Electromagnetic Tracking Research Articles

A Steerable and Electromagnetically Tracked Catheter: Navigation Performance Compared With Image Fusion in a Swine Model

Purpose: Cannulation of visceral vessels is necessary during fenestrated and branched endovascular aortic repair. In an attempt to reduce the associated radiation and contrast dose, an electromagnetically (EM) trackable and manually steerable catheter has been developed. The purpose of this preclinical swine study was to evaluate the cannulation performance and compare the cannulation performance using either EM tracking or image fusion as navigation tools. Materials and Methods: Both renal arteries, the superior mesenteric artery, and the celiac trunk were attempted to be cannulated using a 7F steerable, EM trackable catheter in 3 pigs. Seven operators attempted cannulation using first 3-dimensional (3D) image navigation with EM tracking and then conventional image fusion guidance. The rate of successful cannulation was recorded, as well as procedure time and radiation exposure. Due to the lack of an EM trackable guidewire, cannulations that required more than 1 attempt were attempted only with image fusion. The EM tracking position data were registered to preoperative 3D images using a vessel-based registration algorithm. Results: A total of 72 cannulations were attempted with both methods, and 79% (57) were successful on the first attempt for both techniques. There was no difference in cannulation rate (p=1), and time-use was similar. Successful cannulation with image fusion was achieved in 97% of cases when multiple attempts were allowed. Conclusion: This study demonstrated the feasibility of a steerable and EM trackable catheter with 3D image navigation. Navigation performance with EM tracking was similar to image fusion, without statistically significant differences in cannulation rates and procedure times. Further studies are needed to demonstrate this utility in patients with aortic disease. Clinical Impact Electromagnetic tracking in combination with a novel steerable catheter reduces radiation and contrast media doses while providing three-dimensional visualization and agile navigation during endovascular aortic procedures.

Electromagnetic tracking in interstitial brachytherapy: A systematic review

Brachytherapy is a well-established treatment option for different cancer types. One treatment option, namely temporary afterloading brachytherapy, utilizes an encapsulated radioactive source, which is guided through implanted applicators to pre-defined dwell positions, to deliver highly conformal and concentrated doses to the target volume. However, treatment errors and uncertainties might still occur. The treatment therefore requires a stringent verification on an individual patient level, particularly in the form of applicator reconstruction. Electromagnetic tracking (EMT) is a possible verification option whose application neither relies on direct line of sight nor does it increase the radiation exposure. However, its systematic clinical application is not yet realized. This review will separate the concept of treatment verification through the use of electromagnetic tracking into four focus groups and categorize the relevant papers within said groups. The four focus groups are geometric assessment, applicator reconstruction, patient-individual quality assurance and adaptive treatment planning. The reviewed papers can be mainly sorted into the focus groups of geometric assessment and applicator reconstruction underlining the potential of EMT as an asset for reconstruction and localization. A smaller group of papers can be associated with patient-individual quality assurance where the detection of implant variations such as swaps within the connector cohort or single catheter shifts take center stage. The final focus group, adaptive treatment planning, is sparsely represented, yet the feasibility of an adaptive treatment course can be derived. This review will close with a discussion of possible improvements and illustrate the path ahead to clinical implementation.

Image-guided Raman spectroscopy navigation system to improve transperineal prostate cancer detection. Part 2: in-vivo tumor-targeting using a classification model combining spectral and MRI-radiomics features.

.SignificanceThe diagnosis and treatment of prostate cancer (PCa) are limited by a lack of intraoperative information to accurately target tumors with needles for biopsy and brachytherapy. An innovative image-guidance technique using optical devices could improve the diagnostic yield of biopsy and efficacy of radiotherapy.AimTo evaluate the performance of multimodal PCa detection using biomolecular features from in-situ Raman spectroscopy (RS) combined with image-based (radiomics) features from multiparametric magnetic resonance images (mpMRI).ApproachIn a prospective pilot clinical study, 18 patients were recruited and underwent high-dose-rate brachytherapy. Multimodality image fusion (preoperative mpMRI with intraoperative transrectal ultrasound) combined with electromagnetic tracking was used to navigate an RS needle in the prostate prior to brachytherapy. This resulting dataset consisted of Raman spectra and co-located radiomics features from mpMRI. Feature selection was performed with the constraint that no more than 10 features were retained overall from a combination of inelastic scattering spectra and radiomics. These features were used to train support vector machine classifiers for PCa detection based on leave-one-patient-out cross-validation.ResultsRS along with biopsy samples were acquired from 47 sites along the insertion trajectory of the fiber-optics needle: 26 were confirmed as benign or grade , and 21 as grade group , according to histopathological reports. The combination of the fingerprint region of the RS and radiomics showed an accuracy of 83% ( and a ), outperforming by more than 9% models trained with either spectroscopic or mpMRI data alone. An optimal number of features was identified between 6 and 8 features, which have good potential for discriminating grade group () or grade group ().ConclusionsIn-situ Raman spectroscopy combined with mpMRI radiomics features can lead to highly accurate PCa detection for improved in-vivo targeting of biopsy sample collection and radiotherapy seed placement.

Relooking at double-bundle versus single-bundle anterior cruciate ligament reconstruction: A biomechanical model to evaluate which can confer better rotatory stability

BackgroundTo treat anterior cruciate ligament (ACL) injuries, double-bundle ACL reconstruction has been proposed as a more anatomical approach relative to single-bundle reconstruction. However, controversy remains over which technique is superior in addressing knee instability, particularly rotational laxity. We hypothesize that double-bundle reconstruction better restores rotational knee laxity, while both methods are similar in restoring anterior knee laxity, to intact knee levels. MethodsA controlled laboratory study. Eight cadaveric knees were tested accordingly: (1) static anterior laxity testing under 150 N-anterior tibial loading at 20°, 60° and 90° knee flexion using a material testing machine, followed by (2) dynamic simulated pivot-shift with knee-specific loading involving iliotibial band forces, valgus and internal rotation torques, while the knee was brought from extension to 90° flexion on a 6°-of-freedom custom-designed rig. Tibiofemoral kinematics were recorded using an electromagnetic tracking system for the ACL-intact, ACL-deficient, single-bundle and double-bundle ACL-reconstructed knee conditions. FindingsDouble-bundle reconstruction reduced internal rotation under pivot-shift to levels not significantly different from ACL-intact conditions (P > .173), unlike single-bundle that remained significantly higher at 10–40° flexion (P < .05). For anterior laxity, there was no significant difference between double-bundle, single-bundle, and ACL-intact conditions under static testing (P > .175) or pivot-shift (P = .219). The maximum extent of knee envelope laxity was significantly reduced for double-bundle relative to single-bundle, particularly for the rotatory component (P = .012). InterpretationDouble-bundle was biomechanically superior to single-bundle in addressing envelope of rotation, while both techniques restored anterior knee laxity to ACL-intact levels.

Work space analysis of a new instrument for Natural Orifice Transluminal Endoscopic Surgery (NOTES)

Abstract Minimally invasive procedures such as Natural Orifice Transluminal Endoscopic Surgery (NOTES) require powerful, small, and flexible instruments. A cable-driven instrument was developed, which is able to retract tissue to create sufficient space for an actual operation (e.g. cholecystectomy). In this paper, the work space of a developed instrument is presented. The work space is calculated using direct kinematics equations and verified by measurement using an electromagnetic (EM) tracking system. The angular orientation of the instrument can be up to 85° with a length of the active section of 60 mm. However, a longitudinal rotation up to 17° becomes apparent. This is due to the characteristics of the steel cable used for actuation. Nevertheless, the instrument reaches the intended work space. Further measurements are necessary to evaluate the instrument’s behavior under payload and whether this affects the work space.

Image-guided Raman spectroscopy navigation system to improve transperineal prostate cancer detection. Part 1: Raman spectroscopy fiber-optics system and in situ tissue characterization.

.SignificanceThe diagnosis of prostate cancer (PCa) and focal treatment by brachytherapy are limited by the lack of precise intraoperative information to target tumors during biopsy collection and radiation seed placement. Image-guidance techniques could improve the safety and diagnostic yield of biopsy collection as well as increase the efficacy of radiotherapy.AimTo estimate the accuracy of PCa detection using in situ Raman spectroscopy (RS) in a pilot in-human clinical study and assess biochemical differences between in vivo and ex vivo measurements.ApproachA new miniature RS fiber-optics system equipped with an electromagnetic (EM) tracker was guided by trans-rectal ultrasound-guided imaging, fused with preoperative magnetic resonance imaging to acquire 49 spectra in situ (in vivo) from 18 PCa patients. In addition, 179 spectra were acquired ex vivo in fresh prostate samples from 14 patients who underwent radical prostatectomy. Two machine-learning models were trained to discriminate cancer from normal prostate tissue from both in situ and ex vivo datasets.ResultsA support vector machine (SVM) model was trained on the in situ dataset and its performance was evaluated using leave-one-patient-out cross validation from 28 normal prostate measurements and 21 in-tumor measurements. The model performed at 86% sensitivity and 72% specificity. Similarly, an SVM model was trained with the ex vivo dataset from 152 normal prostate measurements and 27 tumor measurements showing reduced cancer detection performance mostly attributable to spatial registration inaccuracies between probe measurements and histology assessment. A qualitative comparison between in situ and ex vivo measurements demonstrated a one-to-one correspondence and similar ratios between the main Raman bands (e.g., amide I-II bands, phenylalanine).ConclusionsPCa detection can be achieved using RS and machine learning models for image-guidance applications using in situ measurements during prostate biopsy procedures.

Power Compensation-Oriented SVM-DPC Strategy for a Fault-Tolerant Back-to-Back Power Converter Based DFIM Shipboard Propulsion System

For safety critical transportation applications like all-electric ship propulsion systems (SPS), the reliable system operation is definitely the primary concern. In this paper, a fault-tolerant back-to-back power converter based on the four-switch three-phase (FSTP) topology is applied to a doubly-fed induction machine (DFIM) based all-electric SPS. A power compensation-oriented space vector modulation direct power control (PCSVM-DPC) strategy with dc-bus voltage unbalance elimination is proposed to ride through the single bridge arm open-circuit fault in the source-side converter (SSC) and improve the system dynamic performance simultaneously. Besides, the DFIM-SPS is endowed with excellent steady-state performance by applying the proposed control strategy. The dc-bus voltage deviation is suppressed based on the calculation of active and reactive power compensation terms to increase the dc-bus voltage utilization rate. Moreover, good post-fault system operation performance can be achieved with fast active power and electromagnetic torque tracking speeds. The proposed PCSVM-DPC strategy for the fault-tolerant FSTP SSC based DFIM-SPS is easy to implement without high computational burden. The SVM-DPC method is also presented for the load-side converter. The proposed control strategy is verified by experiments on a 1.5 kW DFIM-SPS experimental platform.

Pelvis and Trunk Energy Flow in Collegiate Softball Pitchers With and Without Upper Extremity Pain

Background: The softball pitch is a full-body motion, where efficient proximal to distal energy flow through the kinetic chain is said to reduce stress at the upper extremity. Although altered trunk kinematic parameters are associated with upper extremity pain in softball pitchers, further research is needed to determine whether differences exist in proximal energy flow between softball pitchers with and without pain. Hypothesis/Purpose: To examine pelvis and trunk energy flow during the acceleration phase of the pitch in collegiate softball pitchers with and without upper extremity pain. It was hypothesized that those with upper extremity pain would have less energy flowing into the proximal ends of the pelvis and trunk as well as less energy flowing out of the distal ends of the pelvis and trunk during the acceleration phase when compared with pitchers who did not have upper extremity pain. Study Design: Descriptive laboratory study. Methods: A total of 54 female National Collegiate Athletic Association Division I softball pitchers (age, 20.2 ± 2.0 years; height, 173.5 ± 6.9 cm; weight, 78.5 ± 11.5 kg) were assigned to pain (n = 17) and pain-free (n = 38) groups. Participants pitched 3 maximal effort rise-balls for a strike, and the average of the 3 trials was used for analysis. Kinematic data were collected at 100 Hz using an electromagnetic tracking system. A segment power analysis was performed to quantify energy flow for the pelvis and trunk. The Mann-Whitney U test was used to compare pelvis and trunk energy flow during the acceleration phase of the pitch as well as pitch velocity between collegiate softball pitchers with and without upper extremity pain. Results: No significant differences were found between pelvis and trunk energy flow during the acceleration phase or pitch velocity between collegiate softball pitchers with and without upper extremity pain (all P values >.057). Conclusion: Previous research determined that kinematic parameters differ between collegiate pitchers with and without upper extremity pain. However, the current study found no difference in pelvis and trunk energy flow or pitch velocity. Although altered kinematics in collegiate pitchers with upper extremity pain may serve as compensation patterns to maintain pitch velocity and proximal energy flow, future research is needed to confirm this postulation. Clinical Relevance: The lack of energy flow differences between upper extremity pain groups suggests that pitchers may adapt their biomechanics to maintain trunk and pelvis energy flow patterns. Coaches, athletes, and clinicians should know that movement adaptations can allow for maintained performance levels but may result in the presence of pain that may manifest in other deleterious and injury-susceptible biomechanics.

Electromagnetic Tracking of Elongated Sensors for Endoscopic Navigation

As the prevalence of image-guided interventions increases, electromagnetic tracking (EMT) systems play an important role in modern patient care, as they enable real-time instrument positioning and navigation inside the human body without line-of-sight restrictions. Miniature-size inductive coils are the gold standard in clinical settings, as they provide accurate, passive sensing of the magnetic field. To compensate for their small dimensions, such sensors are designed with an elongated shape, where the coil length is usually 10 to 20 times larger than the diameter. In this article, the benefits of a field model based on the magnetic scalar potential formulation are demonstrated for EMT applications where elongated tracking sensors are used. The novel method resolves the single-point approximation error when the coil length is not negligible, and demonstrates improvements in terms of speed and storage requirements. A detailed analysis is proposed where alternative formulations of the magnetic model used in the tracking algorithm are compared. Although this work does not resolve any substantial limits of EMT used in a clinical environment, which are mainly caused by the presence of magnetic distortions, the proposed method is an improvement over existing EMT systems because it enables more accurate and faster tracking. The method might facilitate the use of longer tracking sensor coils which can achieve high sensitivities without the requirement of a magnetic core. In the envisioned application, such coils may be wound around flexible instruments, such as endoscopes or catheters.

Determine the vertical ground reaction forces and knee mechanics with different gait inclinations in the sheep model.

Our current understanding of knee mechanics and anterior cruciate ligament (ACL) function is predominately based on data recorded during simulations of clinical examinations or the application of nonphysiologic loads and motions. These methodologies provide little information on knee and ACL mechanics during activities of daily living (ADLs). Additionally, researchers have not directly measured knee kinetics, knee contact pressures, and ACL forces, and it is unknown how these parameters change with different activities. This study quantified the effects of activity level on vertical ground reaction forces, knee kinematics, and joint and ligament forces during in vivo motions. Five female Suffolk sheep were walked twice weekly on a treadmill during level (0°), inclined (+6°), and declined (-6°) gait for 12 weeks. Electromagnetic (EM) trackers were surgically implanted onto the left distal femur and the left proximal tibia, and in vivo motions were recorded for all activities. Following sacrifice, the in vivo motions were applied to their respective knees using a serial robot with a multi-axis load cell. In vitro simulations were repeated to measure (a) total knee forces, (b) contact pressure maps, and (c) ACL-only forces. Declining the gait surface led to increased posterior translation during the swing phase and decreased flexion at hoof-strike, decreased medial contact pressure at push-off, decreased ACL force at hoof-strike and increased ACL force at push-off. This study established a system that can be used to examine knee mechanics and ACL forces during ADLs for different knee states to define design requirements for ACL reconstruction techniques.

Shape estimation of the anterior part of a flexible ureteroscope for intraoperative navigation

Flexible ureteroscopy (FURS) plays an important role in the diagnosis and treatment of urological diseases. However, manipulating a flexible ureteroscope to the target quickly and safely may be challenging because of the tortuous lumen or poor visibility. Thus, information on the shape of the anterior part of a flexible ureteroscope in addition to the real-time pose is needed to perform accurate maneuvering in the lumen with minimal impingement on the inner renal wall and resulting tissue damage in FURS. An adaptive mixed-order Bézier curve fitting algorithm and electromagnetic tracking (EMT) technique were developed for shape estimation utilizing the length of the anterior part, kinematic constraints and the pose information provided by two electromagnetic (EM) sensors mounted at the tip and base of the anterior part. A series of experiments were performed to qualitatively and quantitatively verify the validity of our method. Moreover, algorithm threshold conditions with reference significance under various shape cases were studied. The performance of our method was evaluated based on 19 representative planar bending shapes that often appear in FURS and eight non-planar shapes, yielding an average error (AE) of 1.0mm. Moreover, the experiments proved the feasibility of applying our method in cases in which large bending angles (near 270 degrees) occur. Based on data from two EM sensors mounted at the tip and base of the anterior part of a flexible ureteroscope, the proposed algorithm adaptively selects a cubic or quartic Bézier curve to fit the shape of the anterior part. Experimental results prove the feasibility of our shape estimation method over a broad bending range. The proposed method demonstrates significant potential for use in ureteroscopic navigation systems and robot-assisted surgery.

Ultrasound training simulator using augmented reality glasses: an accuracy and precision assessment study.

Ultrasound (US) imaging despite being safe, cost-effective, and radiation-free, presents poor quality and artifacts, requiring specific medical training in US probe handling and image evaluation. The use of simulators to train physicians has proven its effectiveness, but most of them require specific facilities and hardware. In the last few years, augmented reality has gained relevance to simulate real scenarios which can avoid large setups and broaden medical training to more physicians. This work proposes a new framework for the training of US images acquisition. It consists of a custom-made application that runs on AR glasses (Microsoft HoloLens 2) and interacts with a US simulator application. The AR glasses track the orientation of a QR code mounted on a US probe, communicating its orientation with the US simulator application. This allows the physician to interact with a US probe seeing in real-time the US image in the physician's field of view. The QR code tracking assessment of the AR glasses was conducted by measuring the orientation accuracy and precision when compared with the measures of an electromagnetic tracking device (i.e., NDI Aurora). The proposed solution presented a good performance, rendering the US image in AR glasses with real-time feedback. Moreover, it can track the QR code on the US probe with an accuracy of 0.755°, and a precision of 0.018°. Overall, the proposed framework presents promising results and the use of AR glasses as a tracking device reached a good performance. Clinical Relevance- Simulation is a relevant tool to train physicians, especially in US imaging. AR glasses can broaden the training to less trained physicians by reducing the need for complex setups. This technology allows the implementation of a more natural user interface, which can be relevant in scenarios where good coordination between the eyes and hands of the physician is necessary (i.e., Biopsies).

Concept and first Implementation of an intracochlearly navigated Electrode Array for Cochlear Implantation.

Cochlear implants (CI) are an established treatment for people with deafness or severe hearing loss. To restore patients' hearing an electrode array (EA) of the CI is inserted into the cochlea to stimulate the auditory nerve. Thereby, the exact positioning and gentle insertion of the EA is crucial for optimal hearing perception outcome. Currently, only microscopic vision is available for entering the cochlea, but the critical intracochlear process during EA insertion is like a "black box" and the surgeon has to rely on haptic feedback. Methods for visualizing the insertion process during surgery are inaccurate or not suitable for routine use due to radiation exposure. To address this problem, we developed a computer-assisted and image-guided cochlear implantation system with an exact real-time visualization of the EA position during the insertion process. The system is based on an electromagnetic tracking system that measures the position and orientation of a sensor integrated into the tip of a EA prototype and visualizes it in presurgical image data. A first experiment with our system showed that a EA prototype could be inserted into a cochlea of a human temporal bone and placed with an accuracy of [Formula: see text]. A maximum insertion angle of 120° was achieved.

New tools to reduce radiation exposure during aortic endovascular procedures

ABSTRACT Introduction The evolution of endovascular surgery over the past 30 years has made it possible to treat increasingly complex vascular pathologies with an endovascular method. Although this generally speeds up the patient’s recovery, the risks of health problems caused by long-term exposure to radioactive radiation increase. This warrants the demand for radiation-reducing tools to reduce radiation exposure during these procedures. Areas covered For this systematic review Pubmed, Embase and Cochrane library databases were searched on 28 December 2021 to provide an overview of tools that are currently used or have the potential to contribute to reducing radiation exposure during endovascular aortic procedures. In addition, an overview is presented of radiation characteristics of clinical studies comparing a (potential) radiation-reducing device with conventional fluoroscopy use. Expert opinion Radiation-reducing instruments such as fiber optic shape sensing or electromagnetic tracking devices offer the possibility to further reduce or even eliminate the use of radiation during endovascular procedures. In an era of increasing endovascular interventional complexity and awareness of the health risks of long-term radiation exposure, the use of these technologies could have a major impact on an ongoing challenge to move toward radiation-free endovascular surgery.

Electromagnetic-guided puncture: a tool or a tale?

The puncture technique and site of the puncture can impact the clinical outcome and the development of postoperative adverse events following percutaneous nephrolithotomy (PCNL). The aim of the current review was to discuss the available puncture guidance approaches and outline the potential role of the recently introduced electromagnetic-guided method. The puncture and PCNL tract establishment is usually performed using fluoroscopic or ultrasound guidance or a combination of two approaches. Electromagnetic-guided puncture is one of the most recent advancements of technology. The puncture navigation to the renal collecting system is available after placing a special wire with an electromagnetic tracking sensor into the desired calyx through the flexible ureterorenoscope. The available experimental and clinical studies have shown a high first puncture rate, decreased median time for obtaining a puncture, and shorter learning curves for beginners. Fluoroscopic and ultrasound guidance are the main approaches used by urologists. However, these modalities require a steep learning curve, approximately 60 cases for reaching competency. The initial data on electromagnetic navigation have shown the feasibility and potential promising outcomes of this novel approach. New studies are required to investigate its potential implementation opportunities in the daily practice of urologists.

Shoulder kinematics and muscle activity following latissimus dorsi transfer for massive irreparable posterosuperior rotator cuff tears in shoulders with pseudoparalysis.

The aim of this study was to evaluate the thoracohumeral (TH) and glenohumeral (GH) motion with muscle activity after latissimus dorsi transfer (LDT) in a shoulder with a massive irreparable posterosuperior rotator cuff tear (MIRT) and pseudoparalysis compared with the asymptomatic contralateral shoulder (ACS). We recruited and evaluated 13 patients after LDT in a shoulder with preoperative clinical pseudoparalysis and an MIRT on magnetic resonance imaging, with a minimum follow-up period of 1 year, and with a Hamada stage of 3 or less. Three-dimensional electromagnetic tracking was used to assess shoulder active range of motion in both the LDT shoulder and the ACS. The maximal active elevation of the shoulder (MAES) was assessed and consisted of forward flexion, scapular abduction, and abduction in the coronal plane. Maximal active internal rotation and external rotation were assessed separately. Surface electromyography (EMG) was performed to track activation of the latissimus dorsi (LD) and deltoid muscles during shoulder motion. EMG was scaled to its maximal isometric voluntary contraction recorded in specified strength tests. In MAES, TH motion of the LDT shoulder was not significantly different from that of the ACS (F1,12=1.174, P=.300) but the GH contribution was significantly lower in the LDT shoulder for all motions (F1,12=11.230, P=.006). External rotation was significantly greater in the ACS (26°±10° in LDT shoulder vs. 42°±11° in ACS, P<.001). The LD percentage EMG maximum showed no significant difference between the LDT shoulder and ACS during MAES (F1,11=0.005, P=.946). During maximal active external rotation of the shoulder, the LDT shoulder showed a higher percentage EMG maximum than the ACS (3.0%±2.9% for LDT shoulder vs. 1.2%±2.0% for ACS, P=.006). TH motion improved after LDT in an MIRT with pseudoparalysis and was not different from the ACS except for external rotation. However, GH motion was significantly lower after LDT than in the ACS in active-elevation range of motion. The LD was active after LDT but not more than in the ACS except for active external rotation, which we did not consider relevant as the activity did not rise above 3% EMG maximum. The favorable clinical results of LDT do not seem to be related to a change in LD activation and might be explained by its effect in preventing proximal migration of the humeral head in active elevation.

Toward Fluoro-Free Interventions: Using Radial Intracardiac Ultrasound for Vascular Navigation.

Transcatheter cardiovascular interventions have the advantage of patient safety, reduced surgery time and minimal trauma to the patient's body. Transcathether interventions, which are performed percutaneously, are limited by the lack of direct line of sight with the procedural tools and the patient anatomy. Therefore, such interventional procedures rely heavily on image guidance for navigating toward and delivering therapy at the target site. Vascular navigation via the inferior vena cava, from the groin to the heart, is an imperative part of most transcatheter cardiovascular interventions including heart valve repair surgeries and ablation therapy. Traditionally, the inferior vena cava is navigated using fluoroscopic techniques such as venography and computed tomography venography. These X-ray-based techniques can have detrimental effects on the patient as well as the surgical team, causing increased radiation exposure, leading to risk of cancer, fetal defects and eye cataracts. The use of a heavy lead apron has also been reported to cause back pain and spine issues, thus leading to interventionalist's disc disease. We propose the use of a catheter-based ultrasound augmented with electromagnetic tracking technology to generate a vascular roadmap in real time and perform navigation without harmful radiation. In this pilot study, we used spatially tracked intracardiac echocardiography to reconstruct a vessel from a phantom in a 3-D virtual environment. We illustrate how the proposed ultrasound-based navigation will appear in a virtual environment, by navigating a tracked guidewire within the vessels in the phantom without any radiation-based imaging. The geometric accuracy is assessed using a computed tomography scan of the phantom, with a Dice coefficient of 0.79. The average distance between the surfaces of the two models comes out to be 1.7 ± 1.12 mm.

A novel clip-on device for electromagnetic tracking in endobronchial ultrasound bronchoscopy

Introduction The established method for assessment of mediastinal and hilar lymph nodes is endobronchial ultrasound bronchoscopy (EBUS) with needle aspirations. Previously, we presented an electromagnetic navigation platform for this purpose. There were several issues with the permanent electromagnetic tracking (EMT) sensor attachment on the tip of the experimental EBUS bronchoscope. The purpose was to develop a device for on-site attachment of the EMT sensor. Material and methods A clip-on EMT sensor attachment device was 3D-printed in Ultem™ and attached to an EBUS bronchoscope. A specially designed ultrasound probe calibration adapter was developed for on-site and quick probe calibration. Navigation accuracy was studied using a wire cross water phantom and clinical feasibility was tested in a healthy volunteer. Results The device attached to the EBUS bronchoscope increased its diameter from 6.9 mm to 9.5 mm. Average preclinical navigation accuracy was 3.9 mm after adapter calibration. The maneuvering of the bronchoscope examining a healthy volunteer was adequate without harming the respiratory epithelium, and the device stayed firmly attached. Conclusion Development, calibration and testing of a clip-on EMT sensor attachment device for EBUS bronchoscopy was successfully demonstrated. Acceptable accuracy results were obtained, and the device is ready to be tested in patient studies.

A personalized image-guided intervention system for peripheral lung cancer on patient-specific respiratory motion model.

Due to respiratory motion, precise tracking of lung nodule movement is a persistent challenge for guiding percutaneous lung biopsy during image-guided intervention. We developed an automated image-guided system incorporating effective and robust tracking algorithms to address this challenge. Accurate lung motion prediction and personalized image-guided intervention are the key technological contributions of this work. A patient-specific respiratory motion model is developed to predict pulmonary movements of individual patients. It is based on the relation between the artificial 4D CT and corresponding positions tracked by position sensors attached on the chest using an electromagnetic (EM) tracking system. The 4D CT image of the thorax during breathing is calculated through deformable registration of two 3D CT scans acquired at inspiratory and expiratory breath-hold. The robustness and accuracy of the image-guided intervention system were assessed on a static thorax phantom under differentclinical parametric combinations. Real 4D CT images of ten patients were used to evaluate the accuracy of the respiratory motion model. The mean error of the model in different breathing phases was 1.59 ± 0.66mm. Using a static thorax phantom, we achieved an average targeting accuracy of 3.18 ± 1.2mm across 50 independent tests with different intervention parameters. The positive results demonstrate the robustness and accuracy of our system for personalized lung cancer intervention. The proposed system integrates a patient-specific respiratory motion compensation model to reduce the effect of respiratory motion during percutaneous lung biopsy and help interventional radiologists target the lesion efficiently. Our preclinical studies indicate that the image-guided system has the ability to accurately predict and track lung nodules of individual patients and has the potential for use in the diagnosis and treatment of early stage lung cancer.

Ultrasound-based navigation for open liver surgery using active liver tracking.

Despite extensive preoperative imaging, intraoperative localization of liver lesions after systemic treatment can be challenging. Therefore, an image-guided navigation setup is explored that links preoperative diagnostic scans and 3D models to intraoperative ultrasound (US), enabling overlay of detailed diagnostic images on intraoperative US. Aim of this study is to assess the workflow and accuracy of such a navigation system which compensates for liver motion. Electromagnetic (EM) tracking was used for organ tracking and movement of the transducer. After laparotomy, a sensor was attached to the liver surface while the EM-tracked US transducer enabled image acquisition and landmark digitization. Landmarks surrounding the lesion were selected during patient-specific preoperative 3D planning and identified for registration during surgery. Endpoints were accuracy and additional times of the investigative steps. Accuracy was computed at the center of the target lesion. In total, 22 navigated procedures were performed. Navigation provided useful visualization of preoperative 3D models and their overlay on US imaging. Landmark-based registration resulted in a mean fiducial registration error of 10.3 ± 4.3mm, and a mean target registration error of 8.5 ± 4.2mm. Navigation was available after an average of 12.7min. We developed a navigation method combining ultrasound with active liver tracking for organ motion compensation, with an accuracy below 10mm. Fixation of the liver sensor near the target lesion compensates for local movement and contributes to improved reliability during navigation. This represents an important step forward in providing surgical navigation throughout the procedure. This study is registered in the Netherlands Trial Register (number NL7951).