369-382. [PMID: 32048144 DOI: 10.1007/s11682-019-00245-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ε4 allele of the apolipoprotein E (APOE) gene, a risk factor for cognitive decline, is associated with alterations in medial temporal lobe (MTL) structure and function, yet little research has been dedicated to understanding how these alterations might interact to negatively impact cognition. To bridge this gap, the present study employed linear regression models to determine the extent to which APOE genotype (ε4+, ε4-) modifies interactive effects of baseline arterial spin labeling MRI-measured cerebral blood flow (CBF) and FreeSurfer-derived cortical thickness/volume (CT/Vo) in two MTL regions of interest (entorhinal cortex, hippocampus) on memory change in 98 older adults who were cognitively normal at baseline. Baseline entorhinal CBF was positively associated with memory change, but only among ε4 carriers with lower entorhinal CT. Similarly, baseline entorhinal CT was positively associated with memory change, but only among ε4 carriers with lower entorhinal CBF. Findings suggest that APOE ε4 carriers may experience concomitant alterations in neurovascular function and morphology in the MTL that interact to negatively affect cognition prior to the onset of overt clinical symptoms. Results also suggest the presence of distinct multimodal neural signatures in the entorhinal cortex that may signal relative risk for cognitive decline among this group, perhaps reflecting different stages of cerebrovascular compensation (early effective vs. later ineffective).
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Affiliation(s)
- Chelsea C Hays
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 9216, USA.,SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct, Suite 103, San Diego, CA, 92120, USA
| | - Zvinka Z Zlatar
- Department of Psychiatry, UC San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA
| | - M J Meloy
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 9216, USA.,Department of Psychiatry, UC San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA
| | - Mark W Bondi
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 9216, USA.,SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct, Suite 103, San Diego, CA, 92120, USA.,Department of Psychiatry, UC San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA
| | - Paul E Gilbert
- SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct, Suite 103, San Diego, CA, 92120, USA.,Department of Psychology, San Diego State University, 5500 Campanile Drive, San Diego, CA, 92182, USA
| | - Thomas Liu
- Department of Radiology, UC San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA
| | - Jonathan L Helm
- SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct, Suite 103, San Diego, CA, 92120, USA.,Department of Psychology, San Diego State University, 5500 Campanile Drive, San Diego, CA, 92182, USA
| | - Christina E Wierenga
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 9216, USA. .,SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct, Suite 103, San Diego, CA, 92120, USA. .,Department of Psychiatry, UC San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA.
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11
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Delgado PR, Kuehne A, Periquito JS, Millward JM, Pohlmann A, Waiczies S, Niendorf T. B 1 inhomogeneity correction of RARE MRI with transceive surface radiofrequency probes. Magn Reson Med 2020; 84:2684-2701. [PMID: 32447779 DOI: 10.1002/mrm.28307] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/27/2020] [Accepted: 04/13/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE The use of surface radiofrequency (RF) coils is common practice to boost sensitivity in (pre)clinical MRI. The number of transceive surface RF coils is rapidly growing due to the surge in cryogenically cooled RF technology and ultrahigh-field MRI. Consequently, there is an increasing need for effective correction of the excitation field ( B 1 + ) inhomogeneity inherent in these coils. Retrospective B1 correction permits quantitative MRI, but this usually requires a pulse sequence-specific analytical signal intensity (SI) equation. Such an equation is not available for fast spin-echo (Rapid Acquisition with Relaxation Enhancement, RARE) MRI. Here we present, test, and validate retrospective B1 correction methods for RARE. METHODS We implemented the commonly used sensitivity correction and developed an empirical model-based method and a hybrid combination of both. Tests and validations were performed with a cryogenically cooled RF probe and a single-loop RF coil. Accuracy of SI quantification and T1 contrast were evaluated after correction. RESULTS The three described correction methods achieved dramatic improvements in B1 homogeneity and significantly improved SI quantification and T1 contrast, with mean SI errors reduced from >40% to >10% following correction in all cases. Upon correction, images of phantoms and mouse heads demonstrated homogeneity comparable to that of images acquired with a volume resonator. This was quantified by SI profile, SI ratio (error < 10%), and percentage of integral uniformity (PIU > 80% in vivo and ex vivo compared to PIU > 87% with the reference RF coil). CONCLUSION This work demonstrates the efficacy of three B1 correction methods tailored for transceive surface RF probes and RARE MRI. The corrected images are suitable for quantification and show comparable results between the three methods, opening the way for T1 measurements and X-nuclei quantification using surface transceiver RF coils. This approach is applicable to other MR techniques for which no analytical SI exists.
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Affiliation(s)
- Paula Ramos Delgado
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.,Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | | | - João S Periquito
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.,Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Jason M Millward
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Andreas Pohlmann
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Sonia Waiczies
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F), Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.,Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.,MRI.TOOLS GmbH, Berlin, Germany
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12
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Foster C, Steventon JJ, Helme D, Tomassini V, Wise RG. Assessment of the Effects of Aerobic Fitness on Cerebrovascular Function in Young Adults Using Multiple Inversion Time Arterial Spin Labeling MRI. Front Physiol 2020; 11:360. [PMID: 32372976 PMCID: PMC7187806 DOI: 10.3389/fphys.2020.00360] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 03/27/2020] [Indexed: 11/13/2022] Open
Abstract
This cross-sectional study investigated the effects of aerobic fitness on cerebrovascular function in the healthy brain. Gray matter cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were quantified in a sample of young adults within a normal fitness range. Based on existing Transcranial Doppler ultrasound and fMRI evidence, we predicted a positive relationship between fitness and resting gray matter CBF and CVR. Exploratory hypotheses that higher V . O2peak would be associated with higher GM volume and cognitive performance were also investigated. 20 adults underwent a V . O2peak test and a battery of cognitive tests. All subjects also underwent an MRI scan where multiple inversion time (MTI) pulsed arterial spin labeling (PASL) was used to quantify resting CBF and CVR to 5% CO2. Region of interest analysis showed a non-significant inverse correlation between whole-brain gray matter CBF and V . O2peak; r = -0.4, p = 0.08, corrected p (p') = 0.16 and a significant positive correlation between V . O2peak and whole-brain averaged gray matter CVR; r = 0.62, p = 0.003, p' = 0.006. Voxel-wise analysis revealed a significant inverse association between V . O2peak and resting CBF in the left and right thalamus, brainstem, right lateral occipital cortex, left intra-calcarine cortex and cerebellum. The results of this study suggest that aerobic fitness is associated with lower baseline CBF and greater CVR in young adults.
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Affiliation(s)
- Catherine Foster
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom
| | - Jessica J. Steventon
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
- Neuroscience and Mental Health Research Institute (NMHRI), School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Daniel Helme
- Department of Anaesthetics and Intensive Care Medicine, Cardiff University School of Medicine, Cardiff, United Kingdom
| | - Valentina Tomassini
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom
- Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
- Department of Neuroscience, Imaging and Clinical Sciences, “G. D’Annunzio University” of Chieti-Pescara, Chieti, Italy
- Institute for Advanced Biomedical Technologies (ITAB), “G. D’Annunzio University” of Chieti-Pescara, Chieti, Italy
| | - Richard G. Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom
- Department of Neuroscience, Imaging and Clinical Sciences, “G. D’Annunzio University” of Chieti-Pescara, Chieti, Italy
- Institute for Advanced Biomedical Technologies (ITAB), “G. D’Annunzio University” of Chieti-Pescara, Chieti, Italy
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13
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Liu EY, Guo J, Simon AB, Haist F, Dubowitz DJ, Buxton RB. The potential for gas-free measurements of absolute oxygen metabolism during both baseline and activation states in the human brain. Neuroimage 2019; 207:116342. [PMID: 31722231 DOI: 10.1016/j.neuroimage.2019.116342] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 10/13/2019] [Accepted: 11/06/2019] [Indexed: 11/27/2022] Open
Abstract
Quantitative functional magnetic resonance imaging methods make it possible to measure cerebral oxygen metabolism (CMRO2) in the human brain. Current methods require the subject to breathe special gas mixtures (hypercapnia and hyperoxia). We tested a noninvasive suite of methods to measure absolute CMRO2 in both baseline and dynamic activation states without the use of special gases: arterial spin labeling (ASL) to measure baseline and activation cerebral blood flow (CBF), with concurrent measurement of the blood oxygenation level dependent (BOLD) signal as a dynamic change in tissue R2*; VSEAN to estimate baseline O2 extraction fraction (OEF) from a measurement of venous blood R2, which in combination with the baseline CBF measurement yields an estimate of baseline CMRO2; and FLAIR-GESSE to measure tissue R2' to estimate the scaling parameter needed for calculating the change in CMRO2 in response to a stimulus with the calibrated BOLD method. Here we describe results for a study sample of 17 subjects (8 female, mean age = 25.3 years, range 21-31 years). The primary findings were that OEF values measured with the VSEAN method were in good agreement with previous PET findings, while estimates of the dynamic change in CMRO2 in response to a visual stimulus were in good agreement between the traditional hypercapnia calibration and calibration based on R2'. These results support the potential of gas-free methods for quantitative physiological measurements.
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Affiliation(s)
- Eulanca Y Liu
- Neurosciences Graduate Program, Medical Scientist Training Program, University of California, San Diego, USA; Center for Functional MRI, University of California, San Diego, USA
| | - Jia Guo
- Center for Functional MRI, University of California, San Diego, USA; Department of Bioengineering, University of California, Riverside, USA
| | - Aaron B Simon
- Center for Functional MRI, University of California, San Diego, USA; Department of Radiation Medicine and Applied Sciences, University of California, San Diego, USA
| | - Frank Haist
- Psychiatry, University of California, San Diego, USA; Center for Human Development, University of California, San Diego, USA
| | - David J Dubowitz
- Center for Functional MRI, University of California, San Diego, USA; Radiology, University of California, San Diego, USA; University of Auckland, Auckland, New Zealand
| | - Richard B Buxton
- Center for Functional MRI, University of California, San Diego, USA; Radiology, University of California, San Diego, USA.
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14
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Okazaki T, Niwa T, Suzuki K, Shibukawa S, Imai Y. Age related signal changes of the pituitary stalk on thin-slice magnetic resonance imaging in infants. Brain Dev 2019; 41:327-333. [PMID: 30514608 DOI: 10.1016/j.braindev.2018.11.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/24/2018] [Accepted: 11/19/2018] [Indexed: 01/31/2023]
Abstract
PURPOSE Signals of some brain regions change along with development in T1-weighted imaging (T1WI) in infants. This study aimed to assess the association of the signal intensity of the pituitary stalk on thin-slice T1WI with infant age. METHODS This retrospective study was performed in 89 infants (gestational age [GA], 25-41 weeks; postmenstrual age [PMA], 36-46 weeks; chronological age [CA], 4-141 days) without intracranial abnormalities. The signal ratio of the pituitary stalk/pons on thin-slice T1WI was calculated, and its correlations with GA, PMA, and CA were assessed. Additionally, the signal ratio of the anterior pituitary gland/pons was calculated, and its correlation with that of the pituitary stalk was assessed. The signal intensity and distribution of the pituitary stalk were visually rated, and their correlations with GA, PMA, and CA were assessed. RESULTS The signal ratio of the pituitary stalk was significantly positively correlated with GA (P < 0.001) and negatively correlated with CA (P < 0.001), but was not correlated with PMA. Stepwise multiple regression revealed that CA was independently associated with the signal ratio of the pituitary stalk (P < 0.001). GA was significantly higher (P < 0.05) and CA was significantly lower (P < 0.05) in infants with a high signal intensity and wide distribution of high signal intensity of the pituitary stalk. CONCLUSIONS The signal intensity of the pituitary stalk on T1WI was negatively correlated with CA in infants, which might be related to postnatal changes in the pars tuberalis of the pituitary stalk after birth in infants.
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Affiliation(s)
- Takashi Okazaki
- Department of Radiology, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Japan
| | - Tetsu Niwa
- Department of Radiology, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Japan.
| | - Keiji Suzuki
- Department of Pediatrics, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Japan
| | - Shuhei Shibukawa
- Department of Radiology, Tokai University Hospital, 143 Shimokasuya, Isehara 259-1193, Japan
| | - Yutaka Imai
- Department of Radiology, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Japan
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15
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Liu EY, Haist F, Dubowitz DJ, Buxton RB. Cerebral blood volume changes during the BOLD post-stimulus undershoot measured with a combined normoxia/hyperoxia method. Neuroimage 2019; 185:154-163. [PMID: 30315908 PMCID: PMC6292691 DOI: 10.1016/j.neuroimage.2018.10.032] [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: 02/21/2018] [Revised: 10/09/2018] [Accepted: 10/09/2018] [Indexed: 10/28/2022] Open
Abstract
Cerebral blood flow (CBF) and blood oxygenation level dependent (BOLD) signal measurements make it possible to estimate steady-state changes in the cerebral metabolic rate of oxygen (CMRO2) with a calibrated BOLD method. However, extending this approach to measure the dynamics of CMRO2 requires an additional assumption: that deoxygenated cerebral blood volume (CBVdHb) follows CBF in a predictable way. A test-case for this assumption is the BOLD post-stimulus undershoot, for which one proposed explanation is a strong uncoupling of flow and blood volume with an elevated level of CBVdHb during the post-stimulus period compared to baseline due to slow blood volume recovery (Balloon Model). A challenge in testing this model is that CBVdHb differs from total blood volume, which can be measured with other techniques. In this study, the basic hypothesis of elevated CBVdHb during the undershoot was tested, based on the idea that the BOLD signal change when a subject switches from breathing a normoxic gas to breathing a hyperoxic gas is proportional to the absolute CBVdHb. In 19 subjects (8F), dual-echo BOLD responses were measured in primary visual cortex during a flickering radial checkerboard stimulus in normoxia, and the identical experiment was repeated in hyperoxia (50% O2/balance N2). The BOLD signal differences between normoxia and hyperoxia for the pre-stimulus baseline, stimulus, and post-stimulus periods were compared using an equivalent BOLD signal calculated from measured R2* changes to eliminate signal drifts. Relative to the pre-stimulus baseline, the average BOLD signal change from normoxia to hyperoxia was negative during the undershoot period (p = 0.0251), consistent with a reduction of CBVdHb and contrary to the prediction of the Balloon Model. Based on these results, the BOLD post-stimulus undershoot does not represent a case of strong uncoupling of CBVdHb and CBF, supporting the extension of current calibrated BOLD methods to estimate the dynamics of CMRO2.
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Affiliation(s)
- Eulanca Y Liu
- Neurosciences Graduate Program, Medical Scientist Training Program, University of California, San Diego, USA; Center for Functional MRI, University of California, San Diego, USA
| | - Frank Haist
- Psychiatry, University of California, San Diego, USA; Center for Human Development, University of California, San Diego, USA
| | - David J Dubowitz
- Center for Functional MRI, University of California, San Diego, USA; Radiology, University of California, San Diego, USA
| | - Richard B Buxton
- Center for Functional MRI, University of California, San Diego, USA; Radiology, University of California, San Diego, USA.
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16
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Bangen KJ, Werhane ML, Weigand AJ, Edmonds EC, Delano-Wood L, Thomas KR, Nation DA, Evangelista ND, Clark AL, Liu TT, Bondi MW. Reduced Regional Cerebral Blood Flow Relates to Poorer Cognition in Older Adults With Type 2 Diabetes. Front Aging Neurosci 2018; 10:270. [PMID: 30250430 PMCID: PMC6139361 DOI: 10.3389/fnagi.2018.00270] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/22/2018] [Indexed: 12/27/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) increases risk for dementia, including Alzheimer's disease (AD). Many previous studies of brain changes underlying cognitive impairment in T2DM have applied conventional structural magnetic resonance imaging (MRI) to detect macrostructural changes associated with cerebrovascular disease such as white matter hyperintensities or infarcts. However, such pathology likely reflects end-stage manifestations of chronic decrements in cerebral blood flow (CBF). MRI techniques that measure CBF may (1) elucidate mechanisms that precede irreversible parenchymal damage and (2) serve as a marker of risk for cognitive decline. CBF measured with arterial spin labeling (ASL) MRI may be a useful marker of perfusion deficits in T2DM and related conditions. We examined associations among T2DM, CBF, and cognition in a sample of 49 well-characterized nondemented older adults. Along with a standard T1-weighted scan, a pseudocontinuous ASL sequence optimized for older adults (by increasing post-labeling delays to allow more time for the blood to reach brain tissue) was obtained on a 3T GE scanner to measure regional CBF in FreeSurfer derived regions of interest. Participants also completed a neuropsychological assessment. Results showed no significant differences between individuals with and without T2DM in terms of cortical thickness or regional brain volume. However, adjusting for age, sex, comorbid vascular risk factors, and reference CBF (postcentral gyrus) older adults with T2DM demonstrated reduced CBF in the hippocampus, and inferior temporal, inferior parietal, and frontal cortices. Lower CBF was associated with poorer memory and executive function/processing speed. When adjusting for diabetes, the significant associations between lower regional CBF and poorer executive function/processing speed remained. Results demonstrate that CBF is reduced in older adults with T2DM, and suggest that CBF alterations likely precede volumetric changes. Notably, relative to nondiabetic control participants, those with T2DM showed lower CBF in predilection sites for AD pathology (medial temporal lobe and inferior parietal regions). Findings augment recent research suggesting that perfusion deficits may underlie cognitive decrements frequently observed among older adults with T2DM. Results also suggest that CBF measured with ASL MRI may reflect an early and important marker of risk of cognitive impairment in T2DM and related conditions.
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Affiliation(s)
- Katherine J Bangen
- Research Service, VA San Diego Healthcare System, San Diego, CA, United States.,Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Madeleine L Werhane
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States.,Department of Psychology, San Diego State University, San Diego, CA, United States
| | - Alexandra J Weigand
- Research Service, VA San Diego Healthcare System, San Diego, CA, United States.,Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Emily C Edmonds
- Research Service, VA San Diego Healthcare System, San Diego, CA, United States.,Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Lisa Delano-Wood
- Psychology Service, VA San Diego Healthcare System, San Diego, CA, United States.,Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Kelsey R Thomas
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States.,Psychology Service, VA San Diego Healthcare System, San Diego, CA, United States
| | - Daniel A Nation
- Department of Psychology, University of Southern California, Los Angeles, CA, United States
| | | | - Alexandra L Clark
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States.,Department of Psychology, San Diego State University, San Diego, CA, United States
| | - Thomas T Liu
- Department of Radiology and Bioengineering, University of California, San Diego, San Diego, CA, United States
| | - Mark W Bondi
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States.,Psychology Service, VA San Diego Healthcare System, San Diego, CA, United States
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17
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Brady ML, Coffield KS, Kuehl TJ, Raghavan R, Speights VO, Patel B, Wilson S, Wilson M, Odland RM. A pilot study in intraparenchymal therapy delivery in the prostate: a comparison of delivery with a porous needle vs standard needle. BMC Urol 2018; 18:66. [PMID: 30055610 PMCID: PMC6064133 DOI: 10.1186/s12894-018-0378-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 06/20/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND New biologic therapies directly injected into the prostate are in clinical trials for prostatic diseases. There is a need to understand distribution of injected therapies as a function of prostatic anatomy, physiology, and device design. METHODS A needle with a porous length of customizable-length was tested and its performance compared with a standard needle. Injections of magnetic resonance contrast reagent were placed into ex-vivo human prostates after surgical excision in standard of care therapy for invasive bladder cancer patients. Magnetic resonance images were acquired using sequences to quantify volume delivered, distributed, and backflow. RESULTS Magnetic resonance images analysis revealed heterogeneity distribution with injection into the specimens. There was low resistance to flow along ductal pathways and high resistance to flow into glandular nodules and smooth muscle/fibrous parenchyma. Data confirm previous studies showing injection loss via urethra backflow, urethra, and prostatic ducts. Tissue fraction of dose was significantly higher with porous needle compared with standard needle (p = .03). We found that a greater volume of distribution divided by the amount infused (Vd/Vi) increased by 80% with the porous needle, though no statistically significant association due to small sample size. CONCLUSIONS This study demonstrated that prostatic tissue is anatomically heterogenic and limits distribution of needle injection. There is greater distribution in the ex-vivo prostate using a porous needle. The complexity of intra prostatic flow pathways suggests preoperative imaging and pre-treatment planning will enhance therapy.
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Affiliation(s)
| | - King Scott Coffield
- Department of Surgery, Division of Urology, Scott & White Medical Center, Temple, TX, USA. .,Texas A&M Health Science Center College of Medicine, Temple, TX, USA.
| | - Thomas J Kuehl
- Department of Obstetrics & Gynecology, Scott & White Medical Center, Temple, TX, USA.,Departments of Obstetrics & Gynecology, Pediatrics, and Molecular & Cellular Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA
| | | | - V O Speights
- Department of Pathology, Scott & White Medical Center, Temple, TX, USA.,Texas A&M Health Science Center College of Medicine, Temple, TX, USA
| | - Belur Patel
- Department of Surgery, Division of Urology, Scott & White Medical Center, Temple, TX, USA.,Texas A&M Health Science Center College of Medicine, Temple, TX, USA
| | | | | | - Rick M Odland
- Twin Star TDS, LLC, Lexington, KY, USA.,Department of Otolaryngology, Hennepin County Medical Center, University of Minnesota, Minneapolis, MN, USA
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18
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Kim MO, Hong T, Kim DH. Fast B1+ mapping using three consecutive RF pulses and balanced gradients for improved bSSFP imaging. Magn Reson Imaging 2018; 46:40-46. [DOI: 10.1016/j.mri.2017.10.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 10/18/2022]
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19
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Abstract
The direct delivery of drugs and other agents into tissue (in contrast to systemic administration) has been used in clinical trials for brain cancer, neurodegenerative diseases and peripheral tumors. However, continuing evidence suggests that clinical efficacy depends on adequate delivery to a target. Inadequate delivery may have doomed otherwise effective drugs, through failure to distinguish drug inefficacy from poor distribution at the target. Conventional pretreatment clinical images of the patient fail to reveal the complexity and diversity of drug transport pathways in tissue. We discuss the richness of these pathways and argue that development and patient treatment can be sped up and improved by: using quantitative as well as 'real-time' imaging; customized simulations using data from that imaging; and device designs that optimize the drug-device combination.
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20
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Pasha EP, Tarumi T, Haley AP, Tanaka H. Transcranial Doppler of the middle cerebral artery indicates regional gray matter cerebral perfusion. Physiol Meas 2017; 38:2176-2185. [PMID: 29091052 DOI: 10.1088/1361-6579/aa976f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE We determined if transcranial color-coded Doppler derived hemodynamics are associated with MRI-based cerebral blood flow (CBF) in regions clinically important to dementia in healthy middle-aged adults. APPROACH In 30 subjects (18m/12f; age = 52 ± 1 years), blood flow velocity (BFV) and cerebrovascular conductance (CVC) were measured with transcranial color-coded Doppler (TCCD) at the middle cerebral artery (MCA) and cerebral blood flow (CBF) was assessed with arterial spin labeled perfusion MRI. MAIN RESULTS BFV and CVC were associated with hippocampus (r = 0.58 and r = 0.61, both p < 0.01) and occipitoparietal (r = 0.50 and r = 0.58, both p < 0.01) CBF. CVC was further associated with posterior cingulate CBF (r = 0.58 p < 0.01). Independent of age and sex, BFV and CVC were associated with hippocampus (r = 0.59 and r = 0.55, both p < 0.003) and occipitoparietal (r = 0.50 and r = 0.57, both p < 0.01) CBF. CVC was independently associated with posterior cingulate CBF (r = 0.38, p = 0.049). SIGNIFICANCE TCCD-measured BFV and CVC of the MCA are indicators of cerebral perfusion to clinically valuable brain regions in healthy middle-aged adults. TCCD may not be a good indicator of blood flow to cerebral white matter.
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Affiliation(s)
- Evan P Pasha
- Department of Kinesiology and Health Education, Cardiovascular Aging Research Laboratory, The University of Texas at Austin, Austin, TX 78712, United States of America
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21
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Oakden W, Bock NA, Al-Ebraheem A, Farquharson MJ, Stanisz GJ. Early regional cuprizone-induced demyelination in a rat model revealed with MRI. NMR IN BIOMEDICINE 2017; 30:e3743. [PMID: 28544286 DOI: 10.1002/nbm.3743] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 03/23/2017] [Accepted: 04/07/2017] [Indexed: 06/07/2023]
Abstract
The cuprizone model of demyelination is well established in the mouse as a tool for the study of the mechanisms of both demyelination and remyelination. It is often desirable, however, to have a larger model, such as the rat, especially for imaging-based studies, yet initial work has failed to show demyelination in cuprizone-fed rats. Several recent studies have demonstrated demyelination in the rat, but only in the corpus callosum. In this study, we acquired high-resolution, three-dimensional images of the whole brain every 2 weeks, using a T1 -weighted magnetization-prepared rapid acquisition gradient echo imaging sequence, optimized for myelin contrast, in order to assess myelination across the entire rat brain over a period of 8 weeks on a 1% cuprizone diet. We observed a consistent pattern of demyelination, beginning in the cerebellum by 4 weeks and involving more rostral regions of the brain by 8 weeks on the cuprizone diet, with validation using Luxol fast blue histology. This imaging technique permits the effects of cuprizone-induced demyelination to be followed longitudinally in a single animal, over the entire brain. In turn, this may facilitate the establishment of the cuprizone model of demyelination in the rat.
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Affiliation(s)
- Wendy Oakden
- Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Nicholas A Bock
- Psychology, Neuroscience and Behavior, McMaster University, Hamilton, Ontario, Canada
| | - Alia Al-Ebraheem
- School of Interdisciplinary Science, McMaster University, Hamilton, Ontario, Canada
| | | | - Greg J Stanisz
- Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Neurosurgery and Pediatric Neurosurgery, Medical University of Lublin, Lublin, Poland
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22
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Smith ZM, Krizay E, Sá RC, Li ET, Scadeng M, Powell FL, Dubowitz DJ. Evidence from high-altitude acclimatization for an integrated cerebrovascular and ventilatory hypercapnic response but different responses to hypoxia. J Appl Physiol (1985) 2017; 123:1477-1486. [PMID: 28705997 DOI: 10.1152/japplphysiol.00341.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Ventilation and cerebral blood flow (CBF) are both sensitive to hypoxia and hypercapnia. To compare chemosensitivity in these two systems, we made simultaneous measurements of ventilatory and cerebrovascular responses to hypoxia and hypercapnia in 35 normal human subjects before and after acclimatization to hypoxia. Ventilation and CBF were measured during stepwise changes in isocapnic hypoxia and iso-oxic hypercapnia. We used MRI to quantify actual cerebral perfusion. Measurements were repeated after 2 days of acclimatization to hypoxia at 3,800 m altitude (partial pressure of inspired O2 = 90 Torr) to compare plasticity in the chemosensitivity of these two systems. Potential effects of hypoxic and hypercapnic responses on acute mountain sickness (AMS) were assessed also. The pattern of CBF and ventilatory responses to hypercapnia were almost identical. CO2 responses were augmented to a similar degree in both systems by concomitant acute hypoxia or acclimatization to sustained hypoxia. Conversely, the pattern of CBF and ventilatory responses to hypoxia were markedly different. Ventilation showed the well-known increase with acute hypoxia and a progressive decline in absolute value over 25 min of sustained hypoxia. With acclimatization to hypoxia for 2 days, the absolute values of ventilation and O2 sensitivity increased. By contrast, O2 sensitivity of CBF or its absolute value did not change during sustained hypoxia for up to 2 days. The results suggest a common or integrated control mechanism for CBF and ventilation by CO2 but different mechanisms of O2 sensitivity and plasticity between the systems. Ventilatory and cerebrovascular responses were the same for all subjects irrespective of AMS symptoms. NEW & NOTEWORTHY Ventilatory and cerebrovascular hypercapnic response patterns show similar plasticity in CO2 sensitivity following hypoxic acclimatization, suggesting an integrated control mechanism. Conversely, ventilatory and cerebrovascular hypoxic responses differ. Ventilation initially increases but adapts with prolonged hypoxia (hypoxic ventilatory decline), and ventilatory sensitivity increases following acclimatization. In contrast, cerebral blood flow hypoxic sensitivity remains constant over a range of hypoxic stimuli, with no cerebrovascular acclimatization to sustained hypoxia, suggesting different mechanisms for O2 sensitivity in the two systems.
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Affiliation(s)
- Zachary M Smith
- Department of Radiology, Center for Functional MRI, University of California San Diego School of Medicine , La Jolla, California
| | - Erin Krizay
- Department of Radiology, Center for Functional MRI, University of California San Diego School of Medicine , La Jolla, California
| | - Rui Carlos Sá
- Division of Physiology, Department of Medicine, University of California San Diego School of Medicine , La Jolla, California
| | - Ethan T Li
- Department of Radiology, Center for Functional MRI, University of California San Diego School of Medicine , La Jolla, California
| | - Miriam Scadeng
- Department of Radiology, Center for Functional MRI, University of California San Diego School of Medicine , La Jolla, California
| | - Frank L Powell
- Division of Physiology, Department of Medicine, University of California San Diego School of Medicine , La Jolla, California.,White Mountain Research Station, University of California , Bishop, California
| | - David J Dubowitz
- Department of Radiology, Center for Functional MRI, University of California San Diego School of Medicine , La Jolla, California
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23
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Rowley CD, Sehmbi M, Bazin PL, Tardif CL, Minuzzi L, Frey BN, Bock NA. Age-related mapping of intracortical myelin from late adolescence to middle adulthood using T 1 -weighted MRI. Hum Brain Mapp 2017; 38:3691-3703. [PMID: 28462512 DOI: 10.1002/hbm.23624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/10/2017] [Accepted: 04/12/2017] [Indexed: 12/11/2022] Open
Abstract
Magnetic resonance imaging (MRI) studies in humans have reported that the T1 -weighted signal in the cerebral cortex follows an inverted "U" trajectory over the lifespan. Here, we investigated the T1 -weighted signal trajectory from late adolescence to middle adulthood in humans to characterize the age range when mental illnesses tend to present, and efficacy of treatments are evaluated. We compared linear to quadratic predictors of age on signal in 67 healthy individuals, 17-45 years old. We investigated ¼, ½, and ¾ depths in the cortex representing intracortical myelin (ICM), in the superficial white matter (SWM), and in a reference deep white matter tract. We found that the quadratic fit was superior in all regions of the cortex, while signal in the SWM and deep white matter showed no global dependence on age over this range. The signal trajectory in any region followed a similar shape regardless of cortical depth. The quadratic fit was analyzed in 70 cortical regions to obtain the age of maximum signal intensity. We found that visual, cingulate, and left ventromedial prefrontal cortices peak first around 34 years old, whereas motor and premotor areas peak latest at ∼38 years. Our analysis suggests that ICM trajectories over this range can be modeled well in small cohorts of subjects using quadratic functions, which are amenable to statistical analysis, thus suitable for investigating regional changes in ICM with disease. This study highlights a novel approach to map ICM trajectories using an age range that coincides with the onset of many mental illnesses. Hum Brain Mapp 38:3691-3703, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Christopher D Rowley
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - Manpreet Sehmbi
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - Pierre-Louis Bazin
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany
| | - Christine L Tardif
- Brain Imaging Centre, Douglas Mental Health Institute; Department of Psychiatry, McGill University, Montreal, Quebec, H4H 1R3, Canada
| | - Luciano Minuzzi
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Mood Disorders Program and Women's Health Concerns Clinic, St. Joseph's Healthcare, Hamilton, Ontario, L8K 3K7, Canada
| | - Benicio N Frey
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Mood Disorders Program and Women's Health Concerns Clinic, St. Joseph's Healthcare, Hamilton, Ontario, L8K 3K7, Canada
| | - Nicholas A Bock
- McMaster Integrative Neuroscience Discovery and Study Program, McMaster University, Hamilton, Ontario, L8S 4K1, Canada.,Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
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24
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Boudreau M, Tardif CL, Stikov N, Sled JG, Lee W, Pike GB. B 1 mapping for bias-correction in quantitative T 1 imaging of the brain at 3T using standard pulse sequences. J Magn Reson Imaging 2017; 46:1673-1682. [PMID: 28301086 DOI: 10.1002/jmri.25692] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/10/2017] [Indexed: 11/07/2022] Open
Abstract
PURPOSE B1 mapping is important for many quantitative imaging protocols, particularly those that include whole-brain T1 mapping using the variable flip angle (VFA) technique. However, B1 mapping sequences are not typically available on many magnetic resonance imaging (MRI) scanners. The aim of this work was to demonstrate that B1 mapping implemented using standard scanner product pulse sequences can produce B1 (and VFA T1 ) maps comparable in quality and acquisition time to advanced techniques. MATERIALS AND METHODS Six healthy subjects were scanned at 3.0T. An interleaved multislice spin-echo echo planar imaging double-angle (EPI-DA) B1 mapping protocol, using a standard product pulse sequence, was compared to two alternative methods (actual flip angle imaging, AFI, and Bloch-Siegert shift, BS). Single-slice spin-echo DA B1 maps were used as a reference for comparison (Ref. DA). VFA flip angles were scaled using each B1 map prior to fitting T1 ; the nominal flip angle case was also compared. RESULTS The pooled-subject voxelwise correlation (ρ) for B1 maps (BS/AFI/EPI-DA) relative to the reference B1 scan (Ref. DA) were ρ = 0.92/0.95/0.98. VFA T1 correlations using these maps were ρ = 0.86/0.88/0.96, much better than without B1 correction (ρ = 0.53). The relative error for each B1 map (BS/AFI/EPI-DA/Nominal) had 95th percentiles of 5/4/3/13%. CONCLUSION Our findings show that B1 mapping implemented using product pulse sequences can provide excellent quality B1 (and VFA T1 ) maps, comparable to other custom techniques. This fast whole-brain measurement (∼2 min) can serve as an excellent alternative for researchers without access to advanced B1 pulse sequences. LEVEL OF EVIDENCE 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1673-1682.
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Affiliation(s)
- Mathieu Boudreau
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Christine L Tardif
- Cerebral Imaging Centre, Douglas Mental Health University Institute, Montreal, Canada
| | - Nikola Stikov
- Ecole Polytechnique de Montreal, Montreal, Quebec, Canada.,Montreal Heart Institute, University of Montreal, Montreal, Quebec, Canada
| | - John G Sled
- Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Ontario, Canada
| | - Wayne Lee
- Department of Medical Biophysics, University of Toronto, Ontario, Canada
| | - G Bruce Pike
- Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.,Hotchkiss Brain Institute and Department of Radiology, University of Calgary, Calgary, Alberta, Canada
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25
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Wang J, He L, Zheng H, Lu ZL. Improving structural brain images acquired with the 3D FLASH sequence. Magn Reson Imaging 2017; 38:224-232. [PMID: 28109888 DOI: 10.1016/j.mri.2017.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 01/17/2017] [Indexed: 10/20/2022]
Abstract
The three-dimension Fast Low Angle SHot Magnetic Resonance Imaging (3D FLASH) sequence has been widely adopted in medical diagnostic imaging because of its availability, simplicity, and high spatial resolution. To improve the quality of structural brain images acquired with the 3D FLASH sequence, we developed a parameter optimization scheme and image inhomogeneity correction methods. The optimal imaging parameters were determined by maximizing gray-matter and white-matter CNR efficiency. Compared to protocols based on published parameters, applying the proposed optimal imaging parameters increased CNR efficiency by >10%. Image inhomogeneity, including signal and CNR inhomogeneity, was corrected by the choice of an optimal flip angle, estimated transmit function, and estimated receive sensitivity. As a result, our optimization and image inhomogeneity correction greatly improved the quality of images acquired with the 3D FLASH sequence.
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Affiliation(s)
- Jinghua Wang
- Center for Cognitive and Behavioral Brain Imaging, The Ohio State University, Columbus, OH 43210, USA.
| | - Lili He
- Perinatal Institute, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Zhong-Lin Lu
- Center for Cognitive and Behavioral Brain Imaging, The Ohio State University, Columbus, OH 43210, USA
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26
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Simon AB, Dubowitz DJ, Blockley NP, Buxton RB. A novel Bayesian approach to accounting for uncertainty in fMRI-derived estimates of cerebral oxygen metabolism fluctuations. Neuroimage 2016; 129:198-213. [PMID: 26790354 DOI: 10.1016/j.neuroimage.2016.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/30/2015] [Accepted: 01/01/2016] [Indexed: 10/22/2022] Open
Abstract
Calibrated blood oxygenation level dependent (BOLD) imaging is a multimodal functional MRI technique designed to estimate changes in cerebral oxygen metabolism from measured changes in cerebral blood flow and the BOLD signal. This technique addresses fundamental ambiguities associated with quantitative BOLD signal analysis; however, its dependence on biophysical modeling creates uncertainty in the resulting oxygen metabolism estimates. In this work, we developed a Bayesian approach to estimating the oxygen metabolism response to a neural stimulus and used it to examine the uncertainty that arises in calibrated BOLD estimation due to the presence of unmeasured model parameters. We applied our approach to estimate the CMRO2 response to a visual task using the traditional hypercapnia calibration experiment as well as to estimate the metabolic response to both a visual task and hypercapnia using the measurement of baseline apparent R2' as a calibration technique. Further, in order to examine the effects of cerebral spinal fluid (CSF) signal contamination on the measurement of apparent R2', we examined the effects of measuring this parameter with and without CSF-nulling. We found that the two calibration techniques provided consistent estimates of the metabolic response on average, with a median R2'-based estimate of the metabolic response to CO2 of 1.4%, and R2'- and hypercapnia-calibrated estimates of the visual response of 27% and 24%, respectively. However, these estimates were sensitive to different sources of estimation uncertainty. The R2'-calibrated estimate was highly sensitive to CSF contamination and to uncertainty in unmeasured model parameters describing flow-volume coupling, capillary bed characteristics, and the iso-susceptibility saturation of blood. The hypercapnia-calibrated estimate was relatively insensitive to these parameters but highly sensitive to the assumed metabolic response to CO2.
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Affiliation(s)
- Aaron B Simon
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA; Medical Scientist Training Program, University of California San Diego, La Jolla, CA, USA
| | - David J Dubowitz
- Keck Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, USA
| | - Nicholas P Blockley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Richard B Buxton
- Keck Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, USA; Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, CA, USA.
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27
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Wang K, Smith ZM, Buxton RB, Swenson ER, Dubowitz DJ. Acetazolamide during acute hypoxia improves tissue oxygenation in the human brain. J Appl Physiol (1985) 2015; 119:1494-500. [PMID: 26472861 PMCID: PMC4683345 DOI: 10.1152/japplphysiol.00117.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 10/09/2015] [Indexed: 01/29/2023] Open
Abstract
Low doses of the carbonic anhydrase inhibitor acetazolamide provides accelerated acclimatization to high-altitude hypoxia and prevention of cerebral and other symptoms of acute mountain sickness. We previously observed increases in cerebral O2 metabolism (CMRO2 ) during hypoxia. In this study, we investigate whether low-dose oral acetazolamide (250 mg) reduces this elevated CMRO2 and in turn might improve cerebral tissue oxygenation (PtiO2 ) during acute hypoxia. Six normal human subjects were exposed to 6 h of normobaric hypoxia with and without acetazolamide prophylaxis. We determined CMRO2 and cerebral PtiO2 from MRI measurements of cerebral blood flow (CBF) and cerebral venous O2 saturation. During normoxia, low-dose acetazolamide resulted in no significant change in CBF, CMRO2 , or PtiO2 . During hypoxia, we observed increases in CBF [48.5 (SD 12.4) (normoxia) to 65.5 (20.4) ml·100 ml(-1)·min(-1) (hypoxia), P < 0.05] and CMRO2 [1.54 (0.19) to 1.79 (0.25) μmol·ml(-1)·min(-1), P < 0.05] and a dramatic decline in PtiO2 [25.0 to 11.4 (2.7) mmHg, P < 0.05]. Acetazolamide prophylaxis mitigated these rises in CBF [53.7 (20.7) ml·100 ml(-1)·min(-1) (hypoxia + acetazolamide)] and CMRO2 [1.41 (0.09) μmol·ml(-1)·min(-1) (hypoxia + acetazolamide)] associated with acute hypoxia but also reduced O2 delivery [6.92 (1.45) (hypoxia) to 5.60 (1.14) mmol/min (hypoxia + acetazolamide), P < 0.05]. The net effect was improved cerebral tissue PtiO2 during acute hypoxia [11.4 (2.7) (hypoxia) to 16.5 (3.0) mmHg (hypoxia + acetazolamide), P < 0.05]. In addition to its renal effect, low-dose acetazolamide is effective at the capillary endothelium, and we hypothesize that local interruption in cerebral CO2 excretion accounts for the improvements in CMRO2 and ultimately in cerebral tissue oxygenation during hypoxia. This study suggests a potentially pivotal role of cerebral CO2 and pH in modulating CMRO2 and PtiO2 during acute hypoxia.
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Affiliation(s)
- Kang Wang
- Center for Functional MRI, Department of Radiology, University of California, San Diego, California; School of Medicine, University of California, San Diego, California; and
| | - Zachary M Smith
- Center for Functional MRI, Department of Radiology, University of California, San Diego, California
| | - Richard B Buxton
- Center for Functional MRI, Department of Radiology, University of California, San Diego, California
| | - Erik R Swenson
- Department of Medicine, University of Washington and Veterans Affairs Puget Sound Health Care System, Seattle, Washington
| | - David J Dubowitz
- Center for Functional MRI, Department of Radiology, University of California, San Diego, California;
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28
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Rowley CD, Bazin PL, Tardif CL, Sehmbi M, Hashim E, Zaharieva N, Minuzzi L, Frey BN, Bock NA. Assessing intracortical myelin in the living human brain using myelinated cortical thickness. Front Neurosci 2015; 9:396. [PMID: 26557052 PMCID: PMC4615825 DOI: 10.3389/fnins.2015.00396] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 10/08/2015] [Indexed: 01/08/2023] Open
Abstract
Alterations in the myelination of the cerebral cortex may underlie abnormal cortical function in a variety of brain diseases. Here, we describe a technique for investigating changes in intracortical myelin in clinical populations on the basis of cortical thickness measurements with magnetic resonance imaging (MRI) at 3 Tesla. For this, we separately compute the thickness of the shallower, lightly myelinated portion of the cortex and its deeper, heavily myelinated portion (referred to herein as unmyelinated and myelinated cortex, respectively). Our expectation is that the thickness of the myelinated cortex will be a specific biomarker for disruptions in myeloarchitecture. We show representative atlases of total cortical thickness, T, unmyelinated cortical thickness, G, and myelinated cortical thickness, M, for a healthy group of 20 female subjects. We further demonstrate myelinated cortical thickness measurements in a preliminary clinical study of 10 bipolar disorder type-I subjects and 10 healthy controls, and report significant decreases in the middle frontal gyrus in T, G, and M in the disorder, with the largest percentage change occurring in M. This study highlights the potential of myelinated cortical thickness measurements for investigating intracortical myelin involvement in brain disease at clinically relevant field strengths and resolutions.
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Affiliation(s)
- Christopher D Rowley
- Department of Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada ; MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada
| | - Pierre-Louis Bazin
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany
| | - Christine L Tardif
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany
| | - Manpreet Sehmbi
- MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada ; Department of Psychiatry and Behavioural Neurosciences, McMaster University Hamilton, ON, Canada
| | - Eyesha Hashim
- Department of Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada
| | - Nadejda Zaharieva
- Department of Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada ; MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada
| | - Luciano Minuzzi
- MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada ; Department of Psychiatry and Behavioural Neurosciences, McMaster University Hamilton, ON, Canada
| | - Benicio N Frey
- MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada ; Department of Psychiatry and Behavioural Neurosciences, McMaster University Hamilton, ON, Canada
| | - Nicholas A Bock
- Department of Psychology, Neuroscience and Behaviour, McMaster University Hamilton, ON, Canada ; MiNDS Neuroscience Graduate Program, McMaster University Hamilton, ON, Canada
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29
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Varga-Szemes A, Muscogiuri G, Schoepf UJ, De Cecco CN, Wichmann JL, Mangold S, Caruso D, Fuller SR, Spottiswoode BS, van der Geest RJ, Suranyi P. Overview of Myocardial T1 Mapping Applications. CURRENT RADIOLOGY REPORTS 2015. [DOI: 10.1007/s40134-015-0114-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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30
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Laosiripisan J, Tarumi T, Gonzales MM, Haley AP, Tanaka H. Association between cardiovagal baroreflex sensitivity and baseline cerebral perfusion of the hippocampus. Clin Auton Res 2015; 25:213-8. [PMID: 26280218 DOI: 10.1007/s10286-015-0296-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 04/23/2015] [Indexed: 11/28/2022]
Abstract
PURPOSE A failure to control perfusion pressure due to impaired baroreflex sensitivity (BRS) could potentially cause chronic brain hypoperfusion, leading to cognitive dysfunction. The primary aim of this study was to determine whether BRS was associated with regional cerebral blood flow as measured by MRI arterial spin labeling (ASL) technique. METHODS Baroreflex sensitivity was measured using the Valsalva maneuver technique in 52 middle-aged normotensive adults (49 ± 1 years), and phase IV of the Valsalva maneuver was used for analyses. Cerebral perfusion was measured using the ASL MRI technique in 10 pre-determined brain regions of interest. RESULTS Hippocampal perfusion was correlated with BRS (R (2) = 0.17, P = 0.01). No association was observed between BRS and cerebral perfusion in the other brain regions of interest. Partial correlational analyses revealed that BRS was an important predictor of hippocampal perfusion, explaining 11 % of the variability independent of other covariates. When participants were divided into tertiles of BRS (11.8 ± 1.9 and 3.5 ± 0.1 ms/mmHg for the highest and lowest tertiles), regional cerebral perfusion of the hippocampus was significantly lower in the lowest BRS tertile than in the highest tertile (39.1 ± 4.3 and 60.5 ± 8.4 ml/100 g/min). CONCLUSIONS Baroreflex sensitivity in midlife is positively associated with regional cerebral perfusion of the hippocampus, and impaired BRS appears to be related to brain hypoperfusion even in apparently healthy middle-aged adults. Future longitudinal studies based on the present cross-sectional findings may help to further define the relationship between BRS to cognitive dysfunction.
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Affiliation(s)
- Jitanan Laosiripisan
- Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, 78712, USA
| | - Takashi Tarumi
- Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, 78712, USA
| | - Mitzi M Gonzales
- Department of Psychology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Andreana P Haley
- Department of Psychology, University of Texas at Austin, Austin, TX, 78712, USA
| | - Hirofumi Tanaka
- Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, 78712, USA.
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31
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Abstract
Impairment on inhibitory tasks has been well documented in bipolar disorder (BD). Differences in cerebral blood flow (CBF) between BD patients and healthy comparison (HC) participants have also been reported. Few studies have examined the relationship between cognitive performance and regional CBF in this patient population. We hypothesized that group differences on an inhibitory task (the Delis-Kaplan Executive Function Scale's Color-Word Inhibition task) would be associated with differential CBF in bilateral anterior cingulate cortex (ACC), inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) regions. Whole brain resting CBF was measured using Multiphase Pseudocontinuous Arterial Spin Labeling MR imaging for 28 euthymic BD and 36 HC participants. Total gray matter (GM) CBF was measured, and regional CBF values were extracted for each region of interest (ROI) using Freesurfer-based individual parcellations. Group, CBF, and group-by-CBF interaction were examined as predictors of inhibition performance. Groups did not differ in age, gender or education. BD patients performed significantly worse on Color-Word inhibition. There were no significant group differences in CBF in either total GM or in any ROI. There was a group by CBF interaction in the bilateral ACC, right IPL and right DLPFC such that better inhibitory performance was generally associated with higher resting state CBF in BD subjects, but not HC participants. Although CBF was not abnormal in this euthymic BD sample, results confirm previous reports of inter-episode inhibitory deficits and indicate that the perfusion-cognition relationship is different in BD compared to HC individuals.
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32
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Clark LR, Nation DA, Wierenga CE, Bangen KJ, Dev SI, Shin DD, Delano-Wood L, Liu TT, Rissman RA, Bondi MW. Elevated cerebrovascular resistance index is associated with cognitive dysfunction in the very-old. ALZHEIMERS RESEARCH & THERAPY 2015; 7:3. [PMID: 27391477 PMCID: PMC4942967 DOI: 10.1186/s13195-014-0080-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 10/29/2014] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Age-related vascular changes, including blood pressure elevation and cerebral blood flow (CBF) reduction, are associated with cognitive decline and Alzheimer's disease (AD). Evidence suggests that the relationship between blood pressure and dementia risk varies between younger and older samples within the elderly population. METHODS We examined the relationship between mean arterial pressure (MAP), CBF, and cognition in young-old (60 to 75 years of age) versus very-old (80+ years of age) adults. Fifty-eight non-demented older adults completed an arterial spin labeling MRI scan, and an index of cerebrovascular resistance (CVRi) was estimated for each participant by calculating the ratio of MAP and CBF. RESULTS Results demonstrated a similar negative relationship between MAP and CBF across both age groups. However, very-old participants exhibited elevated CVRi and reduced CBF compared to young-old participants in regions implicated in AD and cerebral small vessel disease. Furthermore, significant age by CVRi interactions revealed that elevated CVRi in the thalamus was inversely related to verbal fluency performance in the very-old group. CONCLUSIONS Findings support CVRi as a potential vascular biomarker and suggest that regionally-specific vascular changes may contribute to cognitive decline, particularly in the very-old.
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Affiliation(s)
- Lindsay R Clark
- San Diego State University/University of California, San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA. .,Wisconsin Alzheimer's Institute, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.
| | - Daniel A Nation
- Department of Psychology, University of Southern California, Los Angeles, CA, USA
| | - Christina E Wierenga
- Department of Psychiatry, University of California San Diego, San Diego, CA, USA.,Department of Veterans Affairs, San Diego Healthcare System, San Diego, CA, USA
| | - Katherine J Bangen
- Department of Psychiatry, University of California San Diego, San Diego, CA, USA
| | - Sheena I Dev
- San Diego State University/University of California, San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA, USA
| | - David D Shin
- Center for Functional MRI, University of California San Diego, San Diego, CA, USA
| | - Lisa Delano-Wood
- Department of Psychiatry, University of California San Diego, San Diego, CA, USA.,Department of Veterans Affairs, San Diego Healthcare System, San Diego, CA, USA
| | - Thomas T Liu
- Center for Functional MRI, University of California San Diego, San Diego, CA, USA
| | - Robert A Rissman
- Department of Neurosciences, University of California San Diego, San Diego, CA, USA
| | - Mark W Bondi
- Department of Psychiatry, University of California San Diego, San Diego, CA, USA. .,Department of Veterans Affairs, San Diego Healthcare System, San Diego, CA, USA.
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Alsop DC, Detre JA, Golay X, Günther M, Hendrikse J, Hernandez-Garcia L, Lu H, MacIntosh BJ, Parkes LM, Smits M, van Osch MJP, Wang DJJ, Wong EC, Zaharchuk G. Recommended implementation of arterial spin-labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study group and the European consortium for ASL in dementia. Magn Reson Med 2015; 73:102-16. [PMID: 24715426 PMCID: PMC4190138 DOI: 10.1002/mrm.25197] [Citation(s) in RCA: 1477] [Impact Index Per Article: 164.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 02/08/2014] [Accepted: 02/10/2014] [Indexed: 12/11/2022]
Abstract
This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications. It is a consensus of the ISMRM Perfusion Study Group and the European ASL in Dementia consortium, both of whom met to reach this consensus in October 2012 in Amsterdam. Although ASL continues to undergo rapid technical development, we believe that current ASL methods are robust and ready to provide useful clinical information, and that a consensus statement on recommended implementations will help the clinical community to adopt a standardized approach. In this review, we describe the major considerations and trade-offs in implementing an ASL protocol and provide specific recommendations for a standard approach. Our conclusion is that as an optimal default implementation, we recommend pseudo-continuous labeling, background suppression, a segmented three-dimensional readout without vascular crushing gradients, and calculation and presentation of both label/control difference images and cerebral blood flow in absolute units using a simplified model.
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Affiliation(s)
- David C. Alsop
- Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - John A. Detre
- Departments of Neurology and Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Xavier Golay
- Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, UK
| | - Matthias Günther
- Fraunhofer MEVIS, Bremen, Germany
- University Bremen, Germany
- Mediri GmbH, Heidelberg, Germany
| | - Jeroen Hendrikse
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Luis Hernandez-Garcia
- FMRI Laboratory, Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Hanzhang Lu
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Bradley J. MacIntosh
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Laura M. Parkes
- Centre for Imaging Science, Institute of Population Health, Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK
| | - Marion Smits
- Department of Radiology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Matthias J. P. van Osch
- C.J. Gorter Center for high field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Danny JJ Wang
- Department of Neurology, University of California Los Angeles, Los Angeles, California, USA
| | - Eric C. Wong
- Departments of Radiology and Psychiatry, University of California San Diego, La Jolla, California, USA
| | - Greg Zaharchuk
- Department of Radiology, Stanford University, Stanford, California, USA
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The coupling of cerebral blood flow and oxygen metabolism with brain activation is similar for simple and complex stimuli in human primary visual cortex. Neuroimage 2014; 104:156-62. [PMID: 25312771 DOI: 10.1016/j.neuroimage.2014.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 08/18/2014] [Accepted: 10/01/2014] [Indexed: 11/22/2022] Open
Abstract
Quantitative functional MRI (fMRI) experiments to measure blood flow and oxygen metabolism coupling in the brain typically rely on simple repetitive stimuli. Here we compared such stimuli with a more naturalistic stimulus. Previous work on the primary visual cortex showed that direct attentional modulation evokes a blood flow (CBF) response with a relatively large oxygen metabolism (CMRO2) response in comparison to an unattended stimulus, which evokes a much smaller metabolic response relative to the flow response. We hypothesized that a similar effect would be associated with a more engaging stimulus, and tested this by measuring the primary human visual cortex response to two contrast levels of a radial flickering checkerboard in comparison to the response to free viewing of brief movie clips. We did not find a significant difference in the blood flow-metabolism coupling (n=%ΔCBF/%ΔCMRO2) between the movie stimulus and the flickering checkerboards employing two different analysis methods: a standard analysis using the Davis model and a new analysis using a heuristic model dependent only on measured quantities. This finding suggests that in the primary visual cortex a naturalistic stimulus (in comparison to a simple repetitive stimulus) is either not sufficient to provoke a change in flow-metabolism coupling by attentional modulation as hypothesized, that the experimental design disrupted the cognitive processes underlying the response to a more natural stimulus, or that the technique used is not sensitive enough to detect a small difference.
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Nehrke K, Sprinkart AM, Börnert P. An in vivo comparison of the DREAM sequence with current RF shim technology. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2014; 28:185-94. [DOI: 10.1007/s10334-014-0454-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/19/2014] [Accepted: 06/25/2014] [Indexed: 11/29/2022]
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Bangen KJ, Nation DA, Clark LR, Harmell AL, Wierenga CE, Dev SI, Delano-Wood L, Zlatar ZZ, Salmon DP, Liu TT, Bondi MW. Interactive effects of vascular risk burden and advanced age on cerebral blood flow. Front Aging Neurosci 2014; 6:159. [PMID: 25071567 PMCID: PMC4083452 DOI: 10.3389/fnagi.2014.00159] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 06/19/2014] [Indexed: 01/24/2023] Open
Abstract
Vascular risk factors and cerebral blood flow (CBF) reduction have been linked to increased risk of cognitive impairment and Alzheimer's disease (AD); however the possible moderating effects of age and vascular risk burden on CBF in late life remain understudied. We examined the relationships among elevated vascular risk burden, age, CBF, and cognition. Seventy-one non-demented older adults completed an arterial spin labeling MR scan, neuropsychological assessment, and medical history interview. Relationships among vascular risk burden, age, and CBF were examined in a priori regions of interest (ROIs) previously implicated in aging and AD. Interaction effects indicated that, among older adults with elevated vascular risk burden (i.e., multiple vascular risk factors), advancing age was significantly associated with reduced cortical CBF whereas there was no such relationship for those with low vascular risk burden (i.e., no or one vascular risk factor). This pattern was observed in cortical ROIs including medial temporal (hippocampus, parahippocampal gyrus, uncus), inferior parietal (supramarginal gyrus, inferior parietal lobule, angular gyrus), and frontal (anterior cingulate, middle frontal gyrus, medial frontal gyrus) cortices. Furthermore, among those with elevated vascular risk, reduced CBF was associated with poorer cognitive performance. Such findings suggest that older adults with elevated vascular risk burden may be particularly vulnerable to cognitive change as a function of CBF reductions. Findings support the use of CBF as a potential biomarker in preclinical AD and suggest that vascular risk burden and regionally-specific CBF changes may contribute to differential age-related cognitive declines.
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Affiliation(s)
- Katherine J Bangen
- Psychology Service, VA San Diego Healthcare System San Diego, CA, USA ; Department of Psychiatry, University of California, San Diego La Jolla, CA, USA
| | - Daniel A Nation
- Department of Psychology, University of Southern California Los Angeles, CA, USA
| | - Lindsay R Clark
- San Diego Joint Doctoral Program in Clinical Psychology, San Diego State University/University of California San Diego, CA, USA
| | - Alexandrea L Harmell
- San Diego Joint Doctoral Program in Clinical Psychology, San Diego State University/University of California San Diego, CA, USA
| | - Christina E Wierenga
- Department of Psychiatry, University of California, San Diego La Jolla, CA, USA ; Research Service, VA San Diego Healthcare System San Diego, CA, USA
| | - Sheena I Dev
- San Diego Joint Doctoral Program in Clinical Psychology, San Diego State University/University of California San Diego, CA, USA
| | - Lisa Delano-Wood
- Department of Psychiatry, University of California, San Diego La Jolla, CA, USA ; Research Service, VA San Diego Healthcare System San Diego, CA, USA
| | - Zvinka Z Zlatar
- Department of Psychiatry, University of California, San Diego La Jolla, CA, USA
| | - David P Salmon
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - Thomas T Liu
- Department of Radiology, University of California San Diego, La Jolla, CA, USA
| | - Mark W Bondi
- Psychology Service, VA San Diego Healthcare System San Diego, CA, USA ; Department of Psychiatry, University of California, San Diego La Jolla, CA, USA
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Fast water concentration mapping to normalize (1)H MR spectroscopic imaging. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2014; 28:87-100. [PMID: 24908199 DOI: 10.1007/s10334-014-0451-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/12/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
Abstract
OBJECT To propose a fast and robust acquisition and post-processing pipeline that is time-compatible with clinical explorations to obtain a proton density (ρ) map used as a reference for metabolic map normalization. This allows inter-subject and inter-group comparisons of magnetic resonance spectroscopic imaging (MRSI) data and longitudinal follow-up for single subjects. MATERIALS AND METHODS A multi-echo T 2 (*) mapping sequence, the XEP sequence for B 1 (+) -mapping and Driven Equilibrium Single Pulse Observation of T 1-an optimized variable flip angle method for T 1 mapping used for both B 1 (-) -mapping and M 0 calculation-were used to determine correction factors leading to quantitative water proton density maps at 3T. Normalized metabolite maps were obtained on a phantom and nine healthy volunteers. To show the potential use of this technique at the individual level, we also explored one patient with low-grade glioma. RESULTS Accurate ρ maps were obtained both on phantom and volunteers. After signal normalization with the generated ρ maps, metabolic concentrations determined by the present method differed from theory by <7 % in the phantom and were in agreement with data from the literature for the healthy controls. Using these normalized metabolic values, it was possible to demonstrate in the patient with brain glioma, metabolic abnormalities in normalized N-acetyl aspartate, choline and creatine levels; illustrating the potential for direct use of this technique in clinical studies. CONCLUSION The proposed combination of sequences provides a robust ρ map that can be used to normalize metabolic maps in clinical MRSI studies.
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Using high-resolution quantitative mapping of R1 as an index of cortical myelination. Neuroimage 2014; 93 Pt 2:176-88. [DOI: 10.1016/j.neuroimage.2013.06.005] [Citation(s) in RCA: 253] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 06/03/2013] [Accepted: 06/04/2013] [Indexed: 01/19/2023] Open
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Tsujita N, Kai N, Fujita Y, Hiai Y, Hirai T, Kitajima M, Yamashita Y, Murakami R. Interimager variability in ADC measurement of the human brain. Magn Reson Med Sci 2014; 13:81-7. [PMID: 24769632 DOI: 10.2463/mrms.2012-0098] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Routine clinical practice involves the application of diverse scanning parameters that can affect apparent diffusion coefficient (ADC) values. We evaluated interimager variability in ADC values with respect to their potential effect in clinical applications. METHODS In 7 healthy volunteers, we obtained diffusion-weighted (DW) images using routine clinical parameters and 1.5- (n = 9) and 3-tesla (n = 3) magnetic resonance (MR) imagers from 5 different vendors, performing 84 MR imaging studies. To evaluate the differences in ADC values among the imagers, vendors, and magnetic field strengths, we measured the mean pixel values of the frontal white matter and thalamus (gray matter) in both cerebral hemispheres of the 7 volunteers and used repeated-measures analysis of variance for multiple comparisons. RESULTS The laterality of ADC values in the bilateral structures ranged from one to 3% for the 12 imagers. Although the relative difference in ADC values of white matter was 7% for scanners yielding the highest and lowest mean ADC values (P < 0.01), it was within 2 to 4% for instruments from the same vendors. For gray matter, the interimager difference was 4 to 12%, even among the same vendors (P < 0.05). Among the 3T imagers, the difference for white and gray matter was approximately 3%. CONCLUSIONS There were significant interimager differences in ADC values, especially with respect to gray matter. Taking into consideration the existing laterality, however, the differences among our 3T imagers may be acceptable despite the use of diverse scanning parameters. In routine clinical practice, the existing variability must be considered imager by imager.
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Affiliation(s)
- Naoko Tsujita
- Department of Medical Physics, Faculty of Life Sciences, Kumamoto University
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In vivo performance of a microfabricated catheter for intraparenchymal delivery. J Neurosci Methods 2014; 229:76-83. [PMID: 24747536 DOI: 10.1016/j.jneumeth.2014.03.016] [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: 02/03/2014] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 11/22/2022]
Abstract
BACKGROUND Convection-enhanced delivery (CED) is currently the only effective clinical technique to deliver biological therapeutic agents that would otherwise not cross the blood-brain barrier. Despite the promise of CED, several technical problems have limited its effectiveness. NEW METHOD Brain infusions into a large mammal (pig) were performed with a catheter that was fabricated using micro-electro-mechanical systems (MEMS) technology (Olbricht et al., 2010). The performance of the catheter was evaluated for infusions at increasing infusion rates. Magnetic resonance (MR) images were acquired in real time to examine the distribution of infused tracers in the parenchyma. RESULTS Both backflow and the distribution of CED of infusates into a variety of cytoarchitectures in porcine brain were quantified. Concentration profiles were determined for several MR contrast reagents as well as a fluorescent dye that are the sizes of small molecules, therapeutic proteins and an adeno-associated virus (AAV). The reagents can serve as surrogates for assessing the convective distribution of active molecules. Infusion rates up to 20μL/min were attained without evidence of backflow along the catheter. COMPARISON WITH EXISTING METHODS The device performed well in terms of both backflow and infusion, superior to that of many studies reported in the literature on other catheters. All infused molecules had comparable ratios of distribution to infusion volumes. CONCLUSIONS The catheter described in this report appears able to target tissue structures with precision, deliver therapeutics at high infusion rates, and resist backflow that can compromise the efficacy of CED therapy. The technology allows development of "smart" catheters for future applications.
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Lee Y, Han Y, Park H, Watanabe H, Garwood M, Park JY. New phase-based B1 mapping method using two-dimensional spin-echo imaging with hyperbolic secant pulses. Magn Reson Med 2014; 73:170-81. [PMID: 24459088 DOI: 10.1002/mrm.25110] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 12/07/2013] [Accepted: 12/11/2013] [Indexed: 11/09/2022]
Abstract
PURPOSE To propose a new phase-based B1-mapping method that exploits phase information created by hyperbolic secant (HS) pulses in conventional 2D spin-echo imaging. METHODS In this B1-mapping method, HS pulses are used to accomplish π/2 excitation and π refocusing in standard multislice spin-echo imaging. When setting the ratio of pulse lengths of the π/2 and π HS pulses to 2:1, the spin-echo phase is independent of offset frequency and varies as a function of B1 strength. To eliminate undesired phase accumulations induced by unknown factors other than the B1 strength, two spin-echo images are acquired using HS pulses applied with opposite frequency-sweep directions, and the resulting phase images are subtracted from each other. To demonstrate the performance of the proposed method, phantom and in vivo experiments were performed using a surface coil and a volume coil. RESULTS The B1 maps obtained by using the proposed method were in accordance with the B1 maps obtained using previous methods in both phantom and in vivo experiments. CONCLUSION The proposed method is easy to implement without any sequence modification, is insensitive to B0 inhomogeneity and chemical shift, and is robust in a reasonably wide range of B1 field strength.
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Affiliation(s)
- Yoojin Lee
- Department of Electrical Engineering, Korean Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - Yeji Han
- Department of Electrical Engineering, Korean Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - HyunWook Park
- Department of Electrical Engineering, Korean Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - Hidehiro Watanabe
- Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Japan
| | - Michael Garwood
- The Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Jang-Yeon Park
- School of Biomedical Engineering, College of Biomedical and Health Science, Research Institute of Biomedical Engineering, Konkuk University, Chungju, Korea (ROK)
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Central artery stiffness, neuropsychological function, and cerebral perfusion in sedentary and endurance-trained middle-aged adults. J Hypertens 2013; 31:2400-9. [DOI: 10.1097/hjh.0b013e328364decc] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Altered cerebral perfusion in executive, affective, and motor networks during adolescent depression. J Am Acad Child Adolesc Psychiatry 2013; 52:1076-1091.e2. [PMID: 24074474 PMCID: PMC3825460 DOI: 10.1016/j.jaac.2013.07.008] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 05/11/2013] [Accepted: 07/19/2013] [Indexed: 01/17/2023]
Abstract
OBJECTIVE Although substantial literature has reported regional cerebral blood flow (rCBF) abnormalities in adults with depression, these studies commonly necessitated the injection of radioisotopes into subjects. The recent development of arterial spin labeling (ASL), however, allows noninvasive measurements of rCBF. Currently, no published ASL studies have examined cerebral perfusion in adolescents with depression. Thus, the aim of the present study was to examine baseline cerebral perfusion in adolescent depression using a newly developed ASL technique: pseudocontinuous arterial spin labeling (PCASL). METHOD A total of 25 medication-naive adolescents (13-17 years of age) diagnosed with major depressive disorder (MDD) and 26 well-matched control subjects underwent functional magnetic resonance imaging. Baseline rCBF was measured via a novel PCASL method that optimizes tagging efficiency. RESULTS Voxel-based whole brain analyses revealed significant frontal, limbic, paralimbic, and cingulate hypoperfusion in the group with depression (p < .05, corrected). Hyperperfusion was also observed within the subcallosal cingulate, putamen, and fusiform gyrus (p < .05, corrected). Similarly, region-of-interest analyses revealed amygdalar and insular hypoperfusion in the group with depression, as well as hyperperfusion in the putamen and superior insula (p < .05, corrected). CONCLUSIONS Adolescents with depression and healthy adolescents appear to differ on rCBF in executive, affective, and motor networks. Dysfunction in these regions may contribute to the cognitive, emotional, and psychomotor symptoms commonly present in adolescent depression. These findings point to possible biomarkers for adolescent depression that could inform early interventions and treatments, and establishes a methodology for using PCASL to noninvasively measure rCBF in clinical and healthy adolescent populations.
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Sabati M, Maudsley AA. Fast and high-resolution quantitative mapping of tissue water content with full brain coverage for clinically-driven studies. Magn Reson Imaging 2013; 31:1752-9. [PMID: 24050900 DOI: 10.1016/j.mri.2013.08.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/15/2013] [Accepted: 08/02/2013] [Indexed: 01/31/2023]
Abstract
An efficient method for obtaining longitudinal relaxation time (T1) maps is based on acquiring two spoiled gradient recalled echo (SPGR) images in steady states with different flip angles, which has also been extended, with additional acquisitions, to obtain a tissue water content (M0) map. Several factors, including inhomogeneities of the radio-frequency (RF) fields and low signal-to-noise ratios may negatively affect the accuracy of this method and produce systematic errors in T1 and M0 estimations. Thus far, these limitations have been addressed by using additional measurements and applying suitable corrections; however, the concomitant increase in scan time is undesirable for clinical studies. In this note, a modified dual-acquisition SPGR method based on an optimization of the sequence formulism is presented for good and reliable M0 mapping with an isotropic spatial resolution of 1×1×1mm(3) that covers the entire human brain in 6:30min. A combined RF transmit/receive map is estimated from one of the SPGR scans and the optimal flip angles for M0 map are found analytically. The method was successfully evaluated in eight healthy subjects producing mean M0 values of 69.8% (in white matter) and 80.1% (in gray matter) that are in good agreement with those found in the literature and with high reproducibility. The mean value of the resultant voxel-based coefficients-of-variation was 3.6%.
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Affiliation(s)
- Mohammad Sabati
- Department of Radiology, Miller School of Medicine, University of Miami, Miami, FL 33136.
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Nehrke K, Versluis MJ, Webb A, Börnert P. VolumetricB1+Mapping of the Brain at 7T using DREAM. Magn Reson Med 2013; 71:246-56. [DOI: 10.1002/mrm.24667] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/14/2012] [Accepted: 01/09/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Kay Nehrke
- Research Department Tomographic Imaging Systems, Philips Research Europe; Hamburg Germany
| | - Maarten J. Versluis
- Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
| | - Andrew Webb
- Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
| | - Peter Börnert
- Research Department Tomographic Imaging Systems, Philips Research Europe; Hamburg Germany
- Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
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Optimizing T1-weighted imaging of cortical myelin content at 3.0T. Neuroimage 2013; 65:1-12. [DOI: 10.1016/j.neuroimage.2012.09.051] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 09/16/2012] [Accepted: 09/18/2012] [Indexed: 11/30/2022] Open
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Smith ZM, Krizay E, Guo J, Shin DD, Scadeng M, Dubowitz DJ. Sustained high-altitude hypoxia increases cerebral oxygen metabolism. J Appl Physiol (1985) 2012; 114:11-8. [PMID: 23019310 DOI: 10.1152/japplphysiol.00703.2012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Acute mountain sickness (AMS) is a common condition occurring within hours of rapid exposure to high altitude. Despite its frequent occurrence, the pathophysiological mechanisms that underlie the condition remain poorly understood. We investigated the role of cerebral oxygen metabolism (CMR(O(2))) in AMS. The purpose of this study was to test 1) if CMR(O(2)) changes in response to hypoxia, and 2) if there is a difference in how individuals adapt to oxygen metabolic changes that may determine who develops AMS and who does not. Twenty-six normal human subjects were recruited into two groups based on Lake Louise AMS score (LLS): those with no AMS (LLS ≤ 2), and those with unambiguous AMS (LLS ≥ 5). [Subjects with intermediate scores (LLS 3-4) were not included.] CMR(O(2)) was calculated from cerebral blood flow and arterial-venous difference in O(2) content. Cerebral blood flow was measured using arterial spin labeling MRI; venous O(2) saturation was calculated from the MRI of transverse relaxation in the superior sagittal sinus. Arterial O(2) saturation was measured via pulse oximeter. Measurements were made during normoxia and after 2-day high-altitude exposure at 3,800 m. In all subjects, CMR(O(2)) increased with sustained high-altitude hypoxia [1.54 (0.37) to 1.82 (0.49) μmol·g(-1)·min(-1), n = 26, P = 0.045]. There was no significant difference in CMR(O(2)) between AMS and no-AMS groups. End-tidal Pco(2) was significantly reduced during hypoxia. Low arterial Pco(2) is known to increase neural excitability, and we hypothesize that the low arterial Pco(2) resulting from ventilatory acclimatization causes the observed increase in CMR(O(2)).
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Affiliation(s)
- Zachary M Smith
- Center for Functional MRI, Department of Radiology, University of California San Diego, San Diego, California, USA
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Liang CL, Ances BM, Perthen JE, Moradi F, Liau J, Buracas GT, Hopkins SR, Buxton RB. Luminance contrast of a visual stimulus modulates the BOLD response more than the cerebral blood flow response in the human brain. Neuroimage 2012; 64:104-11. [PMID: 22963855 DOI: 10.1016/j.neuroimage.2012.08.077] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 07/23/2012] [Accepted: 08/28/2012] [Indexed: 11/15/2022] Open
Abstract
The blood oxygenation level dependent (BOLD) response measured with functional magnetic resonance imaging (fMRI) depends on the evoked changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)) in response to changes in neural activity. This response is strongly modulated by the CBF/CMRO(2) coupling relationship with activation, defined as n, the ratio of the fractional changes. The reliability of the BOLD signal as a quantitative reflection of underlying physiological changes depends on the stability of n in response to different stimuli. The effect of visual stimulus contrast on this coupling ratio was tested in 9 healthy human subjects, measuring CBF and BOLD responses to a flickering checkerboard at four visual contrast levels. The theory of the BOLD effect makes a robust prediction-independent of details of the model-that if the CBF/CMRO(2) coupling ratio n remains constant, then the response ratio between the lowest and highest contrast levels should be higher for the BOLD response than the CBF response because of the ceiling effect on the BOLD response. Instead, this response ratio was significantly lower for the BOLD response (BOLD response: 0.23 ± 0.13, mean ± SD; CBF response: 0.42 ± 0.18; p=0.0054). This data is consistent with a reduced dynamic range (strongest/weakest response ratio) of the CMRO(2) response (~1.7-fold) compared to that of the CBF response (~2.4-fold) as luminance contrast increases, corresponding to an increase of n from 1.7 at the lowest contrast level to 2.3 at the highest contrast level. The implication of these results for fMRI studies is that the magnitude of the BOLD response does not accurately reflect the magnitude of underlying physiological processes.
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Affiliation(s)
- Christine L Liang
- Department of Radiology, University of California, San Diego, CA 92093‐0677, USA
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Altered cerebral blood flow and neurocognitive correlates in adolescent cannabis users. Psychopharmacology (Berl) 2012; 222:675-84. [PMID: 22395430 PMCID: PMC3510003 DOI: 10.1007/s00213-012-2674-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 02/13/2012] [Indexed: 10/28/2022]
Abstract
RATIONALE The effects of adolescent marijuana use on the developing brain remain unclear, despite its prevalence. Arterial spin labeling (ASL) is a noninvasive imaging technique that characterizes neurovascular status and cerebral blood flow (CBF), potentially revealing contributors to neuropathological alterations. No studies to date have looked at CBF in adolescent marijuana users. OBJECTIVES This study examined CBF in adolescent marijuana users and matched healthy controls at baseline and after 4 weeks of monitored abstinence. METHODS Heavy adolescent marijuana users (n = 23, >200 lifetime marijuana use days) and demographically matched controls (n = 23) with limited substance exposure underwent an ASL brain scan at an initial session and after 4 weeks of sequential urine toxicology to confirm abstinence. RESULTS Marijuana users showed reduced CBF in four cortical regions including the left superior and middle temporal gyri, left insula, left and right medial frontal gyrus, and left supramarginal gyrus at baseline; users showed increased CBF in the right precuneus at baseline, as compared to controls (corrected p values < 0.05). No between group differences were found at follow-up. CONCLUSIONS Marijuana use may influence CBF in otherwise healthy adolescents acutely; however, group differences were not observed after several weeks of abstinence. Neurovascular alterations may contribute to or underlie changes in brain activation, neuropsychological performance, and mood observed in young cannabis users with less than a month of abstinence.
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Wong CW, Olafsson V, Tal O, Liu TT. Anti-correlated networks, global signal regression, and the effects of caffeine in resting-state functional MRI. Neuroimage 2012; 63:356-64. [PMID: 22743194 DOI: 10.1016/j.neuroimage.2012.06.035] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 06/15/2012] [Accepted: 06/18/2012] [Indexed: 10/28/2022] Open
Abstract
Resting-state functional connectivity magnetic resonance imaging is proving to be an essential tool for the characterization of functional networks in the brain. Two of the major networks that have been identified are the default mode network (DMN) and the task positive network (TPN). Although prior work indicates that these two networks are anti-correlated, the findings are controversial because the anti-correlations are often found only after the application of a pre-processing step, known as global signal regression, that can produce artifactual anti-correlations. In this paper, we show that, for subjects studied in an eyes-closed rest state, caffeine can significantly enhance the detection of anti-correlations between the DMN and TPN without the need for global signal regression. In line with these findings, we find that caffeine also leads to widespread decreases in connectivity and global signal amplitude. Using a recently introduced geometric model of global signal effects, we demonstrate that these decreases are consistent with the removal of an additive global signal confound. In contrast to the effects observed in the eyes-closed rest state, caffeine did not lead to significant changes in global functional connectivity in the eyes-open rest state.
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Affiliation(s)
- Chi Wah Wong
- Center for Functional Magnetic Resonance Imaging, University of California San Diego, 9500 Gilman Drive, MC 0677, La Jolla, CA 92093-0677, USA.
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