样式: 排序: IF: - GO 导出 标记为已读
-
Impact of Patient Body Posture on RF-Induced Energy Absorption by Orthopedic Plates Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2024-4-30 Xiaolin Yang, Jianfeng Zheng, Wolfgang Kainz, Xuemin Chen, Ji Chen
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
-
Odd-Leg Birdcages for Geometric Decoupling in Multinuclear Imaging and Spectroscopy Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2023-4-10 Joseph Busher, Edith Touchet-Valle, Chenhao Sun, Steven M. Wright, Mary P. McDougall
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
-
A General Framework for Automated Accurate Calculation of b-Matrix (Auto-b) in Diffusion MRI Pulse Sequences Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2023-4-5 Lisha Yuan, Dan Wu, Hongjian He, Jianhui Zhong
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
-
Development of Electron Paramagnetic Resonance Magnet System for In Vivo Tooth Dosimetry Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2022-05-27 Kwon Choi, ChangUk Koo, JeongHun Oh, Jong In Park, Hiroshi Hirata, Sung-Joon Ye
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
-
Diagnosis of Alzheimer’s Disease with Extreme Learning Machine on Whole-Brain Functional Connectivity Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2022-05-19 Jia Lu, Weiming Zeng, Lu Zhang, Yuhu Shi
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
-
Study of Correlation between MRI Morphology of Primary Tumor and Extramural Vascular Invasion in Rectal Cancer Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2022-03-10 Baohua Lv, Kai Shang, Ke Wu, Yuanzhong Xie, Zhenghan Yang, Zhenchang Wang, Erhu Jin
Introduction. In clinical settings, nodular projection (NP) and cord sign (CS) at the tumor edge and irregular nodules (IN) in the mesorectum often appeared together with extramural vascular invasion (EMVI). We aim to evaluate the diagnostic efficiency of the MRI morphology of primary tumor in predicting EMVI in patients with rectal cancer (RC). Methods. This retrospective study included 156 patients
-
Study of Endogenous Paramagnetic Centers in Biological Systems from Different Areas Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2021-12-31 Aygun Nasibova, Rovshan Khalilov, Huseyn Abiyev, Taras Kavetskyy, Boris Trubitsin, Cumali Keskin, Elham Ahmadian, Aziz Eftekhari
Plant leaves (Eldar pine (Pinus eldarica M.), fig (Ficus carica L.), and olive (Olea europaea L.)), collected in territories with different ecological conditions, of the Absheron Peninsula (Azerbaijan Republic) were studied by electron paramagnetic resonance spectroscopy (EPR). The generation of nanophase iron oxide magnetic particles in biological systems under the influence of stress factors was
-
Electromagnetic Simulation of Signal Distribution of Various RF Endoluminal Loop Geometries with Coil Orientation: Towards a Reconfigurable Design Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2021-07-28 Hamza Raki, Kevin Tse Ve Koon, Henri Souchay, Fraser Robb, Olivier Beuf
With the objective of improving MR endoluminal imaging of the colonic wall, electromagnetic simulations of different configurations of single-layer and double-layer, and double-turn endoluminal coil geometries were run. Indeed, during colon navigation, variations in coil orientation with respect to B0 are bound to occur, leading to impaired image acquisition due to a loss of signal uniformity. In this
-
Novel Method to Improve the Uniformity of 7T Body MR Images Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2021-05-06 Bu S. Park, Sunder S. Rajan
When using ultrahigh-field MR systems (7T), the variations in the RF magnetic field can lead to significant loss in image uniformity. To optimize the overall MR image quality, the image region is divided into multiple smaller regions of interest (the ROIs), which can be independently optimized using transmit array optimization techniques including RF shimming, to improve RF magnetic fields and image
-
Quasistatic Solutions versus Full-Wave Solutions of Single-Channel Circular RF Receive Coils on Phantoms of Varying Conductivities at 3 Tesla Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2021-04-29 Michael J. Beck, Dennis L. Parker, J. Rock Hadley
Purpose. Although full-wave simulations could be used to aid in RF coil design, the algorithms may be too slow for an iterative optimization algorithm. If quasistatic simulations are accurate within the design tolerance, then their use could reduce simulation time by orders of magnitude compared to full-wave simulations. This paper examines the accuracy of quasistatic and full-wave simulations at 3
-
Capacitive versus Overlap Decoupling of Adjacent Radio Frequency Phased Array Coil Elements: An Imaging Robustness Comparison When Sample Load Varies for 3 Tesla MRI Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2020-12-15 Michael J. Beck, Dennis L. Parker, J. Rock Hadley
Phased array (PA) receive coils are built such that coil elements approximate independent antenna behavior. One method of achieving this goal is to use an available decoupling method to decouple adjacent coil elements. The purpose of this work was to compare the relative performance of two decoupling methods as a function of variation in sample load. Two PA receive coils with 5 channels (5-ch) each
-
SQUID-Based Magnetic Resonance Imaging at Ultra-Low Field Using the Backprojection Method Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2020-10-22 Qingqian Guo, Changyu Ma, Xin Zhang, Yajie Xu, Meisheng Fan, Peng Yu, Tao Hu, Yan Chang, Xiaodong Yang
Ultra-low field magnetic resonance imaging (ULF MRI) is an effective imaging technique that applies the ultrasensitive detector of superconducting quantum interference device (SQUID) sensor to detect the MR signal at a microtesla field range. In this work, we designed and developed a SQUID-based ULF MRI system with a frequency-adjustable measurement field, the performance of which was characterized
-
The “Loopole” Antenna: A Hybrid Coil Combining Loop and Electric Dipole Properties for Ultra-High-Field MRI Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2020-09-07 Karthik Lakshmanan, Martijn Cloos, Ryan Brown, Riccardo Lattanzi, Daniel K. Sodickson, Graham C. Wiggins
Purpose. To revisit the “loopole,” an unusual coil topology whose unbalanced current distribution captures both loop and electric dipole properties, which can be advantageous in ultra-high-field MRI. Methods. Loopole coils were built by deliberately breaking the capacitor symmetry of traditional loop coils. The corresponding current distribution, transmit efficiency, and signal-to-noise ratio (SNR)
-
Traveling-wave meets standing-wave: A simulation study using pair-of-transverse-dipole-ring (PTDR) coils for adjustable longitudinal coverage in ultra-high field MRI. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2019-08-31 Xinqiang Yan,John C Gore,William A Grissom
1.At ultrahigh fields (B 0 ≥7T), it is challenging to cover a large field of view using single-row conventional RF coils (standing wave resonators) due to the limited physical dimensions. In contrast, traveling wave approaches can excite large fields of view even using a relatively simple hardware setup, but suffer from poor efficiency and high local specific absorption rate in non-imaged regions.
-
Tabletop 700 MHz electron paramagnetic resonance imaging spectrometer. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-09-14 Laura A Buchanan,George A Rinard,Richard W Quine,Sandra S Eaton,Gareth R Eaton
Low frequency electron paramagnetic resonance imaging is a powerful tool to non-invasively measure the physiological status of tumors. Here, we report on the design and functionality of a rapid scan and pulse table-top imaging spectrometer based around an arbitrary waveform generator and 25mm cross-loop resonator operating at 700 MHz. Two and four-dimensional rapid scan spectral-spatial images are
-
Comparision of new element designs for combined RF-Shim arrays at 7 T. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-06-07 Simone A Winkler,Paul A Warr,Jason P Stockmann,Azma Mareyam,Boris Keil,Ronald D Watkins,Lawrence L Wald,Brian K Rutt
PURPOSE To identify novel concepts for RF-shim loop architectures suitable for 7T made of two concentric conducting loops fulfilling RF and DC functions, respectively, and to determine their relative SNR performance. The goal is to minimize interference between the two systems while making efficient use of the space closest to the body. THEORY We show by means of theoretical derivation of the frequency
-
250 MHz passive Q-modulator for reflection resonators. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-03-27 Epel Boris,Subramanian V Sundramoorthy,Howard J Halpern
A simple scheme for dynamically switching the quality factor, Q, of a Loop-Gap Resonator (LGR); working at 250 MHz is presented. The addition of this Q-modulator resulted in 30% improvement in Electron Paramagnetic Resonance imager signal-to-noise ratio. During pulse excitation, this scheme lowered the Q, while higher Q was obtained during signal detection. These conditions favored the image acquisition
-
A comparison of Lenz lenses and LC resonators for NMR signal enhancement. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-11-21 Mazin Jouda,Robert Kamberger,Jochen Leupold,Nils Spengler,Jürgen Hennig,Oliver Gruschke,Jan G Korvink
High signal-to-noise ratio (SNR) of the NMR signal has always been a key target that drives massive research effort in many fields. Among several parameters, a high filling factor of the MR coil has proven to boost the SNR. In case of small-volume samples, a high filling factor and thus a high SNR can be achieved through miniaturizing the MR coil. However, under certain circumstances, this can be impractical
-
An RF-gated wireless power transfer system for wireless MRI receive arrays. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-10-01 Kelly Byron,Fraser Robb,Pascal Stang,Shreyas Vasanawala,John Pauly,Greig Scott
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
-
Trap Design and Construction for High-Power Multinuclear Magnetic Resonance Experiments. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-05-23 Joseph V Rispoli,Ivan E Dimitrov,Sergey Cheshkov,Craig Malloy,Steven M Wright,Mary P McDougall
Performing multinuclear experiments requires one or more radiofrequency (RF) coils operating at both the proton and second-nucleus frequencies; however, inductive coupling between coils must be mitigated to retain proton sensitivity and coil tuning stability. The inclusion of trap circuits simplifies placement of multinuclear RF coils while maintaining inter-element isolation. Of the commonly investigated
-
UHF EPR spectrometer operating at frequencies between 400 MHz and 1 GHz. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-02-14 Richard W Quine,George A Rinard,Yilin Shi,Laura Buchanan,Joshua R Biller,Sandra S Eaton,Gareth R Eaton
A spectrometer was designed and constructed to facilitate measurements of T1, T2, spin echo signal-to-noise, and resonator quality factor, Q, between about 400 and 1000 MHz. Pulse patterns are generated at 250 MHz and mixed with the output from a second source to perform excitation and detection. A cross-loop resonator was constructed in which the same sample could be measured in the same resonator
-
Synchronous Radial 1H and 23Na Dual-Nuclear MRI on a Clinical MRI System, Equipped With a Broadband Transmit Channel. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-02-03 Joshua D Kaggie,Nabraj Sapkota,Bijaya Thapa,Kyle Jeong,Xianfeng Shi,Glen Morrell,Neal K Bangerter,Eun-Kee Jeong
The purpose of this work was to synchronously acquire proton (1H) and sodium (23Na) image data on a 3T clinical MRI system within the same sequence, without internal modification of the clinical hardware, and to demonstrate synchronous acquisition with 1H/23Na-GRE imaging with Cartesian and radial k-space sampling. Synchronous dual-nuclear imaging was implemented by: mixing down the 1H signal so that
-
Dependence of B1+ and B1- Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2016-11-01 Manushka V Vaidya,Christopher M Collins,Daniel K Sodickson,Ryan Brown,Graham C Wiggins,Riccardo Lattanzi
In high field MRI, the spatial distribution of the radiofrequency magnetic ( B1) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green's functions, or
-
Effects of Anatomical Differences on Electromagnetic Fields, SAR, and Temperature Change. Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2016-05-03 Leeor Alon,Cem Murat Deniz,Giuseppe Carluccio,Ryan Brown,Daniel K Sodickson,Christopher M Collins
Electromagnetic field simulations are increasingly used to assure RF safety of patients during MRI exams. In practice, however, tissue property distribution of the patient being imaged is not known, but may be represented with a pre-existing model. Repeatedly, agreement in transmit magnetic (B1+) field distributions between two geometries has been used to suggest agreement in heating distributions
-
Thermal Effects Associated with RF Exposures in Diagnostic MRI: Overview of Existing and Emerging Concepts of Protection Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2019-06-17 Johan S. van den Brink
Apart from magnetic attraction risks, the primary biophysical concern associated with MRI is radiofrequency heating of the human body and associated discomfort, health deterioration, or potential burns. This paper reviews experimental data and numerical modeling of systemic (core and brain) temperature and local thermal effects associated with diagnostic MRI exposures at 1.5T (64 MHz) and 3.0T (128
-
Inherent Geometry Correction for Diffusion EPI Using the Reference Echoes as Navigators Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2019-05-26 Johan S. van den Brink, Jos J. Koonen
Diffusion-weighted EPI has become an indispensable tool in body MRI. Geometric distortions due to field inhomogeneities are more prominent at large field–of–view and require correction for comparison with T2W TSE. Several known correction methods require acquisition of additional lengthy scans, which are difficult to apply in body imaging. We implement and evaluate a geometry correction method based
-
Coupled actuators with a mechanically synchronized phase during MR elastography: A phantom feasibility study Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-10-01 Wiebke Neumann,Vanessa R. Lehnart,Yannik Vetter,Andreas Bichert,Lothar R. Schad,Frank G. Zöllner
-
Multi‐channel helical‐antenna inner‐volume RF coils for ultra‐high field MR scanners Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-10-01 Pranav S. Athalye,Milan M. Ilić,Pierre‐Francois Moortele,Andrew J. M. Kiruluta,Branislav M. Notaroš
Ultrahigh field (UHF), high field, and low field magnetic resonance (MR) scanners are usually referring to the main polarizing static magnetic field values of B0 ≥ 7 T (ie, Larmor frequency f0 ≥ 300 MHz), 3 T ≤ B0 < 7 T, and B0 < 3 T, respectively. Whereas most clinical scanners operate at either 1.5 T or 3 T, cuttingedge research centers in neuroscience and/or MR imaging (MRI) tend to favor UHFMR
-
OpenForce MR: A low-cost open-source MR-compatible force sensor Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-10-01 Francesco Santini,Oliver Bieri,Xeni Deligianni
-
Depiction of the perfusion components’ volume fraction distribution in generalized intravoxel incoherent motion by using Gaussian mixture model Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-07-01 Shunli Wang,Wanyu Liu,Zixiang Kuai,Yuemin Zhu
-
A low-cost multi-channel software-defined radio-based NMR spectrometer and ultra-affordable digital pulse programmer Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-07-01 Carl A. Michal
-
General purpose electronics for real-time processing and encoding of non-MR data in MR acquisitions Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-04-01 Jan Ole Pedersen,Christian G. Hanson,Rong Xue,Lars G. Hanson
-
Reducing signal-to-noise ratio degradation due to coil coupling in a receiver array for 35 Cl MRI at 9.4 T: A comparison of matching and decoupling strategies Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-04-01 Matthias Malzacher,Ruomin Hu,Jorge Chacon-Caldera,Lothar R. Schad
-
Design of a high power PIN-diode controlled switchable RF transmit array for TRASE RF imaging Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-02-01 Eric Der,Vyacheslav Volotovskyy,Hongwei Sun,Boguslaw Tomanek,Jonathan C. Sharp
-
Slotted‐waveguide array radio frequency coil for ultra‐high‐field magnetic resonance imaging Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-02-01 Milan M. Ilić,Branislav M. Notaroš
Funding information National Science Foundation, Grant/Award Number: ECCS-1307863; Serbian Ministry of Education, Science, and Technological Development, Grant/Award Number: TR-32005 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
-
High spatial resolution magnetic resonance imaging of insects covered with a hard exoskeleton Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2018-02-01 Youngseob Seo
-
Simulation, design, and test of an elliptical surface coil for magnetic resonance imaging and spectroscopy Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-10-01 Giulio Giovannetti,Alessandra Flori,Daniele De Marchi,Giuseppe Matarazzo,Francesca Frijia,Silvia Burchielli,Domenico Montanaro,Giovanni Donato Aquaro,Luca Menichetti
-
Double-layered dual-tuned RF coil using frequency-selectable PIN-diode control at 7-T MRI Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-10-01 Sang-Doc Han,Phil Heo,Han-Joong Kim,Hyunwoo Song,Donghyuk Kim,Jeung-Hoon Seo,Yeunchul Ryu,Young Noh,Kyoung-Nam Kim
-
Capacitor re-design overcomes the rotation rate limit of MACS resonators Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-10-01 Shyam S. Adhikari,Ulrike Wallrabe,Vlad Badilita,Jan G. Korvink
-
Estimation of losses in strip and circular wire conductors of radiofrequency planar surface coil by using the finite element method Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-07-01 Giulio Giovannetti,Nunzia Fontana,Agostino Monorchio,Michela Tosetti,Gianluigi Tiberi
-
Another alternate integrated circuit approach to modulation of radiofrequency transmission signals in magnetic resonance imaging Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2017-07-01 Benson Yang,Fred Tam,Clare McElcheran,Simon J. Graham
-
Pole plate effected gradient coils design in permanent magnet MRI system Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2016-10-01 Yajie Xu,Hector Sanchez Lopez,Qiaoyan Chen,Xiaodong Yang
-
Digital filters for low-field NMR Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2016-10-01 Andrea Valori,Jonathan Mitchell,Edmund J. Fordham
-
A quadrature volume RF coil for vertical B0field open MRI systems Concepts Magn. Reson. Part B Magn. Reson. Eng. (IF 0.9) Pub Date : 2016-07-01 Boguslaw Tomanek,Vyacheslav Volotovskyy,Randy Tyson,Donghui Yin,Jonathan Sharp,Barbara Blasiak