A Magnetic Ranging-Aided Dead-Reckoning Positioning System for Pedestrian Applications

This study sought to evaluate the safety and feasibility of a magnetic medical positioning system (MPS) to determine the three-dimensional (3D) position and orientation of intracoronary wires and catheters and to guide angiography and percutaneous coronary intervention (PCI). Coronary angiography relies on fluoroscopy for catheter navigation and often fails to accurately portray vessel tortuosity, overlap, and length because of complex anatomy and foreshortening of curved coronary segments. Forty adult participants underwent coronary angiography and/or PCI with MPS guidance. Two interventional cardiologists independently scored (1-5) the accuracy of MPS catheter tracking projected on live fluoroscopy, recorded cine loops, and 3D vessel reconstructions. Measurements from MPS reconstructions were compared to conventional two-dimensional (2D) quantitative coronary angiography (QCA) measurements. Device procedural success was defined as the ability of the MPS-enabled catheter to reach the target vessel, perform the intended operations, and be retrieved without major adverse cardiac events. Diagnostic coronary angiography was performed in 19 (47.5%) and PCI in 21 patients (52.5%). MPS procedural success was achieved in 36 (90%) of the cases. MPS accuracy was highest with the MPS superimposed on live fluoroscopy (4.9 ± 0.2/5) and the 3D vessel reconstruction (4.7 ± 0.5/5). MPS length measurements were more accurate than conventional QCA. This study demonstrates the feasibility and safety of magnetic catheter tracking with 3D positional data during diagnostic angiography and PCI. Catheter position was accurately projected on real-time fluoroscopy, recorded cine loops, and 3D reconstructions. An MPS may serve as a platform for device navigation and positioning during PCI.

본 논문은 아날로그형 자기위치 장치(magnetic positioning system)의 개발과 퍼지 추론 시스템(FIS: fuzzy inference system)을 통한 정밀도 향상에 관한 것이다. 자기위치 장치는 무인운반차(AGV: automatic guided vehicle)의 자기-자이로 유도장치(magnet-gyro guidance system)에 사용되는 장치로, 바닥에 매설된 자석의 위치를 계측하는 장치이다. 기존의 판매되고 있는 자기-자이로 유도 장치는 외국에서 독점 판매되고 있어, 국내에서는 가격이 매우 비싸다. 또한, 자기위치 장치에 디지털 타입의 단극성 홀센서를 이용하기 때문에 위치측정 정밀도가 낮다. 이에, 본 논문에서는 자기위치 장치를 직접 개발하였고 퍼지 추론 시스템을 통해 자기위치 장치의 정밀도 향상시켰다. 실험은 직접 개발한 아날로그형 자기위치 장치를 이용하였으며, 기존의 위치측정 방법과 제안된 방법의 성능을 비교하였다. 실험 결과, 제안된 방법이 자기위치 장치의 정밀도를 향상시킴을 확인하였다. This paper presents a development of an analog type magnetic positioning system and its positioning accuracy improvement using fuzzy inference system. As the magnetic positioning system used on a magnet-gyro guidance system for AGV(automatic guided vehicle), it measures a position of magnet embedded in floor of the work place. The existing product of the magnetic positioning system is very expensive in Korea because it is being sold in a foreign country exclusively. Moreover, the positioning accuracy of the product is low because it uses digital type unipolar hall sensors. Hence, we developed the magnetic positioning system by ourselves and improved the positioning accuracy of the developed magnetic positioning system using fuzzy inference system. For experiment, we used the analog type magnetic positioning system which we have developed, and compared the performance of the proposed method with the performance of the existing positioning method for the magnetic positioning system. In experimental results, we verified that the proposed method improved the positioning accuracy of the magnetic positioning system.

Magnetic position and orientation detection systems are used in various industrial applications. The large production quantities and high safety standards that such systems must often fulfill requires a stable magnetic field signal. In order to evaluate sensors and such reference signals, we introduce a custom made high precision test equipment for magnetic linear position and orientation detection, which can be used to analyze a permanent magnet's magnetic field behavior and a sensor's response to its excitation. A case study shows differences between datasheet values and actual component values for a commercial permanent magnet. The features and validation of the test equipment as well as measurement samples are presented and discussed.

Properties such as high resolution, contactless (and thus wear-free) measurement, low power consumption, robustness against temperature and contamination as well as low cost make magnetic position and orientation systems appealing for a large number of industrial applications. Nevertheless, one major practical challenge is their sensitivity to fabrication tolerances. In this work, we propose a novel method for magnetic position system calibration based on the analytical computation of the magnetic field and on the application of an evolutionary optimization algorithm. This scheme enables the calibration of more than 10 degrees of freedom within a few seconds on standard quad-core ×86 processors, and is demonstrated by calibrating a highly cost-efficient 3D-printed 3-axis magnetic joystick.

In this paper, a magnetic marker localization system using a super-low-frequency signal-around 100 Hz-is proposed for a surgical navigation system. This method avoids the effect of eddy currents flowing inside metallic surgical tools. The frequency dependence of the magnetic field distortion and localization error due to eddy currents were simulated to determine the optimum signal frequency. From the results of the simulation, the influence of eddy currents on the magnetic marker localization can be insignificant below 1 kHz. The prototype system used marker signals at 94 and 143 Hz and comprised 16-channel fluxgate magnetometers. Markers were successfully localized and the developed system was operational even though metal tools were present in the observation area.

To investigate the safety and feasibility of a newly developed magnetic navigation system for intracoronary tracking. The MediGuide Medical Positioning System (MPS) is a navigation system that was developed to facilitate the navigation of enabled devices within the coronary tree using a magnetic tracking technology. The current prospective, non-randomised, single-centre, first-in-man study was conducted at Universitätsklinikum Regensburg (UKR), Germany on an MPS-enabled AXIOM Artis dFC coronary angiography system (Siemens AG, Forchheim, Germany). We enrolled 20 patients who required IVUS assessment or treatment of a single de novo target lesion in a native coronary artery. The performance was evaluated on a semi-quantitative one-to-five scale where a score of five indicates an excellent superimposition with the vessel and a score of one an unacceptable performance. The mean score for tracking as assessed by projection on life fluoroscopy was 4.89 and 3.58 as assessed by projection on recorded cine-loop. Length measurement of a 20 mm distance was significantly better with the MPS (mean deviation of 0.6 mm=3%) as compared to standard QCA (1.5 mm=8%, p<0.05). Creating a 3D reconstruction was possible in 13 out of 20 cases with an average score of 4.68. No adverse events occurred. The MediGuide Medical Positioning System is safe and feasible in man, facilitates intracoronary navigation and allows 3D reconstruction of the investigated coronary segment.

Although capsule endoscopy is already used for diagnosis of the gastrointestinal tract, a method to precisely localize the capsules, important for accurate diagnosis, is lacking. Static magnetic localization is a promising solution for that purpose. In this paper, the simulation of a differential static magnetic localization system with dynamic geomagnetic compensation was optimized. First, a convergence-test for the position and orientation errors as a function of the dimension of the computational domain was conducted. Subsequently, the diameter-to-length ratio of a permanent magnet was varied and the corresponding position and orientation errors, as well as the mean magnetic flux density measured at the sensor positions, were compared. The results revealed that for a computational domain radius of 800 mm, the position and orientation errors converged to less than 0.1 mm and 0.1°, respectively. The position and orientation errors were also of that order, even with the smallest permanent magnet employed in the study. Furthermore, the mean magnetic flux density measured at the sensors of the proposed magnetic localization system would be detectable using state-of-the-art magnetometers. It is concluded that the differential localization method is also feasible for small permanent magnets, which is especially important considering the limited space within endoscopy capsules.

Mathematical Models of 3D Magnetic Field and 3D Positioning System by Magnetic Field

In this paper, a high accuracy linear positioning system with linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying solenoid, the axial force is achieved by boundary effect of magnet poles and utilized to power the linear motion. While the force for levitation is governed by Ampere's law supplied with the same solenoid. With the levitation in radial direction, there is hardly any friction between the rod and the solenoid. The high speed motion can hence be achieved. Besides, the axial force act on the rod is a smooth function of rod position, so the system can provide nanometer resolution linear positioning to the molecule size. Since the force-position relation is highly nonlinear, and mathematical model is derived according to some assumptions, such as equivalent solenoid of the permanently magnetized rod, so there exists unknown dynamics in practical application. Thus robustness is an important issue in controller design. Meanwhile the load effect reacts directly on the servo system without transmission elements, so the capability of rejection is also required. With above consideration, a time-delay control scheme is chosen and applied. By comparing the input-output relation and the mathematical model, the time-delay controller calculates an estimation of unmodelled dynamics and disturbance then composes the desired compensation into the system. Effectiveness of the linear positioning system and control scheme are illustrated with simulation results.

We presents a new closed loop approach for the active actuation of wireless capsule endoscope inside the human GI tract. A magnet is enclosed in the capsule, and its position, orientation, and movement are detected by a magnetic localization system. To actuate the capsule, an external rotative magnetic field is applied around human body such that a driving force is created in the capsule by the magnet. Through the spiral structure on the capsule surface, the capsule is rotated to move forward or backward with the aid of mucus of the GI tract. According to the hydromechanical lubrication theory and Newton viscous law, we build the traction force model, the friction force model and the locomotion speed model. In this paper, the simulation results of all these three mathematical models are given, which will provide theoretical guide to design the spiral impeller structure of the capsule and estimate the motion force induced by external magnetic field.

The authors have used several configurations of a commercial 6D magnetic position and orientation measurement system to track an ultrasound scanhead and reconstruct 2D ultrasound images in 3D space. They have measured precision and accuracy with two magnetic sensors working in parallel, and with a miniaturized magnetic sensor. The use of two standard size sensors has shown limited improvement in precision (1.5 mm RMS uncertainty compared with 1.8 mm for a single sensor). The miniature sensor has an average precision of 2.1 mm over its operating range. The miniature sensor has been calibrated with an imaging system and has been used in 3D reconstructions of the stomach and the carotid artery.

The accuracy of intraoperative localization of tumors undetectable under optical visualization determines surgical quality and survival outcomes in gastrointestinal cancers. Current approaches, however, remain constrained by suboptimal spatial resolution and low procedural efficiency. Additionally, conventional electromagnetic localization techniques based on image registration face challenges in soft tissue deformation scenarios. Here, we developed an electromagnetic localization technology for intraluminal tumor localization based on injectable magnetic hydrogel with sustained magnetization properties (MagLabel-IH). Following endoscopic injection into the gastrointestinal tract and in situ realignment, MagLabel-IH enables continuous intraluminal magnetic signal tracing. Intraoperatively, a dynamic registration framework synchronizes the magnetic coordinate system with real-time anatomical positions under visual guidance, achieving precise localization of optically invisible intraluminal tumors. The system demonstrated exceptional surgical instrument maneuverability (e.g., tissue grasping, resection path selection) during MagLabel-IH detection. In vivo animal evaluations demonstrated significantly enhanced localization accuracy compared to conventional biological dyes tattooing (3.8 ± 0.8 mm vs. 16.8 ± 8.6 mm, P < 0.05). Furthermore, the magnetic labels-based localization system exhibited promising utility for tumor margin demarcation and planning of gastrointestinal functional reconstruction.

To investigate the therapeutic effect of topical corticosteroids injection and systemic application in the treatment of typing idiopathic sudden sensorineural hearing loss (ISSNHL). Total of 438 patients with ISSNHL, including 76 with hearing loss in low-middle frequencies, 43 in middle-high frequencies, 162 in all frequencies and 157 in total deafness, were randomly divided into two groups, the systemic application group: dexamethasone (DEX) was applied by intravenous injection in dose of 10 mg×3 d followed by 5 mg×4 d, and the topical injection group: methylprednisolone sodium succinate of 40 mg was injected into cortical bone of mastoid region every three days. According to the results of pure-tone threshold audiometry, the curative effect among ISSNHL with low-middle frequencies, middle-high frequencies, all frequencies hearing loss, and total deafness were evaluated. SPSS 18.0 software was used to analyze the data. Among 220 patients with systemic application of DEX, 66 subjects (30.0%) cases were recovery, 51 (23.2%) were excellent better, 39 (17.7%) better, 64 (29.1%) were poor, and the total effective rate was 70.9% (156/220) . There was no statistical difference in total effective rate of four typing subgroups (χ(2) = 1.60, P > 0.05). And the recovery rate in total deafness subgroup was significant lower than that in low-middle and all frequencies subgroups (χ(2) = 10.63 and 15.94 respectively, both P < 0.05). In the topical injection group, the recovery rate was 30.3% (66 cases), excellent better 18.8% (41), better 15.6% (34), poor 35.3% (77), and the total effective rate was 64.7% (141/220) . There were statistical differences of total effective rate in low-middle frequencies in comparison with that in all frequencies (χ(2) = 8.38) and total deafness (χ(2) = 7.28) subgroups (both P < 0.05). Regarding recovery rate, there were significant differences between each two typing subgroups, except middle-high frequencies subgroup vs. all frequencies (χ(2) = 1.60) and total deafness (χ(2) = 2.29) subgroups (both P < 0.05). In 76 ISSNHL with hearing loss in low-middle frequencies, the recovery rate in cases with local corticosteroids injection(65.0%) was significantly increased in comparison with that with systemic application (41.7%), χ(2) = 4.15, P < 0.05. There were increasing tendencies of curative effect in other three typing groups by systemic corticosteroids application when compared with local injection, but no statistical significances (all P > 0.05). For low-middle frequencies ISSNHL, the corticosteroids administration of local injection should be the optimization. Systemic application would be applied for middle-high frequencies, all frequencies and total deafness.

Numerous indoor positioning technologies and systems have been proposed to localize people and objects in large buildings. Wi-Fi and Bluetooth positioning systems using fingerprinting have gained popularity, due to the wide availability of existing infrastructure. Unfortunately, the implementation of fingerprinting-based methods requires time-consuming radio surveys to prepare databases (RSSI maps) that serve as a reference for the radio signal. These surveys must be conducted for each individual building. Here, we investigate the possibility of using simulated RSSI maps with fingerprinting-based indoor localization systems. We discuss the suitability of the two popular radio wave propagation models for the preparation of RSSI reference data: ray tracing and multiwall. Based on an analysis of several representative indoor scenarios, we evaluated the performance of RSSI distribution maps obtained from simulations versus maps obtained from measurement campaigns. An experimental positioning system developed by the authors was used in the study. Based on Bluetooth Low Energy beacons and mobile devices (smartphones), the system uses fingerprinting followed by a particle filter algorithm to estimate the user’s current position from RSSI measurements and a reference spatial RSSI distribution database for each Bluetooth beacon in the building. The novelty of our contribution is that we evaluate the performance of the positioning system with RSSI maps prepared both from measurements and using the two most representative indoor propagation methods, in three different environments in terms of structure and size. We compared not only the three RSSI maps, but also how they influence the performance of the fingerprint-based positioning algorithm. Our original findings have important implications for the development of indoor localization systems and may reduce deployment times by replacing reference measurements with computer simulations. Replacing the labor-intensive and time-consuming process of building reference maps with computer modeling may significantly increase their usefulness and ease of adaptation in real indoor environments.

In this paper, we present an omnidirectional artificial landmark model and a robust artificial landmark recognition algorithm for indoor mobile robot positioning. The landmark model encodes identities with nested circles in black and white, which provides stable edge response and enables strong tolerance to various lighting conditions and perspective distortions. The corresponding positioning system uses a single upward-facing webcam as the vision sensor to capture landmarks. To address the effect of the lighting and sensing noise, the topological contour analysis is applied to detect landmarks, and the dynamic illumination adjustment is used to assist landmark recognition. Based on the landmark recognition, the absolute position of the camera in the environment is estimated using a trilateration algorithm. The landmark model and positioning system are tested with a mobile robot in a real indoor environment. The results show that the purposed technique provides autonomous indoor positioning for mobile robots with high robustness and consistency.