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Bhosale AA, Zhao Y, Zhang X. Electric Field and SAR Reduction in High Impedance RF Arrays by Using High Permittivity Materials for 7T MR Imaging. ARXIV 2023:arXiv:2312.04491v1. [PMID: 38106453 PMCID: PMC10723527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Higher frequencies and shorter wavelengths present significant design issues at ultra-high fields, making multi-channel array setup a critical component for ultra-high field MR imaging. The requirement for multi-channel arrays, as well as ongoing efforts to increase the number of channels in an array, are always limited by the major issue known as inter-element coupling. This coupling affects the current and field distribution, noise correlation between channels, and frequency of array elements, lowering imaging quality and performance. To realize the full potential of UHF MRI, we must ensure that the coupling between array elements is kept to a minimum. High-impedance coils allow array systems to completely realize their potential by providing optimal isolation while requiring minimal design modifications. These minor design changes, which demand the use of low capacitance on the conventional loop to induce elevated impedance, result in a significant safety hazard that cannot be overlooked. High electric fields are formed across these low capacitance lumped elements, which may result in higher SAR values in the imaging subject, depositing more power and, ultimately, providing a greater risk of tissue heating-related injury to the human sample. We propose an innovative method of utilizing high-dielectric material to effectively reduce electric fields and SAR values in the imaging sample while preserving the B1 efficiency and inter-element decoupling between the array elements to address this important safety concern with minimal changes to the existing array design comprising high-impedance coils.
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Affiliation(s)
- Aditya A Bhosale
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States
| | - Yunkun Zhao
- 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
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Yang Q, Zhang H, Xia J, Zhang X. Evaluation of magnetic resonance image segmentation in brain low-grade gliomas using support vector machine and convolutional neural network. Quant Imaging Med Surg 2021; 11:300-316. [PMID: 33392030 PMCID: PMC7719950 DOI: 10.21037/qims-20-783] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 08/18/2020] [Indexed: 11/06/2022]
Abstract
BACKGROUND Image segmentation of brain low-grade glioma (LGG) magnetic resonance imaging (MRI) contributes tremendously to diagnosis, classification and treatment of the disease. A tangible, accurate, reliable and fast image segmentation technique is demanded in clinical diagnosis and research. METHODS The emerging machine learning technique has been demonstrated its unique capability in the field of medical image processing, including medical image segmentation. Support vector machine (SVM) and convolutional neural network (CNN) are two widely used machine learning methods. In this work, image segmentation tools based on SVM and CNN are developed and evaluated for brain LGG MR image segmentation studies. The segmentation performance in terms of accuracy and cost is quantitatively analyzed and compared between the SVM and CNN techniques developed. RESULTS Computed on the Google CoLab, each of the 109 SVM models represents an individual patient, is trained using a single image of that patient and takes a few seconds to complete. The CNN model is trained on a drastically larger dataset of 19,760 data augmented images and takes approximately 2 hours to obtain the most optimal result. The SVM models achieved an average and median accuracy of 0.937 and 0.976 respectively, precision of 0.456 and 0.535 respectively, recall of 0.878 and 0.906 respectively, and F1 score of 0.546 and 0.662 respectively. Although the CNN model required a significantly longer calculation time, it surpassed the SVM models in performance in LGG MR image segmentation, achieving an accuracy of 0.998, a precision of 0.999, a recall of 0.999 and an F1 score of 0.999. CONCLUSIONS This study shows that SVM with appropriate filtering techniques is capable of obtaining reliable and fast segmentation of brain LGG MR images with sufficient accuracy and limited image data. CNN technique outperforms SVM in the accuracy of segmentation with requirements of significantly enlarged data set, long computation time and high-performance computer.
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Affiliation(s)
- Qifan Yang
- Department of Biomedical Engineering, Jacobs School of Medicine and Biomedical Sciences, and School of Engineering and Applied Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Huijuan Zhang
- Department of Biomedical Engineering, Jacobs School of Medicine and Biomedical Sciences, and School of Engineering and Applied Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Jun Xia
- Department of Biomedical Engineering, Jacobs School of Medicine and Biomedical Sciences, and School of Engineering and Applied Sciences, State University of New York at Buffalo, Buffalo, NY, USA
| | - Xiaoliang Zhang
- Department of Biomedical Engineering, Jacobs School of Medicine and Biomedical Sciences, and School of Engineering and Applied Sciences, State University of New York at Buffalo, Buffalo, NY, USA
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Li Y, Lee J, Zhang L, Chen Q, Tie C, Luo C, Zhang X, Liang D, Liu X, Zheng H. Design and testing of a 24-channel head coil for MR imaging at 3 T. Magn Reson Imaging 2019; 58:162-173. [DOI: 10.1016/j.mri.2019.01.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/07/2018] [Accepted: 01/22/2019] [Indexed: 11/29/2022]
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Timilsina R, Qian C. A Novel Expandable Catheter Wireless Amplified NMR Detector for MR Sensitivity Accessing the Kidney in Rodent Model. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2019; 13:444-453. [PMID: 30624224 PMCID: PMC6446567 DOI: 10.1109/tbcas.2018.2890657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This paper demonstrates the enlarged effective range for MRI sensitivity enhancement with a deformable catheter MRI coils integrated with a wirelessly powered amplifier. The expandable balloon wireless amplified nuclear magnetic resonance detector (WAND) is constructed on a copper-clad polyimide film to resonate at the first and second harmonics of the proton Larmor frequency at 7 Tesla. The WAND is then mounted on a balloon catheter system for easy delivery inside confined orifice. Upon reaching the region of interest, it is unfolded out of the sheath tube to increase its effective size. Magnetic resonance (MR) imaging experiments with and without the WAND are performed both in a water phantom and in a live rat to evaluate the WAND's sensitivity advantage. Expanded from a 3 mm diameter in its folded state, this deformable WAND can change its width by >100% in its inflated state to at least 6 mm, leading to a sensitive detection region extending to up to 20 mm in the transverse direction. When the deformable WAND is placed in an artery in the region of the kidney of a live rat, it could achieve at least a 10-fold SNR gain over images acquired by a standard external detector of 22 mm diameter, even though the region of interest is separated from the WAND's surface by a distance larger than the WAND's own width. The proposed expandable catheter WAND could significantly enlarge the effective range for MR sensitivity enhancement in-vivo, enabling versatile applications in interventional MRI.
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Chen Q, Xie G, Luo C, Yang X, Zhu J, Lee J, Su S, Liang D, Zhang X, Liu X, Li Y, Zheng H. A Dedicated 36-Channel Receive Array for Fetal MRI at 3T. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:2290-2297. [PMID: 29994303 PMCID: PMC6312740 DOI: 10.1109/tmi.2018.2839191] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Due to a lack of fetal imaging coils, the standard commercial abdominal coil is often used for fetal imaging, the performance of which is limited by its insufficient coverage, element number, and Signal-to-noise ratio (SNR). In this paper, a dedicated 36-channel coil array, of which size can best fit the body sizes of pregnancy gestation from 20 to 37+ weeks, was designed for fetal imaging at 3T. SNR with full phase encoding and G-factor denoted as noise amplification for parallel imaging were quantitatively evaluated by phantom studies. Compared with a commercial abdominal coil array, the proposed 36-channel fetal array provides not only SNR improvements in full phase encoding (with 10% in the region where the whole fetal body was located, and up to 40% in the edge region where the fetal brain and heart may appear) but also an augmented parallel imaging capability and remarkable SNR improvements at high acceleration factors.
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Affiliation(s)
- Qiaoyan Chen
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Guoxi Xie
- School of Basic Science, Guangzhou Medical University, Guangzhou 511436, China
| | - Chao Luo
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Xing Yang
- High-Field Magnetic Resonance Brain Imaging Key Laboratory of Sichuan Province, Chengdu 610054, China
| | - Jin Zhu
- Shenzhen People’s Hospital, Shenzhen 518020, China
| | - Jo Lee
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Shi Su
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Dong Liang
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94158 USA, and also with the UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, CA 94158 USA
| | - Xin Liu
- Lauterbur Imaging Research Center, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China, and also with Shenzhen Key Laboratory for MRI, Shenzhen 518055, China
| | - Ye Li
- Corresponding authors: Ye Li, and Hairong Zheng. ; .
| | - Hairong Zheng
- Corresponding authors: Ye Li, and Hairong Zheng. ; .
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Wireless MRI Colonoscopy for Sensitive Imaging of Vascular Walls. Sci Rep 2017; 7:4228. [PMID: 28652614 PMCID: PMC5484665 DOI: 10.1038/s41598-017-03902-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 05/08/2017] [Indexed: 01/08/2023] Open
Abstract
A Wireless Amplified NMR Detector (WAND) with cylindrical symmetry has been fabricated and non-surgically inserted into a rodent lower digestive track to improve the imaging quality of deep-lying vessels inside the abdominal cavity. This symmetric detector has a compact design using two end-rings and two vertical legs to create two orthogonal resonance modes. Based on the principle of parametric amplification, the detector can harvest wireless pumping power with its end-rings and amplify Magnetic Resonance signals induced on its vertical legs. With good longitudinal and azimuthal homogeneity, the WAND can achieve up to 21-times sensitivity gain over a standard external detector for immediately adjacent regions, and at least 5-times sensitivity gain for regions separated by one diameter away from the detector's cylindrical surface. The WAND can approach the region of interest through the lower digestive track, similar as a colonoscopy detector. But unlike an optical camera, the amplified MR detector can "see" across intestinal boundaries and clearly identify the walls of bifurcated vessels that are susceptible to atherosclerotic lesions. In addition to vascular wall imaging, this detector may also be used as a swallowable capsule to enhance the detection sensitivity of deep-lying organs near the digestive track.
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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.
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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
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Yan X, Wei L, Chu S, Xue R, Zhang X. Eight-Channel Monopole Array Using ICE Decoupling for Human Head MR Imaging at 7 T. APPLIED MAGNETIC RESONANCE 2016; 47:527-538. [PMID: 29033501 PMCID: PMC5638452 DOI: 10.1007/s00723-016-0775-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 03/09/2016] [Indexed: 06/03/2023]
Abstract
Due to the unique structure of radiative coil elements, traditional decoupling methods face technical challenges in reducing the electromagnetic coupling of the radiative arrays. In this study, we aim to investigate the possibility of using the recently introduced induced current elimination (ICE) decoupling technique for cylindrical shaped radiative coil array designs. To evaluate the method, an eight-channel transmit/receive monopole array with the ICE decoupling, suitable for human head imaging at 7 T, was built and comparatively investigated. In vivo human head images were acquired and geometry factor maps were measured and calculated to evaluate the performance of the ICE-decoupled monopole array. Compared with the monopole array without decoupling methods, the ICE-decoupled monopole array had a higher signal-to-noise ratio and demonstrated improved parallel imaging ability. The experimental results indicate that the ICE decoupling method is a promising solution to addressing the coupling issue of radiative array at ultrahigh fields.
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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, Beijing 100101, China
- Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, 19B Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Long Wei
- Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, 19B Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Suoda Chu
- State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Rong Xue
- State Key Laboratory of Brain and Cognitive Science, Beijing MRI Center for Brain Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- Beijing Institute for Brain Disorders, Beijing 100053, China
| | - Xiaoliang Zhang
- Department of Radiology and Biomedical Imaging, University of California San Francisco, Byers Hall, Room 102, 1700 4th ST, San Francisco, CA 941582330, USA
- UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, CA 94158, USA
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