Magnetic Model Calibration for Tetherless Surgical Needle Manipulation using Zernike Polynomial Fitting

Purpose:The objective of this research was to demonstrate accuracy of a real‐time passive ultrasound magnetic needle guidance technology (NGT) and target localization algorithm using conventional anechogenic contact phantoms and a novel fluid‐filled hyperechogenic phantom simulating nerve block technique.Methods:Accuracy (mm to phantom target) was assessed by observing 35 medical practitioners (16 anesthesiologists and 19 residents) performing 560 needle procedures in high‐fidelity ex vivo porcine tissue phantoms. Each practitioner performed 8 tasks with GE Venue 50 magnetic NGT system with PinPoint GT (Bard Access Sys.) and 8 conventional echogenic needle (control) procedures under various conditions (#18/#22 needle gauge, IP/OOP approach, and hyperechogenic simulated block approach targets or anechogenic solid targets). Passes, user feedback, and ergonomics were also assessed.Results:Overlaid visual aids produced in real time (<300 mS delay) by NGT enabled users to consistently perform with better accuracy than control echogenic needle guidance. Accuracy improved by 51.2% at 95% CI [29.8%, 66.7%] (P = 0.0008) among block approach phantoms and 51.4% at 95% CI [34.9%, 64.0%] (P < 0.0001) among placement phantoms. Further, inadvertent contact with targets was reduced by NGT visualizations versus controls in both anesthesiologists (0 vs. 8 contacts; accuracy 2.0±1.7 vs. 4.13±6.7 mm) and novice users (3 vs. 12 contacts; accuracy 2.2±2.3 vs. 2.9±3.7 mm), respectively. Among novice users, NGT visualizations notably reduced quality‐compromising ergonomic observations compared to controls under equivalent conditions.Conclusion:NGT systems employing magnetic field generation and electromagnetic sensors to track needle position and orientation relative to a sonoanatomical target within a magnetic field have the potential to enable greater accuracy for complex needle placements and reduce unintentional needle contact, particularly in novice users. Further, NGT visualizations of needle tip and projected trajectory contribute to positive ergonomics and reducing quality‐compromising behaviors among operators, potentially reducing fatigue and needle progression error.This work was supported by funding provided by the GE Healthcare Ultrasound Business, Milwaukee, WI.

Consistency of lumbar discograms of the same disc obtained twice at a 2-week interval: Influence of needle tip position

The distinctive feature of this astatic magnetometer is that this is set on a 4 square meter sheet of galvanized iron and has no damper, as shown in Figs. 1 and 2.Through several years of experiment, the writer discovered that this magnetometer can record short period change of magnetic field.The period is 1/10-2 second.The writer proved that the induced magnetic field in the galvanized iron sheet can oscillate this magnetic needle, because of the difference of vertical distance of two magnetic needles, as shown in Fig. 2.Figs. 7 and 8 show the relation between the oscillation of magnetic needle and earthqakes.Through the writer's records, it is proved that change of temperature, magnetic storm and daily change of magnetic field and thunder can not be recorded by this magnetometer and that the reason is that they have not 1/10-1 second change of magnetic field.

Herpes zoster (HZ)-related pain, characterized by chronic and persistent pain with a dermatomal distribution, is a relatively common complication of HZ. Pulsed radiofrequency (PRF) can effectively relieve HZ-related pain. There is no study on the effect of the needle tip position in patients with HZ for PRF treatment. This prospective study was conducted to compare two distinct needle tip positions in PRF for HZ-related pain. Seventy-one patients suffering from HZ-related pain were enrolled in this study. According to the dorsal root ganglion (DRG) position and needle tip position, patients were randomly allocated to the IP group (group inside of the pedicle, n=36) and OP group (group outside of the pedicle, n=35). Quality of life and pain control were evaluated with the visual analog scale (VAS) and activities of daily living questionnaires (including 7 items: general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life), which were administered before therapy and at intervals of 1, 7, 30, and 90 days after therapy. Before therapy, the mean pain score was found to be 6.03 ± 0.45 in the IP group and 6.00 ± 0.65 in the OP group (p=0.555). No significant differences were found when the two groups were compared at 1 and 7 days after therapy (p > 0.05). But, the pain score was significantly lower in the IP group at 30 days (1.78 ± 1.31 vs. 2.77 ± 1.31, p=0.006) and 90 days of follow-up (1.29 ± 1.19 vs. 2.15 ± 1.74, p=0.041). Significant differences between the two groups in terms of general activity (2.39 ± 0.87 vs. 2.86 ± 0.77, p=0.035), mood (1.97 ± 1.65 vs. 2.86 ± 1.50, p=0.021), relations with other people (1.94 ± 0.92 vs. 2.51 ± 1.22, p=0.037), sleep (1.64 ± 1.44 vs. 2.97 ± 1.44, p < 0.001), and enjoyment of life (1.58 ± 1.11 vs. 2.43 ± 1.33, p=0.004) were detected after the 30-day follow-up. In addition, scores for the activities of daily living were significantly lower in the IP group than that in the OP group at 90 days after therapy (p < 0.05). The needle tip position had an influence on the PRF treatment in patients with HZ-related pain. Positioning the needle tip in the area between the medial and lateral edges of adjacent pedicles offered good pain relief and improved quality of life in HZ patients.

We present the results of calculations of the bounce‐averaged pitch angle, mixed, and momentum diffusion coefficients in a dipole and two realistic field models (the T01s model for quiet and storm conditions). We consider resonant interactions of the outer radiation belt electrons with oblique chorus waves. We demonstrate that on the dayside, the use of a realistic magnetic field versus a dipole field only makes a significant difference for small equatorial pitch angles at energies larger than E = 1 MeV. On the nightside, the differences between the scattering rates calculated in the Tsyganenko and dipole models can reach several orders of magnitude at various equatorial pitch angles for electrons with E ≥ 0.5 MeV. The most significant changes in the scattering rates computed in the realistic and dipole magnetic fields occur during the geomagnetically active conditions. On the nightside, for E ≥ 0.5 MeV, the diffusion coefficients calculated in the Tsyganenko field show significant scattering near the edge of the loss cone that can produce loss of electrons to the atmosphere, while in the dipole model there is no scattering at small equatorial pitch angles. Our computations in the realistic field show that resonant interactions between electrons with E ≤ 1 MeV and chorus waves can be an effective net loss mechanism on both the dayside and the nightside. To explain the differences in the scattering rates associated with a change in the magnetic field model, we present the contribution of various resonant harmonics to the diffusion and examine the changes in the resonance condition.

In this work, we use the theory of time-scale separation to analyze motion of magnetic needles powered by electromagnetic coils for surgical tasks. In developing model-based controllers for such systems, it is often assumed that the magnetic needle orientation is aligned with the magnetic field direction. This assumption has enabled use of open-loop control techniques for orientation control of the magnetic agent. We provide a framework to show how this assumption might be highly inaccurate for certain system parameters. We show numerical simulations to depict this and validate results with experiments on a real magnetic control system. The results of this work can help ascertain whether the orientation alignment assumption is valid for a given set of parameters, paving the way to enable safe and accurate implementation of surgical tasks using magnetic needles in clinical settings.

Permanent magnet synchronous linear motor (PMSLM) and PM synchronous planar motor are important motion devices in the modern precision industry. Their inherent periodic magnetic fields are highly related to motor position. Correspondingly, the magnetic fields can be utilized to determine their own displacement and replace expensive sensors. However, the measurement result of this strategy seriously depends on magnetic field model (MFM) preciseness. To improve measurement accuracy, a novel MFM with Fourier series is proposed in this paper. First, a high-order theoretical model from theoretical derivation is developed. And the analyses show that even harmonics exist in the magnetic field of motor, which are not included in the theoretical model. This model deviation obviously affects measurement accuracy. Hence, the new MFM is reconstructed based on a high-order theoretical model. Comparative experiments with the three different MFMs are carried out to measure the displacement of the PMSLM. In the experiments, a linear hall sensors array containing eight sensors is self-developed to detect motor magnetic field. The root mean square of displacement measurement errors using a reconstruction model, a high-order theoretical model, and a fundamental model is 4.84, 8.42, and $758~\mu \text{m}$ , respectively. The experimental results validate that the measurement result of the proposed reconstruction MFM is better than the other two MFMs.

Spherical magnetic instabilities in the Earth’s core and equatorial symmetries

MR Imaging‒Guided Intervention: Evaluation of MR Conditional Biopsy and Ablation Needle Tip Artifacts at 3T Using a Balanced Fast Field Echo Sequence

Superparamagnetic nanoparticles can be attached in great numbers to pathogenic cells using specific antibodies so that the magnetically-labeled cells themselves become superparamagnets. The cells can then be manipulated and drawn out of biological fluids, as in a biopsy, very selectively using a magnetic needle. We examine the origins and uncertainties in the forces exerted on magnetic nanoparticles by static magnetic fields, leading to a model for trajectories and collection times of dilute superparamagnetic cells in biological fluids. We discuss the design and application of such magnetic needles and the theory of collection times. We compare the mathematical model to measurements in a variety of media including blood.For more information on this article, see medicalphysicsweb.org

In many subcutaneous needle insertion procedures, measuring needle deflection is necessary in order to accurately guide the needle towards inner body targets. Typically, needle deflection measurement are obtained from 2D ultrasound images, which can only provide the needle tip position, however, having knowledge about the needle tip heading (orientation) is very valuable in predicting the needle's future path for planning and needle steering reasons. Due to the small diameter of the needles and the low resolution of ultrasound imaging, the direct measurement of the needle tip orientation is not a trivial task. This paper represents a model-based non linear observer for partial estimating the needle tip orientation during needle insertion procedures using image-based position measurements. The proposed method employs a 3D kinematic unicycle model expressed in generalized coordinates. Applying nonlinear transformations on system states, the linearized transformed system equations are utilized in the observer design procedure. However, due to the singularities imposed by these transformations, certain assumptions are made for the convergence proof of the observer. The proposed observer is tested in simulations and experiments. In experiments, the observer is fed by the needle tip position measurements, which are obtained from real-time ultrasound images.

In radiation belt physics radial distance is often thought of by L*, which approximates the distance from the Earth’s centre to an equatorial point (if we were to assume a dipole magnetic field). Global magnetic field models allow a subset of locations on the ground to be mapped along field lines to a location in space and transformed into L*, provided that location maps to a closed drift path. This allows observations from ground, or low-altitude space-based platforms to be mapped into space in order to inform radiation belt modelling. In current modelling efforts a decision must therefore be made for the global magnetic field model to implement. Many data-based magnetic field models exist; however these models can significantly disagree on mapped L* values for a single point on the ground, during both quiet times and storms. We present a state of the art probabilistic L* mapping tool, Pro-L*, which produces probability distributions for L* corresponding to a given ground location. Pro-L* is an extensive dataset comprising 11 years worth of hourly L* values for 7 global magnetic field models, spanning a high resolution grid in the Northern Hemisphere where ground instruments for radiation belt studies are mostly located. Accompanying each L* approximation, the McIlwain L, magnetic field amplitude and Cartesian location are also stored. Data was generated using the International Radiation Belt Environment Modelling library (IRBEM-Lib), a collection of FORTRAN 77 processes for radiation belt modelling which compute magnetic coordinates and drift shells using various external magnetic field models, hosted in the Python package Spacepy. The data is formatted in yearly compressed csv files, with each row a particular hour containing all of the mentioned variables for each magnetic field model, the corresponding grid points’ magnetic latitude, magnetic longitude, and magnetic local time (MLT). Therefore, each hour index appears for each grid point.

The resonance regions for resonant interactions of radiation belt electrons with obliquely propagating whistler-mode chorus waves are investigated in detail in the Dungey magnetic fields that are parameterized by the intensity of uniform southward interplanetary magnetic field (IMF) Bz or, equivalently, by the values of D=(M/Bz,0)1/3 (where M is the magnetic moment of the dipole and Bz,0 is the uniform southward IMF normal to the dipole’s equatorial plane). Adoption of background magnetic field model can considerably modify the determination of resonance regions. Compared to the results for the case of D = 50 (very close to the dipole field), the latitudinal coverage of resonance regions for 200 keV electrons interacting with chorus waves tends to become narrower for smaller D-values, regardless of equatorial pitch angle, resonance harmonics, and wave normal angle. In contrast, resonance regions for 1 MeV electrons tend to have very similar spatial lengths along the field line for various Dungey magnetic field models but cover different magnetic field intervals, indicative of a strong dependence on electron energy. For any given magnetic field line, the resonance regions where chorus-electron resonant interactions can take place rely closely on equatorial pitch angle, resonance harmonics, and kinetic energy. The resonance regions tend to cover broader latitudinal ranges for smaller equatorial pitch angles, higher resonance harmonics, and lower electron energies, consistent with the results in Ni and Summers [Phys. Plasmas 17, 042902, 042903 (2010)]. Calculations of quasi-linear bounce-averaged diffusion coefficients for radiation belt electrons due to nightside chorus waves indicate that the resultant scattering rates differ from using different Dungey magnetic field models, demonstrating a strong dependence of wave-induced electron scattering effect on the adoption of magnetic field model. Our results suggest that resonant wave-particle interaction processes should be implemented into a sophisticated, accurate global magnetic field model to pursue comprehensive and complete models of radiation belt electron dynamics.

Introduction . I n vivo model for experimental creation of the necessary pathological processes is an important element of scientific research planning. Numerous series of experiments have demonstrated the relevance of modeling oxidative stress in laboratory rats by exposure to hyperthermia, magnetic field and noise. The problem of finding the advantages of each particular prooxidant factor in modeling stress response underlies the current experiment, and its expediency is induced by the need to generate a robust response of the prooxidant/antioxidant system, with statistically significant changes of its parameters, at various periods of time. The study aims at conducting a comparative assessment of the effect of noise, hyperthermia, and magnetic field on the intensity of lipid peroxidation processes in rats. Materials and Methods. The study was conducted at the Research Laboratory of Amur Medical Academy in 2023–2024. The experiment involved 120 white rats divided into four equal in number groups. The animals in the first group (intact) were not subjected to any impacts; the animals in the second group (experimental group 1) were subjected to hyperthermia; the animals in the third group (experimental group 2) were exposed to magnetic field; and the animals in the fourth group (experimental group 3) were exposed to noise. On 7 th , 14 th , and 21 st days of the experiment the rats were decapitated (10 animals from each group) and their blood was sampled for analysis. Oxidative stress markers were determined using the standard techniques; the results were analysed using the Mann-Whitney and Kruskal-Wallis tests. The critical significance level was set to 0.05 for all assessment procedures. Results. With regard to the influence on the accumulation degree of conjugated dienes, statistically significant advantages of noise model over the magnetic field model were recorded (p=0.000005 on 14 th and 21 st days) and over hyperthermia model (p=0.002039 on 14 th day; p=0.001837 on 21 st day). With regard to malondialdehyde, noise exposure surpassed hyperthermia by the end of the experiment (p=0.000561). With regard to ceruloplasmin, the advantages of the noise model over hyperthermia model were established (p=0.0167980 on 7 th day; p=0.004813 on 21 st day), as well as over the magnetic field model (p=0.000005 at all control points). In relation to vitamin E, the noise model advantages over the magnetic field (p=0.000006 on 21 st day) were revealed. Discussion and Conclusions. Significant advantages of the noise-exposure model over the hyperthermia- and magnetic-field-exposure ones in modeling the oxidative stress were established, along with the respective changes in prooxidant/antioxidant system components. By the end of the first, second, and third weeks of the experiment, the statistically significant deviation of oxidative stress markers in laboratory animals occurred under exposure to noise, unlike exposure to temperature and magnetic field. In future, studies on the acoustic load influence on the adaptive potential of warm-blooded organisms are planned to probe possible pharmacological medications to negative influence of noise.

There are conflicting results with regard to the use of catheter-based techniques for continuous paravertebral block. Local anaesthetic spread within the paravertebral space is limited and the clinical effect is often variable. Discrepancies between needle tip position and final catheter position can also be problematic. The aim of this proof-of-concept study was to assess the reliability of placing a newly developed coiled catheter in human cadavers. Sixty Tuohy needles and coiled catheters were placed under ultrasound guidance, three on each side of the thoracic vertebral column in 10 human cadavers. Computed tomography was used to assess needle tip and catheter tip locations. No catheter was misplaced into the epidural, pleural or prevertebral spaces. The mean (SD) distance between catheter tips and needle tips was 8.2 (4.9) mm. The median (IQR [range]) caudo-cephalad spread of contrast dye injectate through a subset of 20 catheters was 4 (4-5[3-8]) thoracic segments. All catheters were removed without incident. Precise paravertebral catheter placement can be achieved using ultrasound-guided placement of a coiled catheter.