Needle Tracking System Research Articles

A novel multi-modality imaging phantom for validating interstitial needle guidance for high dose rate gynecological brachytherapy.

To design, manufacture, and validate a female pelvic phantom for multi-modality imaging (CT, MRI, US) to benchmark a commercial needle tracking system with application in HDR gynecological (GYN) interstitial procedures. A GYN needle-tracking phantom was designed using CAD software to model an average uterus from a previous patient study, a vaginal canal from speculum dimensions, and a rectum to accommodate a transrectal ultrasound (TRUS) probe. A target volume (CTVHR ) was designed as an extension from the cervix-uterus complex. Negative space molds were created from modeled anatomy and 3D printed. Silicone was used to cast the anatomy molds. A 3D printed box was constructed to house the manufactured anatomy for structural integrity and to accommodate the insertion of a speculum, tandem, needles, and TRUS probe. The phantom was CT-imaged to identify potential imperfections that might impact US visualization. Free-hand TRUS was used to guide interstitial needles into the phantom. The commercial tracking system was used to generate a 3D US volume. After insertion, the phantom was imaged with CT and MR and the uterus and CTVHR dimensions were verified against the CAD model. The manufactured phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom dimensions from the CAD model were verified with those from each imaging modality. The phantom is low cost and can be reproducibly manufactured with the 3D printing and molding processes. Our initial experiments demonstrate the ability to integrate the phantom with a commercial tracking system for future needle tracking validation studies.

Comparative Effectiveness, Efficiency, and ED Nurse Preference Between Two Methods of Visualization for Midline Catheter Insertion: A Pilot Study.

Rapid and reliable peripheral IV access is essential for many patients admitted to the emergency department (ED) to ensure administration of life-saving medications, and successful intravenous cannulation can significantly affect patient care. The objective of this study was to assess the impact of a continuous needle tracking system on the accuracy, speed, and quality of ultrasound-guided peripheral venous catheter insertions. A convenient sample study based on the study setting using simulated tissue was conducted with 49 US-based ED nurses to compare the insertion of a midline catheter using traditional ultrasound guidance versus an advanced needle-tracking technology along with ultrasound guidance. The purpose of this evaluation was to assess the impact of continuous needle tracking system. Informed consent was obtained from all individual participants involved in this study. All participants were made aware that the results may be published. There was no IRB approval for this study. All sources were properly disclosed within the text. The addition of the advanced needle-tracking technology significantly reduced total insertion attempts, insertion time, backwall penetrations, and redirects (probes to hit the target vein), while improving image clarity and confidence for participants. The innovative needle-tracking system evaluated in this pilot study has the potential to improve emergent difficult vascular access. EDs should assess the value of this technology to potentially improve the management of difficult intravenous access patients in their settings.

Friday, June 17, 202212:30 PM - 1:30 PM PHSOR01 Presentation Time: 12:30 PM: Characterization of a Novel Multi-Modality Imaging Phantom for Ultrasound Interstitial Needle Guidance for High Dose Rate Gynecological Brachytherapy

<h3>Purpose</h3> To design, manufacture, and validate a realistic female pelvic phantom for multi-modality imaging on CT, MRI, and transrectal ultrasound (TRUS) to guide and track interstitial needles during an HDR gynecological procedure using a commercial needle tracking system. <h3>Materials and Methods</h3> The pelvic phantom was designed using 3D Slicer and Autodesk Fusion360 to model an average uterus from a 50 patient data study¹, a vaginal canal from KleenSpec speculum dimensions, and a rectum to accommodate a BK 8848 endocavity biplane US probe. A 1.5 cm x 3.0 cm x 1.25 cm (WxLxH) half ellipsoid CTV_HR was also designed. Modeled anatomy was Boolean subtracted from rectangular solids to create a negative space mold. An Ultimaker S3 printer was used to print the 3D molds using polylactic acid. Smooth-On Silicone 20T was used as a casting agent for the uterus, cervix, vaginal canal, and rectum based on their similar mechanical properties. A 3D printed box was constructed to house the designed anatomy to provide structural integrity and allow the insertion of a speculum, tandem and ovoid applicator, needles, and TRUS probe. Agarose gelatin with glycerol and cellulose was used as a background medium to surround and support the pelvic anatomy and to allow for US propagation. After manufacturing, the phantom was imaged with CT to identify potential imperfections that might impact its visualization on US images. Following initial CT validation, the tracking system with the endorectal probe was used to image the phantom. US images from a 180 degree sweep were acquired and a 3D US volume was generated that allowed uterus contouring to aid in real-time insertion of 2 needles (Needle1 in CTV_HR, Needle2 in uterus). After insertion, the phantom was imaged with a Siemens Biograph mCT using a slice thickness of 0.6 mm and with a Siemens Skyra 3T MRI using the institutional HDR brachytherapy MR imaging protocol with T1 and T2 weighted sequences. The CTV_HR and uterus were contoured on CT and MR images and their dimensions were checked against the CAD model. <h3>Results</h3> Fig. 1a shows the CAD model for the anatomy (uterus dimensions of 7.87 cm x 4.45 cm, rectum diameter of 2 cm), the encasing box, and the casting mold used to fabricate the phantom. The volumes of the CTV_HR and uterus reconstructed from the CAD model were 3 cm³ and 76.8 cm³, respectively. Figs. 1b-c show sagittal CT and US images of the phantom. The measurements of uterus dimensions (7.87 cm x 4.4 cm) and rectum diameter (2 cm) on the sagittal CT image demonstrated a high degree of fidelity with the CAD model. The uterus volume (77.1 cm³) reconstructed from CT images was also very similar to that from the CAD model. Fig. 1d shows the phantom setup for US imaging using the needle tracking system and BK 8848 endorectal probe. Representative sagittal images through the phantom at the location of the 2 implanted needles are shown in Figs. 1e-h (CT, T1w MRI, T2w MRI, and US, respectively). The overall volumes CTV_HR (3.2 cm³) and uterus (82.9 cm³) reconstructed from the T2w MR images also agreed with those from the CAD model. Fig. 1f shows axial and sagittal images of the 3D US volume from the tracking software (uterus contour in green). The generated volume allowed for intraoperative needle insertion guidance. <h3>Conclusions</h3> The manufactured pelvic phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom is low cost and can be reproducibly manufactured with the 3D molding process. Our initial experiments demonstrate the ability to integrate the phantom with the commercial tracking system for future needle tracking validation studies. 1. Campelo, et al. (2020). Brachytherapy, 19(6), 767-776

US-CT fusion-guided percutaneous radiofrequency ablation of large substernal benign thyroid nodules

The aim of the present study was to assess feasibility, safety and outcome of ultrasound (US) guided percutaneous radiofrequency (RF) ablation of large substernal benign thyroid nodules assisted by US-computed tomography (CT) fusion imaging and real-time virtual needle tracking (VT) system. Thirty patients (18 females, mean age 56 y, range 32–76 y) with 35 benign nonfunctioning thyroid nodules (mean volume ± SD 26.8 ± 7.6 mL; range 20–38mL) were selected for CT-US fusion guided RF ablation. Nodules’ volume was evaluated before treatment and during 12-months follow-up. Complications’ rate was also evaluated. US-CT fusion imaging with VT system was feasible in all cases (feasibility 100%) and it was always possible to complete the procedure as planned (technical success 100%). Minor complications occurred in 2/30 cases (6.6%). No major complications occurred. 50% volume reduction (technique efficacy) was achieved in 93% cases, with a significant mean volume reduction at 12 months follow-up (68.7 ± 10.8%), (p < .001). The VT system could be useful in thyroid nodules ablation procedures assistance being able to track the RF electrode tip even when this is obscured by the bubbles produced by the ablative process. The combination of fusion imaging with VT assisted RF ablation represents a safe, non-surgical treatment option for patients with large substernal benign thyroid nodules.

Ultrasonic Needle Tracking with Dynamic Electronic Focusing.

Accurate identification of the needle tip is a key challenge with ultrasound-guided percutaneous interventions in regional anaesthesia, foetal surgery and cardiovascular medicine. In this study, we developed an ultrasonic needle tracking system in which the measured needle tip location was used to set the electronic focus of the external ultrasound imaging probe. In this system, needle tip tracking was enabled with a fibre-optic ultrasound sensor that was integrated into a needle stylet, and the A-lines recorded by the sensor were processed to generate tracking images of the needle tip. The needle tip position was estimated from the tracking images. The dependency of the tracking image on the electronic focal depth of the external ultrasound imaging probe was studied in a water bath and with needle insertions into a clinical training phantom. The variability in the estimated tracked position of the needle tip, with the needle tip at fixed depths in the imaging plane across a depth range from 0.5 to 7.5 cm, was studied. When the electronic focus was fixed, the variability of tracked position was found to increase with distance from that focus. The variability with the fixed focus was found to depend on the the relative distance between the needle tip and focal depth. It was found that with dynamic focusing, the maximum variability of tracked position was below 0.31 mm, as compared with 3.97 mm for a fixed focus.

Soft Liver Phantom with a Hollow Biliary System

Hepatobiliary interventions are regarded as difficult minimally-invasive procedures that require experience and skills of physicians. To facilitate the surgical training, we develop a soft, high-fidelity and durable liver phantom with detailed morphology. The phantom is anatomically accurate and feasible for the multi-modality medical imaging, including computer tomography (CT), ultrasound, and endoscopy. The CT results show that the phantom resembles the detailed anatomy of real livers including the biliary ducts, with a spatial root mean square error (RMSE) of 1.7 ± 0.7 mm and 0.9 ± 0.2 mm for the biliary duct and the liver outer shape, respectively. The sonographic signals and the endoscopic appearance highly mimic those of the real organ. An electric sensing system was developed for the real-time quantitative tracking of the transhepatic puncturing needle. The fabrication method herein is accurate and reproducible, and the needle tracking system offers a robust and general approach to evaluate the centesis outcome.

A Prospective Intervention Trial on Tailored Radiofrequency Ablation of Uterine Myomas.

Background and Objective: Investigating the use of radiofrequency myolysis (RFM) for the treatment of fibroids through less invasive access by combining transvaginal ultrasound, hysteroscopy and laparoscopy. Materials and Methods: Fifty-four premenopausal women with 106 symptomatic uterine myomas. Patients underwent RFM in three ways: Vaginal Ultrasound-guided RFM (VU-RFM), Laparoscopic RFM (L-RFM) and Hysteroscopic-RFM (H-RFM). The mean patient age was 43 years; 52 symptomatic uterine myomas were subserosal, 44 intramural and 10 submucosal. The outcomes evaluated at 1 and 12 months after RFM were myoma size (volume-diameter), “Uterine Fibroid Symptom and Quality of Life (UFS-QOL)” questionnaire and a 10-point Visual Analogue Scale (VAS). The therapy was completed with a single ablation in all patients, no complication was registered. The average number of fibroids treated per intervention was two with the use of different accesses: 64/106 VU-RFMs (60.4%), 32/106 L-RFMs (30.2%) and 10/106 H-RFMs (9.4%). Results: Volume and diameter of fibroids were significantly reduced by, respectively, 51.3% and 20.1% in the first 30 days post-intervention (p < 0.001) up to a maximum of 73.5% and 37.1% after the second follow-up visit at 12 months (p < 0.001). A similar trend was shown in terms of disability with a progressive and significant reduction of symptoms (menorrhagia, dysmenorrhea, dyspareunia and pollakiuria) demonstrated by percentage variation of UFS-QOL Symptom Severity and VAS scores to −74.3% and −45.3% as well as −84.9% and −74.3%, respectively, at 1 and 12 months after RFM (p < 0.001). An overall improvement in the quality of life was also demonstrated by a significant increase in the UFS-QOL total score of +38.2% in the first 30 days post-intervention up to +44.9% after the second follow-up visit at 12 months (p < 0.001). The overall average surgery time of the RFM for each patient was 48 minutes, and the time to treat each fibroid by Vaginal Ultrasound-guided RFM (23 min) was found to be significantly less than those of laparoscopy or hysteroscopy (respectively 35 and 34 min) (p < 0.05). An electromagnetic virtual needle tracking system (VNTS) was successfully tested during the RFM procedures, and real-time contrast-enhanced ultrasound (CEUS) has proven to be effective in determining the duration of myolysis through the identification of eventual residual areas of enhancement within the fibroids. Conclusion: Radiofrequency can be considered a minimally invasive and safe procedure for the treatment of uterine myomas through the customization and possible combination of transvaginal, laparoscopic or hysteroscopic accesses. The standardization of the ablation technique with pre-intervention biopsy and new technologies such as VNTS and CEUS spares healthy uterine tissue and may change the future management of symptomatic uterine fibroids.

Ultrasound-guided transvaginal radiofrequency ablation of uterine fibroids assisted by virtual needle tracking system: a preliminary study

Purpose: The purpose of this study was to assess the feasibility and outcome of transvaginal ultrasound (US)-guided radiofrequency ablation of uterine fibroids assisted by a real-time virtual needle tracking (VT) system.Methods: Between January 2017 and February 2018, 19 patients (age 45 ± 8 y, range 36–53 y) with 25 symptomatic uterine fibroids underwent transvaginal radiofrequency ablation (RFA) at a single center. Mean number of fibroids for patient was 1.7 (min, max: 1–3). Patients with more than one fibroid were 10 (52.6%). Uterine fibroids (mean volume: 13.6 mL; range: 5.3–41.9 mL) were treated with a dedicated internally cooled 17 G 35 cm RF needle with 1 cm or variable active tip and the moving shot technique. An electromagnetic system was used for showing a virtual needle during the procedure. Contrast-enhanced ultrasound evaluation was performed before and immediately at the end of procedure. Feasibility of the procedure, technical success rate, volume percentage reduction at 1, 3 and 6 months, clinical outcome (QOL score) and complications were analyzed.Results: Procedure was feasible in 19/19 patients (100%). Technical success was achieved in 100% of 25 treated fibroids. Mean fibroids volume decreased from 13.6 ml at baseline to 5.9 ml at 6 month (reduction rate 62.7%, range 48.5–76.9; p < .05). No major immediate or late complications occurred. Minor complications occurred in two patients. QOL score significantly improved from 68 ± 36 at baseline to 97 ± 16 at six-months follow-up (p < .05).Conclusion: Transvaginal US-guided RFA assisted by a real-time VT system is a feasible, safe and effective technique for the treatment of uterine fibroids.

Ultrasonic Needle Tracking with a Fibre-Optic Ultrasound Transmitter for Guidance of Minimally Invasive Fetal Surgery.

Ultrasound imaging is widely used for guiding minimally invasive procedures, including fetal surgery. Visualisation of medical devices such as medical needles is critically important and it remains challenging in many clinical contexts. During in-plane insertions, a needle can have poor visibility at steep insertion angles and at large insertion depths. During out-of-plane insertions, the needle tip can have a similar ultrasonic appearance to the needle shaft when it intersects with the ultrasound imaging plane. When the needle tip is not accurately identified, it can damage critical structures, with potentially severe consequences, including loss of pregnancy. In this paper, we present a tracking system to directly visualise the needle tip with an ultrasonic beacon. The waves transmitted by the beacon were received by an external ultrasound imaging probe. Pairs of co-registered images were acquired in rapid succession with this probe: a photoacoustic image obtained with the system in receive-only mode, and a conventional B-mode ultrasound image. The beacon comprised a custom elastomeric nanocomposite coating at the distal end of an optical fibre, which was positioned within the lumen of a commercial 22 gauge needle. Delivery of pulsed light to the coating resulted in the photoacoustic generation of ultrasonic waves. The measured tracking accuracies in water in the axial and lateral dimensions were 0.39±0.19 mm and 1.85±0.29 mm, respectively. To obtain a preliminary indication of the clinical potential of this ultrasonic needle tracking system, needle insertions were performed in an in vivo fetal sheep model. The results demonstrate that ultrasonic needle tracking with a fibre-optic transmitter is feasible in a clinically realistic fetal surgery environment, and that it could be useful to guide minimally invasive procedures by providing accurate visualisation of the medical device tip.

Fiber Bragg gratings-based sensing for real-time needle tracking during MR-guided brachytherapy.

The development of MR-guided high dose rate (HDR) brachytherapy is under investigation due to the excellent tumor and organs at risk visualization of MRI. However, MR-based localization of needles (including catheters or tubes) has inherently a low update rate and the required image interpretation can be hampered by signal voids arising from blood vessels or calcifications limiting the precision of the needle guidance and reconstruction. In this paper, a new needle tracking prototype is investigated using fiber Bragg gratings (FBG)-based sensing: this prototype involves a MR-compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. This stylet can be inserted into brachytherapy needles and allows a fast measurement of the needle deflection. This study aims to assess the potential of FBG-based sensing for real-time needle (including catheter or tube) tracking during MR-guided intervention. First, the MR compatibility of FBG-based sensing and its accuracy was evaluated. Different known needle deflections were measured using FBG-based sensing during simultaneous MR-imaging. Then, a needle tracking procedure using FBG-based sensing was proposed. This procedure involved a MR-based calibration of the FBG-based system performed prior to the interventional procedure. The needle tracking system was assessed in an experiment with a moving phantom during MR imaging. The FBG-based system was quantified by comparing the gold-standard shapes, the shape manually segmented on MRI and the FBG-based measurements. The evaluation of the MR compatibility of FBG-based sensing and its accuracy shows that the needle deflection could be measured with an accuracy of 0.27 mm on average. Besides, the FBG-based measurements were comparable to the uncertainty of MR-based measurements estimated at half the voxel size in the MR image. Finally, the mean(standard deviation) Euclidean distance between MR- and FBG-based needle position measurements was equal to 0.79 mm(0.37 mm). The update rate and latency of the FBG-based needle position measurement were 100 and 300 ms, respectively. The FBG-based needle tracking procedure proposed in this paper is able to determine the position of the complete needle, under MR-imaging, with better accuracy and precision, higher update rate, and lower latency compared to current MR-based needle localization methods. This system would be eligible for MR-guided brachytherapy, in particular, for an improved needle guidance and reconstruction.

Comparison of a GPS needle-tracking system, multiplanar imaging and 2D imaging for real-time ultrasound-guided epidural anaesthesia: A randomized, comparative, observer-blinded study on phantoms

BackgroundThe real-time ultrasound-guided paramedian sagittal oblique approach for neuraxial blockade is technically demanding. Innovative technologies have been developed to improve nerve identification and the accuracy of needle placement. The aim of this study was to evaluate three types of ultrasound scans during ultrasound-guided epidural lumbar punctures in a spine phantom. MethodsEleven sets of 20 ultrasound-guided epidural punctures were performed with 2D, GPS, and multiplanar ultrasound machines (660 punctures) on a spine phantom using an in-plane approach. For all punctures, execution time, number of attempts, bone contacts, and needle redirections were noted by an independent physician. Operator comfort and visibility of the needle (tip and shaft) were measured using a numerical scale. ResultsThe use of GPS significantly decreased the number of punctures, needle repositionings, and bone contacts. Comfort of the physician was also significantly improved with the GPS system compared with the 2D and multiplanar systems. With the multiplanar system, the procedure was not facilitated and execution time was longer compared with 2D imaging after Bonferroni correction but interaction between the type of ultrasound system and mean execution time was not significant in a linear mixed model. There were no significant differences regarding needle tip and shaft visibility between the systems. ConclusionsMultiplanar and GPS needle-tracking systems do not reduce execution time compared with 2D imaging using a real-time ultrasound-guided paramedian sagittal oblique approach in spine phantoms. The GPS needle-tracking system can improve performance in terms of operator comfort, the number of attempts, needle redirections and bone contacts.

TU-AB-201-04: Optimizing the Number of Catheter Implants and Their Tracks for Prostate HDR Brachytherapy

Purpose: In prostate HDR brachytherapy, interstitial implants are placed manually on the fly. The aim for this research is to develop a computer algorithm to find optimal and reliable implant trajectories using minimal number of implants. Methods: Our new algorithm mainly uses these key ideas: (1) positive charged static particles are uniformly placed on the surface of prostate and critical structures such as urethra, bladder, and rectum. (2) Positive charged kinetic particles are placed at a cross-section of the prostate with an initial velocity parallel to the principal implant direction. (3) The kinetic particles move through the prostate, interacting with each other, spreading out, while staying away from the prostate surface and critical structures. The initial velocity ensures that the trajectories observe the curvature constraints of typical implant procedures. (4) The finial trajectories of kinetic particles are smoothed using a third-degree polynomial regression, which become the implant trajectories. (5) The dwelling times and final dose distribution are calculated using least-distance programming. Results: (1) We experimented with previously treated cases. Our plan achieves all prescription goals while reducing the number of implants by 41%! Our plan also has less uniform target dose, which implies a higher dose is delivered to the prostate. (2) We expect future implant procedures will be performed under the guidance of such pre-calculated trajectories. To assess the applicability, we randomly perturb the tracks to mimic the manual implant errors. Our studies showed the impact of these perturbations are negligible, which is compensated by the least distance programming. Conclusions: We developed a new inverse planning system for prostate HDR therapy that can find optimal implant trajectories while minimizing the number of implants. For future work, we plan to integrate our new inverse planning system with an existing needle tracking system.

Novice performance of ultrasound-guided needling skills: effect of a needle guidance system.

Ultrasound-guided needle placement is a widely used technical skill that can be challenging to learn. The SonixGPS is a novel ultrasound needle-tracking system that has the potential to improve performance over traditional ultrasound systems. The objective of our study was to determine if the use of the SonixGPS ultrasound system improves performance of novice practitioners in ultrasound-guided needle placement compared with conventional ultrasound in the out-of-plane approach on a simulation model. Twenty-six medical students without previous ultrasound experience were randomized into 2 groups. Each group performed 30 simulated ultrasound nerve blocks on a porcine meat tissue simulation (phantom) model. Both groups used the SonixGPS ultrasound; however, the study group had the needle-tracking system activated, whereas the control group did not. The participants were assessed for success rate, technical aspects of block performance, and certain behaviors that could compromise the quality of the block. Learning curves were developed to assess competence. The needle guidance group reached competence more often. This group had fewer attempts and quality-compromising behaviors than did those using conventional ultrasound. Use of the SonixGPS ultrasound needle guidance system improves the performance of technical needling skills of novice trainees in an ex vivo model. The place of this technology in the wider education of ultrasound-guided regional anesthesia remains to be established.

Performance and suitability assessment of a real-time 3D electromagnetic needle tracking system for interstitial brachytherapy.

PurposeAccurate insertion and overall needle positioning are key requirements for effective brachytherapy treatments. This work aims at demonstrating the accuracy performance and the suitability of the Aurora® V1 Planar Field Generator (PFG) electromagnetic tracking system (EMTS) for real-time treatment assistance in interstitial brachytherapy procedures.Material and methodsThe system's performance was characterized in two distinct studies. First, in an environment free of EM disturbance, the boundaries of the detection volume of the EMTS were characterized and a tracking error analysis was performed. Secondly, a distortion analysis was conducted as a means of assessing the tracking accuracy performance of the system in the presence of potential EM disturbance generated by the proximity of standard brachytherapy components.ResultsThe tracking accuracy experiments showed that positional errors were typically 2 ± 1 mm in a zone restricted to the first 30 cm of the detection volume. However, at the edges of the detection volume, sensor position errors of up to 16 mm were recorded. On the other hand, orientation errors remained low at ± 2° for most of the measurements. The EM distortion analysis showed that the presence of typical brachytherapy components in vicinity of the EMTS had little influence on tracking accuracy. Position errors of less than 1 mm were recorded with all components except with a metallic arm support, which induced a mean absolute error of approximately 1.4 mm when located 10 cm away from the needle sensor.ConclusionsThe Aurora® V1 PFG EMTS possesses a great potential for real-time treatment assistance in general interstitial brachytherapy. In view of our experimental results, we however recommend that the needle axis remains as parallel as possible to the generator surface during treatment and that the tracking zone be restricted to the first 30 cm from the generator surface.

Biomechanics-Based Curvature Estimation for Ultrasound-guided Flexible Needle Steering in Biological Tissues.

Needle-based procedures are commonly performed during minimally invasive surgery for treatment and diagnosis. Accurate needle tip placement is important for the success of the procedures. Misplacement of the needle tip might cause unsuccessful treatment or misdiagnosis. Robot-assisted needle insertion systems have been developed in order to steer flexible bevel-tipped needles. However, current systems depend on the information of maximum needle curvature, which is estimated by performing prior insertions. This work presents a new three-dimensional flexible needle steering system which integrates an optimal steering control, ultrasound-based needle tracking system, needle deflection model, online needle curvature estimation and offline curvature estimation based on biomechanics properties. The online and the offline curvature estimations are used to update the steering control in real time. The system is evaluated by experiments in gelatin phantoms and biological tissues (chicken breast tissues). The average targeting error in gelatin phantoms is 0.42 ± 0.17 mm, and in biological tissues is 1.63 ± 0.29 mm. The system is able to accurately steer a flexible needle in multi-layer phantoms and biological tissues without performing prior insertions to estimate the maximum needle curvature.

Real-Time Ultrasonography-Guided Percutaneous Nephrolithotomy Using SonixGPS Navigation: Clinical Experience and Practice in a Single Center in China

To report our experience and evaluate the efficacy and safety of real-time ultrasonography-guided percutaneous nephrolithotomy (PCNL) using SonixGPS navigation in patients with kidney stones. From December 2012 to May 2013 in our hospital, the SonixGPS needle tracking system was used for real-time ultrasonography-guided puncture during PCNL in 25 patients with kidney stones. All the patients were under general anesthesia, in prone position; holmium laser lithotripsy was used in all patients after renal access was established. The time needed to perform puncture and the success rate of PCNL were recorded as two most important outcomes of this study. All 25 patients underwent PCNL successfully with the help of SonixGPS navigation. The mean puncture time was 5.5 minutes (range 3-9 min), and the mean operative time was 74 minutes (range 30-100 min), respectively. The primary stone clearance rate of PCNL was 92% (23/25); no major intraoperative or postoperative complications occurred. The results of this study indicate that puncture under SonixGPS navigation is safe and efficacious in PCNL, which may provides a new choice for PCNL.

Erratum to: Real-time ultrasound-guided PCNL using a novel SonixGPS needle tracking system

Erratum to: Real-time ultrasound-guided PCNL using a novel SonixGPS needle tracking system

Real-time ultrasound-guided PCNL using a novel SonixGPS needle tracking system.

SonixGPS is a successful ultrasound guidance position system. It helps to improve accuracy in performing complex puncture operations. This study firstly used SonixGPS to perform kidney calyx access in PCNL to investigate its effectiveness and safety. This was a prospectively randomized controlled study performed from September 2011 to October 2012. A total of 97 patients were prospectively randomized into two groups using random number generated from SAS software. 47 Patients were enrolled in conventional ultrasound-guided (US-guided) group and 50 patients were classified into SonixGPS-guided group. Nine patients were lost during follow-up. Hence, a total of 88 patients were qualified and analyzed. Preoperative examinations included urine analysis, urine culture, kidney function, coagulation profile and routine analysis of blood. Ultrasonography was used to evaluate the degree of hydronephrosis. The intraoperative findings, including blood loss, operating time, time to successful puncture, the number of attempts for successful puncture and hospital stay were recorded. The stone clearance rate and complications were analyzed. The present study showed no significant difference between the two groups in terms of demographic data, preoperative markers, stone clearance rate and the stone composition. However, the time to successful puncture, the number of trials for successful puncture, operating time and hospital length of stay were significantly decreased in the SonixGPS-guided group. Furthermore, the hemoglobin decrease was also obviously lower in the SonixGPS group than that in conventional US-guided group. SonixGPS needle tacking system guided PCNL is safe and effective in treating upper urinary tract stones. This novel technology makes puncturing more accuracy and can significantly decrease the incidence of relative hemorrhage and accelerate recovery.

Percutaneous Radiofrequency Ablation of Benign Thyroid Nodules Assisted by a Virtual Needle Tracking System

Our aim was to assess the feasibility and outcome of ultrasound (US)-guided percutaneous radiofrequency (RF) ablation of benign thyroid nodules assisted by a real-time virtual needle tracking (VT) system. Forty-five patients (34 females, mean age ± standard deviation (SD): 44 ± 16 y, range: 29–68 y) with 45 benign non-functioning thyroid nodules (mean volume ± SD: 13.5 ± 6.7 mL, range: 12–22 mL) underwent VT-assisted US-guided RF ablation. Nodule volume was evaluated before treatment and during 6-mo of follow-up. Complication rates and patient satisfaction after treatment were also evaluated. By use of the VT system, the tip of the RF electrode was identified during all ablation procedures. The overall mean volume reduction and complication rate were 72.6 ± 11.3% and 2.5%, respectively. Overall satisfaction at the 6-mo follow-up was rated by patients as positive in 42 cases (93%). The VT system could be useful in thyroid nodule ablation procedures because it is able to track the RF electrode tip even when the tip is obscured by the bubbles produced by the ablative process. VT-assisted RF ablation can be a tolerable, non-surgical treatment for patients with benign non-functioning thyroid nodules.

Single-operator real-time ultrasound-guided spinal injection using SonixGPS™: a case series

The SonixGPS™ is a novel needle tracking system that has recently been approved in Canada for ultrasound-guided needle interventions. It allows optimization of needle-beam alignment by providing a real-time display of current and predicted needle tip position. Currently, there is limited evidence on the effectiveness of this technique for performance of real-time spinal anesthesia. This case series reports performance of the SonixGPS system for real-time ultrasound-guided spinal anesthesia in elective patients scheduled for joint arthroplasty. In this single-centre case series, 20 American Society of Anesthesiologists' class I-II patients scheduled for lower limb joint arthroplasty were recruited to undergo real-time ultrasound-guided spinal anesthesia with the SonixGPS after written informed consent. The primary outcome for this clinical cases series was the success rate of spinal anesthesia, and the main secondary outcome was time required to perform spinal anesthesia. Successful spinal anesthesia for joint arthroplasty was achieved in 18/20 patients, and 17 of these required only a single skin puncture. In 7/20 (35%) patients, dural puncture was achieved on the first needle pass, and in 11/20 (55%) patients, dural puncture was achieved with two or three needle redirections. Median (range) time taken to perform the block was 8 (5-14) min. The study procedure was aborted in two cases because our clinical protocol dictated using a standard approach if spinal anesthesia was unsuccessful after three ultrasound-guided insertion attempts. These two cases were classified as failures. No complications, including paresthesia, were observed during the procedure. All patients with successful spinal anesthesia found the technique acceptable and were willing to undergo a repeat procedure if deemed necessary. This case series shows that real-time ultrasound-guided spinal anesthesia with the SonixGPS system is possible within an acceptable time frame. It proved effective with a low rate of failure and a low rate of complications. Our clinical experience suggests that a randomized trial is warranted to compare the SonixGPS with a standard block technique.