A Non-invasive Real-time Localization System for Enhanced Efficacy in Nasogastric Intubation

Feasibility of a low-cost magnet tracking device in confirming nasogastric tube placement at point of care, a clinical trial

An affordable and reliable way of confirming the placement of nasogastric tube (NGT) at point-of-care is an unmet need. Using a novel algorithm and few sensors, we developed a low-cost magnet tracking device and showed its potential to localize the NGT preclinically. Here, we embark on a first-in-human trial. Six male and 4 female patients with NGT from the general ward of an urban hospital were recruited. We used the device to localize the NGT and compared that against chest X-ray (CXR). In 5 patients, with the sensors placed on the sternal angle, the trajectory of the NGT was reproduced by the tracking device. The tracked location of the NGT deviated from CXR by 0.55 to 1.63 cm, and a downward tracking range of 17 to 22 cm from the sternal angle was achieved. Placing the sensors on the xiphisternum, however, resulted in overt discordance between the device's localization and that on CXR. Short distance between the sternal angle and the xiphisternum, and lower body weight were observed in patients in whom tracking was feasible. Tracking was quick and well tolerated. No adverse event occurred. This device feasibly localized the NGT in 50% of patients when appropriately placed. Further refinement is anticipated.ClinicalTrials.gov identifier: NCT05204901.

Stomach Geometry Reconstruction Using Serosal Transmitting Coils and Magnetic Source Localization

OBJECTIVE

Bioelectric slow waves (SWs) are a key regulator of gastrointestinal motility, and disordered SW activity has been linked to motility disorders. There is currently a lack of practical options for the acquisition of the 3D stomach geometry during research studies when medical imaging is challenging. Accurately recording the geometry of the stomach and co-registering electrode and sensor positions would provide context for in-vivo studies and aid the development of non-invasive methods of gastric SW assessment.

METHODS

A stomach geometry reconstruction method based on the localization of transmitting coils placed on the gastric serosa was developed. The positions and orientations of the coils, which represented boundary points and surface-normal vectors, were estimated using a magnetic source localization algorithm. Coil localization results were then used to generate surface models. The reconstruction method was evaluated against four 3D-printed anatomically realistic human stomach models and applied in a proof of concept in-vivo pig study.

RESULTS

Over ten repeated reconstructions, average Hausdorff distance and average surface-normal vector error values were 4.7 ±0.2 mm and 18.7 ±0.7° for the whole stomach, and 3.6 ±0.2 mm and 14.6 ±0.6° for the corpus. Furthermore, mean intra-array localization error was 1.4 ±1.1 mm for the benchtop experiment and 1.7 ±1.6 mm in-vivo.

CONCLUSION AND SIGNIFICANCE

Results demonstrated that the proposed reconstruction method is accurate and feasible. The stomach models generated by this method, when co-registered with electrode and sensor positions, could enable the investigation and validation of novel inverse analysis techniques.

Reconstruction of stomach geometry using magnetic source localization

Routine diagnosis of gastric motility disorders represents a significant problem to current clinical practice. The non-invasive electrogastrogram (EGG) and magnetogastrogram (MGG) enable the assessment of gastric slow wave (SW) dysrhythmias that are associated with motility disorders. However, both modalities lack standardized methods for reliably detecting patterns of SW activity. Subject-specific anatomical information relating to the geometry of the stomach and its position within the torso have the potential to aid the development of relations between SWs and far-fields. In this study, we demonstrated the feasibility of using magnetic source localization to reconstruct the geometry of an anatomically realistic 3D stomach model. The magnetic fields produced by a small (6.35 × 6.35 mm) N35 neodymium magnet sequentially positioned at 64 positions were recorded by an array of 27 magnetometers. Finally, the magnetic dipole approximation and a particle swarm optimizer were used to estimate the position and orientation of the permanent magnet. Median position and orientation errors of 3.8 mm and 7.3° were achieved. The estimated positions were used to construct a surface mesh, and the Hausdorff Distance and Average Hausdorff Distance dissimilarity metrics for the reconstructed and ground-truth models were 11.6 mm and 2.4 mm, respectively. The results indicate that source localization using the magnetic dipole model can successfully reconstruct the geometry of the stomach.

An overview of percutaneous endoscopic gastrostomy tube placement in the intensive care unit

Critically ill patients are at increased risk for malnutrition as they often have underlying acute and chronic illness, stress related catabolism, decreased appetite, trauma and ongoing inflammation. Malnutrition is recognized as a leading cause of adverse outcomes, higher mortality, and increased hospital costs. Percutaneous endoscopic gastrostomy (PEG) tubes provide a safe and effective route to provide supplemental enteral nutrition to these patients. PEG placement has essentially replaced surgical gastrostomy as the modality of choice for longer term feeding in patients. This is a highly prevalent procedure with 160,000 to 200,000 PEG procedures performed each year in the United States. The purpose of this review is to provide an overview of current knowledge and practice standards with regards to placement of PEG tube in the Intensive Care Unit (ICU). When a patient is considered for a PEG tube, it is important to evaluate the treatment alternatives and identify the best option for each patient. In this review, we provide the advantages and disadvantages of various feeding modalities and devices. We review the indications and contraindications for PEG tube placement as well as the risks of this procedure. We then describe in detail the per-oral pull, per-oral push, and direct percutaneous techniques for PEG tube placement. Additionally, we review the feasibility of having interventional pulmonologists place PEG tubes in the ICU.

A Low-Cost, Point-of-Care Test for Confirmation of Nasogastric Tube Placement via Magnetic Field Tracking

In this work, we aim to achieve low-cost real-time tracking for nasogastric tube (NGT) insertion by using a tracking method based on two magnetic sensors. Currently, some electromagnetic (EM) tracking systems used to detect the misinsertion of the NGT are commercially available. While the EM tracking systems can be advantageous over the other conventional methods to confirm the NGT position, their high costs are a factor hindering such systems from wider acceptance in the clinical community. In our approach, a pair of magnetic sensors are used to estimate the location of a permanent magnet embedded at the tip of the NGT. As the cost of the magnet and magnetic sensors is low, the total cost of the system can be less than one-tenth of that of the EM tracking systems. The experimental results exhibited that tracking can be achieved with a root mean square error (RMSE) of 2-5 mm and indicated a great potential for use as a point-of-care test for NGT insertion, to avoid misplacement into the lung and ensure correct placement in the stomach.

Nasogastric Tube Feeding in Older Patients: A Review of Current Practice and Challenges Faced

Nasogastric tube feeding is an essential way of delivering enteral nutrition when the oral route is insufficient or unsafe. Malnutrition is recognised as a reversible factor for sarcopenia and frailty. It is therefore crucial that malnutrition is treated in older inpatients who have dysphagia and require enteral nutrition. Despite five National Patient Safety Alerts since 2005, “Never Events” related to nasogastric feeding persist. In addition to placement errors, current practice often leads to delays in feeding, which subsequently result in worse patient outcomes. It is crucial that tube placement is confirmed accurately and in a timely way. Medical advancements in this area have been slow to find a solution which meets this need. In this paper, we provide an updated review on the current use of feeding nasogastric tubes in the older population, the issues associated with confirming correct placement, and innovative solutions for improving safety and outcomes in older patients.

Visualising the knowledge structure and evolution of wearable device research

In recent years, the literature associated with wearable devices has grown rapidly, but few studies have used bibliometrics and a visualisation approach to conduct deep mining and reveal a panorama of the wearable devices field. To explore the foundational knowledge and research hotspots of the wearable devices field, this study conducted a series of bibliometric analyses on the related literature, including papers' production trends in the field and the distribution of countries, a keyword co-occurrence analysis, theme evolution analysis and research hotspots and trends for the future. By conducting a literature content analysis and structure analysis, we found the following: (a) The subject evolution path includes sensor research, sensitivity research and multi-functional device research. (b) Wearable device research focuses on information collection, sensor materials, manufacturing technology and application, artificial intelligence technology application, energy supply and medical applications. The future development trend will be further studied in combination with big data analysis, telemedicine and personalised precision medical application.

Two Magnetic Sensor Based Real-Time Tracking of Magnetically Inflated Swallowable Intragastric Balloon

This paper presents a two magnetic sensor based tracking method for a magnetically inflated intragastric balloon capsule (MIBC) which is used for obesity treatment. After the MIBC is swallowed, it is designed to be inflated inside the stomach by approaching a permanent magnet (PM) externally near the abdomen. However, if the balloon inflation is accidentally triggered while the MIBC is still in the esophagus, the esophagus will be damaged. Therefore, to safely inflate the MIBC, we aim to track the MIBC's position along the esophagus and confirm the MIBC passes through. Typically, magnetic sensor based tracking systems tend to be bulky and costly since they involve computationally intensive optimization with many magnetic sensors. To solve those problems, we develop an algorithm that estimates the position of the PM inside the MIBC by using the grid search combined with the dynamically confined search range and search threshold modulation. Our tracking method achieved an average 1D position error of 3.48 mm which is comparable to the up to 4 mm average error for the other magnetic sensor based tracking systems that require more sensors and computational power compared to our system.

Passive magnetic-based localization for precise untethered medical instrument tracking

BACKGROUND AND OBJECTIVE

Motion tracking and navigation systems are paramount for both safety and efficacy in a variety of surgical insertions, interventions and procedures. Among the state-of-art tracking technology, passive magnetic tracking using permanent magnets or passive magnetic sources for localization is an effective technology to provide untethered medical instrument tracking without cumbersome wires needed for signal or power transmission. Motivated by practical needs in two medical insertion procedures: Nasogastric intubation and Ventriculostomy, we propose a unified method based on passive magnetic-field localization, for enhanced efficacy and safety.

METHODS

Traditional approaches to passive magnetic tracking involve solving the inverse localization problem. Limited by the idealistic magnetic field dipole model and computationally intense nonlinear optimization algorithm, the overall accuracy and computational cost are greatly compromised. The method introduced here features direct localization with artificial neural network (ANN) models that bypasses the need to resolve the inverse problem and is adaptable for a variety of real-time localization and tracking applications.

RESULTS

The efficiency of the two methods, the inverse optimization method and the direct ANN method are experimentally evaluated by comparing the estimated position of reference trajectories for typical nasogastric and ventriculostomy insertion paths performed by a dexterous robotic arm which provides ground truth measurement. It was found that within the region of interest (ROI), the direct ANN technique could significantly improve the localization accuracy, with an average experimental localization error of less than 2 mm, while that of the traditional inverse optimization method using a dipole-based mathematical model at greater than 5 mm. Ex-vivo experiments were performed to validate the localization methods in clinical settings.

CONCLUSIONS

While the proposed method for passive magnetic tracking requires a procedure-specific pre-procedural calibration, it is able to provide real-time tracking with high accuracy, robustness and diversity. It could be the missing piece to the puzzle to bring passive magnetic tracking technology into practice, therefore leading to untethered medical instrument tracking.

High Accuracy Passive Magnetic Field-Based Localization for Feedback Control Using Principal Component Analysis

In this paper, a novel magnetic field-based sensing system employing statistically optimized concurrent multiple sensor outputs for precise field-position association and localization is presented. This method capitalizes on the independence between simultaneous spatial field measurements at multiple locations to induce unique correspondences between field and position. This single-source-multi-sensor configuration is able to achieve accurate and precise localization and tracking of translational motion without contact over large travel distances for feedback control. Principal component analysis (PCA) is used as a pseudo-linear filter to optimally reduce the dimensions of the multi-sensor output space for computationally efficient field-position mapping with artificial neural networks (ANNs). Numerical simulations are employed to investigate the effects of geometric parameters and Gaussian noise corruption on PCA assisted ANN mapping performance. Using a 9-sensor network, the sensing accuracy and closed-loop tracking performance of the proposed optimal field-based sensing system is experimentally evaluated on a linear actuator with a significantly more expensive optical encoder as a comparison.