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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: 16] [Impact Index Per Article: 8.0] [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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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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Wang F, Akashi K, Murakami Y, Inoue Y, Furuta T, Yamada H, Ohtomo K, Kiryu S. Detection of lung tumors in mice using a 1-tesla compact magnetic resonance imaging system. PLoS One 2014; 9:e94945. [PMID: 24743153 PMCID: PMC3990561 DOI: 10.1371/journal.pone.0094945] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 03/20/2014] [Indexed: 11/18/2022] Open
Abstract
Due to their small size, lung tumors in rodents are typically investigated using high-field magnetic resonance (MR) systems (4.7 T or higher) to achieve higher signal-to-noise ratios, although low-field MR systems are less sensitive to susceptibility artifacts caused by air in the lung. We investigated the feasibility of detecting lung tumors in living, freely breathing mice with a 1-T compact permanent magnet MR system. In total, 4 mice were used, and MR images of mouse lungs were acquired using a T1-weighted three-dimensional fast low-angle shot sequence without cardiac or respiratory gating. The delineation and size of lung tumors were assessed and compared with histopathological findings. Submillimeter lesions were demonstrated as hyperintense, relative to the surrounding lung parenchyma, and were delineated clearly. Among the 13 lesions validated in histopathological sections, 11 were detected in MR images; the MR detection rate was thus 84.6%. A strong correlation was obtained in size measurements between MR images and histological sections. Thus, a dedicated low-field MR system can be used to detect lung tumors in living mice noninvasively without gating.
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Affiliation(s)
- Fang Wang
- Department of Radiology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
- Department of Radiology, Qi Lu Hospital of Shandong University, Jinan, China
| | - Ken Akashi
- Division of Molecular Pathology, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, Japan
| | - Yoshinori Murakami
- Division of Molecular Pathology, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, Japan
| | - Yusuke Inoue
- Department of Diagnostic Radiology, Kitasato University School of Medicine, Minami-ku, Sagamihara, Kanagawa, Japan
| | - Toshihiro Furuta
- Department of Radiology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Haruyasu Yamada
- Department of Radiology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Kuni Ohtomo
- Department of Radiology, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shigeru Kiryu
- Department of Radiology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
- * E-mail:
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Umutlu L, Forsting M, Ladd ME. Ultrahigh-field magnetic resonance imaging: the clinical potential for anatomy, pathogenesis, diagnosis and treatment planning in neck and spine disease. Neuroimaging Clin N Am 2012; 22:363-71, xii. [PMID: 22548937 DOI: 10.1016/j.nic.2012.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An increase of the magnetic field strength to ultrahigh-field yields advantageous as well as disadvantageous changes in physical effects. The beneficial increase in signal/noise ratio can be leveraged into higher spatiotemporal resolution, and an exacerbation of artifacts can impede ultrahigh-field imaging. With the successful introduction of intracranial and musculoskeletal imaging at 7 T, recent advances in coil design have created opportunities for further applications of ultrahigh-field magnetic resonance (MR) imaging in other parts of the body. Initial studies in 7 T neck and spine MR imaging have revealed promising insights and new challenges, demanding further research and methodological optimization.
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Affiliation(s)
- Lale Umutlu
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Hufelandstr. 55, D-45122 Essen, Germany.
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Bouhrara M, Bonny JM. B₁ mapping with selective pulses. Magn Reson Med 2012; 68:1472-80. [PMID: 22246956 DOI: 10.1002/mrm.24146] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 12/09/2011] [Accepted: 12/13/2011] [Indexed: 11/05/2022]
Abstract
Knowledge of B₁⁺ distribution is crucial for many applications, such as quantitative MRI. A novel method has been developed to improve the accuracy of the conventionally applied double-angle method for B₁⁺ mapping. It solves the remaining issues raised by the use of selective pulses for slice selection to accelerate the acquisition process. A general approach for reconstructing B₁⁺ maps is presented first. It takes B₁⁺-induced slice profile distortions over off-resonance frequencies into account. It is then shown how the ratio between the prescribed flip angles can be adjusted to reach a compromise between the level of noise propagated onto B₁⁺ maps and the width of the range in which the field can be mapped. Lastly, several solutions are proposed for reducing the B₁⁺-dependent pollution of regions distal to the image slice which participates significantly in the inaccuracy of B₁⁺ mapping. These methods were experimentally tested by comparison with gold standard B₁⁺ maps obtained on a phantom using a non-selective and thus much slower technique. As they are independent and lead to significant improvements, these solutions can be combined to achieve high precision and fast B₁⁺ mapping using spin-echo DAM.
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Lutti A, Hutton C, Finsterbusch J, Helms G, Weiskopf N. Optimization and validation of methods for mapping of the radiofrequency transmit field at 3T. Magn Reson Med 2010; 64:229-38. [PMID: 20572153 PMCID: PMC3077518 DOI: 10.1002/mrm.22421] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
MRI techniques such as quantitative imaging and parallel transmit require precise knowledge of the radio-frequency transmit field (B(1) (+)). Three published methods were optimized for robust B(1) (+) mapping at 3T in the human brain: three-dimensional (3D) actual flip angle imaging (AFI), 3D echo-planar imaging (EPI), and two-dimensional (2D) stimulated echo acquisition mode (STEAM). We performed a comprehensive comparison of the methods, focusing on artifacts, reproducibility, and accuracy compared to a reference 2D double angle method. For the 3D AFI method, the addition of flow-compensated gradients for diffusion damping reduced the level of physiological artifacts and improved spoiling of transverse coherences. Correction of susceptibility-induced artifacts alleviated image distortions and improved the accuracy of the 3D EPI imaging method. For the 2D STEAM method, averaging over multiple acquisitions reduced the impact of physiological noise and a new calibration method enhanced the accuracy of the B(1) (+) maps. After optimization, all methods yielded low noise B(1) (+) maps (below 2 percentage units), of the nominal flip angle value (p.u.) with a systematic bias less than 5 p.u. units. Full brain coverage was obtained in less than 5 min. The 3D AFI method required minimal postprocessing and showed little sensitivity to off-resonance and physiological effects. The 3D EPI method showed the highest level of reproducibility. The 2D STEAM method was the most time-efficient technique.
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Affiliation(s)
- Antoine Lutti
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, UK.
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Chen PF, Steen RG, Yezzi A, Krim H. Joint brain parametric T1-map segmentation and RF inhomogeneity calibration. Int J Biomed Imaging 2009; 2009:269525. [PMID: 19710938 PMCID: PMC2730594 DOI: 10.1155/2009/269525] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 05/11/2009] [Accepted: 06/07/2009] [Indexed: 11/30/2022] Open
Abstract
We propose a constrained version of Mumford and Shah's (1989) segmentation model with an information-theoretic point of view in order to devise a systematic procedure to segment brain magnetic resonance imaging (MRI) data for parametric T(1)-Map and T(1)-weighted images, in both 2-D and 3D settings. Incorporation of a tuning weight in particular adds a probabilistic flavor to our segmentation method, and makes the 3-tissue segmentation possible. Moreover, we proposed a novel method to jointly segment the T(1)-Map and calibrate RF Inhomogeneity (JSRIC). This method assumes the average T(1) value of white matter is the same across transverse slices in the central brain region, and JSRIC is able to rectify the flip angles to generate calibrated T(1)-Maps. In order to generate an accurate T(1)-Map, the determination of optimal flip-angles and the registration of flip-angle images are examined. Our JSRIC method is validated on two human subjects in the 2D T(1)-Map modality and our segmentation method is validated by two public databases, BrainWeb and IBSR, of T(1)-weighted modality in the 3D setting.
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Affiliation(s)
- Ping-Feng Chen
- Department of Electrical and Computer Engineering, North Carolina State University, NC 27695, USA.
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Helms G, Dathe H, Dechent P. Quantitative FLASH MRI at 3T using a rational approximation of the Ernst equation. Magn Reson Med 2008; 59:667-72. [PMID: 18306368 DOI: 10.1002/mrm.21542] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Gunther Helms
- MR Forschung in der Neurologie und Psychiatrie, Universitätsmedizin, Göttingen, Germany.
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9
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Neelavalli J, Haacke EM. A simplified formula for T1 contrast optimization for short-TR steady-state incoherent (spoiled) gradient echo sequences. Magn Reson Imaging 2007; 25:1397-401. [PMID: 17509786 DOI: 10.1016/j.mri.2007.03.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Revised: 03/15/2007] [Accepted: 03/21/2007] [Indexed: 11/25/2022]
Abstract
There are certain instances in practical magnetic resonance imaging where T1 changes by a small amount relative to a neighboring pixel or between scans for a given pixel. The source of these small changes in T1 can be caused either by changes in tissue water content or by the uptake of a contrast agent. For short repetition time (TR) spoiled gradient echo imaging, we show that a robust and a simple, easy to use back-of-the-envelope expression for the flip angle that optimizes contrast under these conditions is given by radical 3theta E in radians or (180/pi) radical6TR/T1 in degrees. We show that for a TR/T1 ratio of up to 0.3 and for a T1 change of up to +/-50%, this approximation to the optimal flip angle produces a contrast to within 6% of the theoretical maximum value and that these predictions are in good agreement with experiment.
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Abstract
MR imaging using anatomic, chemical, and functional information offers huge potential for the management of the gynecologic patient. By differentiating benign from malignant disease with very high specificity, it can aid the selection of patients requiring further treatment and determine the level of urgency. Staging accuracy, which equals that obtained at laparotomy, allows appropriate clinical expertise to be organized before surgery or the deferment of surgery until later in the treatment pathway and is a cost-effective use of resources. This article compares and contrasts MR imaging of gynecologic conditions at 1.5 and 3T and defines a role for high field imaging for these clinical conditions.
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Affiliation(s)
- Lindsay Turnbull
- Centre for MR Investigations, Hull Royal Infirmary, Anlaby Road, Hull HU3 2JZ, UK.
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Abstract
OBJECTIVE To expatiate on the possible advantages and disadvantages of high magnetic field strengths for magnetic resonance imaging and, in particular, for magnetic resonance angiography. METHODS AND RESULTS A review of the available literature is given, presenting many of the advantages and disadvantages of imaging at higher field strengths. Focus is put on imaging at 3 to 7 T. Early results at 7 T are presented; these results indicate that several of the angiographic techniques commonly used at lower field strengths show promise for improvement by taking advantage of the higher signal and susceptibility sensitivity at 7 T. CONCLUSIONS The drive toward higher field strengths, both for the purpose of fundamental research and for clinical diagnostic imaging, is likely to continue. New applications using the unique properties of high field strength will almost certainly emerge as researchers gain more experience. The ultimate limiting factor is likely to be the physiological effects at high field strengths. However, this limit seems to lie at field strengths higher than 7 T because early experience shows good tolerance of 7 T examinations.
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Affiliation(s)
- Mark E Ladd
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany.
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12
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Abstract
Clinical MRI at a field strength of 3.0T is finding increasing use. However, along with the advantages of 3.0T, such as increased SNR, there can be drawbacks, including increased levels of imaging artifacts. Although every imaging artifact observed at 3.0T can also be present at 1.5T, the intensity level is often higher at 3.0T and thus the artifact is more objectionable. This review describes some of the imaging artifacts that are commonly observed with 3.0T imaging, and their root causes. When possible, countermeasures that reduce the artifact level are described.
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Affiliation(s)
- Matt A Bernstein
- Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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Eissa AM, Wilman AH. Effects of RF inhomogeneity at 3.0T on ramped RF excitation: Application to 3D time-of-flight MR angiography of the intracranial arteries. J Magn Reson Imaging 2007; 25:466-72. [PMID: 17279502 DOI: 10.1002/jmri.20832] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To demonstrate the effects of inherent RF inhomogeneity on ramped RF excitation at 3.0T, and to introduce a simple correction for improving visualization of distal intracranial arteries in three-dimensional time-of-flight MR angiography (3D-TOF-MRA). MATERIALS AND METHODS At 3.0T, the effects of RF inhomogeneity arising from RF interference were demonstrated for ramped RF excitation in intracranial 3D-TOF-MRA. Computer simulations and experiments on phantoms and eight normal volunteers were performed. Four different ramp shapes were tested as a possible means of countering the reduced RF field that affects the distal intracranial arteries. RESULTS RF destructive interference alters the ramp pulse shape, which is problematic for vessels that proceed from the center to the edge of the brain. Increasing the ramp pulse slope was shown to be an effective yet simple correction to counter the falling-off of the RF field toward the periphery of the head. With this approach, circle-of-Willis 3D-TOF-MRA studies had improved distal visibility. CONCLUSION Ramped RF excitation is severely affected by RF interference at 3.0T, which makes the ramp profile suboptimal for distal intracranial blood vessels. A simple correction of the ramp slope can make a marked improvement.
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Affiliation(s)
- Amir M Eissa
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
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Bammer R, Skare S, Newbould R, Liu C, Thijs V, Ropele S, Clayton DB, Krueger G, Moseley ME, Glover GH. Foundations of advanced magnetic resonance imaging. NeuroRx 2005; 2:167-96. [PMID: 15897944 PMCID: PMC1064985 DOI: 10.1602/neurorx.2.2.167] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
During the past decade, major breakthroughs in magnetic resonance imaging (MRI) quality were made by means of quantum leaps in scanner hardware and pulse sequences. Some advanced MRI techniques have truly revolutionized the detection of disease states and MRI can now-within a few minutes-acquire important quantitative information noninvasively from an individual in any plane or volume at comparatively high resolution. This article provides an overview of the most common advanced MRI methods including diffusion MRI, perfusion MRI, functional MRI, and the strengths and weaknesses of MRI at high magnetic field strengths.
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Affiliation(s)
- Roland Bammer
- Lucas MRS/I Center, Department of Radiology, Stanford University, California, USA.
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Bammer R, Skare S, Newbould R, Liu C, Thijs V, Ropele S, Clayton DB, Krueger G, Moseley ME, Glover GH. Foundations of advanced magnetic resonance imaging. Neurotherapeutics 2005. [DOI: 10.1007/bf03206665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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