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Gruber B, Stockmann JP, Mareyam A, Keil B, Bilgic B, Chang Y, Kazemivalipour E, Beckett AJ, Vu AT, Feinberg D, Wald LL. A 128-channel receive array for cortical brain imaging at 7 T. Magn Reson Med 2023; 90:2592-2607. [PMID: 37582214 PMCID: PMC10543549 DOI: 10.1002/mrm.29798] [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: 12/24/2022] [Revised: 06/27/2023] [Accepted: 06/28/2023] [Indexed: 08/17/2023]
Abstract
PURPOSE A 128-channel receive-only array for brain imaging at 7 T was simulated, designed, constructed, and tested within a high-performance head gradient designed for high-resolution functional imaging. METHODS The coil used a tight-fitting helmet geometry populated with 128 loop elements and preamplifiers to fit into a 39 cm diameter space inside a built-in gradient. The signal-to-noise ratio (SNR) and parallel imaging performance (1/g) were measured in vivo and simulated using electromagnetic modeling. The histogram of 1/g factors was analyzed to assess the range of performance. The array's performance was compared to the industry-standard 32-channel receive array and a 64-channel research array. RESULTS It was possible to construct the 128-channel array with body noise-dominated loops producing an average noise correlation of 5.4%. Measurements showed increased sensitivity compared with the 32-channel and 64-channel array through a combination of higher intrinsic SNR and g-factor improvements. For unaccelerated imaging, the 128-channel array showed SNR gains of 17.6% and 9.3% compared to the 32-channel and 64-channel array, respectively, at the center of the brain and 42% and 18% higher SNR in the peripheral brain regions including the cortex. For R = 5 accelerated imaging, these gains were 44.2% and 24.3% at the brain center and 86.7% and 48.7% in the cortex. The 1/g-factor histograms show both an improved mean and a tighter distribution by increasing the channel count, with both effects becoming more pronounced at higher accelerations. CONCLUSION The experimental results confirm that increasing the channel count to 128 channels is beneficial for 7T brain imaging, both for increasing SNR in peripheral brain regions and for accelerated imaging.
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Affiliation(s)
- Bernhard Gruber
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
- High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University Vienna, Austria
| | - Jason P. Stockmann
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Azma Mareyam
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Boris Keil
- Institute of Medical Physics and Radiation Protection, Department of Life Science Engineering, Mittelhessen University of Applied Sciences, Giessen, Germany
- Department of Diagnostic and Interventional Radiology, University Hospital Marburg, Philipps University of Marburg, Marburg, Germany
| | - Berkin Bilgic
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Yulin Chang
- Siemens Medical Solutions USA, Inc., Malvern, PA, USA
| | - Ehsan Kazemivalipour
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Alexander J.S. Beckett
- Advanced MRI Technologies, Sebastopol, CA, USA
- Helen Wills Institute for Neuroscience, University of California, Berkeley, CA, USA
| | - An T. Vu
- Radiology, University of California, San Francisco, CA, USA
- San Francisco Veteran Affairs Health Care System, San Francisco, CA, USA
| | - David Feinberg
- Advanced MRI Technologies, Sebastopol, CA, USA
- Helen Wills Institute for Neuroscience, University of California, Berkeley, CA, USA
| | - Lawrence L. Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
- Division of Health Sciences Technology, Harvard - Massachusetts Institute of Technology, Cambridge, MA, USA
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Guryev GD, Milshteyn E, Giannakopoulos II, Lattanzi R, Wald LL, Adalsteinsson E, White JK. MARIE 2.0: A Perturbation Matrix Based Patient-Specific MRI Field Simulator. IEEE Trans Biomed Eng 2023; 70:1575-1586. [PMID: 36383593 PMCID: PMC10689076 DOI: 10.1109/tbme.2022.3222748] [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] [Indexed: 11/18/2022]
Abstract
High static field MR scanners can produce human tissue images of astounding clarity, but rely on high frequency electromagnetic radiation that generates complicated in-tissue field patterns that are patient-specific and potentially harmful. Many such scanners use parallel transmitters to better control field patterns, but then adjust the transmitters based on general guidelines rather than optimizing for the specific patient, mostly because computing patient-specific fields was presumed far too slow. It was recently demonstrated that the combination of fast low-resolution tissue mapping and fast voxel-based field simulation can be used to perform a patient-specific MR safety check in minutes. However, the field simulation required several of those minutes, making it too slow to perform the dozens of simulations that would be needed for patient-specific optimization. In this paper we describe a compressed-perturbation-matrix technique that nearly eliminates the computational cost of including complex coils (or coils and shields) in voxel-based field simulation of tissue, thereby reducing simulation time from minutes to seconds. The approach is demonstrated on a wide variety of head+coil and head+coil+shield configurations, using the implementation in MARIE 2.0, the latest version of the open-source MR field simulator MARIE.
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Seo JH, Jo YS, Oh CH, Chung JY. A New Combination of Radio-Frequency Coil Configurations Using High-Permittivity Materials and Inductively Coupled Structures for Ultrahigh-Field Magnetic Resonance Imaging. SENSORS (BASEL, SWITZERLAND) 2022; 22:8968. [PMID: 36433565 PMCID: PMC9694602 DOI: 10.3390/s22228968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 11/03/2022] [Accepted: 11/17/2022] [Indexed: 06/16/2023]
Abstract
In ultrahigh-field (UHF) magnetic resonance imaging (MRI) system, the RF power required to excite the nuclei of the target object increases. As the strength of the main magnetic field (B0 field) increases, the improvement of the RF transmit field (B1+ field) efficiency and receive field (B1- field) sensitivity of radio-frequency (RF) coils is essential to reduce their specific absorption rate and power deposition in UHF MRI. To address these problems, we previously proposed a method to simultaneously improve the B1+ field efficiency and B1- field sensitivity of 16-leg bandpass birdcage RF coils (BP-BC RF coils) by combining a multichannel wireless RF element (MCWE) and segmented cylindrical high-permittivity material (scHPM) comprising 16 elements in 7.0 T MRI. In this work, we further improved the performance of transmit/receive RF coils. A new combination of RF coil with wireless element and HPM was proposed by comparing the BP-BC RF coil with the MCWE and the scHPM proposed in the previous study and the multichannel RF coils with a birdcage RF coil-type wireless element (BCWE) and the scHPM proposed in this study. The proposed 16-ch RF coils with the BCWE and scHPM provided excellent B1+ field efficiency and B1- field sensitivity improvement.
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Affiliation(s)
- Jeung-Hoon Seo
- Neuroscience Research Institute, Gachon University, Incheon 21988, Republic of Korea
| | - Young-Seung Jo
- Neuroscience Research Institute, Gachon University, Incheon 21988, Republic of Korea
- Department of Electronics and Information Engineering, Korea University, Sejong 30019, Republic of Korea
| | - Chang-Hyun Oh
- Department of Electronics and Information Engineering, Korea University, Sejong 30019, Republic of Korea
| | - Jun-Young Chung
- Department of Neuroscience, College of Medicine, Gachon University, Incheon 21565, Republic of Korea
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Platt T, Ladd ME, Paech D. 7 Tesla and Beyond: Advanced Methods and Clinical Applications in Magnetic Resonance Imaging. Invest Radiol 2021; 56:705-725. [PMID: 34510098 PMCID: PMC8505159 DOI: 10.1097/rli.0000000000000820] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 08/07/2021] [Accepted: 08/07/2021] [Indexed: 12/15/2022]
Abstract
ABSTRACT Ultrahigh magnetic fields offer significantly higher signal-to-noise ratio, and several magnetic resonance applications additionally benefit from a higher contrast-to-noise ratio, with static magnetic field strengths of B0 ≥ 7 T currently being referred to as ultrahigh fields (UHFs). The advantages of UHF can be used to resolve structures more precisely or to visualize physiological/pathophysiological effects that would be difficult or even impossible to detect at lower field strengths. However, with these advantages also come challenges, such as inhomogeneities applying standard radiofrequency excitation techniques, higher energy deposition in the human body, and enhanced B0 field inhomogeneities. The advantages but also the challenges of UHF as well as promising advanced methodological developments and clinical applications that particularly benefit from UHF are discussed in this review article.
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Affiliation(s)
- Tanja Platt
- From the Medical Physics in Radiology, German Cancer Research Center (DKFZ)
| | - Mark E. Ladd
- From the Medical Physics in Radiology, German Cancer Research Center (DKFZ)
- Faculty of Physics and Astronomy
- Faculty of Medicine, University of Heidelberg, Heidelberg
- Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen
| | - Daniel Paech
- Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg
- Clinic for Neuroradiology, University of Bonn, Bonn, Germany
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Han S, Eun S, Cho H, Uludaǧ K, Kim SG. Improvement of sensitivity and specificity for laminar BOLD fMRI with double spin-echo EPI in humans at 7 T. Neuroimage 2021; 241:118435. [PMID: 34324976 DOI: 10.1016/j.neuroimage.2021.118435] [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] [Received: 06/17/2021] [Accepted: 07/26/2021] [Indexed: 12/19/2022] Open
Abstract
Mapping mesoscopic cortical functional units such as columns or laminae is increasingly pursued by ultra-high field (UHF) functional magnetic resonance imaging (fMRI). The most popular approach for high-resolution fMRI is currently gradient-echo (GE) blood oxygenation level-dependent (BOLD) fMRI. However, its spatial accuracy is reduced due to its sensitivity to draining vessels, including pial veins, whereas spin-echo (SE) BOLD signal is expected to have higher spatial accuracy, albeit with lower sensitivity than the GE-BOLD signal. Here, we introduce a new double spin-echo (dSE) echo-planar imaging (EPI) method to improve the sensitivity of SE-BOLD contrast by averaging two spin-echoes using three radiofrequency pulses. Human fMRI experiments were performed with slices perpendicular to the central sulcus between motor and sensory cortices at 7 T during fist-clenching with touching. First, we evaluated the feasibility of single-shot dSE-EPI for BOLD fMRI with 1.5 mm isotropic resolution and found that dSE-BOLD fMRI has higher signal-to-noise ratio (SNR), temporal SNR (tSNR), and higher functional sensitivity than conventional SE-BOLD fMRI. Second, to investigate the laminar specificity of dSE-BOLD fMRI, we implemented a multi-shot approach to achieve 0.8-mm isotropic resolution with sliding-window reconstruction. Unlike GE-BOLD fMRI, the cortical profile of dSE-BOLD fMRI peaked at ~ 1.0 mm from the surface of the primary motor and sensory cortices, demonstrating an improvement of laminar specificity in humans over GE-BOLD fMRI. The proposed multi-shot dSE-EPI method is viable for high spatial resolution UHF-fMRI studies in the pursuit of resolving mesoscopic functional units.
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Affiliation(s)
- SoHyun Han
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
| | - Seulgi Eun
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - HyungJoon Cho
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Kâmil Uludaǧ
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea; Techna Institute & Koerner Scientist in MR Imaging, University Health Network, Toronto, Canada
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea; Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea.
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Tarao K, Nozaki A, Komatsu H, Komatsu T, Taguri M, Tanaka K, Yoshida T, Koyasu H, Chuma M, Numata K, Maeda S. Comparison of unenhanced magnetic resonance imaging and ultrasound in detecting very small hepatocellular carcinoma. World J Hepatol 2021; 13:699-708. [PMID: 34239704 PMCID: PMC8239491 DOI: 10.4254/wjh.v13.i6.699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 03/09/2021] [Accepted: 05/20/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND In hepatocellular carcinoma (HCC), detection and treatment prior to growth beyond 2 cm are important as a larger tumor size is more frequently associated with microvascular invasion and/or satellites. In the surveillance of very small HCC nodules (≤ 2 cm in maximum diameter, Barcelona clinical stage 0), we demonstrated that the tumor markers alpha-fetoprotein and PIVKA-Ⅱ are not so useful. Therefore, we must survey with imaging modalities. The superiority of magnetic resonance imaging (MRI) over ultrasound (US) to detect HCC was confirmed in many studies. Although enhanced MRI is now performed to accurately diagnose HCC, in conventional clinical practice for HCC surveillance in liver diseases, unenhanced MRI is widely performed throughout the world. While, MRI has made marked improvements in recent years.
AIM To make a comparison of unenhanced MRI and US in detecting very small HCC that was examined in the last ten years in patients in whom MRI and US examinations were performed nearly simultaneously.
METHODS In 394 patients with very small HCC nodules, those who underwent MRI and US at nearly the same time (on the same day whenever possible or at least within 14 days of one another) at the first diagnosis of HCC were selected. The detection rate of HCC with unenhanced MRI was investigated and compared with that of unenhanced US.
RESULTS The sensitivity of unenhanced MRI for detecting very small HCC was 95.1% (97/102, 95% confidence interval: 90.9-99.3) and that of unenhanced US was 69.6% (71/102, 95% confidence interval: 60.7-78.5). The sensitivity of unenhanced MRI for detecting very small HCC was significantly higher than that of unenhanced US (P < 0.001). Regarding the location of HCC in the liver in patients in whom detection by US was unsuccessful, S7-8 was identified in 51.7%.
CONCLUSION Currently, unenhanced MRI is a very useful tool for the surveillance of very small HCC in conventional clinical follow-up practice.
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Affiliation(s)
- Kazuo Tarao
- Tarao's Gastroenterological Clinic, Yokohama 241-0821, Japan
| | - Akito Nozaki
- Gastroenterological Center, Yokohama City University Medical Center, Yokohama 232-0024, Japan
| | - Hirokazu Komatsu
- Department of Gastroenterology, Yokohama Municipal Citizen's Hospital, Yokohama 240-0855, Japan
| | - Tatsuji Komatsu
- Department of Clinical Research, National Hospital Organization, Yokohama Medical Center, Yokohama 245-8575, Japan
| | - Masataka Taguri
- Department of Data Science, Yokohama City University, Yokohama 236-0004, Japan
| | - Katsuaki Tanaka
- Department of Gastroenterology, Hadano Red Cross Hospital, Hadano City 257-0017, Japan
| | - Testuo Yoshida
- Department of Radiology, Ashigarakami Hospital, Yokohama 258-0003, Japan
| | - Hideki Koyasu
- Department of Radiology, Koyasu Clinic, Yokohama 241-0821, Japan
| | - Makoto Chuma
- Gastroenterological Center, Yokohama City University Medical Center, Yokohama 232-0024, Japan
| | - Kazushi Numata
- Gastroenterological Center, Yokohama City University Medical Center, Yokohama 232-0024, Japan
| | - Shin Maeda
- Department of Gastroenterology, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
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High-performance hepatobiliary dysprosium contrast agent for ultra-high-field magnetic resonance imaging. J IND ENG CHEM 2020. [DOI: 10.1016/j.jiec.2020.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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A health and safety model for occupational exposure to radiofrequency fields and static magnetic fields from 1.5 and 3 T MRI scanners. HEALTH AND TECHNOLOGY 2020. [DOI: 10.1007/s12553-019-00379-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ladd ME, Bachert P, Meyerspeer M, Moser E, Nagel AM, Norris DG, Schmitter S, Speck O, Straub S, Zaiss M. Pros and cons of ultra-high-field MRI/MRS for human application. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2018; 109:1-50. [PMID: 30527132 DOI: 10.1016/j.pnmrs.2018.06.001] [Citation(s) in RCA: 267] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 06/06/2018] [Accepted: 06/07/2018] [Indexed: 05/08/2023]
Abstract
Magnetic resonance imaging and spectroscopic techniques are widely used in humans both for clinical diagnostic applications and in basic research areas such as cognitive neuroimaging. In recent years, new human MR systems have become available operating at static magnetic fields of 7 T or higher (≥300 MHz proton frequency). Imaging human-sized objects at such high frequencies presents several challenges including non-uniform radiofrequency fields, enhanced susceptibility artifacts, and higher radiofrequency energy deposition in the tissue. On the other side of the scale are gains in signal-to-noise or contrast-to-noise ratio that allow finer structures to be visualized and smaller physiological effects to be detected. This review presents an overview of some of the latest methodological developments in human ultra-high field MRI/MRS as well as associated clinical and scientific applications. Emphasis is given to techniques that particularly benefit from the changing physical characteristics at high magnetic fields, including susceptibility-weighted imaging and phase-contrast techniques, imaging with X-nuclei, MR spectroscopy, CEST imaging, as well as functional MRI. In addition, more general methodological developments such as parallel transmission and motion correction will be discussed that are required to leverage the full potential of higher magnetic fields, and an overview of relevant physiological considerations of human high magnetic field exposure is provided.
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Affiliation(s)
- Mark E Ladd
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Medicine, University of Heidelberg, Heidelberg, Germany; Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany; Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany.
| | - Peter Bachert
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany.
| | - Martin Meyerspeer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria; MR Center of Excellence, Medical University of Vienna, Vienna, Austria.
| | - Ewald Moser
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria; MR Center of Excellence, Medical University of Vienna, Vienna, Austria.
| | - Armin M Nagel
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - David G Norris
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands; Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany.
| | - Sebastian Schmitter
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.
| | - Oliver Speck
- Department of Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany; German Center for Neurodegenerative Diseases, Magdeburg, Germany; Center for Behavioural Brain Sciences, Magdeburg, Germany; Leibniz Institute for Neurobiology, Magdeburg, Germany.
| | - Sina Straub
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
| | - Moritz Zaiss
- High-Field Magnetic Resonance Center, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany.
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Goebel J, Nensa F, Schemuth HP, Maderwald S, Schlosser T, Orzada S, Rietsch S, Quick HH, Nassenstein K. Feasibility of aortic valve planimetry at 7 T ultrahigh field MRI: Comparison to aortic valve MRI at 3 T and 1.5 T. Eur J Radiol Open 2018; 5:159-164. [PMID: 30225274 PMCID: PMC6138940 DOI: 10.1016/j.ejro.2018.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 08/27/2018] [Accepted: 08/27/2018] [Indexed: 11/29/2022] Open
Abstract
Introduction This study examined the feasibility of aortic valve planimetry at 7 T ultrahigh field MRI in intraindividual comparison to 3 T and 1.5 T MRI. Material and methods Aortic valves of eleven healthy volunteers (mean age, 26.4 years) were examined on a 7 T, 3 T, and 1.5 T MR system using FLASH and TrueFISP sequences. Two experienced radiologists evaluated overall image quality, the presence of artefacts, tissue contrast ratios, identifiability, and image details of the aortic valve opening area (AVOA). Furthermore, AVOA was quantified twice by reader 1 and once by reader 2. Correlation analysis between artefact severity and employed magnetic field strength was performed by modified Fisher’s exact-test. Paired t-test was used to analyse for AVOA differences, and Bland-Altman plots were used to analyse AVOA intra-rater and inter-rater variability. Results Aortic valve imaging at 7 T, 3 T, and 1.5 T with using FLASH was less hampered by artefacts than TrueFISP imaging at 3 T and 1.5 T. Tissue contrast and image details were rated best at 7 T. AVOA was measured slightly smaller at 7 T compared to 3 T (TrueFISP, p-value = 0.057; FLASH, p-value = 0.016) and 1.5 T (TrueFISP, p-value = 0.029; FLASH, p-value = 0.018). Intra-rater and inter-rater variability of AVOA tended to be slightly smaller at 7 T than at 3 T and 1.5 T. Conclusion Aortic valve planimetry at 7 T ultrahigh field MRI is technically feasible and in healthy volunteers offers an improved tissue contrast and a slightly better reproducibility than MR planimetry at 1.5 T and 3 T.
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Affiliation(s)
- Juliane Goebel
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
| | - Felix Nensa
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
| | - Haemi P Schemuth
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
| | - Stefan Maderwald
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
| | - Thomas Schlosser
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
| | - Stephan Orzada
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
| | - Stefan Rietsch
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
| | - Harald H Quick
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany.,High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany
| | - Kai Nassenstein
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
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Pfaffenrot V, Brunheim S, Rietsch SHG, Koopmans PJ, Ernst TM, Kraff O, Orzada S, Quick HH. An 8/15-channel Tx/Rx head neck RF coil combination with region-specific B1+ shimming for whole-brain MRI focused on the cerebellum at 7T. Magn Reson Med 2018; 80:1252-1265. [DOI: 10.1002/mrm.27125] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/17/2018] [Accepted: 01/18/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Viktor Pfaffenrot
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- High Field and Hybrid MR Imaging, University Hospital Essen; University of Duisburg-Essen; Essen Germany
| | - Sascha Brunheim
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- High Field and Hybrid MR Imaging, University Hospital Essen; University of Duisburg-Essen; Essen Germany
| | - Stefan H. G. Rietsch
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- High Field and Hybrid MR Imaging, University Hospital Essen; University of Duisburg-Essen; Essen Germany
| | - Peter J. Koopmans
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- High Field and Hybrid MR Imaging, University Hospital Essen; University of Duisburg-Essen; Essen Germany
| | - Thomas M. Ernst
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- Department of Neurology, University Hospital Essen; University of Duisburg-Essen; Essen Germany
| | - Oliver Kraff
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
| | - Stephan Orzada
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
| | - Harald H. Quick
- Erwin L. Hahn Institute for Magnetic Resonance Imaging; University of Duisburg-Essen; Essen Germany
- High Field and Hybrid MR Imaging, University Hospital Essen; University of Duisburg-Essen; Essen Germany
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Haast RAM, Ivanov D, IJsselstein RJT, Sallevelt SCEH, Jansen JFA, Smeets HJM, de Coo IFM, Formisano E, Uludağ K. Anatomic & metabolic brain markers of the m.3243A>G mutation: A multi-parametric 7T MRI study. NEUROIMAGE-CLINICAL 2018; 18:231-244. [PMID: 29868447 PMCID: PMC5984598 DOI: 10.1016/j.nicl.2018.01.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 12/13/2017] [Accepted: 01/15/2018] [Indexed: 02/08/2023]
Abstract
One of the most common mitochondrial DNA (mtDNA) mutations, the A to G transition at base pair 3243, has been linked to changes in the brain, in addition to commonly observed hearing problems, diabetes and myopathy. However, a detailed quantitative description of m.3243A>G patients' brains has not been provided so far. In this study, ultra-high field MRI at 7T and volume- and surface-based data analyses approaches were used to highlight morphology (i.e. atrophy)-, microstructure (i.e. myelin and iron concentration)- and metabolism (i.e. cerebral blood flow)-related differences between patients (N = 22) and healthy controls (N = 15). The use of quantitative MRI at 7T allowed us to detect subtle changes of biophysical processes in the brain with high accuracy and sensitivity, in addition to typically assessed lesions and atrophy. Furthermore, the effect of m.3243A>G mutation load in blood and urine epithelial cells on these MRI measures was assessed within the patient population and revealed that blood levels were most indicative of the brain's state and disease severity, based on MRI as well as on neuropsychological data. Morphometry MRI data showed a wide-spread reduction of cortical, subcortical and cerebellar gray matter volume, in addition to significantly enlarged ventricles. Moreover, surface-based analyses revealed brain area-specific changes in cortical thickness (e.g. of the auditory cortex), and in T1, T2* and cerebral blood flow as a function of mutation load, which can be linked to typically m.3243A>G-related clinical symptoms (e.g. hearing impairment). In addition, several regions linked to attentional control (e.g. middle frontal gyrus), the sensorimotor network (e.g. banks of central sulcus) and the default mode network (e.g. precuneus) were characterized by alterations in cortical thickness, T1, T2* and/or cerebral blood flow, which has not been described in previous MRI studies. Finally, several hypotheses, based either on vascular, metabolic or astroglial implications of the m.3243A>G mutation, are discussed that potentially explain the underlying pathobiology. To conclude, this is the first 7T and also the largest MRI study on this patient population that provides macroscopic brain correlates of the m.3243A>G mutation indicating potential MRI biomarkers of mitochondrial diseases and might guide future (longitudinal) studies to extensively track neuropathological and clinical changes.
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Key Words
- 15-WLT, 15-Words Learning Task
- 7T MRI
- ADL, Activities daily life
- ASL, Arterial spin labeling
- Brain
- CBF, Cerebral blood flow
- CN, Caudate nucleus
- CNR, Contrast-to-noise ratio
- CSF, Cerebral spinal fluid
- DN, Dentate nucleus
- EPI, Echo planar imaging
- FWHM, Full-width half maximum
- GM, Gray matter
- GP, Globus pallidus
- IQR, Interquartile range
- LDST, Letter-Digit Substitution test
- Leu, Leucine
- MANOVA, Multivariate analysis of variance
- MELAS, Mitochondrial encephalopathy lactic acidosis and stroke-like episodes
- MIDD, Mitochondrial inherited deafness and diabetes
- Mitochondrial
- NMDAS, Newcastle Mitochondrial Disease Adult Scale
- OXPHOS, Oxidative phosphorylation
- Pu, Putamen
- Quantitative
- RF, Radio frequency
- RN, Red nucleus
- ROI, Region of interest
- SLEs, Stroke-like cortical episodes
- SN, Substantia nigra
- SNR, Signal-to-noise ratio
- T, Tesla
- UECs, Urine epithelial cells
- UHF, Ultra-high field
- WM, White matter
- WMLs, White matter lesions
- cGM, Cortical gray matter
- eTIV, Estimated total intracranial volume
- m.3243A>G
- mtDNA, Mitochondrial DNA
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Affiliation(s)
- Roy A M Haast
- Department of Cognitive Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands; Maastricht Centre for Systems Biology, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands.
| | - Dimo Ivanov
- Department of Cognitive Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands
| | | | - Suzanne C E H Sallevelt
- Department of Clinical Genetics, Maastricht University Medical Centre, PO Box 5800, 6202AZ Maastricht, Netherlands
| | - Jacobus F A Jansen
- Department of Radiology, Maastricht University Medical Centre and School for Mental Health and Neuroscience, Maastricht University, PO Box 5800, 6202AZ Maastricht, Netherlands
| | - Hubert J M Smeets
- Department of Genetics and Cell Biology, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands; NeMo Expertise Centre, Postbus 2060, 3000CB Rotterdam, Netherlands; Research School GROW, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands
| | - Irenaeus F M de Coo
- Department of Neurology, Erasmus MC, Postbus 2040, 3000CA Rotterdam, Netherlands; NeMo Expertise Centre, Postbus 2060, 3000CB Rotterdam, Netherlands
| | - Elia Formisano
- Department of Cognitive Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands; Maastricht Centre for Systems Biology, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands
| | - Kâmil Uludağ
- Department of Cognitive Neuroscience, Maastricht University, PO Box 616, 6200MD Maastricht, Netherlands.
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14
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Ivanov D, Gardumi A, Haast RA, Pfeuffer J, Poser BA, Uludağ K. Comparison of 3 T and 7 T ASL techniques for concurrent functional perfusion and BOLD studies. Neuroimage 2017; 156:363-376. [DOI: 10.1016/j.neuroimage.2017.05.038] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 05/17/2017] [Accepted: 05/17/2017] [Indexed: 02/04/2023] Open
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15
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Stabler CL, Long RC, Constantinidis I, Sambanis A. In Vivo Noninvasive Monitoring of a Tissue Engineered Construct Using 1H NMR Spectroscopy. Cell Transplant 2017; 14:139-49. [PMID: 15881423 DOI: 10.3727/000000005783983197] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Direct, noninvasive monitoring of tissue engineered substitutes containing live, functional cells would provide valuable information on dynamic changes that occur postimplantation. Such changes include remodeling both within the construct and at the interface of the implant with the surrounding host tissue, and may result in changes in the number of viable cells in the construct. This study investigated the use of 1H NMR spectroscopy in noninvasively monitoring the viable cell number within a tissue engineered construct in vivo. The construct consisted of mouse βTC3 insulinomas in a disk-shaped agarose gel, surrounded by a cell-free agarose gel layer. Localized 1H NMR spectra were acquired from within implanted constructs, and the total choline resonance was measured. Critical issues that had to be addressed in accurately quantifying total choline from the implanted cells included avoiding signal from host tissue and correcting for interfering signal from diffusing solutes. In vivo NMR measurements were correlated with MTT assays and NMR measurements performed in vitro on explanted constructs. Total choline measurements accurately and noninvasively quantified viable βTC3 cell numbers in vivo, in the range of 1 × 106 to more than 14 × 106 cells, and monitored changes in viable cell number that occurred in the same construct over time. This is the first study using NMR techniques to monitor viable cell numbers in an implanted tissue substitute. It established architectural characteristics that a construct should have to be amenable to NMR monitoring, and it set the foundation for future in vivo investigations with other tissue engineered implants.
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Affiliation(s)
- C L Stabler
- Georgia Institute of Technology/Emory University Center for the Engineering of Living Tissues, 315 Ferst Drive, Atlanta, GA 30332-0363, USA
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16
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Zhu HB, Wang L, Li ZY, Li XT, Zhang XY, Sun YS. Sphincter-preserving surgery for low-middle rectal cancer: Can we predict feasibility with high-resolution magnetic resonance imaging? Medicine (Baltimore) 2017; 96:e7418. [PMID: 28723750 PMCID: PMC5521890 DOI: 10.1097/md.0000000000007418] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The study proposed to evaluate the feasibility of predicting sphincter-sparing surgery (SSS) preoperatively in low-middle rectal cancer by using magnetic resonance (MR).The study included both retrospective and prospective design. In the retrospective design, the distance from lower edge of tumor to upper margin of the internal sphincter (Dis1) and distance to anal verge (Dis2) were measured on MR, the distance to anal verge recorded by colonoscopy (Dis3) and digital rectal examination (Dis4) were also obtained. ROC analysis was conducted and cut-off value was determined with overall and stratified analysis. The prospective part was designed to validate the predictive capability of the optimal distance.The retrospective design included 278 patients with middle or lower rectal adenocarcinoma, the prospective design included 106 patients with neoadjuvant therapies. The primary outcome was the actual surgical method and pathological distal resection margin. Dis1 obtained from MRI presented better performance than other distances in determining the surgical approach, with AUC of 0.997 (95% CI, 0.934-1.000). Dis1 was selected as the optimal distance and a cut-off value of 2 cm was determined. Dis1 and the cut-off value were also validated in the prospective sample, with AUC of 0.996 (95% CI, 0.989-1.000) and an overall accuracy of 99.1%.MR-based distance from lower edge of tumor to upper margin of the internal sphincter could be used to help the surgeons to predict the feasibility of SSS preoperatively.
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Affiliation(s)
- Hai-Bin Zhu
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiology
| | - Lin Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Colorectal Surgery
| | - Zi-Yu Li
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Gastrointestinal Surgery, Peking University Cancer Hospital & Institute, Hai Dian District, Beijing, China
| | - Xiao-Ting Li
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiology
| | - Xiao-Yan Zhang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiology
| | - Ying-Shi Sun
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiology
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17
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Chen Z, Solbach K, Erni D, Rennings A. Field Distribution and Coupling Investigation of an Eight-Channel RF Coil Consisting of Different Dipole Coil Elements for 7 T MRI. IEEE Trans Biomed Eng 2017; 64:1297-1304. [DOI: 10.1109/tbme.2016.2602441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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McMahon MT, Gilad AA. Cellular and Molecular Imaging Using Chemical Exchange Saturation Transfer. Top Magn Reson Imaging 2017; 25:197-204. [PMID: 27748713 DOI: 10.1097/rmr.0000000000000105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Chemical exchange saturation transfer (CEST) is a powerful new tool well suited for molecular imaging. This technology enables the detection of low concentration probes through selective labeling of rapidly exchanging protons or other spins on the probes. In this review, we will highlight the unique features of CEST imaging technology and describe the different types of CEST agents that are suited for molecular imaging studies, including CEST theranostic agents, CEST reporter genes, and CEST environmental sensors.
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Affiliation(s)
- Michael T McMahon
- *F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute †The Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research ‡Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD
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19
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Ivanov D, Poser BA, Huber L, Pfeuffer J, Uludağ K. Optimization of simultaneous multislice EPI for concurrent functional perfusion and BOLD signal measurements at 7T. Magn Reson Med 2016; 78:121-129. [PMID: 27465273 PMCID: PMC5484334 DOI: 10.1002/mrm.26351] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 06/29/2016] [Accepted: 06/30/2016] [Indexed: 11/17/2022]
Abstract
Purpose To overcome limitations of previous ultra‐high‐field arterial spin labeling (ASL) techniques concerning temporal resolution and brain coverage by utilizing the simultaneous multi‐slice (SMS) approach. Methods An optimized, flow‐alternating inversion recovery quantitative imaging of perfusion using a single subtraction II scheme was developed that tackles the challenges of 7 tesla (T) ASL. The implementation of tailored labeling radiofrequency pulses reduced the effect of transmit field (
B1+) inhomogeneities. The proposed approach utilizes an SMS echo‐planar imaging (EPI) readout to efficiently achieve large brain coverage. Results A pulsed ASL (PASL) technique with large brain coverage is described and optimized that can be applied at temporal resolutions below 2.5 s, similar to those achievable at 1.5 and 3T magnetic field strength. The influences of within‐ and through‐slice acceleration factors and reconstruction parameters on perfusion and blood‐oxygenation‐level‐dependent (BOLD)‐signal image and temporal signal‐to‐noise ratio (SNR) are presented. The proposed approach yielded twice the brain coverage as compared to conventional PASL at 7T, without notable loss in image quality. Conclusion The presented SMS EPI PASL at 7T overcomes current limitations in SNR, temporal resolution, and spatial coverage for functional perfusion and BOLD signal as well as baseline perfusion measurements. Magn Reson Med 78:121–129, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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Affiliation(s)
- Dimo Ivanov
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Benedikt A Poser
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
| | - Laurentius Huber
- SFIM at the National Institute of Mental Health, Bethesda, Maryland, USA
| | - Josef Pfeuffer
- Siemens Healthcare, MR Application Development, Erlangen, Germany
| | - Kâmil Uludağ
- Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands
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20
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Song SW, Son YD, Cho ZH, Paek SH. Experience with 7.0 T MRI in Patients with Supratentorial Meningiomas. J Korean Neurosurg Soc 2016; 59:405-9. [PMID: 27446524 PMCID: PMC4954891 DOI: 10.3340/jkns.2016.59.4.405] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 10/21/2015] [Accepted: 10/27/2015] [Indexed: 11/27/2022] Open
Abstract
Meningiomas are typically diagnosed by their characteristic appearance on conventional magnetic resonance imaging (MRI). However, detailed image findings regarding peri- and intra-tumoral anatomical structures, tumor consistency and vascularity are very important in pre-surgical planning and surgical outcomes. At the 7.0 T MRI achieving ultra-high resolution, it could be possible to obtain more useful information in surgical strategy. Four patients who were radiologically diagnosed with intracranial meningioma in 1.5 T MRI underwent a 7.0 T MRI. Three of them underwent surgery afterwards, and one received gamma knife radiosurgery. In our study, the advantages of 7.0 T MRI over 1.5 T MRI were a more detailed depiction of the peri- and intra-tumoral vasculature and a clear delineation of tumor-brain interface. In the safety issues, all patients received 7.0 T MRI without any adverse event. One disadvantage of 7.0 T MRI was the reduced image quality of skull base lesions. 7.0 T MRI in patients with meningiomas could provide useful information in surgical strategy, such as the peri-tumoral vasculature and the tumor-brain interface.
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Affiliation(s)
- Sang Woo Song
- Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.; Department of Neurosurgery, Konkuk University Medical Center, Seoul, Korea
| | - Young Don Son
- Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Zang-Hee Cho
- Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Sun Ha Paek
- Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.; Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea
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21
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High-resolution T 2-weighted cervical cancer imaging: a feasibility study on ultra-high-field 7.0-T MRI with an endorectal monopole antenna. Eur Radiol 2016; 27:938-945. [PMID: 27246722 PMCID: PMC5306309 DOI: 10.1007/s00330-016-4419-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 05/03/2016] [Accepted: 05/13/2016] [Indexed: 11/25/2022]
Abstract
Objectives We studied the feasibility of high-resolution T2-weighted cervical cancer imaging on an ultra-high-field 7.0-T magnetic resonance imaging (MRI) system using an endorectal antenna of 4.7-mm thickness. Methods A feasibility study on 20 stage IB1–IIB cervical cancer patients was conducted. All underwent pre-treatment 1.5-T MRI. At 7.0-T MRI, an external transmit/receive array with seven dipole antennae and a single endorectal monopole receive antenna were used. Discomfort levels were assessed. Following individualised phase-based B1+ shimming, T2-weighted turbo spin echo sequences were completed. Results Patients had stage IB1 (n = 9), IB2 (n = 4), IIA1 (n = 1) or IIB (n = 6) cervical cancer. Discomfort (ten-point scale) was minimal at placement and removal of the endorectal antenna with a median score of 1 (range, 0–5) and 0 (range, 0–2) respectively. Its use did not result in adverse events or pre-term session discontinuation. To demonstrate feasibility, T2-weighted acquisitions from 7.0-T MRI are presented in comparison to 1.5-T MRI. Artefacts on 7.0-T MRI were due to motion, locally destructive B1 interference, excessive B1 under the external antennae and SENSE reconstruction. Conclusions High-resolution T2-weighted 7.0-T MRI of stage IB1–IIB cervical cancer is feasible. The addition of an endorectal antenna is well tolerated by patients. Key Points • High resolution T2-weighted 7.0-T MRI of the inner female pelvis is challenging • We demonstrate a feasible approach for T2-weighted 7.0-T MRI of cervical cancer • An endorectal monopole receive antenna is well tolerated by participants • The endorectal antenna did not lead to adverse events or session discontinuation Electronic supplementary material The online version of this article (doi:10.1007/s00330-016-4419-y) contains supplementary material, which is available to authorized users.
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22
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Fifty Years of Technological Innovation: Potential and Limitations of Current Technologies in Abdominal Magnetic Resonance Imaging and Computed Tomography. Invest Radiol 2016; 50:584-93. [PMID: 26039773 DOI: 10.1097/rli.0000000000000173] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Magnetic resonance imaging (MRI) has become an important modality for the diagnosis of intra-abdominal pathology. Hardware and pulse sequence developments have made it possible to derive not only morphologic but also functional information related to organ perfusion (dynamic contrast-enhanced MRI), oxygen saturation (blood oxygen level dependent), tissue cellularity (diffusion-weighted imaging), and tissue composition (spectroscopy). These techniques enable a more specific assessment of pathologic lesions and organ functionality. Magnetic resonance imaging has thus transitioned from a purely morphologic examination to a modality from which image-based disease biomarkers can be derived. This fits well with several emerging trends in radiology, such as the need to accurately assess response to costly treatment strategies and the need to improve lesion characterization to potentially avoid biopsy. Meanwhile, the cost-effectiveness, availability, and robustness of computed tomography (CT) ensure its place as the current workhorse for clinical imaging. Although the lower soft tissue contrast of CT relative to MRI is a long-standing limitation, other disadvantages such as ionizing radiation exposure have become a matter of public concern. Nevertheless, recent technical developments such as dual-energy CT or dynamic volume perfusion CT also provide more functional imaging beyond morphology.The aim of this article was to review and discuss the most important recent technical developments in abdominal MRI and state-of-the-art CT, with an eye toward the future, providing examples of their clinical utility for the evaluation of hepatic and renal pathologies.
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23
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Benjamin P, Viessmann O, MacKinnon AD, Jezzard P, Markus HS. 7 Tesla MRI in Cerebral Small Vessel Disease. Int J Stroke 2015; 10:659-64. [PMID: 25845965 DOI: 10.1111/ijs.12490] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/04/2015] [Indexed: 11/29/2022]
Abstract
Cerebral small vessel disease (SVD) is a major cause of stroke and cognitive decline. Magnetic resonance imaging (MRI) currently plays a central role in diagnosis, and advanced MRI techniques are widely used in research but are limited by spatial resolution. Human 7 Tesla (7T) MRI has recently become available offering the ability to image at higher spatial resolution. This may provide additional insights into both the vascular pathology itself as well as parenchymal markers which could only previously be examined post mortem. In this review we cover the advantages and limitations of 7T MRI, review studies in SVD performed to date, and discuss potential future insights into SVD which 7T MRI may provide.
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Affiliation(s)
- Philip Benjamin
- Neurosciences Research Centre, St George's University of London, London, UK
| | - Olivia Viessmann
- Functional MRI of the Brain (FMRIB) Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Andrew D. MacKinnon
- Atkinson Morley Regional Neuroscience Centre, St George's NHS Healthcare Trust, London, UK
| | - Peter Jezzard
- Functional MRI of the Brain (FMRIB) Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Hugh S. Markus
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Feldman RE, Islam HM, Xu J, Balchandani P. A SEmi-Adiabatic matched-phase spin echo (SEAMS) PINS pulse-pair for B1 -insensitive simultaneous multislice imaging. Magn Reson Med 2015; 75:709-17. [PMID: 25753055 DOI: 10.1002/mrm.25654] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/13/2015] [Accepted: 01/21/2015] [Indexed: 12/24/2022]
Abstract
PURPOSE Simultaneous multislice (SMS) imaging is a powerful technique that can reduce image acquisition time for anatomical, functional, and diffusion weighted magnetic resonance imaging. At higher magnetic fields, such as 7 Tesla, increased radiofrequency (RF) field inhomogeneity, power deposition, and changes in relaxation parameters make SMS spin echo imaging challenging. We designed an adiabatic 180° Power Independent of Number of Slices (PINS) pulse and a matched-phase 90° PINS pulse to generate a SEmi-Adiabatic Matched-phase Spin echo (SEAMS) PINS sequence to address these issues. METHODS We used the adiabatic Shinnar Le-Roux (SLR) algorithm to generate a 180° pulse. The SLR polynomials for the 180° pulse were then used to create a matched-phase 90° pulse. The pulses were sub-sampled to produce a SEAMS PINS pulse-pair and the performance of this pulse-pair was validated in phantoms and in vivo. RESULTS Simulations as well as phantom and in vivo results, demonstrate multislice capability and improved B1 -insensitivity of the SEAMS PINS pulse-pair when operating at RF amplitudes of up to 40% above adiabatic threshold. CONCLUSION The SEAMS PINS approach presented here achieves multislice spin echo profiles with improved B1 -insensitivity when compared with a conventional spin echo.
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Affiliation(s)
- Rebecca E Feldman
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Haisam M Islam
- Bioengineering Department, Stanford University, Stanford, California, USA
| | - Junqian Xu
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
| | - Priti Balchandani
- Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA
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25
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Baeck A, Kravitz D, Baker C, Op de Beeck HP. Influence of lexical status and orthographic similarity on the multi-voxel response of the visual word form area. Neuroimage 2015; 111:321-328. [PMID: 25665965 DOI: 10.1016/j.neuroimage.2015.01.060] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 01/06/2015] [Accepted: 01/30/2015] [Indexed: 10/24/2022] Open
Abstract
Previous studies demonstrated that a region in the left fusiform gyrus, often referred to as the 'visual word form area' (VWFA), is responsive to written words, but the precise functional role of VWFA remains unclear. In the present study, we investigated the influence of orthographic similarity, and lexical factors on the multivoxel response patterns to written stimuli. Using high-resolution fMRI at 7 T, we compared the organization of visual word representations in VWFA to the organization in early visual cortex and a language region in the superior temporal gyrus. Sets of four letter words and pseudowords were presented, in which orthographic similarity was parametrically manipulated. We found that during a lexical decision task VWFA is responsive to the lexical status of a stimulus, but both real words and pseudowords were further processed in terms of orthographic similarity. In contrast, early visual cortex was only responsive to the visual aspects of the stimuli and in the left superior temporal gyrus there was an interaction between lexical status and orthography such that only real words were processed in terms of orthographic similarity. These findings indicate that VWFA represents the word/non-word status of letter strings as well as their orthographic similarity.
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Affiliation(s)
- Annelies Baeck
- Laboratory of Biological Psychology, University of Leuven (KULeuven), Tiensestraat 102, 3000 Leuven, Belgium Laboratory of Experimental Psychology, University of Leuven (KULeuven), Tiensestraat 102, 3000 Leuven, Belgium Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 30901 USA
| | - Dwight Kravitz
- Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 30901 USA
| | - Chris Baker
- Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 30901 USA
| | - Hans P Op de Beeck
- Laboratory of Biological Psychology, University of Leuven (KULeuven), Tiensestraat 102, 3000 Leuven, Belgium
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Varela M, Petersen ET, Golay X, Hajnal JV. Cerebral blood flow measurements in infants using look-locker arterial spin labeling. J Magn Reson Imaging 2014; 41:1591-600. [DOI: 10.1002/jmri.24716] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 07/12/2014] [Accepted: 07/15/2014] [Indexed: 11/09/2022] Open
Affiliation(s)
- Marta Varela
- Department of Biomedical Engineering; Division of Imaging Sciences; King's College London; London UK
- Imaging Sciences Department; MRC Clinical Sciences Centre, Imperial College London; London UK
| | - Esben T. Petersen
- Department of Radiology; University Medical Center; Utrecht The Netherlands
| | - Xavier Golay
- UCL Institute of Neurology; University College London; London UK
| | - Joseph V. Hajnal
- Department of Biomedical Engineering; Division of Imaging Sciences; King's College London; London UK
- Imaging Sciences Department; MRC Clinical Sciences Centre, Imperial College London; London UK
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Paek SH, Hwang JH, Kim DG, Choi SH, Sohn CH, Park SH, Son YD, Kim YB, Cho ZH. A case report of preoperative and postoperative 7.0T brain MRI in a patient with a small cell glioblastoma. J Korean Med Sci 2014; 29:1012-7. [PMID: 25045237 PMCID: PMC4101769 DOI: 10.3346/jkms.2014.29.7.1012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/08/2014] [Indexed: 11/20/2022] Open
Abstract
A 45-yr-old female patient was admitted with one-month history of headache and progressive left hemiparesis. Brain magnetic resonance imaging (MRI) demonstrated a mass lesion in her right frontal lobe. Her brain tumor was confirmed as a small cell glioblastoma. Her follow-up brain MRI, taken at 8 months after her initial surgery demonstrated tumor recurrence in the right frontal lobe. Contrast-enhanced 7.0T brain magnetic resonance imaging (MRI) was safely performed before surgery and at the time of recurrence. Compared with 1.5T and 3.0T brain MRI, 7.0T MRI showed sharpened images of the brain tumor contexture with detailed anatomical information. The fused images of 7.0T and 1.5T brain MRI taken at the time of recurrence demonstrated no significant discrepancy in the positions of the anterior and the posterior commissures. It is suggested that 7.0T MRI can be safely utilized for better images of the maligant gliomas before and after surgery.
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Affiliation(s)
- Sun Ha Paek
- Department of Neurosurgery, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Jae Ha Hwang
- Department of Neurosurgery, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Dong Gyu Kim
- Department of Neurosurgery, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Seung Hong Choi
- Department of Radiology, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Chul-Ho Sohn
- Department of Radiology, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Sung Hye Park
- Department of Pathology, Seoul National University Hospital, Cancer Research Institute, Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Young Don Son
- Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Young Bo Kim
- Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea
| | - Zang-Hee Cho
- Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea
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Abstract
A plethora of magnetic resonance (MR) techniques developed in the last two decades provide unique and noninvasive measurement capabilities for studies of basic brain function and brain diseases in humans. Animal model experiments have been an indispensible part of this development. MR imaging and spectroscopy measurements have been employed in animal models, either by themselves or in combination with complementary and often invasive techniques, to enlighten us about the information content of such MR methods and/or verify observations made in the human brain. They have also been employed, with or independently of human efforts, to examine mechanisms underlying pathological developments in the brain, exploiting the wealth of animal models available for such studies. In this endeavor, the desire to push for ever-higher spatial and/or spectral resolution, better signal-to-noise ratio, and unique image contrast has inevitably led to the introduction of increasingly higher magnetic fields. As a result, today, animal model studies are starting to be conducted at magnetic fields ranging from ~ 11 to 17 Tesla, significantly enhancing the armamentarium of tools available for the probing brain function and brain pathologies.
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Affiliation(s)
- Gülin Öz
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
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Abstract
Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultrahigh fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques.
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Kraff O, Fischer A, Nagel AM, Mönninghoff C, Ladd ME. MRI at 7 Tesla and above: demonstrated and potential capabilities. J Magn Reson Imaging 2014; 41:13-33. [PMID: 24478137 DOI: 10.1002/jmri.24573] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 01/03/2014] [Indexed: 12/29/2022] Open
Abstract
With more than 40 installed MR systems worldwide operating at 7 Tesla or higher, ultra-high-field (UHF) imaging has been established as a platform for clinically oriented research in recent years. Along with technical developments that, in part, have also been successfully transferred to lower field strengths, MR imaging and spectroscopy at UHF have demonstrated capabilities and potentials for clinical diagnostics in a variety of studies. In terms of applications, this overview article focuses on already achieved advantages for in vivo imaging, i.e., in imaging the brain and joints of the musculoskeletal system, but also considers developments in body imaging, which is particularly challenging. Furthermore, new applications for clinical diagnostics such as X-nuclei imaging and spectroscopy, which only really become feasible at ultra-high magnetic fields, will be presented.
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Affiliation(s)
- Oliver Kraff
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
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31
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Abstract
CLINICAL/METHODICAL ISSUE The spatial, temporal and spectral resolution in magnetic resonance imaging (MRI) is in many cases currently not sufficient to detect submillimeter lesions or to image the dynamics of the beating heart. STANDARD RADIOLOGICAL METHODS At present MRI systems at 1.5 T and 3 T are the standard units for clinical imaging. METHODICAL INNOVATIONS The use of ultrahigh magnetic fields of 7 T and higher increases the signal-to-noise ratio, which holds promise for a significant improvement of the spatial and/or temporal resolution as well as for new contrast mechanisms. PERFORMANCE With 7 T MRI, images of the brain have been acquired routinely with a spatial resolution of 0.3 mm. The theoretical improvement of the signal-to-noise ratio is often not fully realized due to B1 inhomogeneities and contrast variations. ACHIEVEMENTS With MRI at 7 T a notable increase in spatial resolution can be achieved. Methods such as time-of-flight MR angiography and susceptibility-weighted imaging (e.g. neurofunctional MRI, fMRI) profit especially from the higher field strengths. Transmission field inhomogeneities are still a major challenge for ultrahigh field (UHF) MRI and are also a partially unsolved safety problem. PRACTICAL RECOMMENDATIONS The use of UHF MRI is currently limited to special applications and the expected gain of the high field must be weighed against technical limitations in both image acquisition and interpretation.
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Affiliation(s)
- M E Ladd
- Erwin L. Hahn Institute for Magnetic Resonance Imaging, Institut für Diagnostische und Interventionelle Radiologie und Neuroradiologie, Universität Duisburg-Essen, Universitätsklinikum Essen, Arendahls Wiese 199, 45141, Essen, Deutschland.
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32
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Practical dynamic contrast enhanced MRI in small animal models of cancer: data acquisition, data analysis, and interpretation. Pharmaceutics 2013; 4:442-78. [PMID: 23105959 PMCID: PMC3480221 DOI: 10.3390/pharmaceutics4030442] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) consists of the continuous acquisition of images before, during, and after the injection of a contrast agent. DCE-MRI allows for noninvasive evaluation of tumor parameters related to vascular perfusion and permeability and tissue volume fractions, and is frequently employed in both preclinical and clinical investigations. However, the experimental and analytical subtleties of the technique are not frequently discussed in the literature, nor are its relationships to other commonly used quantitative imaging techniques. This review aims to provide practical information on the development, implementation, and validation of a DCE-MRI study in the context of a preclinical study (though we do frequently refer to clinical studies that are related to these topics).
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Fowler KJ, McConathy J, Narra VR. Whole-body simultaneous positron emission tomography (PET)-MR: Optimization and adaptation of MRI sequences. J Magn Reson Imaging 2013; 39:259-68. [DOI: 10.1002/jmri.24308] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 06/18/2013] [Indexed: 11/12/2022] Open
Affiliation(s)
- Kathryn J. Fowler
- Department of Radiology; Washington University; St. Louis Missouri USA
| | - Jon McConathy
- Department of Radiology; Washington University; St. Louis Missouri USA
| | - Vamsi R. Narra
- Department of Radiology; Washington University; St. Louis Missouri USA
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Kunz N, Sizonenko SV, Hüppi PS, Gruetter R, van de Looij Y. Investigation of field and diffusion time dependence of the diffusion-weighted signal at ultrahigh magnetic fields. NMR IN BIOMEDICINE 2013; 26:1251-1257. [PMID: 23533088 DOI: 10.1002/nbm.2945] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 06/02/2023]
Abstract
Over the last decade, there has been a significant increase in the number of high-magnetic-field MRI magnets. However, the exact effect of a high magnetic field strength (B0 ) on diffusion-weighted MR signals is not yet fully understood. The goal of this study was to investigate the influence of different high magnetic field strengths (9.4 T and 14.1 T) and diffusion times (9, 11, 13, 15, 17 and 24 ms) on the diffusion-weighted signal in rat brain white matter. At a short diffusion time (9 ms), fractional anisotropy values were found to be lower at 14.1 T than at 9.4 T, but this difference disappeared at longer diffusion times. A simple two-pool model was used to explain these findings. The model describes the white matter as a first hindered compartment (often associated with the extra-axonal space), characterized by a faster orthogonal diffusion and a lower fractional anisotropy, and a second restricted compartment (often associated with the intra-axonal space), characterized by a slower orthogonal diffusion (i.e. orthogonal to the axon direction) and a higher fractional anisotropy. Apparent T2 relaxation time measurements of the hindered and restricted pools were performed. The shortening of the pseudo-T2 value from the restricted compartment with B0 is likely to be more pronounced than the apparent T2 changes in the hindered compartment. This study suggests that the observed differences in diffusion tensor imaging parameters between the two magnetic field strengths at short diffusion time may be related to differences in the apparent T2 values between the pools.
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Affiliation(s)
- Nicolas Kunz
- Division of Child Growth and Development, University of Geneva, Geneva, Switzerland; Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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Kido A, Fujimoto K, Okada T, Togashi K. Advanced MRI in malignant neoplasms of the uterus. J Magn Reson Imaging 2013; 37:249-64. [PMID: 23355429 DOI: 10.1002/jmri.23716] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 05/02/2012] [Indexed: 12/17/2022] Open
Abstract
Conventional magnetic resonance imaging (MRI) such as T1-weighted and T2-weighted images of the female pelvis provide morphological information with excellent tissue contrast, which reflects the pathology of malignant diseases of the uterus. Owing to the recent improvement in hardware and software, in combination with extensive research in imaging techniques, not only MRI at higher magnetic field was facilitated, but also insight into tumor pathophysiology was provided. These methods include diffusion-weighted imaging (DWI), dynamic contrast-enhanced MRI (DCE-MRI) with pharmacokinetic analysis, and MR spectroscopy (MRS). The application of these techniques is expanding from the brain to the body because information on the tissue microenvironment and cytoarchitecture is helpful for lesion characterization, evaluation of treatment response after chemotherapy or radiation, differentiating posttherapeutic changes from residual active tumor, and for detecting recurrent cancer. These techniques may provide clues to optimize the treatment of patients with malignant diseases of the uterus. In the first half of this article we provide an overview of the technical aspects of MRI of the female pelvis, especially focusing on the state-of-the-art techniques such as 3 T MRI, DCE-MRI, DWI, etc. For the latter half we review the clinical aspects of these newly developed techniques, focusing on how these techniques are applicable, what has been revealed with respect to clinical impact, and the remaining problems.
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Affiliation(s)
- Aki Kido
- Department of Diagnostic Radiology and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
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Wijtenburg SA, Rowland LM, Edden RA, Barker PB. Reproducibility of brain spectroscopy at 7T using conventional localization and spectral editing techniques. J Magn Reson Imaging 2013; 38:460-7. [PMID: 23292856 PMCID: PMC3620961 DOI: 10.1002/jmri.23997] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 11/20/2012] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate the reproducibility of spectroscopic measurements from the anterior cingulate (AC) and the dorsolateral prefrontal cortex (DLPFC) regions at 7T using a 32-channel head coil. MATERIALS AND METHODS Spectra were acquired in four healthy subjects each scanned twice using a stimulated echo acquisition mode (STEAM) sequence, and a MEGA-PRESS-IVS sequence for gamma-aminobutyric acid (GABA) editing. STEAM spectra were quantified using LCModel, whereas MEGA-PRESS-IVS data were analyzed using peak integrals determined using in-house software. Mean coefficient of variation (CV) and mean absolute difference between visits were calculated. RESULTS For the AC STEAM dataset, the mean CV between visits was 6.2% for prominent metabolites such as N-acetylaspartate (NAA), total creatine (tCr), and total choline (tCho) and 6.3% for low signal-to-noise ratio (SNR) metabolites such as glutamate (Glu), glutamine (Gln), and GABA. The mean CV between visits for the DLPFC STEAM dataset was 8.5% for prominent metabolites and 21% for lower SNR metabolites. In the AC, the reproducibility measures for GABA were superior for STEAM compared to MEGA-PRESS-IVS (mean CV of 3.5% vs. 13.6%), but the opposite pattern was observed in the DLPFC region (mean CV of 16.2% vs. 13.4%). CONCLUSION 7T MR spectroscopy of the AC and DLPFC using both short TE STEAM and MEGA-PRESS-IVS sequences provide excellent reproducibility of 12 metabolites, including GABA.
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Affiliation(s)
- S. Andrea Wijtenburg
- Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Laura M. Rowland
- Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Richard A.E. Edden
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Peter B. Barker
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
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37
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Liu G, Song X, Chan KWY, McMahon MT. Nuts and bolts of chemical exchange saturation transfer MRI. NMR IN BIOMEDICINE 2013; 26:810-28. [PMID: 23303716 PMCID: PMC4144273 DOI: 10.1002/nbm.2899] [Citation(s) in RCA: 233] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 10/23/2012] [Accepted: 11/01/2012] [Indexed: 05/03/2023]
Abstract
Chemical exchange saturation transfer (CEST) has emerged as a novel MRI contrast mechanism that is well suited for molecular imaging studies. This new mechanism can be used to detect small amounts of contrast agent through the saturation of rapidly exchanging protons on these agents, allowing a wide range of applications. CEST technology has a number of indispensable features, such as the possibility of simultaneous detection of multiple 'colors' of agents and of changes in their environment (e.g. pH, metabolites, etc.) through MR contrast. Currently, a large number of new imaging schemes and techniques are being developed to improve the temporal resolution and specificity and to correct for the influence of B0 and B1 inhomogeneities. In this review, the techniques developed over the last decade are summarized with the different imaging strategies and post-processing methods discussed from a practical point of view, including the description of their relative merits for the detection of CEST agents. The goal of the present work is to provide the reader with a fundamental understanding of the techniques developed, and to provide guidance to help refine future applications of this technology. This review is organized into three main sections ('Basics of CEST contrast', 'Implementation' and 'Post-processing'), and also includes a brief Introduction and Summary. The 'Basics of CEST contrast' section contains a description of the relevant background theory for saturation transfer and frequency-labeled transfer, and a brief discussion of methods to determine exchange rates. The 'Implementation' section contains a description of the practical considerations in conducting CEST MRI studies, including the choice of magnetic field, pulse sequence, saturation pulse, imaging scheme, and strategies to separate magnetization transfer and CEST. The 'Post-processing' section contains a description of the typical image processing employed for B0 /B1 correction, Z-spectral interpolation, frequency-selective detection and improvement of CEST contrast maps.
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Affiliation(s)
- Guanshu Liu
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
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38
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Hahn A, Kranz GS, Seidel EM, Sladky R, Kraus C, Küblböck M, Pfabigan DM, Hummer A, Grahl A, Ganger S, Windischberger C, Lamm C, Lanzenberger R. Comparing neural response to painful electrical stimulation with functional MRI at 3 and 7 T. Neuroimage 2013; 82:336-43. [PMID: 23769917 DOI: 10.1016/j.neuroimage.2013.06.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 04/19/2013] [Accepted: 06/05/2013] [Indexed: 12/21/2022] Open
Abstract
Progressing from 3T to 7 T functional MRI enables marked improvements of human brain imaging in vivo. Although direct comparisons demonstrated advantages concerning blood oxygen level dependent (BOLD) signal response and spatial specificity, these mostly focused on single brain regions with rather simple tasks. Considering that physiological noise also increases with higher field strength, it is not entirely clear whether the advantages of 7T translate equally to the entire brain during tasks which elicit more complex neuronal processing. Therefore, we investigated the difference between 3T and 7 T in response to transcutaneous electrical painful and non-painful stimulation in 22 healthy subjects. For painful stimuli vs. baseline, stronger activations were observed at 7 T in several brain regions including the insula and supplementary motor area, but not the secondary somatosensory cortex (p<0.05 FWE-corrected). Contrasting painful vs. non-painful stimulation limited the differences between the field strengths to the periaqueductal gray (PAG, p<0.001 uncorrected) due to a similar signal increase at 7 T for both the target and specific control condition in most brain regions. This regional specificity obtained for the PAG at higher field strengths was confirmed by an additional spatial normalization strategy optimized for the brainstem. Here, robust BOLD responses were obtained in the dorsal PAG at 7 T (p<0.05 FWE-corrected), whereas at 3T activation was completely missing for the contrast against non-painful stimuli. To summarize, our findings support previously reported benefits obtained at ultra-high field strengths also for complex activation patterns elicited by painful electrical stimulation. However, this advantage depends on the region and even more on the contrast of interest. The greatest gain at 7 T was observed within the small brainstem region of the PAG, where the increased field strength offered marked improvement for the localization of activation foci with high spatial specificity.
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Affiliation(s)
- Andreas Hahn
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria
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Chen JH, Su MY. Clinical application of magnetic resonance imaging in management of breast cancer patients receiving neoadjuvant chemotherapy. BIOMED RESEARCH INTERNATIONAL 2013; 2013:348167. [PMID: 23862143 PMCID: PMC3687601 DOI: 10.1155/2013/348167] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Accepted: 05/17/2013] [Indexed: 12/21/2022]
Abstract
Neoadjuvant chemotherapy (NAC), also termed primary, induction, or preoperative chemotherapy, is traditionally used to downstage inoperable breast cancer. In recent years it has been increasingly used for patients who have operable cancers in order to facilitate breast-conserving surgery, achieve better cosmetic outcome, and improve prognosis by reaching pathologic complete response (pCR). Many studies have demonstrated that magnetic resonance imaging (MRI) can assess residual tumor size after NAC, and that provides critical information for planning of the optimal surgery. NAC also allows for timely adjustment of administered drugs based on response, so ineffective regimens could be terminated early to spare patients from unnecessary toxicity while allowing other effective regimens to work sooner. This review article summarizes the clinical application of MRI during NAC. The use of different MR imaging methods, including dynamic contrast-enhanced MRI, proton MR spectroscopy, and diffusion-weighted MRI, to monitor and evaluate the NAC response, as well as how changes of parameters measured at an early time after initiation of a drug regimen can predict final treatment outcome, are reviewed. MRI has been proven a valuable tool and will continue to provide important information facilitating individualized image-guided treatment and personalized management for breast cancer patients undergoing NAC.
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Affiliation(s)
- Jeon-Hor Chen
- Center for Functional Onco-Imaging, Department of Radiological Sciences, University of California, Irvine, CA 92697-5020, USA
- Department of Radiology, E-Da Hospital and I-Shou University, Kaohsiung 82445, Taiwan
| | - Min-Ying Su
- Center for Functional Onco-Imaging, Department of Radiological Sciences, University of California, Irvine, CA 92697-5020, USA
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Holland DJ, Liu C, Song X, Mazerolle EL, Stevens MT, Sederman AJ, Gladden LF, D'Arcy RCN, Bowen CV, Beyea SD. Compressed sensing reconstruction improves sensitivity of variable density spiral fMRI. Magn Reson Med 2013; 70:1634-43. [DOI: 10.1002/mrm.24621] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 11/30/2012] [Accepted: 12/11/2012] [Indexed: 01/25/2023]
Affiliation(s)
- D. J. Holland
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| | - C. Liu
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
| | - X. Song
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
| | - E. L. Mazerolle
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
- Department of Psychology and Neuroscience; Dalhousie University; Halifax Nova Scotia Canada
| | - M. T. Stevens
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
- Department of Physics; Dalhousie University; Halifax Nova Scotia Canada
| | - A. J. Sederman
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| | - L. F. Gladden
- Department of Chemical Engineering and Biotechnology; University of Cambridge; Cambridge UK
| | - R. C. N. D'Arcy
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
- Department of Psychology and Neuroscience; Dalhousie University; Halifax Nova Scotia Canada
- Department of Radiology; Dalhousie University; Halifax Nova Scotia Canada
| | - C. V. Bowen
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
- Department of Physics; Dalhousie University; Halifax Nova Scotia Canada
- Department of Radiology; Dalhousie University; Halifax Nova Scotia Canada
- School of Biomedical Engineering; Dalhousie University; Halifax Nova Scotia Canada
| | - S. D. Beyea
- Institute for Biodiagnostics (Atlantic); National Research Council Canada; Halifax Nova Scotia Canada
- Department of Physics; Dalhousie University; Halifax Nova Scotia Canada
- Department of Radiology; Dalhousie University; Halifax Nova Scotia Canada
- School of Biomedical Engineering; Dalhousie University; Halifax Nova Scotia Canada
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41
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Guo ZY, Chen J, Liang QZ, Liao HY, Cheng QY, Fu SX, Chen CX, Yu D. RETRACTED: High-resolution MRI of cranial nerves in posterior fossa at 3.0 T. ASIAN PAC J TROP MED 2013; 6:159-61. [DOI: 10.1016/s1995-7645(13)60015-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 11/27/2012] [Accepted: 12/28/2012] [Indexed: 10/27/2022] Open
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Uterine cervical carcinoma: a comparison of two- and three-dimensional T2-weighted turbo spin-echo MR imaging at 3.0 T for image quality and local-regional staging. Eur Radiol 2012; 23:1150-7. [PMID: 22868482 DOI: 10.1007/s00330-012-2603-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 07/13/2012] [Indexed: 10/28/2022]
Abstract
OBJECTIVE To compare three-dimensional (3D) T2-weighted turbo spin-echo (TSE) with multiplanar two-dimensional (2D) T2-weighted TSE for the evaluation of invasive cervical carcinoma. METHODS Seventy-five patients with cervical carcinoma underwent MRI of the pelvis at 3.0 T, using both 5-mm-thick multiplanar 2D (total acquisition time = 12 min 25 s) and 1-mm-thick coronal 3D T2-weighted TSE sequences (7 min 20 s). Quantitative analysis of signal-to-noise ratio (SNR) and qualitative analysis of image quality were performed. Local-regional staging was performed in 45 patients who underwent radical hysterectomy. RESULTS The estimated SNR of cervical carcinoma and the relative tumour contrast were significantly higher on 3D imaging (P < 0.0001). Tumour conspicuity was better with the 3D sequence, but the sharpness of tumour margin was better with the 2D sequence. No significant difference in overall image quality was noted between the two sequences (P = 0.38). There were no significant differences in terms of the diagnostic accuracy, sensitivity, and specificity of parametrial invasion, vaginal invasion, and lymph node metastases. CONCLUSION Multiplanar reconstruction 3D T2-weighted imaging is largely equivalent to 2D T2-weighted imaging for overall image quality and staging accuracy of cervical carcinoma with a shorter MR data acquisition, but has limitations with regard to the sharpness of the tumour margin.
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Wu Q, Li MH. A comparison of 4D time-resolved MRA with keyhole and 3D time-of-flight MRA at 3.0 T for the evaluation of cerebral aneurysms. BMC Neurol 2012; 12:50. [PMID: 22784396 PMCID: PMC3492185 DOI: 10.1186/1471-2377-12-50] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 06/15/2012] [Indexed: 01/13/2023] Open
Abstract
Background A subarachnoid hemorrhage (SAH) due to the rupture of a cerebral aneurysm (CA) is a devastating event associated with high rates of mortality. Magnetic resonance angiography (MRA), as a noninvasive technique, is typically used initially. The object of our study is to evaluate the feasibility of 4D time-resolved MRA with keyhole (4D-TRAK) for the diagnostic accuracy and reliability of the detection and characterization of cerebral aneurysms (CAs), with a comparison of 3D time-of-flight MRA (3D-TOF-MRA) by using DSA as a reference. Methods 3D-TOF-MRA, 4D-TRAK and 3D-DSA were performed sequentially in 52 patients with suspected CAs. 4D-TRAK was acquired using a combination of sensitivity encoding (SENSE) and CE timing robust angiography (CENTRA) k-space sampling techniques at a contrast dose of 10 ml at 3 T. Accuracy, sensitivity, specificity of 4D-TRAK and 3D-TOF-MRA were calculated and compared for the detection of CAs on patient-based and aneurysm-based evaluation using 3D-DSA as a reference. Results The overall image quality of 4D-TRAK with a contrast dose of 10 ml was in the diagnostic range but still cannot be compared with that of 3D-TOF-MRA. In 52 patients with suspected CAs, fifty-eight CAs were confirmed on 3D-DSA finally. Fifty-one (with 2 false-positives and 9 false-negatives) and 58 (with 1 false-positive and 1 false-negative) CAs were visualized on 4D-TRAK and 3D-TOF-MRA, respectively. Accuracy, sensitivity and specificity on patient-based evaluation of 4D-TRAK and 3D-TOF-MRA were 92.31%, 93.33%, 85.71% and 98.08%, 100%, 85.71%, respectively, and 74.07%, 75.00%, 66.67% and 96.30%, 95.83%, 100% on aneurysm-based evaluation in patients with multiple CAs, respectively. Subgroup analysis revealed that for 19 very small CAs (maximal diameter <3 mm, measured on 3D-DSA), 9 were missed on 4D-TRAK and 1 on 3D-TOF-MRA (P = 0.008). However, for 39 CAs with maximal diameter ≥ 3 mm, the diagnostic accuracy is equally (39 on 4D-TRAK vs. 39 on 3D-TOF-MRA) (P = 1). In four larger CAs with maximal diameter ≥ 10 mm, 4D-TRAK provided a better characterization of morphology than 3D-TOF-MRA. Conclusion 4D-TRAK at a lower contrast dose of 10 ml with a combination of SENSE and CENTRA at 3 T could provide similar diagnostic accuracy rate for CAs with maximal diameter ≥ 3 mm, and a better characterization of morphology for larger CAs with maximal diameter ≥ 10 mm compared to 3D-TOF-MRA. However, further study is still needed to improve the “vascular edge” artifact and the compromise in spatial resolution in depiction of CAs with maximal diameter<3 mm.
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Affiliation(s)
- Qian Wu
- Dept of Radiology, The Sixth Affiliated People's Hospital; Medical school of Shanghai Jiaotong University, No, 600# Yishan Road, Shanghai, 200233, China
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Koning W, Bluemink JJ, Langenhuizen EAJ, Raaijmakers AJ, Andreychenko A, van den Berg CAT, Luijten PR, Zwanenburg JJM, Klomp DWJ. High-resolution MRI of the carotid arteries using a leaky waveguide transmitter and a high-density receive array at 7 T. Magn Reson Med 2012; 69:1186-93. [PMID: 22760686 DOI: 10.1002/mrm.24345] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/12/2012] [Accepted: 05/01/2012] [Indexed: 11/09/2022]
Affiliation(s)
- W. Koning
- Department of Radiology; UMC; Utrecht The Netherlands
| | - J. J. Bluemink
- Department of Radiotherapy; UMC; Utrecht The Netherlands
| | | | | | | | | | - P. R. Luijten
- Department of Radiology; UMC; Utrecht The Netherlands
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Moser E, Stahlberg F, Ladd ME, Trattnig S. 7-T MR--from research to clinical applications? NMR IN BIOMEDICINE 2012; 25:695-716. [PMID: 22102481 DOI: 10.1002/nbm.1794] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 08/25/2011] [Accepted: 08/31/2011] [Indexed: 05/31/2023]
Abstract
Over 20,000 MR systems are currently installed worldwide and, although the majority operate at magnetic fields of 1.5 T and below (i.e. about 70%), experience with 3-T (in high-field clinical diagnostic imaging and research) and 7-T (research only) human MR scanners points to a future in functional and metabolic MR diagnostics. Complementary to previous studies, this review attempts to provide an overview of ultrahigh-field MR research with special emphasis on emerging clinical applications at 7 T. We provide a short summary of the technical development and the current status of installed MR systems. The advantages and challenges of ultrahigh-field MRI and MRS are discussed with special emphasis on radiofrequency inhomogeneity, relaxation times, signal-to-noise improvements, susceptibility effects, chemical shifts, specific absorption rate and other safety issues. In terms of applications, we focus on the topics most likely to gain significantly from 7-T MR, i.e. brain imaging and spectroscopy and musculoskeletal imaging, but also body imaging, which is particularly challenging. Examples are given to demonstrate the advantages of susceptibility-weighted imaging, time-of-flight MR angiography, high-resolution functional MRI, (1)H and (31)P MRSI in the human brain, sodium and functional imaging of cartilage and the first results (and artefacts) using an eight-channel body array, suggesting future areas of research that should be intensified in order to fully explore the potential of 7-T MR systems for use in clinical diagnosis.
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Affiliation(s)
- Ewald Moser
- Centre for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
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McRobbie DW. Occupational exposure in MRI. Br J Radiol 2012; 85:293-312. [PMID: 22457400 PMCID: PMC3486652 DOI: 10.1259/bjr/30146162] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 04/13/2011] [Accepted: 05/04/2011] [Indexed: 11/05/2022] Open
Abstract
This article reviews occupational exposure in clinical MRI; it specifically considers units of exposure, basic physical interactions, health effects, guideline limits, dosimetry, results of exposure surveys, calculation of induced fields and the status of the European Physical Agents Directive. Electromagnetic field exposure in MRI from the static field B(0), imaging gradients and radiofrequency transmission fields induces electric fields and currents in tissue, which are responsible for various acute sensory effects. The underlying theory and its application to the formulation of incident and induced field limits are presented. The recent International Commission on Non-Ionizing Radiation Protection (ICNIRP) Bundesministerium für Arbeit und Soziales and Institute of Electrical and Electronics Engineers limits for incident field exposure are interpreted in a manner applicable to MRI. Field measurements show that exposure from movement within the B(0) fringe field can exceed ICNIRP reference levels within 0.5 m of the bore entrance. Rate of change of field dB/dt from the imaging gradients is unlikely to exceed the new limits, although incident field limits can be exceeded for radiofrequency (RF) exposure within 0.2-0.5 m of the bore entrance. Dosimetric surveys of routine clinical practice show that staff are exposed to peak values of 42 ± 24% of B(0), with time-averaged exposures of 5.2 ± 2.8 mT for magnets in the range 0.6-4 T. Exposure to time-varying fields arising from movement within the B(0) fringe resulted in peak dB/dt of approximately 2 T s(-1). Modelling of induced electric fields from the imaging gradients shows that ICNIRP-induced field limits are unlikely to be exceeded in most situations; however, movement through the static field may still present a problem. The likely application of the limits is discussed with respect to the reformulation of the European Union (EU) directive and its possible implications for MRI.
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Affiliation(s)
- D W McRobbie
- Radiological Sciences Unit, Imperial College Healthcare NHS Trust, Charing Cross Hospital, London, UK.
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Dimopoulos JCA, Petrow P, Tanderup K, Petric P, Berger D, Kirisits C, Pedersen EM, van Limbergen E, Haie-Meder C, Pötter R. Recommendations from Gynaecological (GYN) GEC-ESTRO Working Group (IV): Basic principles and parameters for MR imaging within the frame of image based adaptive cervix cancer brachytherapy. Radiother Oncol 2012; 103:113-22. [PMID: 22296748 PMCID: PMC3336085 DOI: 10.1016/j.radonc.2011.12.024] [Citation(s) in RCA: 312] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 11/28/2011] [Accepted: 12/28/2011] [Indexed: 12/18/2022]
Abstract
The GYN GEC-ESTRO working group issued three parts of recommendations and highlighted the pivotal role of MRI for the successful implementation of 3D image-based cervical cancer brachytherapy (BT). The main advantage of MRI as an imaging modality is its superior soft tissue depiction quality. To exploit the full potential of MRI for the better ability of the radiation oncologist to make the appropriate choice for the BT application technique and to accurately define the target volumes and the organs at risk, certain MR imaging criteria have to be fulfilled. Technical requirements, patient preparation, as well as image acquisition protocols have to be tailored to the needs of 3D image-based BT. The present recommendation is focused on the general principles of MR imaging for 3D image-based BT. Methods and parameters have been developed and progressively validated from clinical experience from different institutions (IGR, Universities of Vienna, Leuven, Aarhus and Ljubljana) and successfully applied during expert meetings, contouring workshops, as well as within clinical and interobserver studies. It is useful to perform pelvic MRI scanning prior to radiotherapy (“Pre-RT-MRI examination”) and at the time of BT (“BT MRI examination”) with one MR imager. Both low and high-field imagers, as well as both open and close magnet configurations conform to the requirements of 3D image-based cervical cancer BT. Multiplanar (transversal, sagittal, coronal and oblique image orientation) T2-weighted images obtained with pelvic surface coils are considered as the golden standard for visualisation of the tumour and the critical organs. The use of complementary MRI sequences (e.g. contrast-enhanced T1-weighted or 3D isotropic MRI sequences) is optional. Patient preparation has to be adapted to the needs of BT intervention and MR imaging. It is recommended to visualise and interpret the MR images on dedicated DICOM-viewer workstations, which should also assist the contouring procedure. Choice of imaging parameters and BT equipment is made after taking into account aspects of interaction between imaging and applicator reconstruction, as well as those between imaging, geometry and dose calculation. In a prospective clinical context, to implement 3D image-based cervical cancer brachytherapy and to take advantage of its full potential, it is essential to successfully meet the MR imaging criteria described in the present recommendations of the GYN GEC-ESTRO working group.
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Mao XA. Improve the selectively refocused INEPT pulse sequence for detecting phosphomonoesters and phosphodiesters. Magn Reson Med 2011; 68:332-8. [PMID: 22190173 DOI: 10.1002/mrm.23233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 07/20/2011] [Accepted: 09/06/2011] [Indexed: 12/15/2022]
Abstract
In application of the (31)P selectively refocused insensitive nuclei enhanced polarization transfer (srINEPT) technique to the detection of phosphomono- and diesters in tissues, homonuclear couplings between the CH(2)O protons and the NCH(2) protons seriously attenuate the sensitivity. These couplings can be conventionally removed by two soft 180° pulses in the (1)H evolution period which selectively invert the NCH(2) magnetizations. However, the srINEPT pulse sequence can be simplified by replacing the pulse train "soft 180°-hard 180°-soft 180°" with a single soft 180° pulse that selectively inverts the CH(2)O magnetizations. Theoretical analysis in this study demonstrates the correctness of this approach in principle. Validation on a milk phantom allowed us to investigate and discuss advantages and disadvantages of the proposed srINEPT with respect to the original srINEPT. Furthermore, comparison of different selective pulses made it possible to demonstrate that the proposed srINEPT experiment is not sensitive to errors in pulse length, offset, and B(1) field strength of the selective pulse when ReBurp pulse is used for selective refocusing.
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Affiliation(s)
- Xi-an Mao
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
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Basse-Lüsebrink TC, Kampf T, Fischer A, Sturm VJF, Neumann D, Köstler H, Hahn D, Stoll G, Jakob PM. SAR-reduced spin-echo-based Bloch-Siegert B1+ mapping: BS-SE-BURST. Magn Reson Med 2011; 68:529-36. [DOI: 10.1002/mrm.23259] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 08/31/2011] [Accepted: 09/26/2011] [Indexed: 11/11/2022]
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Advances in High-Field BOLD fMRI. MATERIALS 2011; 4:1941-1955. [PMID: 28824116 PMCID: PMC5448847 DOI: 10.3390/ma4111941] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/07/2011] [Accepted: 10/19/2011] [Indexed: 11/17/2022]
Abstract
This review article examines the current state of BOLD fMRI at a high magnetic field strength of 7 Tesla. The following aspects are covered: a short description of the BOLD contrast, spatial and temporal resolution, BOLD sensitivity, localization and spatial specificity, technical challenges as well as an outlook on future developments are given. It is shown that the main technical challenges of performing BOLD fMRI at high magnetic field strengths-namely development of array coils, imaging sequences and parallel imaging reconstruction-have been solved successfully. The combination of these developments has lead to the availability of high-resolution BOLD fMRI protocols that are able to cover the whole brain with a repetition time (TR) shorter than 3 s. The structural information available from these high-resolution fMRI images itself is already very detailed, which helps to co-localize structure and function. Potential future applications include whole-brain connectivity analysis on a laminar resolution and single subject examinations.
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