Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering最新文献_第4页

Slotted-waveguide array radio frequency coil for ultra-high-field magnetic resonance imaging 用于超高场磁共振成像的开槽波导阵列射频线圈

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-24 DOI: 10.1002/cmr.b.21367

Milan M. Ilić, Branislav M. Notaroš

{"title":"Slotted-waveguide array radio frequency coil for ultra-high-field magnetic resonance imaging","authors":"Milan M. Ilić, Branislav M. Notaroš","doi":"10.1002/cmr.b.21367","DOIUrl":"10.1002/cmr.b.21367","url":null,"abstract":"A novel radio frequency (RF) coil for ultra-high-field MRI in the form of a slotted waveguide array (SWGA) filled with a low-loss high-permittivity dielectric is proposed, evaluated, and demonstrated. A comprehensive computational electromagnetics study, along with basic RF measurements, to characterize the SWGA RF coil at 7T is presented. Slotted waveguides are robust structures capable of handling high powers. They are inherently narrow-band and have well defined linear polarization. When arranged in an array, they effectively generate high-quality field with strong and extremely low and components. With added dielectric lenses, the observed transmit efficiencies exceed in the human head model phantom, which is much higher than all results reported in literature. Moreover, we show that the proposed exciter, as an array with well-decoupled elements (measured isolation between elements is 33 dB or higher), can effectively be used for RF shimming. The novel coil generates RF magnetic field with excellent circular polarization, good uniformity, and negligible axial z-component, and it provides arbitrarily large or small field of view and excellent transmit efficiency, with and without dielectric lenses. It features well-defined narrowband operation, excellent isolation between ports/channels, and inherent possibilities for field optimizations via RF shimming and parallel imaging.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"48B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21367","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85062358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

DVD Review DVD的评论

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-13 DOI: 10.1002/cmr.b.21340

引用次数: 0

NMR Concepts 核磁共振的概念

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-13 DOI: 10.1002/cmr.b.21339

引用次数: 0

High spatial resolution magnetic resonance imaging of insects covered with a hard exoskeleton 覆盖着坚硬外骨骼的昆虫的高空间分辨率磁共振成像

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-13 DOI: 10.1002/cmr.b.21366

Youngseob Seo

{"title":"High spatial resolution magnetic resonance imaging of insects covered with a hard exoskeleton","authors":"Youngseob Seo","doi":"10.1002/cmr.b.21366","DOIUrl":"10.1002/cmr.b.21366","url":null,"abstract":"The morphological investigation of insects is usually performed using histologic serial sections and subsequent reconstruction of the structures from these sections. The achievement of cross sections for microtomy is time-consuming and the risk of damaging sections is inevitable. Recently, X-ray computed tomography (micro-CT) was used to provide adequate spatial resolution without destroying the specimens. Micro-CT is limited by the low x-ray contrast of the insect soft tissues and image quality is relatively poor. Magnetic resonance imaging (MRI) allows the study of morphologic classification of the insects with sufficient spatial resolution and provides a noninvasive mean to determine disease abnormalities and progression in vivo and longitudinally. The morphologic classification of the insects with sufficient spatial resolution analyzed the potential of MR imaging. However, a stag beetle has a particularly hard exoskeleton protecting internal organs and nerves. It is challenge to obtain high spatial resolution images using MRI. The aim of this study was to characterize optimal MRI protocols for the investigation of stag beetles and to evaluate the morphologic characterization of the stag beetles by a 9.4 T MRI scanner. In this study, MR imaging provided the spatial resolution necessary for the examination of morphologic structures of the insects on our hardware-software platform. This study plays a significant role in providing the high spatial resolution, ideally required for routine application to the study of internal morphology of insects, arachnids and crustaceans whose organs, nerves and muscles are protected by the hard exoskeleton.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"48B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21366","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73163271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Comparison of new element designs for combined RF-shim arrays at 7 T 7 T下组合RF-shim阵列新元件设计比较

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-07 DOI: 10.1002/cmr.b.21364

Simone A. Winkler, Paul A. Warr, Jason P. Stockmann, Azma Mareyam, Boris Keil, Ronald D. Watkins, Lawrence L. Wald, Brian K. Rutt

{"title":"Comparison of new element designs for combined RF-shim arrays at 7 T","authors":"Simone A. Winkler, Paul A. Warr, Jason P. Stockmann, Azma Mareyam, Boris Keil, Ronald D. Watkins, Lawrence L. Wald, Brian K. Rutt","doi":"10.1002/cmr.b.21364","DOIUrl":"https://doi.org/10.1002/cmr.b.21364","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 In this work we identify novel concepts for RF-shim loop architectures suitable for 7 T made of 2 concentric conducting loops fulfilling RF and DC functions, respectively, and to determine their relative SNR performance. The goal is to minimize interference between the 2 systems while making efficient use of the space closest to the body. We show by means of theoretical derivation of the frequency spectrum that the proposed 2-loop structure exhibits an anti-resonant null and a resonant peak in the frequency domain. The proposed structure is comprised of 2 concentric wire loops either arranged as nested loops or in the form of a coaxial cable, in which the 2 conductors carry the RF and shim signals, respectively. We use theory, simulation, and phantom measurements to obtain frequency spectra and SNR maps for the proposed structures. Retained SNR is found to be 75% in the coaxial loop and ranges from 57% to 67% in 3 different coaxial configurations. We have found both implementations to be a viable concept for the use in RF-shim devices if remaining SNR limitations can be overcome. We have investigated 2 new design modalities in 7 T RF-shim coil design that separate the RF and shim conductors such that the previously proposed toroidal chokes are eliminated—thereby removing undesired additional loss, bulk, and design complexity.\u0000 </section>\u0000 </div>","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"48B 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21364","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92199227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Design of a high power PIN-diode controlled switchable RF transmit array for TRASE RF imaging 用于TRASE射频成像的高功率pin二极管控制可切换射频发射阵列的设计

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-06-07 DOI: 10.1002/cmr.b.21365

Eric Der, Vyacheslav Volotovskyy, Hongwei Sun, Boguslaw Tomanek, Jonathan C. Sharp

引用次数: 6

Double-layered dual-tuned RF coil using frequency-selectable PIN-diode control at 7-T MRI 采用频率可选pin二极管控制的7-T MRI双层双调谐射频线圈

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-05-21 DOI: 10.1002/cmr.b.21363

Sang-Doc Han, Phil Heo, Han-Joong Kim, Hyunwoo Song, Donghyuk Kim, Jeung-Hoon Seo, Yeunchul Ryu, Young Noh, Kyoung-Nam Kim

{"title":"Double-layered dual-tuned RF coil using frequency-selectable PIN-diode control at 7-T MRI","authors":"Sang-Doc Han, Phil Heo, Han-Joong Kim, Hyunwoo Song, Donghyuk Kim, Jeung-Hoon Seo, Yeunchul Ryu, Young Noh, Kyoung-Nam Kim","doi":"10.1002/cmr.b.21363","DOIUrl":"10.1002/cmr.b.21363","url":null,"abstract":"This article presents a dual-tuned (DT) radiofrequency (RF) coil for signal acquisition of 2 nuclei, namely, hydrogen (1H) and sodium (23Na), in the ultra-high magnetic field of a 7-T magnetic resonance imaging (MRI) system. The double-layered dual-tuned (DLDT) coil comprises a 2-loop coil configuration per single-pair geometry, with the 1H and 23Na coils being located on the outside and inside, respectively. The 1H and 23Na single-pair elements are tuned to resonance frequencies of 297.20 and 78.61 MHz, respectively. The single-pair geometry of the DLDT coil is extended to an 8-pair configuration to cover the human head, and the operation mode is transmission/reception (Tx/Rx). The 8-pair DLDT Tx/Rx coil array is designed with a non-overlapped single pair between the 1H coil elements for geometric decoupling, and capacitive decoupling is implemented to minimize the mutual inductance coupling. The 2 resonance frequencies are fed through a single RF port to a common matching board, and each frequency is selected using the voltages at both ends of a PIN diode. Through use of the PIN diode in the DLDT coil configuration, with a voltage drop at both ends, different resonance frequencies can be selected for each coil element in accordance with the diode ON/OFF state. The experiments conducted showed that the proposed DLDT coil is effective in acquiring signals of 1H and 23Na in the MRI system.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 4","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21363","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89961449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 13

Capacitor re-design overcomes the rotation rate limit of MACS resonators 电容器的重新设计克服了MACS谐振器的转速限制

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-05-21 DOI: 10.1002/cmr.b.21362

Shyam S. Adhikari, Ulrike Wallrabe, Vlad Badilita, Jan G. Korvink

{"title":"Capacitor re-design overcomes the rotation rate limit of MACS resonators","authors":"Shyam S. Adhikari, Ulrike Wallrabe, Vlad Badilita, Jan G. Korvink","doi":"10.1002/cmr.b.21362","DOIUrl":"10.1002/cmr.b.21362","url":null,"abstract":"The magic angle coil spinning (MACS) technique has provided a breakthrough in enhancing sensitivity in magic angle spinning (MAS) NMR. However, efforts in improving the MACS detector for higher spinning speeds have been lacking. One published MACS construction technique is to solder a handwound solenoidal coil to a commercial non-magnetic capacitor and subsequently centering the detector inside the MAS rotor. An alternative method to realize these detectors is by using MEMS fabrication at the wafer scale, potentially capable of achieving reproducible MACS detectors. However, it is also important that the performance of the sensors does not deteriorate as a result of microfabrication constraints. The footprint of the detectors is a limiting factor in achieving higher spinning speeds. One of the key elements of a micro-resonator is its tuning capacitor, whose geometry has a significant influence on its electrical and mechanical performance. The quality factor of the capacitor, along with the induced eddy currents, are the key performance parameters considered. The article addresses these concerns by presenting a study of microfabricated on-chip capacitors for magic angle coil spinning (MACS) detectors. The capacitors are juxtaposed with commercially available capacitors and the most suitable fit to be integrated with a micro-coil is established.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 4","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21362","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77992346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Simulation, design, and test of an elliptical surface coil for magnetic resonance imaging and spectroscopy 用于磁共振成像和光谱学的椭圆表面线圈的模拟、设计和测试

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-02-19 DOI: 10.1002/cmr.b.21361

Giulio Giovannetti, Alessandra Flori, Daniele De Marchi, Giuseppe Matarazzo, Francesca Frijia, Silvia Burchielli, Domenico Montanaro, Giovanni Donato Aquaro, Luca Menichetti

{"title":"Simulation, design, and test of an elliptical surface coil for magnetic resonance imaging and spectroscopy","authors":"Giulio Giovannetti, Alessandra Flori, Daniele De Marchi, Giuseppe Matarazzo, Francesca Frijia, Silvia Burchielli, Domenico Montanaro, Giovanni Donato Aquaro, Luca Menichetti","doi":"10.1002/cmr.b.21361","DOIUrl":"10.1002/cmr.b.21361","url":null,"abstract":"The simplest design of surface coils for magnetic resonance imaging (MRI) applications is circular and square loops, both producing a magnetic field perpendicular to the coil plane in the central region-of-interest (ROI), with an amplitude that decreases along the coil axis. However, a surface coil constituted by a loop with different geometry could be necessary when particular field-of-views (FOVs) are desired, especially for performing imaging in an elongated region. This can be achieved by using an elliptical loop, which can guarantee a wide longitudinal FOV and a good penetration in deep sample regions. This work proposes the application of a method for elliptical coil Signal-to-Noise Ratio (SNR) estimation previously developed for circular and square loop design, in which coil inductance and resistance are analytically calculated and the magnetic field pattern is estimated using the magnetostatic approach, while the sample-induced resistance is calculated with the vector potential calculation method. In the second part of the paper, we propose the simulation and the design of a transmit/receive elliptical coil for MRI in mice with a 3T clinical scanner. We also evaluated the coil performance in a preliminary magnetic resonance spectroscopy (MRS) study in phantom.","PeriodicalId":50623,"journal":{"name":"Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering","volume":"47B 4","pages":""},"PeriodicalIF":0.9,"publicationDate":"2018-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.b.21361","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81197161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

An RF-gated wireless power transfer system for wireless MRI receive arrays 一种用于无线MRI接收阵列的射频门控无线电力传输系统

IF 0.9 4区医学

Concepts in Magnetic Resonance Part B-Magnetic Resonance Engineering Pub Date : 2018-02-14 DOI: 10.1002/cmr.b.21360

Kelly Byron, Fraser Robb, Pascal Stang, Shreyas Vasanawala, John Pauly, Greig Scott

引用次数: 13