srbadv0208

Implementation of MRI guidance in place of CT or X-ray would reduce ionizing radiation exposure and provide better soft tissue contrast in a wide range of musculoskeletal targets in children. We developed an augmented reality guidance system for MRI-guided interventions. The purpose of this study was to evaluate the feasibility of using this system to target shoulder, hip, sacroiliac joints and liver in a cadaver.

The LUMENA AR system is designed to operate in an interventional MRI suite. Specially designed fiducial markers placed on the skin surface and needle hub are used to track needle position in real-time during advancement. T1-weighted images acquired after fiducial placement allow interventional radiologists to plan optimal needle paths to selected targets by choosing skin entry and target points on an in-room planning console. Two interventional radiologists placed 12 needles along planned trajectories by following the guidance plan projected onto the skin by the optical head. Each MRI scan required approximately 2 min, and each insertion was completed within 1 minute. “User error” was defined as the distance between final needle tip location and selected target after insertion. “Overall error” was calculated as the distance between the selected target and postinsertion MRI-derived needle tip locations. All errors were reported as average ± standard deviation across all locations.

Overall, 12 locations were targeted (3 shoulder, 4 hip, 1 liver, and 4 SI joint). The system operated as expected and all needles were placed successfully. User error was 2.4±1.1 mm (range: 0.8 – 4.2 mm). Overall targeting error was 2.6±0.6 mm (range: 1.5 – 3.6 mm).

The study demonstrates feasibility of using augmented reality to place needles under MRI guidance in a cadaver. The system was subjectively judged to be easy to use and to fit within the established clinical workflow of image-guided needle-based interventions.

To improve dynamic needle-tip visualization, nurse anesthesiology students were evaluated during simulated ultrasound-guided procedures. This quasiexperimental study utilized two computed tomography 3D printed models. Thirty-two students performed each procedure twice, once without and once with needle guidance. Measures focused on accuracy and procedural performance to determine the impact that guidance versus no guidance had on attempts. Students evaluated their experiences, self-confidence, feasibility, and usability using needle guidance technology. Needle guidance improved the distance to target, total procedure time, phantom penetration time, number of attempts, completion rate, and effectiveness in both procedures. Overall, a decrease in distance to target in millimeters was uncovered when needle guidance was utilized (Z = -5.723, P < .001). Needle guidance showed a decrease of 3.96 attempts when guidance was utilized for the infraclavicular (F[1, 22] = 51.79, P < .001) and 0.96 attempts during the thoracic paravertebral procedure (F[1, 22] = 6.02, P = .023). Students found that needle guidance enhanced ease, speed, and overall performance, while feeling significantly more confident performing the infraclavicular (P < .001) and thoracic paravertebral (P < .001) procedures. The use of needle guidance technology showed improvement in accuracy comparable with results obtained using external tracking technology.

PURPOSE: To present the preliminary results of a 30-patient clinical study evaluating a transperineal guidance system (Clear Guide SCENERGY TP) for MRI-guided procedures.

MATERIALS AND METHODS: We utilized the SCENERGY TP guidance system (www.scenergytp.com) to guide 14G needles towards selected targets through patients’ perineum. Prior to imaging, the clinical staff mounted a grid template with embedded markers visible in the MRI next to the perineum. Once the initial MRI volume was acquired, we sent it to the SCENERGY TP for automatic registration (Fig. 1). Given the registration, the system projected the grid holes onto each slice of the volume as shown in Fig. 2. The physician then selected a target by browsing through the MRI scan and tapping on the screen. The system highlighted the target along with the alphanumerical identifier of the closest hole and the depth of insertion. The physician was able turn the grid projection off allowing them to track the planned trajectory of the needle path through the slices prior to insertion. An augmented reality (AR) view was also available for some cases which showed the planned grid hole and the depth of insertion (Fig. 3). The clinical trial recruited 30 patients undergoing MRI-guided transperineal procedures following the IRB protocol. The device has obtained FDA clearance following the successful completion of this trial. The procedures included 20 prostate cryoablations, 5 prostate biopsies, 3 seminal vesicle cryoablation, 1 pelvic lymph node cryoablation, and 1 combination of prostate biopsy and cryoablation in one session.

RESULTS: All the procedures were completed safely and successfully. The system worked as expected with needle placement verified by post-MRI scans. Needle accuracy was evaluated by manually segmenting the needle shaft at an average depth of 67mm (min:32.8mm, max: 127.4mm) and comparing it with the expected location based on the plan. The average error was 1.46±0.78mm.

CONCLUSIONS: Compared to the current alternatives, the device offers a superior workflow which is easy to follow. This workflow eliminates the need for manual segmentation of grid fiducials in MRI volumes since the markers are automatically detected. Accurate and fast placement of needle in the MRI suite is key for wide adoption of interventional MRI procedures. Combination of biopsy followed by cryoablation in one session can increase overall efficiency and potentially reduce patient anxiety.

Purpose: CT and X-ray imaging for needle guidance exposes patients and interventionalists to ionizing radiation and can
increase risk of some forms of cancer. While ultrasound imaging offers a radiation-free alternative for some procedures, use of MRI guidance would eliminate ionizing radiation exposure while also providing better soft tissue contrast and visualization of targets not seen with ultrasound and other imaging modalities. Therefore, especially in young children, MRI guidance for interventional procedures would be preferred. However, the MRI environment poses several challenges that have slowed widespread adoption. First, the closed bore size of MRI scanners places ergonomic restrictions on operators and limits access to some target locations. Second, the currently used “advance-andcheck” approach used for CT-guided procedures is too time consuming for MRI-guided interventions. To address these limitations, we developed an augmented reality guidance system for use in the interventional MR suite and we are evaluating this system through an ongoing clinical trial.

Materials and Methods: The LUMENA AR system (Clear Guide Medical Inc., Baltimore, MD, USA) is designed to operate inside an interventional MRI suite. The system enables interactive path planning during needle insertion based on a registered high-resolution MRI dataset. The system tracks the needle and skin surface position and orientation using a combination of artificial intelligence-based tracking and optically tracked fiducials. During needle advancement, the system provides guidance to the interventionist by projecting a guidance plan onto the skin around the needle entry point in real time. The in-room planning console allows further optimization of workflow, enabling continuous visualization of progress based on MR images. Phantom and cadaver studies in which interventional radiologists used the system to place needles along planned trajectories to target bone, joint, and soft tissue targets demonstrated adequate needle placement accuracy and an acceptable clinical workflow. Based on these results, we began an early phase first-in-human clinical trial (NCT#06224933) to evaluate feasibility and safety of using this AR system in pediatric patients undergoing MRI-guided interventions.

Results: The LUMENA AE system operated as expected in phantoms and cadaver studies and all needles were placed successfully. The MRI-verified overall spatial targeting accuracy was 2.3±1.1 mm and 2.6±0.6 mm for the phantom and cadaver trials, respectively. The system was also subjectively judged as “easy to use” by the operators. We have successfully completed three of twelve clinical cases in the ongoing clinical trial and plan to complete the trial in twelve months. As in earlier studies, clinical cases required only 2 MRI scans: one for planning and one for confirmation of needle position (Figure 1), without intermediate scanning steps that “advance-and-check” approach used in MRI-guided interventions.

Conclusion: Our studies demonstrate feasibility of using the LUMENA AR system to accurately place injection and biopsy needles under MRI guidance. The results of phantom and cadaver studies showed acceptable accuracy and allowed us to develop and optimize a clinical workflow that is currently being evaluated in a clinical trial. The system’s features enable improvement of current clinical workflow for needle-based MRIguided interventions, potentially shortening such procedures.

Acknowledgements: This work was supported by the National Institutes of Health (NIH) grant 5R44EB028722.

This paper presents the development and evaluation of an educational system for training and skills assessment of students performing ultrasound-guided interventional procedures. The system consists of: a needle guidance software which overlays virtual needle trajectories on the ultrasound screen, a custom course creation module, an automated procedure logging and evaluation module, and custom anatomical phantoms tailored to specific anesthesiology procedures. The system serves two distinct functions. As a learning tool, it provides guidance overlays that show the trajectory of the needle in real-time, aiding the development of skills required to handle the ultrasound probe and needle to achieve the correct trajectory. As an evaluation tool, it quantifies learning and provides feedback to the student and instructor. A set of 13 quantitative metrics were identified for student skill assessment, notably “distance of the needle tip to target,” “total procedure time,” and “total number of attempts.” The system was evaluated in a semester-long study involving 35 nursing students covering four regional anesthesia procedures. Each student performed the procedures twice: once with instrument guidance, once without instrument guidance. Statistically significant differences were found between the with-guidance and without-guidance groups. The study was able to show that students consistently performed better under EDU’s guidance for all four procedures.

Abstract
As one of the most commonly performed spinal interventions in routine clinical practice, lumbar punctures are usually done with only hand palpation and trial-and-error. Failures can prolong procedure time and introduce complications such as cerebrospinal fluid leaks and headaches. Therefore, an effective needle insertion guidance method is desired. In this work, we present a complete lumbar puncture guidance system with the integration of (1) a wearable mechatronic ultrasound imaging device, (2) volume-reconstruction and bone surface estimation algorithms and (3) two alternative augmented reality user interfaces for needle guidance, including a HoloLens-based and a tablet-based solution. We conducted a quantitative evaluation of the end-to-end navigation accuracy, which shows that our system can achieve an overall needle navigation accuracy of 2.83 mm and 2.76 mm for the Tablet-based and the HoloLens-based solutions, respectively. In addition, we conducted a preliminary user study to qualitatively evaluate the effectiveness and ergonomics of our system on lumbar phantoms. The results show that users were able to successfully reach the target in an average of 1.12 and 1.14 needle insertion attempts for Tablet-based and HoloLens-based systems, respectively, exhibiting the potential to reduce the failure rates of lumbar puncture procedures with the proposed lumbar-puncture guidance.

Purpose
To develop and evaluate an augmented reality instrument guidance system for MRI-guided needle placement procedures such as musculoskeletal biopsy and arthrography. Our system guides the physician to insert a needle toward a target while looking at the insertion site without requiring special headgear.

Methods
The system is comprised of a pair of stereo cameras, a projector, and a computational unit with a touch screen. All components are designed to be used within the MRI suite (Zone 4). Multi-modality fiducial markers called VisiMARKERs, detectable in both MRI and camera images, facilitate automatic registration after the initial scan. The navigation feedback is projected directly onto the intervention site allowing the interventionalist to keep their focus on the insertion site instead of a secondary monitor which is often not in front of them.

Results
We evaluated the feasibility and accuracy of this system on custom-built shoulder phantoms. Two radiologists used the system to select targets and entry points on initial MRIs of these phantoms over three sessions. They performed 80 needle insertions following the projected guidance. The system targeting error was 1.09 mm, and the overall error was 2.29 mm.

Conclusion
We demonstrated both feasibility and accuracy of this MRI navigation system. The system operated without any problems inside the MRI suite close to the MRI bore. The two radiologists were able to easily follow the guidance and place the needle close to the target without any intermediate imaging.

This paper describes a perineal access tool for MRI-guided prostate interventions and evaluates it using a phantom study. The development of this device has been driven by the clinical need and a close collaboration effort. The device seamlessly fits into the workflow of MRI-guided prostate procedures such as cryoablation and biopsies. It promises a significant cut in the procedure time, accurate needle placement, lower number of insertions, and a potential for better patient outcomes. The current embodiment includes a frame which is placed next to the
perineum and incorporates both visual and MRI-visible markers. These markers are automatically detected both in MRI and by a pair of stereo cameras (optical head) allowing for automatic optical registration. The optical head illuminates the procedure area and can track instruments and ultrasound probes. The frame has a window to access the perineum. Multiple swappable grids may be placed in this window depending on the application. It is also possible to entirely remove the grid for freehand procedures. All the components are designed to be used inside the MRI suite. To test this system, we built a custom phantom with MRI visible targets and planned 21 needle insertions with three grid types using the SCENERGY software. With an average insertion depth of about 85 mm, the average error of needle tip placement was 2.74 mm. We estimated the error by manually segmenting the needle tip in post-insertion MRIs of the phantom and comparing that to the plan.

PURPOSE: To describe the testing and feasibility of a transperineal guide grid based on optical fusion to aid in needle placement for biopsy and ablation.

MATERIALS AND METHODS: The transperineal guide grid with optical fusion was developed by Clear Guide Medical in collaboration with Mayo Clinic. The proposed tool is intended to be used in combination with the Clear Guide’s existing SCENERGY guidance software program, Clear Guide VisiMARKER, Clear Guide Optical Head, and Clear Guide CORE hardware. The hardware consists of a base plate situated under the supine semi-lithotomy patient on the MRI table (Fig 1 with visible imbedded markers and leg holder plates to create workable space for needle placement. Guide grid is placed in the grid holder for needle guidance. The software will pull in a MRI T2 sequence which is used for automatic registration. Once registered the images can be scrolled with overlay of the biopsy grid. Specific needle paths can be selected and scrolled to be able to determine needle path in relation to adjacent structures.

RESULTS: The initial testing with volunteers demonstrates feasibility of grid positioning with the plate providing a stable platform (Fig 2). From an acquired T2 image sequence covering the grid and prostate, the software is able to automatically register the grid position and project the needle paths into the image dataset (Fig 3 and 4).

CONCLUSION: This system will potentially offer an optical fusion system for transperineal needle placement in the MRI environment, but it will have the flexibility to be utilized with CT or US as well. Initial testing demonstrates feasibility. Subsequent testing will be performed with patients undergoing prostate biopsy or ablation to determine the accuracy of needle guidance at the distance of the prostate (10 cm depth).