Low Field Strength Research Articles

Development and validation of a controlled heating apparatus for long‐term MRI of 3D microfluidic tumor models

AbstractConventional testing of novel contrast agents for magnetic resonance imaging (MRI) involves cell and animal studies. However, 2D cultures lack dynamic flow and in vivo MRI is limited by regulatory approval of long‐term anesthesia use. Microfluidic tumor models (MTMs) offer a cost‐effective, reproducible, and high throughput platform for bridging cell and animal models. Yet, MRI of microfluidic devices is challenging, due to small fluid volumes generating low sensitivity. For the first time, an MRI of MTMs was performed at low field strength (1 T) using conventional imaging equipment without microcoils. To enable longitudinal MRI, we developed (1) CHAMP‐3 (controlled heating apparatus for microfluidics and portability) which heats MTMs during MRI scans and (2) an MRI‐compatible temperature monitoring system. CHAMP‐3 maintained chip surface temperature at ~37°C and the media inside at ~35.5°C. Enhanced T1‐weighted MRI contrast was achieved in 3D MTMs with free manganese (Mn2+) solutions and Mn2+ labeled tumor cells.

Characteristics and Source Regions of Slow Alfvénic Solar Wind Observed by Parker Solar Probe

Using a classification scheme for solar-wind type based on the heliocentric distance of the observation, we look at near-perihelion observations from Parker Solar Probe Encounters 4 to 14 to study the sources of the slow Alfvénic solar wind (SASW). Through Potential Field Source Surface (PFSS) modeling and ballistic mapping, we connect streams to their solar source and find that a primary population of SASW comes from low magnetic field strength regions (low-B 0), likely small coronal holes (CHs) and their overexpanded boundaries, while a second population of high field strength (high-B 0) seems to emerge from non-CH structures potentially through interchange reconnection with nearby open field lines. This low-B 0 SASW shows larger expansion than the fast solar wind (FSW) but similar mass flux, potentially indicating additional heating below the critical point, and emergence from a cooler structure, which could lead to slower wind emerging from CH-like structures. We show that this low-B 0 SASW shows stronger preferential acceleration of alpha particles (similar to the FSW) than the high-B 0 SASW, and that this is a velocity-dependent phenomenon as found in previous studies. To have additional confidence in our mapping results, we quantify the error on both the PFSS model and ballistic mapping and discuss how additional multipoint observations of plasma parameters and composition would allow us to better constrain our models and connect the solar wind to its source.

Field cycling imaging to characterise breast cancer at low and ultra-low magnetic fields below 0.2 T

BackgroundThis prospective feasibility study explores Field-Cycling Imaging (FCI), a new MRI technology that measures the longitudinal relaxation time across a range of low magnetic field strengths, providing additional information about the molecular properties of tissues. This study aims to assess the performance of FCI and investigate new quantitative biomarkers at low fields within the context of breast cancer.MethodsWe conducted a study involving 9 people living with breast cancer (10 tumours in total, mean age, 54 ± 10 years). FCI images were obtained at four magnetic field strengths (2.3 mT to 200 mT). FCI images were processed to generate T1 maps and 1/T1 dispersion profiles from regions of tumour, normal adipose tissue, and glandular tissue. The dispersion profiles were subsequently fitted using a power law model. Statistical analysis focused on comparing potential FCI biomarkers using a Mann-Whitney U or Wilcoxon signed rank test.ResultsWe show that low magnetic fields clearly differentiate tumours from adipose and glandular tissues without contrast agents, particularly at 22 mT (1/T1, median [IQR]: 6.8 [3.9–7.8] s−1 vs 9.1 [8.9–10.2] s−1 vs 8.1 [6.2–9.2] s−1, P < 0.01), where the tumour-to-background contrast ratio was highest (62%). Additionally, 1/T1 dispersion indicated a potential to discriminate invasive from non-invasive cancers (median [IQR]: 0.05 [0.03–0.09] vs 0.19 [0.09–0.26], P = 0.038).ConclusionsTo the best of our knowledge, we described the first application of in vivo FCI in breast cancer, demonstrating relevant biomarkers that could complement diagnosis of current imaging modalities, non-invasively and without contrast agents.

Experimental Evaluation of a Modular Electric Barrier for the Deterrence of Invasive Carp

Abstract We conducted a series of studies to assess the effectiveness of an electric barrier in deterring the movements of freshwater fish. Fish responses (detections·individual−1·hr−1 within the 3 m exclusion zone) were quantified for a mixed assemblage of native and nonnative fishes within 0.4 ha ponds. Additionally, we mapped the surface voltages generated by the electric barrier in a nearby stream. The electric barrier (operated at 10 kW) was effective at deterring native and invasive fishes, as &amp;gt; 99% of all fish detections within the exclusion zone occurred while the electric barrier was off. However, some fish detections occurred while the system was operated at full power, indicating the electric barrier was not 100% effective. A follow-up study found that fish responses differed between low (3.6 kW), medium (6.6 kW), and high (10 kW) field strengths, with smallmouth buffalo Ictiobus bubalus exhibiting a greater sensitivity to the low setting than bighead carp Hypophthalmichthys nobilis and silver carp H. molitrix. Maps of the surface voltages within a nearby stream indicated that the electric barrier was strong enough to deter silver carp (&amp;gt; 1 V/cm). However, the surface voltages quickly dissipated upstream and downstream of the electrodes. Overall, the electric barrier appears to be an effective tool that can be used to combat the spread of invasive fishes in freshwater environments. However, more evaluations are needed to test how the system performs in different conditions and to identify whether fish of varying sizes or life stages respond similarly.

Smart Biopolymer Scaffolds Based on Hyaluronic Acid and Carbonyl Iron Microparticles: 3D Printing, Magneto-Responsive, and Cytotoxicity Study.

This study deals with utilization of the hyaluronic acid (HA) and carbonyl iron (CI) microparticles to fabricate the magneto-responsive hydrogel scaffolds that can provide triggered functionality upon application of an external magnetic field. The various combinations of the HA and CI were investigated from the rheological and viscoelastic point of view to clearly show promising behavior in connection to 3D printing. Furthermore, the swelling capabilities with water diffusion kinetics were also elucidated. Magneto-responsive performance of bulk hydrogels and their noncytotoxic nature were investigated,, and all hydrogels showed cell viability in the range 75-85%. The 3D printing of such developed systems was successful, and fundamental characterization of the scaffolds morphology (SEM and CT) has been presented. The magnetic activity of the final scaffolds was confirmed at a very low magnetic field strength of 140 kA/m, and such a scaffold also provides very good biocompatibility with NIH/3T3 fibroblasts.

Recovering MRI magnetic field strength properties using machine learning based on image compression quality scores

AbstractOver the years, significant hardware advancements have led to higher magnetic field MRI (Magnetic Resonance Imaging) acquisitions, providing improved diagnostic image quality at a higher cost. While higher image quality is desired, the investment required for high-field MRI imaging systems remains a significant consideration. Furthermore, historical patient records may still contain low-field magnetic strength MRI data. In this work, we present how image compression quality scores of MRI images could be used to recover their magnetic field strength properties. This work presents an interesting inverse problem scenario where output properties are used to recover an input property of an image. We implemented supervised machine learning models that utilize compressed image quality scores - based on Mean Squared Error (MSE), Structural Similarity Index (SSIM), Visual Information Fidelity (VIF), and Earth Movers Distance (EM) metrics - as inputs. These models classify images into specific classes of magnetic field strength at which they were acquired (Low, Medium, and High) based solely on the quality scores of their compressed copies. The trained machine learning models (Support Vector Machine (SVM), Logistic Regression, K-nearest Neighbours (KNN), Decision Tree and Random Forest) achieved nearly 100% performance efficiency based on accuracy and F-1 score for all considered quality measures. This comprehensive evaluation offers insights into how compression techniques and quality factors impact image fidelity across various MRI magnetic field strengths. The findings of this study may prove valuable in recovering missing meta-tag information in historical image DICOM records and Context-Based Retrieval Systems (CBRS). The approach of using quality scores as features in training machine learning models, as demonstrated in this work, can be extended to other image groups where input parameters create statistically significant distinctions or are challenging to extract from images.

Multidimensional RF pulse design with consideration of concomitant field effects.

To develop a small-tip multidimensional RF pulse design procedure that incorporates linear time-invariant gradient imperfections and concomitant field effects. This could be particularly important for contemporary low-field MRI systems with high-performance gradients. We developed an extension of the small-tip excitation k-space formalism, where concomitant fields were approximated as a Bloch-Siegert shift in the rotating frame. This was evaluated using realistic simulations of 2D selective excitation at various field strengths (0.2T, 0.55T, 1.5T, 3T, and 7T) with single and parallel transmit. Simulated excitation profiles from the original and extended k-space formalisms were compared. Experimental validations were performed at 0.55T with a single-channel transmit. The extended formalism provides improved 2D excitation profiles in all scenarios simulated, compared against the original formalism. The proposed method corrects the concomitant field effects on 2D selective excitations for B0 > 0.2T when the magnitude of the B0 is far larger than that of nonrotating concomitant fields. Simulation and phantom experiments at 0.55T match well for both original and proposed methods, with the proposed method providing sharper and more accurate excitation profiles at off-isocenter distances up to 15 cm. The impact of the proposed method is greatest in scenarios where concomitant fields are substantial, such as low field strengths and off-isocenter. Concomitant fields can be modeled as a Bloch-Siegert shift in the rotating frame during multidimensional RF pulse design, resulting in improved excitation profiles with sharp edges. This is important to consider for off-isocenter excitations and imaging at low field strengths with strong gradients.

Radiation therapy systems using linear accelerator, importance of its components and their development

Given the importance of devices used in the field of medicine in terms of diagnosis and treatment, and the great importance of this topic in accelerating early diagnosis and saving the lives of the largest possible number of people, we decided to study one of these devices to better define its components and review some of the difficulties. Many linear accelerators for hybrid magnetic resonance imaging have been developed as a result of the need to profit from directed images of tissues and various body sections during radiation therapy (linear accelerators). There are now a number of linear accelerators for magnetic resonance imaging that cover both low and high magnetic field strengths as well as two directions of the beam field; these systems have the potential to be beneficial. This technology has only recently been used in clinical trials. However, its continued usage as a routine radiation therapy procedure is certain. The majority of the key elements and difficulties encountered in the creation of such technology as well as its present state are outlined in this review article.

Development of novel ionization chambers for reference dosimetry in electron flash radiotherapy

AbstractBackgroundReference dosimetry in ultra‐high dose rate (UHDR) beamlines is significantly hindered by limitations in conventional ionization chamber design. In particular, conventional chambers suffer from severe charge collection efficiency (CCE) degradation in high dose per pulse (DPP) beams.PurposeThe aim of this study was to optimize the design and performance of parallel plate ion chambers for use in UHDR dosimetry applications, and evaluate their potential as reference class chambers for calibration purposes. Three chamber designs were produced to determine the influence of the ion chamber response on electrode separation, field strength, and collection volume on the ion chamber response under UHDR and ultra‐high dose per pulse (UHDPP) conditions.MethodsThree chambers were designed and produced: the A11‐VAR (0.2–1.0 mm electrode gap, 20 mm diameter collector), the A11‐TPP (0.3 mm electrode gap, 20 mm diameter collector), and the A30 (0.3 mm electrode gap, 5.4 mm diameter collector). The chambers underwent full characterization using an UHDR 9 MeV electron beam with individually varied beam parameters of pulse repetition frequency (PRF, 10–120 Hz), pulse width (PW, 0.5–4 µs), and pulse amplitude (0.01–9 Gy/pulse). The response of the ion chambers was evaluated as a function of the DPP, PRF, PW, dose rate, electric field strength, and electrode gap.ResultsThe chamber response was found to be dependent on DPP and PW, and these dependencies were mitigated with larger electric field strengths and smaller electrode spacing. At a constant electric field strength, we measured a larger CCE as a function of DPP for ion chambers with a smaller electrode gap in the A11‐VAR. For ion chambers with identical electrode gap (A11‐TPP and A30), higher electric field strengths were found to yield better CCE at higher DPP. A PW dependence was observed at low electric field strengths (500 V/mm) for DPP values ranging from 1 to 5 Gy at PWs ranging from 0.5 to 4 µs, but at electric field strengths of 1000 V/mm and higher, these effects become negligible.ConclusionThis study confirmed that the CCE of ion chambers depends strongly on the electrode spacing and the electric field strength, and also on the DPP and the PW of the UHDR beam. A significant finding of this study is that although chamber performance does depend on PW, the effect on the CCE becomes negligible with reduced electrode spacing and increased electric field. A CCE of ≥95% was achieved for DPPs of up to 5 Gy with no observable dependence on PW using the A30 chamber, while still achieving an acceptable performance in conventional dose rate beams, opening up the possibility for this type of chamber to be used as a reference class chamber for calibration purposes of electron FLASH beamlines.

Fetal body organ T2* relaxometry at low field strength (FOREST)

Fetal Magnetic Resonance Imaging (MRI) at low field strengths is an exciting new field in both clinical and research settings. Clinical low field (0.55T) scanners are beneficial for fetal imaging due to their reduced susceptibility-induced artifacts, increased T2* values, and wider bore (widening access for the increasingly obese pregnant population). However, the lack of standard automated image processing tools such as segmentation and reconstruction hampers wider clinical use. In this study, we present the Fetal body Organ T2* RElaxometry at low field STrength (FOREST) pipeline that analyzes ten major fetal body organs. Dynamic multi-echo multi-gradient sequences were acquired and automatically reoriented to a standard plane, reconstructed into a high-resolution volume using deformable slice-to-volume reconstruction, and then automatically segmented into ten major fetal organs. We extensively validated FOREST using an inter-rater quality analysis. We then present fetal T2* body organ growth curves made from 100 control subjects from a wide gestational age range (17–40 gestational weeks) in order to investigate the relationship of T2* with gestational age. The T2* values for all organs except the stomach and spleen were found to have a relationship with gestational age (p<0.05). FOREST is robust to fetal motion, and can be used for both normal and fetuses with pathologies. Low field fetal MRI can be used to perform advanced MRI analysis, and is a viable option for clinical scanning.

Laying the foundations for selective-fish guidance using electricity: multi-species response to pulsed direct currents

To develop effective technology that employs electric fields to simultaneously guide valued freshwater fish whilst limiting the range expansion of undesirable invasive species, there is a need to quantify the electrosensitivity of multiple families. This experimental study quantified the electrosensitivity of two carp species that, in UK, are invasive (grass carp, Ctenopharyngodon idella, and common carp, Cyprinus carpio) and compared the values with those previously obtained for adult European eel (Anguilla anguilla), a species of conservation concern in Europe. Electric field strengths (V/cm) required to elicit physiological responses (twitch, loss of orientation and tetany) were identified across four pulsed direct current (PDC) electric waveforms (single pulse-2 Hz, double pulse-2 Hz, single pulse-3 Hz and double pulse-3 Hz). Grass carp were sensitive to differences in waveform with tetany exhibited at lower field strengths in the single pulse-2 Hz treatment. Both cyprinid species responded similarly and were less sensitive to PDC than adult European eel, although loss of orientation occurred at lower field strengths for grass than common carp in the single pulse-3 Hz waveform treatment. This variation in electrosensitivity, likely due to differences in body length, indicates potential for electric fields to selectively guide fish in areas where invasive and native species occur in sympatry.

Structural and functional fetal cardiac imaging using low field (0.55 T) MRI.

This study aims to investigate the feasibility of using a commercially available clinical 0.55 T MRI scanner for comprehensive structural and functional fetal cardiac imaging. Balanced steady-state free precession (bSSFP) and phase contrast (PC) sequences were optimized by in utero studies consisting of 14 subjects for bSSFP optimization and 9 subjects for PC optimization. The signal-to-noise ratio (SNR) of the optimized sequences were investigated. Flow measurements were performed in three vessels, umbilical vein (UV), descending aorta (DAo), and superior vena cava (SVC) using the PC sequences and retrospective gating. The optimized bSSFP, PC and half-Fourier single shot turbo spin-echo (HASTE) sequences were acquired in a cohort of 21 late gestation-age fetuses (>36 weeks) to demonstrate the feasibility of a fetal cardiac exam at 0.55 T. The HASTE stacks were reconstructed to create an isotropic reconstruction of the fetal thorax, followed by automatic great vessel segmentations. The intra-abdominal UV blood flow measurements acquired with MRI were compared to ultrasound UV free-loop flow measurements. Using the parameters from 1.5 T as a starting point, the bSSFP sequences were optimized at 0.55 T, resulting in a 1.6-fold SNR increase and improved image contrast compared to starting parameters, as well as good visibility of most cardiac structures as rated by two experienced fetal cardiologists. The PC sequence resulted in increased SNR and reduced scan time, subsequent retrospective gating enabled successful blood flow measurements. The reconstructions and automatic great vessel segmentations showed good quality, with 18/21 segmentations requiring no or minor refinements. Blood flow measurements were within the expected range. A comparison of the UV measurements performed with ultrasound and MRI showed agreement between the two sets of measurements, with better correlation observed at lower flows. We demonstrated the feasibility of low-field (0.55 T) MRI for fetal cardiac imaging. The reduced SNR at low field strength can be effectively compensated for by strategically optimizing sequence parameters. Major fetal cardiac structures and vessels were consistently visualized, and flow measurements were successfully obtained. The late gestation study demonstrated the robustness and reproducibility at low field strength. MRI performed at 0.55 T is a viable option for fetal cardiac examination.

Linear Bloch-Siegert phase-encoded low-field MRI: RF coils, pulse sequence, and image reconstruction.

Conventional gradient systems have several weaknesses including high cost and bulk. As a step towards addressing these while providing new degrees of freedom for spatial encoding and system design in Magnetic Resonance Imaging (MRI), a radio frequency (RF) gradient encoding system and pulse sequence for phase encoding using the Bloch-Siegert (BS) shift were developed. Optimized BS spatial encoding coils with bucking windings (counter-wound loops) were designed and constructed, along with compatible homogeneous imaging coils for excitation and signal reception. Two coil systems were developed: one for phantom imaging and a second for human wrist imaging. BS phase-encoded imaging and BS RF pulse simulations were performed. Pulse sequences were designed for linear stepping in k-space and implemented on a 47.5-mT scanner to image resolution phantoms in both coil setups. Reconstructions were performed using both the full -based encoding fields for each BS pulse amplitude and using inverse discrete Fourier transforms. A gradient was used for frequency encoding during signal readout, and the third axis was projected. Specific absorption ratio (SAR) calculations were performed for the wrist coil to determine the safety of BS-based RF encoding for fields in the low field MRI regime. The optimized RF spatial encoding coils resulted in higher linearity ( and 0.9921 in the phantom and wrist coils, respectively) than coils used in previous work. The phantom and wrist imaging coils were validated in simulations and experimentally to produce a peak G and 0.8 G with 12-W input power, respectively, in the field-of-view (length = 11 cm) used for imaging. Nominal imaging resolutions of 5.22 and 7.21 mm were, respectively, achieved by the two-coil systems in the RF phase-encoded dimension. Coil systems, pulse sequences, and image reconstructions were developed for linear RF phase encoding using the BS shift and validated using a 47.5-mT open low field scanner, establishing a key component required for gradient-free imaging at low field strengths.

Feasibility of 3D MRI fingerprinting for rapid knee cartilage T1, T2, and T1ρ mapping at 0.55T: Comparison with 3T.

Low-field strength scanners present an opportunity for more inclusive imaging exams and bring several challenges including lower signal-to-noise ratio (SNR) and longer scan times. Magnetic resonance fingerprinting (MRF) is a rapid quantitative multiparametric method that can enable multiple quantitative maps simultaneously. To demonstrate the feasibility of an MRF sequence for knee cartilage evaluation in a 0.55T system we performed repeatability and accuracy experiments with agar-gel phantoms. Additionally, five healthy volunteers (age 32 ±4years old, 2 females) were scanned at 3T and 0.55T. The MRI acquisition protocols include a stack-of-stars T1ρ-enabled MRF sequence, a VIBE sequence with variable flip angles (VFA) for T1 mapping, and fat-suppressed turbo flash (TFL) sequences for T2 and T1ρ mappings. Double-Echo steady-state (DESS) sequence was also used for cartilage segmentation. Acquisitions were performed at two different field strengths, 0.55T and 3T, with the same sequences but protocols were slightly different to accommodate differences in signal-to-noise ratio and relaxation times. Cartilage segmentation was done using five compartments. T1, T2, and T1ρ values were measured in the knee cartilage using both MRF and conventional relaxometry sequences. The MRF sequence demonstrated excellent repeatability in a test-retest experiment with model agar-gel phantoms, as demonstrated with correlation and Bland-Altman plots. Underestimation of T1 values was observed on both field strengths, with the average global difference between reference values and the MRF being 151 ms at 0.55T and 337 ms at 3T. At 0.55T, MRF measurements presented significant biases but strong correlations with the reference measurements. Although a larger error was present in T1 measurements, MRF measurements trended similarly to the conventional measurements for human subjects and model agar-gel phantoms.

An optical measurement method of DC total electric field with space charges based on probe self-rotation modulation

Researching the measurement of DC total electric field with space charges (Poisson field) can help establish a monitoring system for the electromagnetic environment of UHVDC transmission lines and protect the health of the ecological environment. This paper proposes a DC total electric field optical measurement method based on the Pockels effect and probe self-rotation modulation. It can address the issues of internal charge drift and external charge accumulation in traditional optical probes when measuring DC electric fields with space charges. Theoretical analysis was conducted on measurement under probe rotation, and the optical modulation system was integrated into a probe with dimensions of 60 mm × 30 mm × 20 mm. A self-rotating platform for the probe was designed, and the influence of rotation mode on the results was analyzed. It was found that the sensitivity was higher when using the horizontal-horizontal mode. The signal processing system was tested, showing that the probe retained around 50 % of its original output when rotating at low speeds (frequency 1–3 Hz), fully meeting the measurement requirements. The test platform has been constructed, and the probe’s sensitivity was assessed under an AC electric field and validated under a DC electric field. Finally, the optical method proposed in this paper was used to measure the DC total electric field with space charges under a small model of a unipolar HVDC transmission line. Five locations under the line were selected as measurement points, and the results were compared with those obtained from a field mill probe and numerical simulation. This comparison indicates that the proposed method agrees with experimental and simulation results. The average sensitivity of the self-rotating optical probe was 3.71 mV/(kV/m). The error did not exceed 5 % in high-field strength areas (above 20 kV/m) and was also controlled within 15 % in low-field strength areas (below 20 kV/m).

Enhancing Energy Storage Performance of 0.85Bi0.5Na0.5TiO3-0.15LaFeO3 Lead-Free Ferroelectric Ceramics via Buried Sintering.

Bismuth sodium titanate (Bi0.5Na0.5TiO3, BNT) ceramics are expected to replace traditional lead-based materials because of their excellent ferroelectric and piezoelectric characteristics, and they are widely used in the industrial, military, and medical fields. However, BNT ceramics have a low breakdown field strength, which leads to unsatisfactory energy storage performance. In this work, 0.85Bi0.5Na0.5TiO3-0.15LaFeO3 ceramics are prepared by the traditional high-temperature solid-phase reaction method, and their energy storage performance is greatly enhanced by improving the process of buried sintering. The results show that the buried sintering method can inhibit the formation of oxygen vacancy, reduce the volatilization of Bi2O3, and greatly improve the breakdown field strength of the ceramics so that the energy storage performance can be significantly enhanced. The breakdown field strength increases from 210 kV/cm to 310 kV/cm, and the energy storage density increases from 1.759 J/cm3 to 4.923 J/cm3. In addition, the energy storage density and energy storage efficiency of these ceramics have good frequency stability and temperature stability. In this study, the excellent energy storage performance of the ceramics prepared by the buried sintering method provides an effective idea for the design of lead-free ferroelectric ceramics with high energy storage performance and greatly expands its application field.

7 T Lumbosacral Plexus Neurography: Feasibility and Comparison of Spinal Nerve Visualization With 3 T MRI.

7 T magnetic resonance (MR) imaging can offer superior spatial resolution compared with lower field strengths. However, its use for imaging of the lumbosacral plexus has been constrained by technical challenges and therefore remained relatively unexplored. Therefore, this study investigated the feasibility of 7 T MR neurography by means of comparing the visibility of the spinal nerves and image quality to 3 T MR neurography. In this monocentric, institutional review board-approved, prospective study, 30 healthy subjects underwent acquisition time-matched 7 T MR neurography and 3 T MR neurography of the lumbar spine using a 3-dimensional dual-echo steady-state sequence. Visibility of the nerve root, dorsal root ganglia, and spinal nerve fascicles of L1-S1, along with image artifacts and overall image quality, were compared between the different field strengths by 2 radiologists using 4-point Likert scales (1 = poor, 4 = excellent). Comparisons between field strengths were made using the Wilcoxon signed rank test, and interobserver agreement was assessed. 7 T MR neurography enabled significantly improved visualization of the lumbar nerve roots, dorsal root ganglia, and spinal nerve fascicles (P ≤ 0.002). Compared with 3 T MR neurography, no difference in overall image quality was observed (P = 0.211), although 7 T MR imaging exhibited significantly increased image artifacts (P < 0.001). Interobserver agreement (κ) for qualitative measures ranged from 0.71 to 0.88 for 7 T, and from 0.75 to 0.91 for 3 T. 7 T MR neurography allowed for improved visualization of lumbar spinal nerves, whereas overall image quality was comparable to 3 T MR neurography. This supports the feasibility of 7 T MR neurography of the lumbosacral plexus, even though image artifacts at 7 T were significantly increased.

Thermally-assisted magnetization of magnetic composites for enhanced micro actuator performance: a low-cost approach using permanent magnets

A micro actuator based on magnetic composite materials can control its deformation and movement through varying magnetic fields, showcasing significant applications in fields such as soft robotics and biomedicine. However, existing magnetic composite materials still require complex magnetization processes involving sophisticated equipment and demanding external magnetic fields. This paper proposed a low-cost, thermally-assisted magnetization process based on permanent magnets. It was observed that the maximum magnetic induction intensity on the surface of magnetic composites is linearly correlated with the heating temperature. Additionally, magnetically treated materials at elevated temperatures can achieve traditional high-field magnetization effects at lower field strengths. Specifically, we synthesized a magnetic composite with 50%wt NdFeB@PDMS and investigated the conditions of the thermally-assisted magnetization process based on permanent magnets, along with mechanical and magnetic performance characterization methods. Experimental results indicate that below 200 °C, the tensile strength and elastic modulus of the base material increase with rising temperatures, demonstrating a trend of high-temperature hardening. However, when the temperature exceeds 200 °C, the elevated temperature leads to the decomposition of the base material, resulting in a rapid decrease in the tensile strength and elastic modulus of the magnetic composite. Furthermore, high temperatures can disrupt the magnetic domains of the magnetic material, reducing its coercive force and making it more susceptible to external magnetic fields and heat, thereby compromising the stability of the magnetic material. These findings provide new insights into the development of more stable and controllable magnetic composite materials.

Identification by HSQC and quantification by qHNMR innovate pharmaceutical amino acid analysis

This study introduces a new NMR-based methodology for identification (ID) and quantification (purity, strength) assays of widely used amino acids. A detailed analysis of four amino acids and their available salts was performed with both a high-field (600 MHz) and a benchtop (60 MHz) NMR instrument. To assess sensitivity constraints, samples for 1H NMR analysis were initially prepared using only 10 mg of analyte and 1 mg of maleic acid (MA) as an internal calibrant (IC) and secondary chemical shift reference. The characteristic dispersion of the peak patterns indicating the presence or absence of a counterion (mostly chloride) was conserved at both high and low-field strength instruments, showing that the underlying NMR spectroscopic parameters, i.e., chemical shifts and coupling constants, are independent of the magnetic field strength. However, as the verbal descriptions of 1H NMR spectra are challenging in the context of reference materials and pharmaceutical monographs, an alternative method for the identification (ID) of amino acids is proposed that uses 13C NMR patterns from multiplicity-edited HSQC (ed-HSQC), which are both compound-specific and straightforward to document. For ed-HSQC measurements, the sample amount was increased to 30 mg of the analyte and several acquisition parameters were tested, including t1 increments used in the pulse program, number of scans, and repetition time. Excellent congruence with deviations <0.1 ppm was achieved for the 13C chemical shifts from 1D 13C NMR spectra (150 MHz) vs. those extracted from ed-HSQC (15 MHz traces). Finally, all samples of amino acid candidate reference materials were quantified by 1H qNMR (abs-qHNMR) at both 600 and 60 MHz. At high field, both IC and relative quantitations were performed, however, with the low-field instrument, only the IC method was used. The results showed that the analyzed reference material candidates were generally highly pure compounds. To achieve adequately low levels of uncertainty for such high-purity materials, the sample amounts were increased to 100 mg of analytes and 10 mg of the IC and replicates were analyzed for selected amino acids.

Evaluating the role of 7-Tesla magnetic resonance imaging in neurosurgery: Trends in literature since clinical approval.

After approval for clinical use in 2017, early investigations of ultra-high-field abdominal magnetic resonance imaging (MRI) have demonstrated its feasibility as well as diagnostic capabilities in neuroimaging. However, there are no to few systematic reviews covering the entirety of its neurosurgical applications as well as the trends in the literature with regard to the aforementioned application. To assess the impact of 7-Tesla MRI (7T MRI) on neurosurgery, focusing on its applications in diagnosis, treatment planning, and postoperative assessment, and to systematically analyze and identify patterns and trends in the existing literature related to the utilization of 7T MRI in neurosurgical contexts. A systematic search of PubMed was conducted for studies published between January 1, 2017, and December 31, 2023, using MeSH terms related to 7T MRI and neurosurgery. The inclusion criteria were: Studies involving patients of all ages, meta-analyses, systematic reviews, and original research. The exclusion criteria were: Pre-prints, studies with insufficient data (e.g., case reports and letters), non-English publications, and studies involving animal subjects. Data synthesis involved standardized extraction forms, and a narrative synthesis was performed. We identified 219 records from PubMed within our defined period, with no duplicates or exclusions before screening. After screening, 125 articles were excluded for not meeting inclusion criteria, leaving 94 reports. Of these, 2 were irrelevant to neurosurgery and 7 were animal studies, resulting in 85 studies included in our systematic review. Data were categorized by neurosurgical procedures and diseases treated using 7T MRI. We also analyzed publications by country and the number of 7T MRI facilities per country was also presented. Experimental studies were classified into comparison and non-comparison studies based on whether 7T MRI was compared to lower field strengths. 7T MRI holds great potential in improving the characterization and understanding of various neurological and psychiatric conditions that may be neurosurgically treated. These include epilepsy, pituitary adenoma, Parkinson's disease, cerebrovascular diseases, trigeminal neuralgia, traumatic head injury, multiple sclerosis, glioma, and psychiatric disorders. Superiority of 7T MRI over lower field strengths was demonstrated in terms of image quality, lesion detection, and tissue characterization. Findings suggest the need for accelerated global distribution of 7T magnetic resonance systems and increased training for radiologists to ensure safe and effective integration into routine clinical practice.