磁共振概念 B 部分汇集了参与设计和开发用于磁共振技术的硬件和软件的工程师和物理学家。该杂志欢迎主要来自磁共振成像 (MRI)、核磁共振 (NMR) 和电子顺磁共振 (EPR) 领域的投稿，但也鼓励提交与不太常见的磁共振成像和分析方法相关的投稿。学术界和工业界，报告仪器和计算机编程发展的最新进展，以支持医学、非医学和分析磁共振技术。

Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering brings together engineers and physicists involved in the design and development of hardware and software for magnetic resonance technology. The journal welcomes submissions primarily from the fields of Magnetic Resonance Imaging (MRI), Nuclear Magnetic Resonance (NMR), and Electron Paramagnetic Resonance (EPR), but also encourages contributions related to less common magnetic resonance imaging and analysis methods. Both academia and industry are invited to report the latest advancements in instrument and computer programming developments to support medical, non-medical, and analytical magnetic resonance technologies.

《Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering》汇集了参与设计和开发磁共振技术硬件和软件的工程师和物理学家。该杂志欢迎来自磁共振成像 (MRI)、核磁共振 (NMR) 和电子顺磁共振 (EPR) 领域的投稿，同时也鼓励与不太常见的磁共振成像和分析方法相关的研究。无论是学术界还是工业界，均可报告仪器和计算机编程发展的最新进展，以支持医学、非医学和分析磁共振技术。

Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering

Abstract The simulation and the design of radiofrequency ( RF ) coils are fundamental tasks to maximize Signal‐to‐Noise Ratio ( SNR ) in Magnetic Resonance ( MR ) applications. The estimation of coil resistance, that is, the losses within the coil conductors, which depends on tuning frequency, allows the prediction of coil performance and data SNR . At RF , the conductor resistance is increased due to the skin effect, which distributes the current primarily near the conductor surface instead of uniformly over the cross section. Moreover, the radiative losses estimation as a function of tuning frequency permits a total coil performance characterization, especially for high‐frequency tuned coils when this loss mechanism could be the dominant one. In this work we compared Finite Element Method ( FEM ) simulations with analytical calculations performed in wire loop RF coils for MR applications. Our results showed that FEM can predict the losses within the coil conductors at 5.7 MH z with a relative difference of &lt;3% compared to analytical calculation, while the relative difference increased to 58% at 127.8 MH z. Concerning the radiative losses, the relative difference between analytical formulation and FEM was lower than 3% at 5.7 MH z, and increasing to 44% at 127.8 MH z. Experimental measurements on a circular coil prototype were also performed at 85.2 MH z and 127.8 MH z, showing a better agreement with FEM simulations than with analytical calculations.

Giulio Giovannetti

Gianluigi Tiberi

Michela Tosetti

Concepts in Magnetic Resonance Part B

Finite element method‐based approach for radiofrequency magnetic resonance coil losses estimation

基于有限元法的射频磁共振线圈损耗估算方法

ABSTRACT Design of magnetic resonance imaging (MRI) radiofrequency (RF) coils using lumped circuit modeling based techniques begins to fail at high frequencies, and therefore more accurate models based on the electromagnetic field calculations must be used. Field calculations are also necessary to understand the interactions between the RF field and the subject inside the coil. Furthermore, observing the resonance behavior of the coil and the fields at the resonance frequencies have importance for design and analysis. In this study, finite element method (FEM) based methods have been proposed for accurate time‐harmonic electromagnetic simulations, estimation of the tuning capacitors on the rungs or end rings, and the resonant mode analysis of the birdcage coils. Capacitance estimation was achieved by maximizing the magnitude of the port impedance at the desired frequency while simultaneously minimizing the variance of RF magnetic field in the region of interest. In order for the proposed methods to be conveniently applicable, two software tools, resonant mode and frequency domain analyzer (RM‐FDA) and Optimum Capacitance Finder (OptiCF), were developed. Simulation results for the validation and verification of the software tools are provided for different cases including human head simulations. Additionally, two handmade birdcage coils (low‐pass and high‐pass) were built and resonance mode measurements were made. Results of the software tools are compared with the measurement results as well as with the results of the lumped circuit modeling based method. It has been shown that the proposed software tools can be used for accurate simulation and design of birdcage coils. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 13–32, 2015

Necip Gurler

Yusuf Ziya Ider

Numerical methods and software tools for simulation, design, and resonant mode analysis of radio frequency birdcage coils used in <scp>MRI</scp>

用于磁共振成像的射频鸟笼线圈的仿真、设计及谐振模式分析的数值方法与软件工具

Abstract In MRI systems, cable‐free receive arrays would simplify setup while reducing the bulk and weight of coil arrays and improve patient comfort and throughput. Since battery power would limit scan time, wireless power transfer (WPT) is a viable option to continuously supply several watts of power to on‐coil electronics. To minimize added noise and decouple the wireless power system from MRI coils, restrictions are placed on the coil geometry of the wireless power system, which are shown to limit its efficiency. Continuous power harvesting can also cause a large increase in the background noise of the image due to diode rectifier up‐conversion of noise around the frequency of the transmitted power. However, by RF gating the transmitted power off during the MRI receive time while continuing to supply power from a storage capacitor, WPT is demonstrated to have minimal impact on image quality at received power levels up to 11 W. The integration of WPT with a 1.5T scanner is demonstrated.

Kelly Byron

Fraser Robb

Pascal Stang

Shreyas Vasanawala

John Pauly

Greig Scott

An RF‐gated wireless power transfer system for wireless MRI receive arrays

用于无线MRI接收阵列的RF门控无线电力传输系统

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.

Shyam S. Adhikari

Ulrike Wallrabe

Vlad Badilita

Jan G. Korvink

Capacitor re‐design overcomes the rotation rate limit of <scp>MACS</scp> resonators

电容器重新设计克服了<scp>MACS</scp>谐振器的转速限制

Abstract This article presents a dual‐tuned (DT) radiofrequency (RF) coil for signal acquisition of 2 nuclei, namely, hydrogen ( 1 H) and sodium ( 23 Na), 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 1 H and 23 Na coils being located on the outside and inside, respectively. The 1 H and 23 Na 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 1 H 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 1 H and 23 Na in the MRI system.

Sang‐Doc Han

Phil Heo

Han‐Joong Kim

Hyunwoo Song

Donghyuk Kim

Jeung‐Hoon Seo

Yeunchul Ryu

Young Noh

Kyoung‐Nam Kim

Double‐layered dual‐tuned RF coil using frequency‐selectable PIN‐diode control at 7‐T MRI

双层双调谐7T MRI射频线圈采用频率可选择的PIN二极管控制

This study investigates variations in radiofrequency- (RF-) induced energy absorption by orthopedic plates within the human body during 1.5T and 3T magnetic resonance imaging (MRI) scans, considering diverse postures. Using the poseable Duke model, we developed typical postures (O-posture, X-posture, Y-posture, and Z-posture) and placed anatomically correct representations of various orthopedic plates within these postures. Numerical simulations were conducted to evaluate electromagnetic fields and RF-induced energy absorption in these postures near orthopedic plates during MRI scans. Comparing RF-induced energy absorption (peak spatial averaged SAR over 1 g, pSAR1g) in postured models to the original posture reveals substantial variations. The pSAR1g differences for X-posture, Y-posture, and Z-posture reach 48%, 134%, and 32% at 1.5T, and 36%, 83%, and 101% at 3T, respectively. Changing posture can lead to higher or lower pSAR1g. These findings underscore the impact of patient posture on RF-induced energy absorption in orthopedic plates on the ulna bone. The study recommends considering representative body postures in future evaluations for MR conditional labeling of passive implants. Until then, maintaining a neutral posture during MR scans is advised to mitigate unforeseen RF-induced heating risks.

Xiaolin Yang

Jianfeng Zheng

Wolfgang Kainz

Xuemin Chen

Ji Chen

Impact of Patient Body Posture on RF-Induced Energy Absorption by Orthopedic Plates

患者体位对骨科钢板射频诱导能量吸收的影响

The utility of interleaved odd-number leg birdcage coils is demonstrated for decoupling in double- and triple-tuned multinuclear applications. The birdcage was designed to geometrically decouple from a planar double-tuned (1H-23Na) array and from a 31P saddle coil insert to create a triple-tuned configuration. Comparisons between an actively detuned coil and a purely geometrically decoupled architecture were used to demonstrate the capabilities of the design. In particular cases, the simplicity and adaptability of the interleaved nine-leg design for multinuclear nuclear magnetic resonance (NMR) offer a straightforward alternative to the often complex and lossy designs currently available for multinuclear birdcages and volume coils.

Joseph Busher

Edith Touchet-Valle

Chenhao Sun

Steven M. Wright

Mary P. McDougall

Odd-Leg Birdcages for Geometric Decoupling in Multinuclear Imaging and Spectroscopy

多核成像与光谱学中的几何解耦奇腿鸟笼线圈

To derive accurate diffusion metrics, both imaging and diffusion-sensitizing gradient pulses should be accounted for when calculating the diffusion-weighted b-matrix. However, it is complex to derive analytical solutions due to complicated interactions between gradient pulses, including orthogonal directions. This study proposes a general framework to calculate the b-matrix automatically (dubbed as Auto-b). Based on the divide-and-conquer approach, the b-matrix calculation is appropriately segmented, and the symbolic mathematical library is applied to handle integration operations for each interval. If the specifications of all gradient pulses are provided to Auto-b, an accurate b-matrix can be obtained. Three examples are explored to validate the accuracy of Auto-b and to detect b-value errors when using approximate calculations. (1) In the conventional spin-echo example, Auto-b exhibits high accuracy, as indicated by the maximum relative deviation of 1.68‰ between its calculated b-matrices and those obtained from analytical expressions. (2) Auto-b is applied to investigate the contribution of imaging gradients to the b-matrix in an optimized spin-echo echo planar imaging sequence at submillimeter resolution. Specifically, ignoring the contribution of imaging gradients results in a b-value error of 12.16 s/mm2 at the 0.8 × 0.8 × 0.8 mm3 resolution and 22.47 s/mm2 at the 0.6 × 0.6 × 0.8 mm3 resolution, respectively, when nominal b = 0. (3) Auto-b is also utilized to analyze the influence of approximate calculations in the spatiotemporally encoded sequence. The results showed that neglecting the contribution of phase-encoding blips causes large b-value errors up to 11.02 s/mm2. In addition, the rectangularization of trapezoidal waveforms led to a high relative b-value error of 39.91%. This study validates the high accuracy of Auto-b and underscores the importance of accurate b-value calculations in both submillimeter imaging and spatiotemporally encoded sequences. Attributed to its automation, accuracy, and broad applicability, Auto-b is helpful for developers of diffusion sequences.

Lisha Yuan

Dan Wu

Hongjian He

Jianhui Zhong

A General Framework for Automated Accurate Calculation of b-Matrix (Auto-b) in Diffusion MRI Pulse Sequences

扩散MRI脉冲序列中b矩阵自动化精确计算的通用框架（Auto-b）

As part of a homebuilt continuous wave electron paramagnetic resonance (EPR) spectrometer operating at 1.2 GHz, a magnet system for in vivo tooth dosimetry was developed. The magnet was designed by adopting NdFeB permanent magnet (PM) for the main magnetic field generation. For each pole of the magnet, 32 cylindrical PMs were arranged in 2 axially aligned ring arrays. The pole gap was 18 cm, which was wide enough for a human head breadth. The measured magnetic field was compared with the magnetic field distribution calculated in a finite element method (FEM) simulation. EPR spectra of intact human teeth irradiated 5 and 30 Gy were measured for the performance test with the developed magnet system and spectrometer. The measured mean magnetic flux density was estimated to be 44.45 mT with homogeneity of 1,600 ppm in a 2 cm diameter of the spherical volume of the XY plane, which was comparable to the FEM simulation results. The sweep coefficient of the magnetic field sweep coil was 0.35 mT per Ampere in both the measurement and FEM simulation. With ±9 A current, the sweep range was 5.7 mT, which was sufficiently wide to measure the tooth radiation-induced signal (RIS) and reference material. The peak-to-peak amplitude of the measured modulation field was 0.38 mT at the center of the magnet. With the developed magnet fully integrated into an EPR system, the EPR spectra of 5 and 30 Gy irradiated teeth were successfully acquired. The developed magnet system showed sufficiently acceptable performance in terms of magnetic flux density and homogeneity. The EPR spectrum of tooth RIS could be measured ex vivo. The RIS of 5 and 30 Gy irradiated teeth was clearly distinguishable from intact human teeth.

Kwon Choi

ChangUk Koo

JeongHun Oh

Jong In Park

Hiroshi Hirata

Sung-Joon Ye

Development of Electron Paramagnetic Resonance Magnet System for In Vivo Tooth Dosimetry

体内牙齿剂量测定的电子顺磁共振磁系统的发展

The analysis of human brain fMRI subjects can research neuro-related diseases and explore the related rules of human brain activity. In this paper, we proposed an algorithm framework to analyze the functional connectivity network of the whole brain and to distinguish Alzheimer’s disease (AD), mild cognitive impairment (MCI), and cognitively normal (CN). In other studies, they use algorithms to select features or extract abstract features, or even manually select features based on prior information. Then, a classifier is constructed to classify the selected features. We designed a concise algorithm framework that uses whole-brain functional connectivity for classification without feature selection. The algorithm framework is a two-hidden-layer neural network based on extreme learning machine (ELM), which overcomes the instability of classical ELM in high-dimensional data scenarios. We use this method to conduct experiments for AD, MCI, and CN data and perform 10-fold cross-validation. We found that it has several advantages: (1) the proposed method has excellent classification accuracy with high speed. The classification accuracy of AD vs. CN is 96.85%, and the accuracy of MCI vs. CN is 95.05%. Their AUC (area under curve) of ROC (receiver operating characteristic curve) reached 0.9891 and 0.9888, respectively. Their sensitivities are 97.1% and 94.7%, and specificities are 96.3% and 95.3%, respectively. (2) Compared with other studies, the proposed method is concise. Construction of a two-hidden-layer neural network is to learn features of the whole brain for the diagnosis of AD and MCI, without the feature screening. It avoids the negative effects of feature screening by algorithm or prior information. (3) The proposed method is suitable for small sample and high-dimensional data. It meets the requirements of medical image analysis. In other studies, its classifiers usually deal with several to dozens of feature dimensions. The proposed method deals with 4005 feature dimensions.

Jia Lu

Weiming Zeng

Lu Zhang

Yuhu Shi

Diagnosis of Alzheimer’s Disease with Extreme Learning Machine on Whole-Brain Functional Connectivity

基于全脑功能连接的阿尔茨海默病极端学习机诊断

Abbreviation	Concepts Magn Reson
Journal Impact	0.82
Quartiles(Global)	SPECTROSCOPY(Q4)

Publication Information	Publisher: Hindawi Publishing Corporation，Publishing cycle: Quarterly，Journal Type: journal，Open Access Journals: Yes
Basic data	Year of publication: 2002，Proportion of original research papers: 100.00%，Self Citation Rate:0.00%， Gold OA Rate: 100.00%
Journal Fees	$1550Details
Average review cycle	网友分享经验：>12周，或约稿
Average recruitment ratio	网友分享经验：容易

Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering

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