Volume Coil Research Articles

A novel multifrequency-tuned transceiver array for human-brain 31P-MRSI at 7 T.

Phosphorus-31 (31P) MR spectroscopy imaging (MRSI) at 7 T is a powerful tool for investigating high-energy phosphate metabolism in human brains with significantly improved signal-to-noise ratio (SNR) and spectral resolution. However, this imaging technique requires dual-frequency radiofrequency coil for performing brain anatomical imaging and B0 shimming at proton (1H) operation frequency, and 31P MRSI at lower operation frequency. Herein, we introduce a novel 31P-1H dual-frequency radiofrequency coil design using a double-tuned and double-matched (DODO) coil that does not require complex circuitry or two coil layers and exhibits similar imaging performance as to single-frequency control coils for both 31P and 1H imaging operations. We constructed an eight-element 31P-1H dual-frequency DODO transceiver array and compared its performance with a quadrature-driven dual-tuned eight-element 31P and eight-element 1H transverse electromagnetic volume coil for both phantom and in vivo human-brain 31P-MRSI studies at 7 T. The DODO transceiver array achieved high spatiotemporal resolution 31P MRSI with 2.5-cc nominal voxel size and 22-min scan time covering the entire human brain, showing excellent SNR for mapping cerebral phosphorous metabolites such as phosphocreatine, adenosine triphosphate, and other low-concentration metabolites. Compared with the transverse electromagnetic volume coil, the DODO array demonstrated large improvements in 31P-MRSI SNR in both phantom and human brain studies, with over 5-fold SNR gain in peripheral regions and over 2-fold SNR gain in central brain regions. This simple and cost-effective array design and excellent performance can greatly benefit human-brain 31P-MRSI applications at 7 T.

Adaptable, wearable, and stretchable coils: A review.

Over the last four decades, there have been various evolutions in the design and development of coils, from volume coils to the recent introduction of wireless receive arrays. A recent aim has been to develop coils that can closely conform to the anatomy of interest to increase the acquired signal. This goal has given rise to designs ranging from adaptable transmit coils to on-body stretchable receive arrays made using fabric or elastomer substrates. This review covers the design, fabrication details, experimental setup, and MRI results of adaptable, wearable, and stretchable MRI coils. The active and passive automatic tuning and matching strategies are examined with respect to mitigating signal-to-noise ratio reduction when the coil form is altered. A brief discussion of wireless MRI coils, which provide a solution to overcome the cabling issues associated with MRI coil development, is also included. The adaptable, wearable, and stretchable coils and various coil tuning techniques represent innovative radiofrequency coil solutions that pave the way for next-generation MRI hardware development.

Magnetic field probe-based co-simulation method for irregular volume-type inductively coupled wireless MRI radiofrequency coils.

Inductively coupled wireless coils are increasingly used in MRI due to their cost-effectiveness and simplicity, eliminating the need for expensive components like preamplifiers, baluns, coil plugs, and coil ID circuits. Existing tools for predicting component values and electromagnetic (EM) fields are primarily designed for cylindrical volume coils, making them inadequate for irregular volume-type wireless coils. The aim of this study is to introduce and validate a novel magnetic (H-) field probe-based co-simulation method to accurately predict capacitance values and EM fields for irregular volume-type wireless coils, thereby addressing the limitations of current prediction tools. The proposed method involves several key steps: modeling the coil in EM simulation software, replacing lumped components with 50-Ω ports, placing well-decoupled double pick-up sniffer probes within the wireless coil, conducting full-wave EM simulations, and exporting the S-parameter matrix to an RF circuit simulation tool for optimization. The RF circuit simulation optimizes component values by maximizing the average magnitude of the root square of Sxys (mean_√Sxy) of double probes and minimizing the normalized standard deviation of √Sxy (normStd_√Sxy). The optimized capacitance values are validated through re-performing EM simulations, and hardware prototypes are fabricated and tested in MRI experiments. The method was validated using bottle-shaped and dome-shaped Litzcage coils designed for 1.5T MRI. Consistent resonant peaks and magnetic field distributions were observed across different coil designs. The optimized capacitance values obtained from circuit-level simulations were confirmed through EM simulations. Significant SNR enhancements were observed in MRI experiments, with the wireless hand and wrist/head coil showing an overall SNR enhancement of 12.8/3.4-fold in EM simulation and 13.4/3.8-fold in MRI experiments, compared to the body coil alone. The H-field probe-based co-simulation method provides an efficient and accurate solution for designing and optimizing irregular wireless RF coils in MRI. By integrating EM simulation, H-field probes, and RF circuit optimization, this method reduces the need for extensive full-wave EM simulations and accurately predicts capacitance values and EM fields. The validation using irregular Litzcage coils demonstrated the method's efficacy, contributing to improved imaging quality in MRI applications. This approach offers a valuable tool for coil developers and researchers, facilitating the development of high-quality irregular wireless coils for enhanced MRI performance.

A multimodal axial array resonator and its application in radiofrequency (RF) volume coil designs for low-field open magnetic resonance imaging (MRI).

Low-field open magnetic resonance imaging (MRI) systems, typically operating at magnetic field strengths below 1 Tesla, has greatly expanded the accessibility of MRI technology to meet a wide range of patient needs. However, the inherent challenges of low-field MRI, such as limited signal-to-noise ratios and limited availability of dedicated radiofrequency (RF) coils, have prompted the need for innovative coil designs that can improve imaging quality and diagnostic capabilities. In this work, we introduce a multimodal axial array resonator and its implementation in a volume coil, or referred to as a coupled stack-up volume coil, to address these challenges in low-field open MRI. A prototype coupled stack-up volume coil was designed with optimized coil spacing to improve B1 field homogeneity. Finite difference time-domain (FDTD) simulations were conducted to evaluate the coil's performance, including B1 field efficiency and specific absorption rate (SAR). Bench tests were performed to validate the simulated results using oil phantoms. Comparisons were made with a solenoid coil, a birdcage coil, and an equal gap coupled coil throughout the study. Numeral electromagnetic studies demonstrate the superior performance of the proposed coupled stack-up volume coil, achieving 47.7% higher transmit/receive efficiency and 68% more uniform magnetic field distribution compared to conventional birdcage coils. The results of the bench tests show that the achieved B1 field efficiency of the coupled stack-up volume coil is 11.48 , representing a 57.3% improvement in comparison to that of a conventional birdcage coil. A multimodal axial array resonator technique or coupled stack-up technique is successfully developed for the design of low field MR RF volume coils. The proposed coupled stack-up volume coil outperforms the conventional volume coils in terms of B1 efficiency, imaging coverage, and low-frequency operation capability. This design provides a robust and simple solution to the low-field MR RF coil design.

TMET-20. A METABOLIC BIOMARKER IN GLIOBLASTOMA: A PROMISING APPLICATION OF CO-POLARIZED [1-13C]PYRUVATE AND [1-13C]DEHYDROASCORBATE

Abstract BACKGROUND Noninvasive biomarkers for treatment response in glioblastoma are needed to improve patient outcomes. Our understanding of redox biology in treatment resistance is rapidly evolving, and interrogation of tumor metabolism represents an ideal opportunity to meet this need. In this study, the utility of co-hyperpolarized [1-13C]pyruvate and [1-13C]dehydroascorbate (HP PA/DHA) to simultaneously evaluate brain tumor metabolism and oxidative stress in orthotopically implanted mice is investigated. METHODS To characterize HP PA/DHA, mice were treated with 0-4mM diethyl maleate and 1D slab dynamic acquisitions were performed over the mouse brain. As an initial evaluation of the utility of HP DHA/PA in brain tumors, athymic nude mice (n=8) underwent orthotopic U87 glioblastoma implantation. After treatment with 8Gy in one fraction, mice were injected with HP DHA/PA dissolved in D2O. T2-weighted and 13C Chemical Shift Imaging sequences were obtained on a 3T MRI using a quadrature double-tuned 1H/13C volume coil. RESULTS HP DHA/PA detected differential lactate and vitamin C generation over the mouse brain. Treatment with diethyl maleate, which depletes the cofactor glutathione, diminished fractional vitamin C generation (0.1 vs 0.03, p=0.0009). Elevation in tumor lactate generation was seen in untreated (125.1±17.6µM, p=0.005) and radiated mice (149.4±32.6µM, p=0.01). Treatment with radiation generated higher vitamin C concentrations in tumors relative to contralateral brain (46.8±4.8µM, p=0.002). Radiated tumors were distinguished by higher ratio of lactate to vitamin C compared to untreated tumor controls (3.7 vs 2.5, p=0.07), and the same relationship was preserved between treated and untreated non-tumor brain. CONCLUSION The ratio of vitamin C/lactate detects the metabolic effects of radiation in brain tumors, inspiring its’ potential as a biomarker for treatment response. To further characterize these findings, examination of survival and modulation of radiosensitivity are ongoing.

Sodium MRI of the skin using a surface coil to investigate and reduce signal loss and bias.

The purpose was to improve sodium MRI of human skin using a surface coil and twisted projection imaging with smaller, reshaped voxels. Calf skin sodium images were acquired in 14 healthy adults using twisted projection imaging with short TE ˜ 0.1 ms, first with a volume coil and voxels (1.5 × 1.5 × 15 = 34 mm3) reflecting the widely adopted skin imaging protocol (VolPencil). A 5-cm-diameter surface coil then facilitated 5× smaller (0.8 × 0.8 × 10 = 6.4 mm3) voxels with similar signal to noise ratio (SNR) in the same 12-min scan time (SurfPencil). "Pencil-shaped" voxels were then replaced with "pancake-shaped" (0.4 × 4 × 4 = 6.4 mm3) voxels, matching the anatomy of pressed flat skin (SurfPancake). Surface coil B1 was investigated with the novel use of spin-3/2 simulation. Protocol modifications were tested for signal increase (reduced loss) and correlation with (bias by) skin thickness. Higher resolution SurfPencil yielded 44% ± 16% greater skin sodium image intensity than VolPencil, whereas SurfPancake yielded an additional 20% ± 9% (p < 1e-8), reflecting reduced signal loss. Over the 1.0 to 1.8 mm skin thickness across participants, sodium intensity significantly increased 56% ± 19% and 44% ± 12% for VolPencil and SurfPencil, respectively (p < 0.003), but not for SurfPancake, reflecting reduced bias. Imaging yielded skin sodium concentration of 34 ± 5 mM for SurfPancake. This is greater than the ˜20 mM measures from the widely adopted protocol, but simulation (matching experimental trends) identified a remaining 64% signal loss; compensation yields 95 ± 15 mM. Surface coil imaging and "pancake" voxel reshaping increased skin sodium intensity and reduced bias by skin thickness. Simulated loss compensation yields skin sodium concentration similar to that measured by atomic absorption spectroscopy.

Exploring Metabolic Aberrations after Intracerebral Hemorrhage In Vivo with Deuterium Metabolic Spectroscopy Imaging.

Aberrations in metabolism after intracerebral hemorrhage (ICH), particularly lactate metabolism, play a crucial role in the pathophysiology and patient outcome. To date, the evaluation of metabolism relies heavily on invasive methods such as microdialysis, restricting a comprehensive understanding of the metabolic mechanisms associated with ICH. This study proposes a noninvasive metabolic imaging method based on 2H magnetic resonance spectroscopy and imaging (2H-MRS/MRSI) to detect metabolic changes after ICH in vivo. To overcome the low-sensitivity limitation of 2H, we designed a new 1H-2H double-resonance coil with 2H-channel active detuning and proposed chemical shift imaging based on the balanced steady-state free precession method (CSI-bSSFP). Compared with the volume coil, the signal-to-noise ratio (SNR) of the new coil was increased by 4.5 times. In addition, the SNR of CSI-bSSFP was 1.5 times higher than that of conventional CSI. These two technologies were applied to measure lactate metabolic flux at different phases of ICH. The results show a higher lactate concentration in ICH rats than in control rats, which is in line with the increased expression of lactate dehydrogenase measured via immunohistochemistry staining (AUCLac_area/Glc_area: control, 0.08 ± 0.02 vs ICH-3d, 0.39 ± 0.05 vs ICH-7d, 0.18 ± 0.02, P < 0.01; H-score: control, 126.4 ± 5.03 vs ICH-3d, 168.4 ± 5.71 vs ICH-7d,133.6 ± 7.70, P < 0.05). A higher lactate signal also appeared near the ICH region than in normal brain tissue. In conclusion, 2H-MRS/MRSI shows potential as a useful method for in vivo metabolic imaging and noninvasive assessment of ICH.

Research on FPC coils with limited turns in planar electromagnetic tomography

Electromagnetic tomography (EMT) is a non-destructive testing method that reconstructs electrical parameter distribution based on boundary electromagnetic measurement data along electromagnetic rotation projection. The coil is a critical component of the EMT system, used to excite and detect changing magnetic fields. The performance of excitation-detection with specific coils directly affects the quality of the reconstructed image. The traditional EMT coils are wound coils. The excitation-detection performance of the coils is enhanced by increasing the number of turns to obtain better imaging quality. A larger coil volume has better sensitivity, but it cannot meet the space constraints of many applications. To solve this problem, this paper proposes a method using extremely thin FPC coil arrays as EMT sensors. To verify the feasibility of FPC coil imaging with a limited number of turns, firstly, this article analyses the excitation-detection capabilities of FPC coil with 1 to 12 turns through a combination of simulation and experiment. Secondly, the impact of excitation-detection capability on the EMT sensitivity matrix was studied. Finally, a 4×4 8-Turns FPC coil sensor was designed for image reconstruction experiments. The experimental results show that FPC coils with limited turns can be used for image reconstruction and to solve the problem of planar nondestructive testing in a small space.

RF coil that minimizes electronic components while enhancing performance for rodent MRI at 7 Tesla.

This study introduces a novel volume coil design that features two slotted end-plates connected by six rungs, resembling the traditional birdcage coil. The end rings are equipped with six evenly distributed circular slots, inspired by Mansfield's cavity resonator theory, which suggests that circular slots can generate a baseline resonant frequency. One notable advantage of this proposed coil design is its reduced reliance on electronic components compared to other volume coils, making it more efficient. Additionally, the dimensions of the coil can be theoretically computed in advance, enhancing its practicality. To evaluate the performance and safety of the coil, electromagnetic field and specific absorption rate simulations were simulated using a cylindrical saline phantom and the finite element method. Furthermore, a transceiver coil prototype optimized for 7 Tesla and driven in quadrature was constructed, enabling whole-body imaging of rats. The resonant frequency of the coil prototype obtained through experimental measurements closely matched the theoretical frequency derived from Mansfield's theory. To validate the coil design, phantom images were acquired to demonstrate its viability and assess its performance. These images also served to validate the magnetic field simulations. The experimental results aligned well with the simulation findings, confirming the reliability of the proposed coil design. Importantly, the prototype coil showcased significant improvements over a similarly-sized birdcage coil, indicating its potential for enhanced performance. The noise figure was lower in the prototype versus the birdcage coil (NFbirdcage-NFslotcage= 0.7). Phantom image data were also used to compute the image SNR, giving SNRslotcage/SNRbirdcage= 34.36/24.34. By proving the feasibility of the coil design through successful rat whole-body imaging, the study provides evidence supporting its potential as a viable option for high-field MRI applications on rodents.

Sensitive Determination of Hydrochlorothiazide Drug in the Various Samples Via Developed Method of CFIA System

تحديد عقار هايدروكلوروثيازايد في العينات الصيدلانية والبايولوجية الادرار باستخدام تقنية جديدة لتحليل الحقن الجرياني المستمر وهي سريعة , بسيطة ,اقتصادية وحساسة. المعقد المتكون بواسطة تفاعل هيدروكلوروثيازايد مع اورثوفانيلين داي امين مع فيروسيانيد البوتاسيوم لانتاج ناتج ملون برتقالي عند طول موجي 480 نانومتر كان الاساس للطريقة المطورة . العوامل الكيميائية و الفيزيائية الاخرى التي لها تؤثر على استقرارية وتطور الناتج الملون المستخدم في هذه الطريقة المطورة تضمنت حجم العينة,معدل التدفق,تركيز الكاشف وملف التفاعل ,خطية الطريقة المقترحة كانت 5-150 مايكروغرام .مل-1 ومعامل الارتباط كان0.9988 و كانت قيم النسبة المئوية للأسترداد والخطاء النسبي٪100.88, 0.88 على التوالي .قيم حد الكشف والحد الكمي 2.622,7.97 . نمذجة العينة 90 نموذج لكل ساعة تم استخدام النهج الجديد بشكل فعال لتحديد الهايدروكلورثيازايد في العينات النقية ,البايولوجية وا لصيدلانية

Coupled stack-up volume RF coils for low-field open MR imaging.

Low-field open magnetic resonance imaging (MRI) systems, typically operating at magnetic field strengths below 1 Tesla, has greatly expanded the accessibility of MRI technology to meet a wide range of patient needs. However, the inherent challenges of low-field MRI, such as limited signal-to-noise ratios and limited availability of dedicated radiofrequency (RF) coils, have prompted the need for innovative coil designs that can improve imaging quality and diagnostic capabilities. In response to these challenges, we introduce the coupled stack-up volume coil, a novel RF coil design that addresses the shortcomings of conventional birdcage in the context of low-field open MRI. The proposed coupled stack-up volume coil design utilizes a unique architecture that optimizes both transmit/receive efficiency and RF field homogeneity and offers the advantage of a simple design and construction, making it a practical and feasible solution for low-field MRI applications. This paper presents a comprehensive exploration of the theoretical framework, design considerations, and experimental validation of this innovative coil design. We demonstrate the superior performance of the coupled stack-up volume coil in achieving 47.7% higher transmit/receive efficiency and 68% more uniform magnetic field distribution compared to traditional birdcage coils in electromagnetic simulations. Bench tests results show that the B1 field efficiency of coupled stack-up volume coil is 57.3% higher compared with that of conventional birdcage coil. The proposed coupled stack-up volume coil outperforms the conventional birdcage coil in terms of B1 efficiency, imaging coverage, and low-frequency operation capability. This design provides a robust and simple solution to low-field MR RF coil design.

Multimodal surface coils for low field MR imaging

Low field MRI is safer and more cost effective than the high field MRI. One of the inherent problems of low field MRI is its low signal-to-noise ratio or sensitivity. In this work, we introduce a multimodal surface coil technique for signal excitation and reception to improve the RF magnetic field (B1) efficiency and potentially improve MR sensitivity. The proposed multimodal surface coil consists of multiple identical resonators that are electromagnetically coupled to form a multimodal resonator. The field distribution of its lowest frequency mode is suitable for MR imaging applications. The prototype multimodal surface coils are built, and the performance is investigated and validated through numerical simulation, standard RF measurements and tests, and comparison with the conventional surface coil at low fields. Our results show that the B1 efficiency of the multimodal surface coil outperforms that of the conventional surface coil which is known to offer the highest B1 efficiency among all coil categories, i.e., volume coil, half-volume coil and surface coil. In addition, in low-field MRI, the required low-frequency coils often use large value capacitance to achieve the low resonant frequency which makes frequency tuning difficult. The proposed multimodal surface coil can be conveniently tuned to the required low frequency for low-field MRI with significantly reduced capacitance value, demonstrating excellent low-frequency operation capability over the conventional surface coil.

Enhancing a loosely coupled inductive wireless power transfer system for LED-driven slurry photocatalytic reactors

To improve the irradiation profile in a conventional photocatalytic reactor, an LED-based light emitter energized by the inductive power transmission (IPT) method has been proposed recently. However, technical challenges such as low coupling due to the asymmetrical wireless coupler, dynamic impedance due to multiple receivers and changing magnetic properties in the transmitter core, and ease in upscaling remain to be addressed. This work proposes an IPT system for an LED-based photocatalytic reactor using a toroidal transformer to match the impedance between a modified Helmholtz transmitter coil and a class-E inverter. A finite element magnetic field simulation and analytical calculation of the induced voltage are used to assess the field uniformity inside the coil. The mutual inductance at selected locations within the coil volume and the power transfer efficiency (PTE) are evaluated. The proposed system requires less than 2 W to generate a uniform magnetic field inside a 10.6 L acrylic cylinder with an induced voltage of 13.9 ± 0.95 Vrms along the cylinder’s central axis. The proposed wireless coupler achieves a coupling coefficient of 0.013–0.034 and a PTE of 23.7%, outperforming similar systems with asymmetrical coupler design while offering a versatile solution for integrating IPT technology into wastewater treatment.

Advanced modeling of segmented Halbach cylinder for ironless brushless permanent-magnet two-phase motor

Compared with conventional permanent magnet (PM) cylinders, Halbach magnet cylinders have the advantage of strengthening the magnetic field on one side and canceling the field on the other side of the magnet structure. Outer-rotor radial-flux brushless ironless PM machines using a Halbach cylinder, therefore, can have a higher torque density compared with the ironless PM machines using a conventional magnet cylinder with the same magnet and coil volume and same air gap. For outer-rotor Halbach cylinder motors, existing designs usually take advantage of the fundamental harmonics of the magnetic field to obtain a linear toque model and to avoid the torque ripples from the higher-order field harmonics. To achieve this, the Lorentz coils must be placed where the fundamental harmonics of the field is dominant and the higher order harmonics can be negligible. With this, the coils should be sufficiently far from the magnet cylinder’s surface. However, how far the coils should be (from the magnet) is not clarified from the reported designs. To provide guidance on where to optimally place the Lorentz coils and to make the best use of the Halbach cylinders, there is a critical need for a simple but comprehensive analysis to find out all the field harmonics everywhere for both the ideal and segmented Halbach cylinders. This work is to provide that analysis.

Hardware and Software Setup for Quantitative 23Na Magnetic Resonance Imaging at 3T: A Phantom Study.

Magnetic resonance (MR) with sodium (23Na) is a noninvasive tool providing quantitative biochemical information regarding physiology, cellular metabolism, and viability, with the potential to extend MR beyond anatomical proton imaging. However, when using clinical scanners, the low detectable 23Na signal and the low 23Na gyromagnetic ratio require the design of dedicated radiofrequency (RF) coils tuned to the 23Na Larmor frequency and sequences, as well as the development of dedicated phantoms for testing the image quality, and an MR scanner with multinuclear spectroscopy (MNS) capabilities. In this work, we propose a hardware and software setup for evaluating the potential of 23Na magnetic resonance imaging (MRI) with a clinical scanner. In particular, the reliability of the proposed setup and the reproducibility of the measurements were verified by multiple acquisitions from a 3T MR scanner using a homebuilt RF volume coil and a dedicated sequence for the imaging of a phantom specifically designed for evaluating the accuracy of the technique. The final goal of this study is to propose a setup for standardizing clinical and research 23Na MRI protocols.

Comparative study on heteropolar/homopolar magnetic bearings for high-speed rotating applications

Bearing technology must be supported to attain high-speed and high-efficiency rotating applications. Previous research focused on performance enhancement and optimization, rather than comparative studies among magnetic bearings. This study presents the design and comparison of five magnetic bearing types for high-speed rotating applications: an 8-pole conventional heteropolar, fork-type heteropolar, hybrid fork-type homopolar, and hybrid homopolar magnetic bearings. For quantitative evaluation, mechanical parameters were selected to ensure a uniform coil volume and current supply. The heteropolar magnetic bearings employed 35PN440 steel, whereas the homopolar magnetic bearings utilized pure solid iron. The bias currents were determined based on the respective material properties. The driving circuits were compared by comparing models with and without permanent magnets. The magnetic flux density was assessed at equilibrium and maximum control current, and the loss characteristics were evaluated at 30 000 rpm. Linear control regions were identified by analyzing the relationships between the electromagnetic force, current, and displacement. As a result, the most suitable magnetic bearing for high-speed rotating applications is proposed.

A proof-of-concept Bitter-like HTS electromagnet fabricated from a silver-infiltrated (RE)BCO ceramic bulk

A novel concept for a compact high-field magnet coil is introduced. This is based on stacking slit annular discs cut from bulk rare-earth barium cuprate ((RE)BCO) ceramic in a Bitter-like architecture. Finite-element modelling shows that a small 20 turn stack (with a total coil volume of < 20 cm3) is capable of generating a central bore magnetic field of > 2 T at 77 K and > 20 T at 30 K. Unlike resistive Bitter magnets, the high-temperature superconducting (HTS) Bitter stack exhibits significant non-linear field behaviour during current ramping, caused by current filling proceeding from the inner radius outwards in each HTS layer. Practical proof-of-concept for this architecture was then demonstrated through fabricating an uninsulated four-turn prototype coil stack and operating this at 77 K. A maximum central field of 0.382 T was measured at 1.2 kA, with an accompanying 6.1 W of internal heat dissipation within the coil. Strong magnetic hysteresis behaviour was observed within the prototype coil, with ≈30% of the maximum central field still remaining trapped 45 min after the current had been removed. The coil was thermally stable during a 15 min hold at 1 kA, and survived thermal cycling to room temperature without noticeable deterioration in performance. A final test-to-destruction of the coil showed that the limiting weak point in the stack was growth-sector boundaries present in the original (RE)BCO bulk.

High signal intensity of the intraaneurysmal sac on T1 CUBE imaging as a predictor of aneurysm stability after coil embolization.

Histopathological studies of aneurysms after coil embolization showed that thrombus formation during the first month after endovascular treatment (EVT) played an important role in the healing process. The authors hypothesized that dedicated T1-weighted imaging may be used to predict stable aneurysms by visualizing the thrombus status within coil-treated aneurysms. Therefore, this study investigated the relationship between the signal intensity (SI) of the intraaneurysmal sac after coil embolization and aneurysm stability. The study population included 82 patients with 86 aneurysms who underwent T1-weighted 3D black-blood fast spin-echo (T1 CUBE) imaging within 1 month after coil embolization between 2019 and 2022. The relative SI of a coil-treated aneurysm (RSIcoiled) was calculated as follows: the mean SI of the intraaneurysmal sac/the mean SI of the genu of the corpus callosum. Aneurysms with enlarged remnants on MR angiography (MRA) within 6 months after EVT were defined as recurrence, while a decrease of intraaneurysmal flow on MRA was defined as improved embolization status. Stable aneurysms were defined as improvement or no change in embolization status 6 months after coil embolization. The volume embolization ratio (VER) was calculated as the ratio of the packed coil volume to the aneurysm volume. Differences between stable and recurrent aneurysms were examined. All aneurysms were divided into high and low RSIcoiled groups based on the cutoff value of RSIcoiled, and differences between the two groups were also evaluated. Recurrence was confirmed for 26 of 86 aneurysms. A univariable analysis showed that small aneurysms, high VER, and high RSIcoiled were associated with aneurysm stability. In the receiver operating characteristic curve analysis, the optimal cutoff value for RSIcoiled to differentiate stable from recurrent aneurysms was 0.54. The cutoff value for RSIcoiled was selected as 0.50 (sensitivity 0.77, specificity 0.70) because it was half the value of the SI of the corpus callosum and close to the optimal cutoff value. In a multivariable analysis, RSIcoiled > 0.50 (OR 8.1, 95% CI 2.5-27) remained a significant factor for aneurysm stability. The high RSIcoiled group showed a higher rate of an improved embolization status (26% vs 6.1%, p = 0.022) and stable aneurysms (85% vs 15%, p = 0.0002). RSIcoiled was associated with postcoiling aneurysm stability. High RSIcoiled might imply intraaneurysmal thrombus formation associated with the healing process of coil-treated aneurysms.

Magnetostatic Simulation and Design of Novel Radiofrequency Coils Based on Transverse Field Current Elements for Magnetic Resonance Applications.

Radiofrequency (RF) coils are key components in Magnetic Resonance (MR) systems and can be categorized into volume and surface coils according to their shapes. Volume RF coils can generate a uniform field in a large central sample's region, while surface RF coils, usually smaller than volume coils, typically have a higher Signal-to-Noise Ratio (SNR) in a reduced Region Of Interest (ROI) close to the coil plane but a relatively poorer field homogeneity. Circular and square loops are the simplest and most used design for developing axial field surface RF coils. However, for specific MR applications, the use of dedicated transverse field RF coils can be necessary or advantageous. Building on a previously developed and validated RF coil simulator, based on the magnetostatic approach, here we explore the potential applications of novel multiple axial field and transverse field surface RF coils in non-standard configurations. We demonstrate via numerical simulations that simple volume RF coils, matching a Helmholtz-like design, can be built with two identical transverse field RF coils separated by a given distance. Following well-known principles, the SNR of such novel configurations can be improved by a factor of up to √2 by combining two 90° rotated coils, producing, inside a central ROI, a circularly polarized B1 field.

Investigation of the influence of technological factors on the throughput capacity of the dispenser of a pneumatic sowing machine

One of the significant directions of scientific research in terms of improving the design of sowing machines and increasing their adaptability to modern requirements of automation is the creation of dispensers that provide adjustment of the seeding rate during the operation of the sowing machine. Specialists of the Siberian Research Institute of Mechanization and Electrification of Agriculture have developed a sample of a pneumatic sowing machine dispenser, which was used as a prototype in the study. The dispenser used allows for a smooth adjustment of the seed rate in accordance with the map task, as well as automatic shut-off of the seed supply to the seed line when the machine turns at the headland to prevent overconsumption of seeds and reseeding. The purpose of the research is to determine the design and technological parameters of the experimental dispenser of the pneumatic sowing machine. To achieve the set goal the following tasks were formulated: 1) to conduct a laboratory study of the process of seed metering in the experimental dispenser of the pneumatic seeding machine; 2) to determine the regularities of mutual influence of significant factors on the throughput capacity of the dispenser and describe them by regression equations. In accordance with the listed tasks the process of seed dosing on the laboratory unit was studied. In the course of experimental data processing, regression dependencies were obtained. According to the characteristics of the obtained equations, it is found that the most significant influence on the throughput capacity of the dispenser is the volume of the dispenser coil. Maximum performance of the dispenser is noted at rotor speeds in the range of 80–100 rpm. The highest feed rate and avoidance of spontaneous seed leakage from the dispenser into the seed pipe are achieved at a gate height of the dispenser discharge window within 2 cm. The results of the research can be used to finalize the design of the dispenser in order to use it as an actuator of the system of complex automation of the sowing unit.