1
|
Payne K, Zhao Y, Bhosale AA, Zhang X. Dual-Tuned Coaxial-Transmission-Line RF Coils for Hyperpolarized 13C and Deuterium 2H Metabolic MRS Imaging at Ultrahigh Fields. IEEE Trans Biomed Eng 2024; 71:1521-1530. [PMID: 38090865 PMCID: PMC11095995 DOI: 10.1109/tbme.2023.3341760] [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: 12/26/2023]
Abstract
OBJECTIVE Information on the metabolism of tissues in healthy and diseased states plays a significant role in the detection and understanding of tumors, neurodegenerative diseases, diabetes, and other metabolic disorders. Hyperpolarized carbon-13 magnetic resonance imaging (13C-HPMRI) and deuterium metabolic imaging (2H-DMI) are two emerging X-nuclei used as practical imaging tools to investigate tissue metabolism. However due to their low gyromagnetic ratios (ɣ13C = 10.7 MHz/T; ɣ2H = 6.5 MHz/T) and natural abundance, such method required a sophisticated dual-tuned radiofrequency (RF) coil. METHODS Here, we report a dual-tuned coaxial transmission line (CTL) RF coil agile for metabolite information operating at 7T with independent tuning capability. The design analysis has demonstrated how both resonant frequencies can be individually controlled by simply varying the constituent of the design parameters. RESULTS Numerical results have demonstrated a broadband tuning range capability, covering most of the X-nucleus signal, especially the 13C and 2H spectra at 7T. Furthermore, in order to validate the feasibility of the proposed design, both dual-tuned 1H/13C and 1H/2H CTLs RF coils are fabricated using a semi-flexible RG-405 .086" coaxial cable and bench test results (scattering parameters and magnetic field efficiency/distribution) are successfully obtained. CONCLUSION The proposed dual-tuned RF coils reveal highly effective magnetic field obtained from both proton and heteronuclear signal which is crucial for accurate and detailed imaging. SIGNIFICANCE The successful development of this new dual-tuned RF coil technique would provide a tangible and efficient tool for ultrahigh field metabolic MR imaging.
Collapse
|
2
|
Zhao Y, Bhosale AA, Zhang X. Multimodal surface coils for small animal MR imaging at ultrahigh fields. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2024; 32:1596. [PMID: 38948448 PMCID: PMC11214661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Motivation High performance RF coils are needed for better SNR so that higher resolution and spectral dispersion can be obtained in small animal MR imaging. Goals To develop a surface coil with improved SNR over the conventional surface coil for small animal imaging at 7T. Approach A small animal surface coil is designed based on multimodal surface coil technique. The coil is investigated and compared with conventional surface coil using full-wave electromagnetic simulations. Results The multimodal surface coil shows superior B1 field efficiency and lower E field over standard coils, indicating a potential to gain SNR and resolution. Impact The proposed multimodal surface coil can operate at high frequency and provides improved SNR over conventional surface coils at 7T, opening avenues for highly efficient coil design in small animal imaging, ultimately enabling the detection of previously indiscernible physiological details.
Collapse
Affiliation(s)
- Yunkun Zhao
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| | - Aditya Ashok Bhosale
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| | - Xiaoliang Zhang
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
- Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| |
Collapse
|
3
|
Zhao Y, Bhosale AA, Zhang X. Multimodal surface coils for low-field MR imaging. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2024; 32:1325. [PMID: 38948447 PMCID: PMC11214663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Affiliation(s)
- Yunkun Zhao
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| | - Aditya Ashok Bhosale
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| | - Xiaoliang Zhang
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
- Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| |
Collapse
|
4
|
Payne K, Zhao Y, Bhosale AA, Zhang X. Dual-tuned Coaxial-transmission-line RF coils for Hyperpolarized 13C and Deuterium 2H Metabolic MRS Imaging at Ultrahigh Fields. ARXIV 2023:arXiv:2307.11221v3. [PMID: 37502626 PMCID: PMC10370217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Objective Information on the metabolism of tissues in healthy and diseased states plays a significant role in the detection and understanding of tumors, neurodegenerative diseases, diabetes, and other metabolic disorders. Hyperpolarized carbon-13 magnetic resonance imaging (13C-HPMRI) and deuterium metabolic imaging (2H-DMI) are two emerging X-nuclei used as practical imaging tools to investigate tissue metabolism. However due to their low gyromagnetic ratios (ɣ13C = 10.7 MHz/T; ɣ 2H = 6.5 MHz/T) and natural abundance, such method required a sophisticated dual-tuned radiofrequency (RF) coil. Methods Here, we report a dual-tuned coaxial transmission line (CTL) RF coil agile for metabolite information operating at 7T with independent tuning capability. The design analysis has demonstrated how both resonant frequencies can be individually controlled by simply varying the constituent of the design parameters. Results Numerical results have demonstrated a broadband tuning range capability, covering most of the X-nucleus signal, especially the 13C and 2H spectra at 7T. Furthermore, in order to validate the feasibility of the proposed design, both dual-tuned 1H/13C and 1H/2H CTLs RF coils are fabricated using a semi-flexible RG-405 .086" coaxial cable and bench test results (scattering parameters and magnetic field efficiency/distribution) are successfully obtained. Conclusion The proposed dual-tuned RF coils reveal highly effective magnetic field obtained from both proton and heteronuclear signal which is crucial for accurate and detailed imaging. Significance The successful development of this new dual-tuned RF coil technique would provide a tangible and efficient tool for ultrahigh field metabolic MR imaging.
Collapse
Affiliation(s)
- Komlan Payne
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY 14260 USA
| | - Yunkun Zhao
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY 14260 USA
| | - Aditya Ashok Bhosale
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY 14260 USA
| | - Xiaoliang Zhang
- Departments of Biomedical Engineering and Electrical Engineering, State University of New York at Buffalo, Buffalo, NY 14260 USA
| |
Collapse
|
5
|
Marwah H, Pant J, Yadav J, Shah K, Dewangan HK. Biosensor Detection of COVID-19 in Lung Cancer: Hedgehog and Mucin Signaling Insights. Curr Pharm Des 2023; 29:3442-3457. [PMID: 38270161 DOI: 10.2174/0113816128276948231204111531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 10/25/2023] [Indexed: 01/26/2024]
Abstract
Coronavirus disease 2019 is a global pandemic, particularly affecting individuals with pre-existing lung conditions and potentially leading to pulmonary fibrosis. Age and healthcare system limitations further amplify susceptibility to both diseases, especially in low- and middle-income countries. The intricate relationship between Coronavirus disease 2019 and lung cancer highlights their clinical implications and the potential for early detection through biosensor techniques involving hedgehog and mucin signaling. This study highlights the connection between Coronavirus disease 2019 and lung cancer, focusing on the mucosa, angiotensin- altering enzyme 2 receptors, and their impact on the immune system. It details the inflammatory mechanisms triggered by Coronavirus disease 2019, which can result in pulmonary fibrosis and influence the cancer microenvironment. Various cytokines like Interleukins-6 and Tumor Necrosis Factor-alpha are examined for their roles in both diseases. Moreover, the review delves into the Hedgehog signaling pathways and their significance in lung cancer, particularly their influence on embryonic cell proliferation and tissue integrity. Mucin signaling is another vital aspect, highlighting the diverse mucin expression patterns in respiratory epithelial tissues and their potential as biomarkers. The review concludes with insights into diagnostic imaging techniques like chest computed tomography, Positron Emission Tomography and Computed Tomography, and Magnetic Resonance Imaging for early lung cancer detection, emphasizing the crucial role of biosensors in identifying specific biomarkers for early disease detection. This review provides a comprehensive overview of the clinical impact of Coronavirus disease 2019 on lung cancer patients and the potential for biosensors utilizing hedgehog and mucin signaling for early detection. It underscores the ongoing need for research and innovation to address these critical healthcare challenges.
Collapse
Affiliation(s)
- Harneet Marwah
- University Institute of Pharma Sciences (UIPS), Chandigarh University, NH-95 Chandigarh Ludhiana Highway, Mohali, Punjab, India
| | - Janmejay Pant
- University Institute of Pharma Sciences (UIPS), Chandigarh University, NH-95 Chandigarh Ludhiana Highway, Mohali, Punjab, India
| | - Jiten Yadav
- University Institute of Pharma Sciences (UIPS), Chandigarh University, NH-95 Chandigarh Ludhiana Highway, Mohali, Punjab, India
| | - Kamal Shah
- Institute of Pharmaceutical Research (IPR), GLA University Mathura, NH-2 Delhi Mathura Road, Po-CHaumuhan, Uttar Pradesh, India
| | - Hitesh Kumar Dewangan
- University Institute of Pharma Sciences (UIPS), Chandigarh University, NH-95 Chandigarh Ludhiana Highway, Mohali, Punjab, India
| |
Collapse
|
6
|
Vazquez F, Marrufo O, Solis-Najera SE, Martin R, Rodriguez AO. External Waveguide Magnetic Resonance Imaging for lower limbs at 3 T. Med Phys 2021; 49:158-168. [PMID: 34633673 DOI: 10.1002/mp.15281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 09/01/2021] [Accepted: 09/21/2021] [Indexed: 11/09/2022] Open
Abstract
INTRODUCTION We report a method based on the travelling-wave MRI approach, in order to acquire images of human lower limbs with an external waveguide at 3 T. METHOD We use a parallel-plate waveguide and an RF surface coil for reception, while a whole-body birdcage is used for transmission. The waveguide and the surface coil are located right outside the magnet, in the MR conditional devices zone. We ran numerical simulations to investigate the B1 field generated by the surface coil located at one of the waveguides, as well as a saline-solution phantom positioned on the opposite side (150 cm away) inside the magnet. RESULTS We obtained phantom images by varying the distance between the coil and the phantom, in order to investigate the signal-to-noise ratio and to validate our numerical simulations. Lower limb images of a healthy volunteer were also acquired, demonstrating the viability of this approach. Standard pulse sequences were used and no physical modifications were made to the MR imager. CONCLUSIONS These numerical and experimental results show that travelling-wave MRI can produce high-quality images with only a simple waveguide and an RF coil located outside the magnet. This can be particularly favorable when acquiring images of lower limbs requiring a larger field of view.
Collapse
Affiliation(s)
- F Vazquez
- Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
| | - O Marrufo
- Department of Neuroimage, Instituto Nacional de Neurologia y Neurocirugia MVS, Mexico City, 14269, Mexico
| | - S E Solis-Najera
- Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
| | - R Martin
- Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
| | - A O Rodriguez
- Department of Electrical Engineering, Universidad Autonoma Metropolitama Iztapalapa, Mexico City, 09340, Mexico
| |
Collapse
|
7
|
Ye JC. Compressed sensing MRI: a review from signal processing perspective. BMC Biomed Eng 2019; 1:8. [PMID: 32903346 PMCID: PMC7412677 DOI: 10.1186/s42490-019-0006-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 02/04/2019] [Indexed: 11/27/2022] Open
Abstract
Magnetic resonance imaging (MRI) is an inherently slow imaging modality, since it acquires multi-dimensional k-space data through 1-D free induction decay or echo signals. This often limits the use of MRI, especially for high resolution or dynamic imaging. Accordingly, many investigators has developed various acceleration techniques to allow fast MR imaging. For the last two decades, one of the most important breakthroughs in this direction is the introduction of compressed sensing (CS) that allows accurate reconstruction from sparsely sampled k-space data. The recent FDA approval of compressed sensing products for clinical scans clearly reflect the maturity of this technology. Therefore, this paper reviews the basic idea of CS and how this technology have been evolved for various MR imaging problems.
Collapse
Affiliation(s)
- Jong Chul Ye
- Department of Bio and Brain Engineering, Korea Adv. Inst. of Science & Technology (KAIST), 291 Daehak-ro, Daejeon, Korea
| |
Collapse
|
8
|
Zhang X. Sensitivity enhancement of traveling wave MRI using free local resonators: an experimental demonstration. Quant Imaging Med Surg 2017; 7:170-176. [PMID: 28516042 DOI: 10.21037/qims.2017.02.10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Traveling wave MR uses the far fields in signal excitation and reception, therefore its acquisition efficiency is low in contrast to the conventional near field magnetic resonance (MR). Here we show a simple and efficient method based on the local resonator to improving sensitivity of traveling wave MR technique. The proposed method utilizes a standalone or free local resonator to amplify the radio frequency magnetic fields in the interested target. The resonators have no wire connections to the MR system and thus can be conveniently placed to any place around imaging simples. METHODS A rectangular loop L/C resonator to be used as the free local resonator was tuned to the proton Larmor frequency at 7T. Traveling wave MR experiments with and without the wireless free local resonator were performed on a living rat using a 7T whole body MR scanner. The signal-to-noise ratio (SNR) or sensitivity of the images acquired was compared and evaluated. RESULTS In vivo 7T imaging results show that traveling wave MR with a wireless free local resonator placed near the head of a living rat achieves at least 10-fold SNR gain over the images acquired on the same rat using conventional traveling wave MR method, i.e. imaging with no free local resonators. CONCLUSIONS The proposed free local resonator technique is able to enhance the MR sensitivity and acquisition efficiency of traveling wave MR at ultrahigh fields in vivo. This method can be a simple solution to alleviating low sensitivity problem of traveling wave MRI.
Collapse
Affiliation(s)
- Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, School of Medicine, University of California, San Francisco, CA, USA.,UC Berkeley/UCSF Joint Graduate Group in Bioengineering, University of California, San Francisco, CA, USA.,California Institute for Quantitative Biosciences (QB3), San Francisco, CA, USA
| |
Collapse
|
9
|
Zhang X, Martin A, Jordan C, Lillaney P, Losey A, Pang Y, Hu J, Wilson M, Cooke D, Hetts SW. Design of catheter radio frequency coils using coaxial transmission line resonators for interventional neurovascular MR imaging. Quant Imaging Med Surg 2017; 7:187-194. [PMID: 28516044 DOI: 10.21037/qims.2016.12.05] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND It is technically challenging to design compact yet sensitive miniature catheter radio frequency (RF) coils for endovascular interventional MR imaging. METHODS In this work, a new design method for catheter RF coils is proposed based on the coaxial transmission line resonator (TLR) technique. Due to its distributed circuit, the TLR catheter coil does not need any lumped capacitors to support its resonance, which simplifies the practical design and construction and provides a straightforward technique for designing miniature catheter-mounted imaging coils that are appropriate for interventional neurovascular procedures. The outer conductor of the TLR serves as an RF shield, which prevents electromagnetic energy loss, and improves coil Q factors. It also minimizes interaction with surrounding tissues and signal losses along the catheter coil. To investigate the technique, a prototype catheter coil was built using the proposed coaxial TLR technique and evaluated with standard RF testing and measurement methods and MR imaging experiments. Numerical simulation was carried out to assess the RF electromagnetic field behavior of the proposed TLR catheter coil and the conventional lumped-element catheter coil. RESULTS The proposed TLR catheter coil was successfully tuned to 64 MHz for proton imaging at 1.5 T. B1 fields were numerically calculated, showing improved magnetic field intensity of the TLR catheter coil over the conventional lumped-element catheter coil. MR images were acquired from a dedicated vascular phantom using the TLR catheter coil and also the system body coil. The TLR catheter coil is able to provide a significant signal-to-noise ratio (SNR) increase (a factor of 200 to 300) over its imaging volume relative to the body coil. CONCLUSIONS Catheter imaging RF coil design using the proposed coaxial TLR technique is feasible and advantageous in endovascular interventional MR imaging applications.
Collapse
Affiliation(s)
- Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,UC Berkeley/UCSF Joint Bioengineering Program, University of California, Berkeley, San Francisco, CA, USA
| | - Alastair Martin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Caroline Jordan
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Prasheel Lillaney
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Aaron Losey
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Yong Pang
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jeffrey Hu
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Mark Wilson
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Daniel Cooke
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Steven W Hetts
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| |
Collapse
|
10
|
Yan X, Zhang X, Gore JC, Grissom WA. Improved traveling-wave efficiency in 7T human MRI using passive local loop and dipole arrays. Magn Reson Imaging 2017; 39:103-109. [PMID: 28189821 DOI: 10.1016/j.mri.2017.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/01/2017] [Accepted: 02/07/2017] [Indexed: 12/19/2022]
Abstract
Traveling-wave MRI, which uses relatively small and simple RF antennae, has robust matching performance and capability for large field-of-view (FOV) imaging. However, the power efficiency of traveling-wave MRI is much lower than conventional methods, which limits its application. One simple approach to improve the power efficiency is to place passive resonators around the subject being imaged. The feasibility of this approach has been demonstrated in previous works using a single small resonant loop. In this work, we aim to explore how much the improvements can be maintained in human imaging using an array design, and whether electric dipoles can be used as local elements. First, a series of electromagnetic (EM) simulations were performed on a human model. Then RF coils were constructed and the simulation results using the best setup for head imaging were validated in MR experiments. By using the passive local loop and transverse dipole arrays, respectively, the transmit efficiency (B1+) of traveling-wave MRI can be improved by 3-fold in the brain and 2-fold in the knee. The types of passive elements (loops or dipoles) should be carefully chosen for brain or knee imaging to maximize the improvement, and the enhancement depends on the local body configuration.
Collapse
Affiliation(s)
- Xinqiang Yan
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA.
| | - Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, CA, USA
| | - John C Gore
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - William A Grissom
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| |
Collapse
|
11
|
Yan X, Zhang X, Wei L, Xue R. Design and Test of Magnetic Wall Decoupling for Dipole Transmit/Receive Array for MR Imaging at the Ultrahigh Field of 7T. APPLIED MAGNETIC RESONANCE 2015; 46:59-66. [PMID: 28955135 PMCID: PMC5612434 DOI: 10.1007/s00723-014-0612-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Radio-frequency coil arrays using dipole antenna technique have been recently applied for ultrahigh field magnetic resonance (MR) imaging to obtain the better signal-noise-ratio (SNR) gain at the deep area of human tissues. However, the unique structure of dipole antennas makes it challenging to achieve sufficient electromagnetic decoupling among the dipole antenna elements. Currently, there is no decoupling methods proposed for dipole antenna arrays in MR imaging. The recently developed magnetic wall (MW) or induced current elimination decoupling technique has demonstrated its feasibility and robustness in designing microstrip transmission line arrays, L/C loop arrays and monopole arrays. In this study, we aim to investigate the possibility and performance of MW decoupling technique in dipole arrays for MR imaging at the ultrahigh field of 7T. To achieve this goal, a two-channel MW decoupled dipole array was designed, constructed and analyzed experimentally through bench test and MR imaging. Electromagnetic isolation between the two dipole elements was improved from about -3.6 dB (without any decoupling treatments) to -16.5 dB by using the MW decoupling method. MR images acquired from a water phantom using the MW decoupled dipole array and the geometry factor maps were measured, calculated and compared with those acquired using the dipole array without decoupling treatments. The MW decoupled dipole array demonstrated well-defined image profiles from each element and had better geometry factor over the array without decoupling treatments. The experimental results indicate that the MW decoupling technique might be a promising solution to reducing the electromagnetic coupling of dipole arrays in ultrahigh field MRI, consequently improving their performance in SNR and parallel imaging.
Collapse
Affiliation(s)
- Xinqiang Yan
- State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Bldg. 11, 15 Datun Road, Chaoyang District, Beijing 100101, China
| | - Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, Byers Hall, Room 102, 1700 4th ST, San Francisco, CA 94158-2330, USA
| | - Long Wei
- Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Rong Xue
- State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Bldg. 11, 15 Datun Road, Chaoyang District, Beijing 100101, China
| |
Collapse
|
12
|
Webb A. Cavity- and waveguide-resonators in electron paramagnetic resonance, nuclear magnetic resonance, and magnetic resonance imaging. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 83:1-20. [PMID: 25456314 DOI: 10.1016/j.pnmrs.2014.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/30/2014] [Accepted: 09/30/2014] [Indexed: 06/04/2023]
Abstract
Cavity resonators are widely used in electron paramagnetic resonance, very high field magnetic resonance microimaging and also in high field human imaging. The basic principles and designs of different forms of cavity resonators including rectangular, cylindrical, re-entrant, cavity magnetrons, toroidal cavities and dielectric resonators are reviewed. Applications in EPR and MRI are summarized, and finally the topic of traveling wave MRI using the magnet bore as a waveguide is discussed.
Collapse
Affiliation(s)
- Andrew Webb
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
| |
Collapse
|
13
|
Wang YXJ, Lo GG, Yuan J, Larson PEZ, Zhang X. Magnetic resonance imaging for lung cancer screen. J Thorac Dis 2014; 6:1340-8. [PMID: 25276380 DOI: 10.3978/j.issn.2072-1439.2014.08.43] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 08/20/2014] [Indexed: 12/11/2022]
Abstract
Lung cancer is the leading cause of cancer related death throughout the world. Lung cancer is an example of a disease for which a large percentage of the high-risk population can be easily identified via a smoking history. This has led to the investigation of lung cancer screening with low-dose helical/multi-detector CT. Evidences suggest that early detection of lung cancer allow more timely therapeutic intervention and thus a more favorable prognosis for the patient. The positive relationship of lesion size to likelihood of malignancy has been demonstrated previously, at least 99% of all nodules 4 mm or smaller are benign, while noncalcified nodules larger than 8 mm diameter bear a substantial risk of malignancy. In the recent years, the availability of high-performance gradient systems, in conjunction with phased-array receiver coils and optimized imaging sequences, has made MR imaging of the lung feasible. It can now be assumed a threshold size of 3-4 mm for detection of lung nodules with MRI under the optimal conditions of successful breath-holds with reliable gating or triggering. In these conditions, 90% of all 3-mm nodules can be correctly diagnosed and that nodules 5 mm and larger are detected with 100% sensitivity. Parallel imaging can significantly shorten the imaging acquisition time by utilizing the diversity of sensitivity profile of individual coil elements in multi-channel radiofrequency receive coil arrays or transmit/receive coil arrays to reduce the number of phase encoding steps required in imaging procedure. Compressed sensing technique accelerates imaging acquisition from dramatically undersampled data set by exploiting the sparsity of the images in an appropriate transform domain. With the combined imaging algorithm of parallel imaging and compressed sensing and advanced 32-channel or 64-channel RF hardware, overall imaging acceleration of 20 folds or higher can then be expected, ultimately achieve free-breathing and no ECG gating acquisitions in lung cancer MRI screening. Further development of protocols, more clinical trials and the use of advanced analysis tools will further evaluate the real significance of lung MRI.
Collapse
Affiliation(s)
- Yi-Xiang J Wang
- 1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China ; 2 Department of Diagnostic Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 3 Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 4 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA ; 5 UCSF/UC Berkeley Joint Bioengineering Program, San Francisco and Berkeley, CA, USA
| | - Gladys G Lo
- 1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China ; 2 Department of Diagnostic Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 3 Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 4 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA ; 5 UCSF/UC Berkeley Joint Bioengineering Program, San Francisco and Berkeley, CA, USA
| | - Jing Yuan
- 1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China ; 2 Department of Diagnostic Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 3 Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 4 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA ; 5 UCSF/UC Berkeley Joint Bioengineering Program, San Francisco and Berkeley, CA, USA
| | - Peder E Z Larson
- 1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China ; 2 Department of Diagnostic Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 3 Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 4 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA ; 5 UCSF/UC Berkeley Joint Bioengineering Program, San Francisco and Berkeley, CA, USA
| | - Xiaoliang Zhang
- 1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China ; 2 Department of Diagnostic Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 3 Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China ; 4 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA ; 5 UCSF/UC Berkeley Joint Bioengineering Program, San Francisco and Berkeley, CA, USA
| |
Collapse
|
14
|
Yan X, Zhang X, Feng B, Ma C, Wei L, Xue R. 7T transmit/receive arrays using ICE decoupling for human head MR imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2014; 33:1781-1787. [PMID: 24710826 DOI: 10.1109/tmi.2014.2313879] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In designing large-sized volume type phased array coils for human head imaging at ultrahigh fields, e.g., 7T, minimizing electromagnetic coupling among array elements is technically challenging. A new decoupling method based on induced current compensation or elimination (ICE) for a microstrip line planar array has recently been proposed. In this study, an eight-channel transmit/receive volume array with ICE-decoupled loop elements was built and investigated to demonstrate its feasibility and robustness for human head imaging at 7T. Isolation between adjacent loop elements was better than - 25 dB with a human head load. The worst-case of the isolation between all of the elements was about - 17.5 dB. All of the MRI experiments were performed on a 7T whole-body human MR scanner. Images of the phantom and human head were acquired and g-factor maps were measured and calculated to evaluate the performance of the coil array. Compared with the conventional capacitively decoupled array, the ICE-decoupled array demonstrated improved parallel imaging ability and had a higher SNR. The experimental results indicate that the transceiver array design with ICE decoupling technique might be a promising solution to designing high performance transmit/receive coil arrays for human head imaging at ultrahigh fields.
Collapse
|
15
|
Yan X, Zhang X, Wei L, Xue R. Magnetic wall decoupling method for monopole coil array in ultrahigh field MRI: a feasibility test. Quant Imaging Med Surg 2014; 4:79-86. [PMID: 24834419 DOI: 10.3978/j.issn.2223-4292.2014.04.10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 04/21/2014] [Indexed: 11/14/2022]
Abstract
Ultrahigh field (UHF) MR imaging of deeply located target in high dielectric biological samples faces challenges due to the reduced penetration depth at the corresponding high frequencies. Radiative coils, e.g., dipole and monopole coils, have recently been applied for UHF MRI applications to obtain better signal-noise-ratio (SNR) in the area deep inside the human head and body. However, due to the unique structure of radiative coil elements, electromagnetic (EM) coupling between elements in radiative coil arrays cannot be readily addressed by using traditional decoupling methods such as element overlapping and L/C decoupling network. A new decoupling method based on induced current elimination (ICE) or magnetic wall technique has recently been proposed and has demonstrated feasibility in designing microstrip transmission line (MTL) arrays and L/C loop arrays. In this study, an array of two monopole elements decoupled using magnetic wall decoupling technique was designed, constructed and analyzed numerically and experimentally to investigate the feasibility of the decoupling technique in radiative coil array designs for MR imaging at 7 T. An L-shaped capacitive network was employed as the matching circuit and the reflection coefficients (S11) of the monopole element achieved -30 dB or better. Isolation between the two monopole elements was improved from about -10 dB (without decoupling treatment) to better than -30 dB with the ICE/magnetic wall decoupling method. B1 maps and MR images of the phantom were acquired and SNR maps were measured and calculated to evaluate the performance of the ICE/magnetic wall decoupling method. Compared with the monopole elements without decoupling methods, the ICE-decoupled array demonstrated more independent image profiles from each element and had a higher SNR in the peripheral area of the imaging subject. The experimental and simulation results indicate that the ICE/magnetic wall decoupling technique might be a promising solution to reducing the EM coupling of monopole arrays for UHF MRI.
Collapse
Affiliation(s)
- Xinqiang Yan
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 University of Chinese Academy of Sciences, Beijing 100049, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| | - Xiaoliang Zhang
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 University of Chinese Academy of Sciences, Beijing 100049, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| | - Long Wei
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 University of Chinese Academy of Sciences, Beijing 100049, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| | - Rong Xue
- 1 State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China ; 2 Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China ; 3 Beijing Engineering Research Center of Radiographic Techniques and Equipment, Beijing 100049, China ; 4 University of Chinese Academy of Sciences, Beijing 100049, China ; 5 Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California 94158, USA ; 6 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158, USA
| |
Collapse
|
16
|
Frydman L. High magnetic field science and its application in the United States: a magnetic resonance perspective. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 242:256-264. [PMID: 24618413 DOI: 10.1016/j.jmr.2014.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 01/28/2014] [Indexed: 06/03/2023]
|
17
|
Li Y, Yu B, Pang Y, Vigneron DB, Zhang X. Planar quadrature RF transceiver design using common-mode differential-mode (CMDM) transmission line method for 7T MR imaging. PLoS One 2013; 8:e80428. [PMID: 24265823 PMCID: PMC3827179 DOI: 10.1371/journal.pone.0080428] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 10/02/2013] [Indexed: 11/19/2022] Open
Abstract
The use of quadrature RF magnetic fields has been demonstrated to be an efficient method to reduce transmit power and to increase the signal-to-noise (SNR) in magnetic resonance (MR) imaging. The goal of this project was to develop a new method using the common-mode and differential-mode (CMDM) technique for compact, planar, distributed-element quadrature transmit/receive resonators for MR signal excitation and detection and to investigate its performance for MR imaging, particularly, at ultrahigh magnetic fields. A prototype resonator based on CMDM method implemented by using microstrip transmission line was designed and fabricated for 7T imaging. Both the common mode (CM) and the differential mode (DM) of the resonator were tuned and matched at 298MHz independently. Numerical electromagnetic simulation was performed to verify the orthogonal B1 field direction of the two modes of the CMDM resonator. Both workbench tests and MR imaging experiments were carried out to evaluate the performance. The intrinsic decoupling between the two modes of the CMDM resonator was demonstrated by the bench test, showing a better than -36 dB transmission coefficient between the two modes at resonance frequency. The MR images acquired by using each mode and the images combined in quadrature showed that the CM and DM of the proposed resonator provided similar B1 coverage and achieved SNR improvement in the entire region of interest. The simulation and experimental results demonstrate that the proposed CMDM method with distributed-element transmission line technique is a feasible and efficient technique for planar quadrature RF coil design at ultrahigh fields, providing intrinsic decoupling between two quadrature channels and high frequency capability. Due to its simple and compact geometry and easy implementation of decoupling methods, the CMDM quadrature resonator can possibly be a good candidate for design blocks in multichannel RF coil arrays.
Collapse
Affiliation(s)
- Ye Li
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States of America
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Baiying Yu
- Magwale, Palo Alto, California, United States of America
| | - Yong Pang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States of America
| | - Daniel B. Vigneron
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States of America
- UC Berkeley/UCSF Joint Graduate Group in Bioengineering, Berkeley & San Francisco, California, United States of America
- California Institute for Quantitative Biosciences (QB3), San Francisco, California, United States of America
| | - Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, United States of America
- UC Berkeley/UCSF Joint Graduate Group in Bioengineering, Berkeley & San Francisco, California, United States of America
- California Institute for Quantitative Biosciences (QB3), San Francisco, California, United States of America
| |
Collapse
|
18
|
Li Y, Wang C, Yu B, Vigneron D, Chen W, Zhang X. Image homogenization using pre-emphasis method for high field MRI. Quant Imaging Med Surg 2013; 3:217-23. [PMID: 24040618 DOI: 10.3978/j.issn.2223-4292.2013.07.01] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 07/16/2013] [Indexed: 11/14/2022]
Abstract
Radiofrequency (RF) field (B 1) inhomogeneity due to shortened wavelength at high field is a major cause of magnetic resonance imaging (MRI) nonuniformity in high dielectric biological samples (e.g., human body). In this work, we propose a method to improve the B 1 and MRI homogeneity by using pre-emphasized non-uniform B 1 distribution. The intrinsic B 1 distribution that could be generated by a RF volume coil, specifically a microstrip transmission line (MTL) coil used in this work, was pre-emphasized in the sample's periphery region of interest to compensate for the central brightness induced by high frequency interference effect due to shortened wave length. This pre-emphasized non-uniform B 1 can be realized by varying the parameters of microstrip elements, such as the substrate thickness of MTL volume coil. Both numerical simulation and phantom MR imaging studies were carried out to investigate the feasibility and merit of the proposed method in achieving homogeneous MR images. The simulation results demonstrate that by using a pre-emphasized B 1 distribution generated by the MTL volume coil, relatively uniform B 1 distribution and homogeneous MR image (98% homogeneity) within the spherical phantom (15 cm diameter) were achieved with 4.5 mm thickness. The B 1 and MRI intensity distributions of a 16-element MTL volume coil with fixed substrate thickness and five varied saline loads were modeled and experimentally tested. Similar results from both simulation and experiments were obtained, suggesting substantial improvements of B 1 and MRI homogeneities within the phantom containing 125 mM saline. The overall results demonstrate an efficient B 1 shimming approach for improving high field MRI.
Collapse
Affiliation(s)
- Ye Li
- Department of Radiology and Biomedical Imaging, UC San Francisco, San Francisco, CA, USA
| | | | | | | | | | | |
Collapse
|
19
|
Andreychenko A, Kroeze H, Boer VO, Lagendijk JJW, Luijten PR, van den Berg CAT. Improved steering of the RF field of traveling wave MR with a multimode, coaxial waveguide. Magn Reson Med 2013; 71:1641-9. [DOI: 10.1002/mrm.24807] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 03/29/2013] [Accepted: 04/21/2013] [Indexed: 01/04/2023]
Affiliation(s)
- A. Andreychenko
- Imaging Division; University Medical Center Utrecht; The Netherlands
| | - H. Kroeze
- Imaging Division; University Medical Center Utrecht; The Netherlands
| | - V. O. Boer
- Imaging Division; University Medical Center Utrecht; The Netherlands
| | | | - P. R. Luijten
- Imaging Division; University Medical Center Utrecht; The Netherlands
| | | |
Collapse
|
20
|
Pang Y, Yu B, Zhang X. Hepatic fat assessment using advanced Magnetic Resonance Imaging. Quant Imaging Med Surg 2012; 2:213-8. [PMID: 23256082 DOI: 10.3978/j.issn.2223-4292.2012.08.05] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 08/31/2012] [Indexed: 01/12/2023]
Affiliation(s)
- Yong Pang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States
| | | | | |
Collapse
|
21
|
Multi-reception strategy with improved SNR for multichannel MR imaging. PLoS One 2012; 7:e42237. [PMID: 22879921 PMCID: PMC3411773 DOI: 10.1371/journal.pone.0042237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 07/04/2012] [Indexed: 12/03/2022] Open
Abstract
A multi-reception strategy with extended GRAPPA is proposed in this work to improve MR imaging performance at ultra-high field MR systems with limited receiver channels. In this method, coil elements are separated to two or more groups under appropriate grouping criteria. Those groups are enabled in sequence for imaging first, and then parallel acquisition is performed to compensate for the redundant scan time caused by the multiple receptions. To efficiently reconstruct the data acquired from elements of each group, a specific extended GRAPPA was developed. This approach was evaluated by using a 16-element head array on a 7 Tesla whole-body MRI scanner with 8 receive channels. The in-vivo experiments demonstrate that with the same scan time, the 16-element array with twice receptions and acceleration rate of 2 can achieve significant SNR gain in the periphery area of the brain and keep nearly the same SNR in the center area over an eight-element array, which indicates the proposed multi-reception strategy and extended GRAPPA are feasible to improve image quality for MRI systems with limited receive channels. This study also suggests that it is advantageous for a MR system with N receiver channels to utilize a coil array with more than N elements if an appropriate acquisition strategy is applied.
Collapse
|
22
|
Geschewski FH, Brenner D, Felder J, Shah NJ. Optimum coupling and multimode excitation of traveling-waves in a whole-body 9.4T scanner. Magn Reson Med 2012; 69:1805-12. [PMID: 22782491 DOI: 10.1002/mrm.24403] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 05/16/2012] [Accepted: 06/10/2012] [Indexed: 11/08/2022]
Abstract
Given the absence of a body coil, the radio frequency screen of a whole-body 9.4T magnetic resonance imaging scanner can be used as a circular waveguide. In the unloaded case, the screen allows propagation of the dominant TE11- as well as the TM01-mode. In the first part of this study, the optimum coupling of a circular polarized TE11-mode was determined empirically for excitation and reception with a rectangular patch antenna. Employing full-wave simulations, two simulation models and two phantoms, different patch positions were tested to find the optimum position with respect to coupled power and homogenous excitation field. The best simulation results were validated with measurements. The second part of this study describes the design and measurements of a multimode excitation device. Using the parallel transmit system of the MR scanner, all propagable traveling wave modes could be excited and detected independently. The performance of the multimode device related to field of view, B1+-efficiency and radio frequency shimming was assessed by phantom measurements. Initial results show that three modes are sufficient to homogeneously excite regions of interest at 9.4 T.
Collapse
Affiliation(s)
- Frank H Geschewski
- Institute of Neuroscience and Medicine-4, Forschungszentrum Jülich, Jülich, Germany.
| | | | | | | |
Collapse
|
23
|
Pang Y, Vigneron DB, Zhang X. Parallel traveling-wave MRI: a feasibility study. Magn Reson Med 2011; 67:965-78. [PMID: 21858863 DOI: 10.1002/mrm.23073] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 05/18/2011] [Accepted: 06/06/2011] [Indexed: 01/23/2023]
Abstract
Traveling-wave magnetic resonance imaging utilizes far fields of a single-piece patch antenna in the magnet bore to generate radio frequency fields for imaging large-size samples, such as the human body. In this work, the feasibility of applying the "traveling-wave" technique to parallel imaging is studied using microstrip patch antenna arrays with both the numerical analysis and experimental tests. A specific patch array model is built and each array element is a microstrip patch antenna. Bench tests show that decoupling between two adjacent elements is better than -26-dB while matching of each element reaches -36-dB, demonstrating excellent isolation performance and impedance match capability. The sensitivity patterns are simulated and g-factors are calculated for both unloaded and loaded cases. The results on B 1- sensitivity patterns and g-factors demonstrate the feasibility of the traveling-wave parallel imaging. Simulations also suggest that different array configuration such as patch shape, position and orientation leads to different sensitivity patterns and g-factor maps, which provides a way to manipulate B(1) fields and improve the parallel imaging performance. The proposed method is also validated by using 7T MR imaging experiments.
Collapse
Affiliation(s)
- Yong Pang
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | | | | |
Collapse
|