Clinical Application of an Augmented Reality Navigation System for Transforaminal Epidural Injection: A Randomized Controlled Trial.

Objectives: Augmented reality (AR) navigation systems are emerging to simplify and enhance the precision of medical procedures. Lumbosacral transforaminal epidural injection is a commonly performed procedure for the treatment and diagnosis of radiculopathy. Accurate needle placement while avoiding critical structures remains a challenge. For this purpose, we conducted a randomized controlled trial for our augmented reality navigation system. Methods: This randomized controlled study involved 28 patients, split between a traditional C-arm guided group (control) and an AR navigation guided group (AR-NAVI), to compare procedure efficiency and radiation exposure. The AR-NAVI group used a real-time tracking system displaying spinal structure and needle position on an AR head-mounted display. The procedural time and C-arm usage (radiation exposure) were measured. Results: All patients underwent successful procedures without complications. The AR-NAVI group demonstrated significantly reduced times and C-arm usage for needle entry to the target point (58.57 ± 33.31 vs. 124.91 ± 41.14, p < 0.001 and 3.79 ± 1.97 vs. 8.86 ± 3.94, p < 0.001). Conclusions: The use of the AR navigation system significantly improved procedure efficiency and safety by reducing time and radiation exposure, suggesting a promising direction for future enhancements and validation.

Augmented Reality-Assisted Navigation System for Transforaminal Epidural Injection.

Purpose: Multiple studies have attempted to demonstrate the benefits of augmented reality (AR)-assisted navigation systems in surgery. Lumbosacral transforaminal epidural injection is an effective treatment commonly used in patients with radiculopathy due to spinal degenerative pathologies. However, few studies have applied AR-assisted navigation systems to this procedure. The study aimed to investigate the safety and effectiveness of an AR-assisted navigation system for transforaminal epidural injection. Patients and Methods: Through a real-time tracking system and a wireless network to the head-mounted display, computed tomography images of the spine and the path of a spinal needle to the target were visualized on a torso phantom with respiration movements installed. From L1/L2 to L5/S1, needle insertions were performed using an AR-assisted system on the left side of the phantom, and the conventional method was performed on the right side. Results: The procedure duration was approximately three times shorter, and the number of radiographs required was reduced in the experimental group compared to the control group. The distance from the needle tips to the target areas in the plan showed no significant difference between the two groups. (AR group 1.7 ± 2.3mm, control group 3.2 ± 2.8mm, P value 0.067). Conclusion: An AR-assisted navigation system may be used to reduce the time required for spinal interventions and ensure the safety of patients and physicians in view of radiation exposure. Further studies are essential to apply AR-assisted navigation systems to spine interventions.

Augmented Reality Assisted Surgical Navigation System for Epidural Needle Intervention.

An augmented reality (AR)-assisted surgical navigation system was developed for epidural needle intervention. The system includes three components: a virtual reality-based surgical planning software, a patient and tool tracking system, and an AR-based surgical navigation system. A three-dimensional (3D) path plan for the epidural needle was established on the preoperative computed tomography (CT) image. The plan is then registered to the intraoperative space by 3D models of the target vertebrae using skin markers and real-time tracking information. In the procedure, the plan and tracking information are transmitted to the head-mounted display (HMD) through a wireless network such that the device directly visualizes the plan onto the back surface of the patient. The physician determines the entry point and inserts the needle into the target based on the direct visual guidance of the system. An experiment was conducted to validate the system using two torso phantoms that mimic human respiration. The experimental results demonstrated that the time and the number of X-rays required for needle insertion were significantly decreased by the proposed method (43.6±20.55sec, 2.9±1.3times) compared to those of the conventional fluoroscopy-guided approach (124.5 ± 46.7s, 9.3±2.4times), whereas the average targeting errors were similar in both cases. The proposed system may potentially decrease ionizing radiation exposure not only to the patient but also to the medical team.

Developing a Quantifying Device for Soft Tissue Material Prop-Erties around Lumbar Spines.

Knowing the material properties of the musculoskeletal soft tissue could be important to develop rehabilitation therapy and surgical procedures. However, there is a lack of devices and information on the viscoelastic properties of soft tissues around the lumbar spine. The goal of this study was to develop a portable quantifying device for providing strain and stress curves of muscles and ligaments around the lumbar spine at various stretching speeds. Each sample was conditioned and applied for 20 repeatable cyclic 5 mm stretch-and-relax trials in the direction and perpendicular direction of the fiber at 2, 3 and 5 mm/s. Our device successfully provided the stress and strain curve of the samples and our results showed that there were significant effects of speed on the young's modulus of the samples (p < 0.05). Compared to the expensive commercial device, our lower-cost device provided comparable stress and strain curves of the sample. Based on our device and findings, various sizes of samples can be measured and viscoelastic properties of the soft tissues can be obtained. Our portable device and approach can help to investigate young's modulus of musculoskeletal soft tissues conveniently, and can be a basis for developing a material testing device in a surgical room or various lab environments.

Topological recovery for non-rigid 2D/3D registration of coronary artery models.

BACKGROUND AND OBJECTIVE: Intra-operative X-ray angiography, the current standard method for visualizing and diagnosing cardiovascular disease, is limited in its ability to provide essential 3D information. These limitations are disadvantages in treating patients. For example, it is a cause of lowering the success rate of interventional procedures. Here, we propose a novel 2D-3D non-rigid registration method to understand vascular geometry during percutaneous coronary intervention. METHODS: The proposed method uses the local bijection pair distance as a cost function to minimize the effect of inconsistencies from center-line extraction. Moreover, novel cage-based 3D deformation and multi-threaded particle swarm optimization are utilized to implement real-time registration. We evaluated the proposed method for 154 examinations from 10 anonymous patients by coverage percentage, comparing the average distance of the 2D extracted center-line with that of the registered 3D center-line. RESULTS: The proposed 2D-3D non-rigid registration method achieved an average distance of 1.98 mm with a 0.54 s computation time. Additionally, in aiming to reduce the uncertainty of XA images, we used the proposed method to retrospectively visualize the connections between 2D vascular segments and the distal part of occlusions. CONCLUSIONS: Ultimately, the proposed 2D/3D non-rigid registration method can successfully register the 3D center-line of coronary arteries with corresponding 2D XA images, and is computationally sufficient for online usage. Therefore, this method can improve the success rate of such procedures as a percutaneous coronary intervention and provide the information necessary to diagnose cardiovascular diseases better.

Spatiotemporal Free-Form Registration Method Assisted by a Minimum Spanning Tree During Discontinuous Transformations.

The sliding motion along the boundaries of discontinuous regions has been actively studied in B-spline free-form deformation framework. This study focusses on the sliding motion for a velocity field-based 3D+t registration. The discontinuity of the tangent direction guides the deformation of the object region, and a separate control of two regions provides a better registration accuracy. The sliding motion under the velocity field-based transformation is conducted under the [Formula: see text]-Rényi entropy estimator using a minimum spanning tree (MST) topology. Moreover, a new topology changing method of the MST is proposed. The topology change is performed as follows: inserting random noise, constructing the MST, and removing random noise while preserving a local connection consistency of the MST. This random noise process (RNP) prevents the [Formula: see text]-Rényi entropy-based registration from degrading in sliding motion, because the RNP creates a small disturbance around special locations. Experiments were performed using two publicly available datasets: the DIR-Lab dataset, which consists of 4D pulmonary computed tomography (CT) images, and a benchmarking framework dataset for cardiac 3D ultrasound. For the 4D pulmonary CT images, RNP produced a significantly improved result for the original MST with sliding motion (p<0.05). For the cardiac 3D ultrasound dataset, only a discontinuity-based registration indicated activity of the RNP. In contrast, the single MST without sliding motion did not show any improvement. These experiments proved the effectiveness of the RNP for sliding motion.

Lumbar Vertebrae Synthetic Segmentation in Computed Tomography Images Using Hybrid Deep Generative Adversarial Networks.

The lumbar vertebrae segmentation in Computed tomography (CT) is challenging due to the scarcity of the labeled training data that we define as paired training data for the deep learning technique. Much of the available data is limited to the raw CT scans, unlabeled by radiologists. To handle the scarcity of labeled data, we utilized a hybrid training system by combining paired and unpaired training data and construct a hybrid deep segmentation generative adversarial network (Hybrid-SegGAN). We develop a total automatic approach for lumbar vertebrae segmentation in CT images using Hybrid-SegGAN for synthetic segmentation. Our network receives paired and unpaired data, discriminates between the two sets of data, and processes each through separate phases. We used CT images from 120 patients to demonstrate the performance of the proposed method and extensively evaluate the segmentation results against their ground truth by using 12 performance measures. The result analysis of the proposed method suggests its feasibility to improve the capabilities of deep learning segmentation without demanding the time-consuming annotation procedure for labeled and paired data.

3D Pose and Curvature Estimation of Bendable Interventional Device using Single-view X-ray Image.

We present a novel method to estimate the 3D pose and curvature of bendable interventional devices using a single X-ray image. A preliminary experiment was performed to demonstrate the feasibility of the proposed method. The mean estimation accuracies were 3.48mm and 0.59mm for the 3D pose and the radius of curvature of the bendable cardiac ablation catheter, respectively. This method has the potential to help clinicians to make a better intraoperative decision during the procedure, resulting in expedite surgery and reduce exposure to ionizing radiation.Clinical relevance- This novel method has the potential to improve clinician's intraoperative decision-making by providing the 3D pose and curvature information of bendable interventional devices, such as flexible catheter and endoscope.

An anatomical neurovascular study for procedures targeting peri-articular nerves in patients with anterior knee pain.

BACKGROUND: Radiofrequency ablation (RFA) of the articular branches innervating the anterior knee capsule has been studied as a possible alternative to surgery for degenerative arthritis. However, the neurovascular topography of the anterior knee capsule remains unclear. METHODS: One leg from each of the 20 formalin-embalmed cadaveric specimens was investigated. Modified ablation points (MAPs) were evaluated for a possible alternative for conventional target points (CAPs). RESULTS: For the nerve to vastus medialis (NVM), the probability of identifying the nerve was higher at MAP compared with CAP (62.5% vs. 25%). The mean shortest distance from the nerve was shorter at MAP compared with CAP (18.0 mm vs. 29.9 mm). The probabilities and distances for other nerves were not significantly different between the points. However, the probability of identifying the artery was significantly lower at MAPs compared with CAPs for arteries (0%, 5.3%, and 0% vs. 84.2%, 84.2%, and 73.3% for superior medial genicular, superior lateral genicular, and inferior medial genicular artery, respectively). For the recurrent peroneal nerve (RPN), a new target point was set in MAPs. CONCLUSIONS: The current landmark for genicular nerve procedures may not accurately target the correct nerve position, or reduce the risk for vessel damage. A more proximal target may reduce complications and increase the probability of successful procedures, although clinical correlation is needed.

A Patient-Specific 3Dt Coronary Artery Motion Modeling Method Using Hierarchical Deformation with Electrocardiogram.

Cardiovascular-related diseases are one of the leading causes of death worldwide. An understanding of heart movement based on images plays a vital role in assisting postoperative procedures and processes. In particular, if shape information can be provided in real-time using electrocardiogram (ECG) signal information, the corresponding heart movement information can be used for cardiovascular analysis and imaging guides during surgery. In this paper, we propose a 3D+t cardiac coronary artery model which is rendered in real-time, according to the ECG signal, where hierarchical cage-based deformation modeling is used to generate the mesh deformation used during the procedure. We match the blood vessel's lumen obtained from the ECG-gated 3D+t CT angiography taken at multiple cardiac phases, in order to derive the optimal deformation. Splines for 3D deformation control points are used to continuously represent the obtained deformation in the multi-view, according to the ECG signal. To verify the proposed method, we compare the manually segmented lumen and the results of the proposed method for eight patients. The average distance and dice coefficient between the two models were 0.543 mm and 0.735, respectively. The required time for registration of the 3D coronary artery model was 23.53 s/model. The rendering speed to derive the model, after generating the 3D+t model, was faster than 120 FPS.

Multicolor fluorescence imaging using a single RGB-IR CMOS sensor for cancer detection with smURFP-labeled probiotics.

A multicolor fluorescence imaging device was recently developed for image-guided surgery. However, conventional systems are typically bulky and function with two cameras. To overcome these issues, we developed an economical home-built fluorescence imaging device based on a single RGB-IR sensor that can acquire both color and fluorescence images simultaneously. The technical feasibility of RGB-IR imaging was verified ex vivo in chicken breast tissue using fluorescein isothiocyanate (FITC), cyanine 5 (Cy5), and indocyanine green (ICG) as fluorescent agents. The minimum sensitivities for FITC, Cy5, and ICG were 0.200 µM, 0.130 µM, and 0.065 µM, respectively. In addition, we validated the fluorescence imaging of this device in vitro during a minimally invasive procedure using smURFP-labeled probiotics, which emit a spectrum similar to that of Cy5. Our preliminary study of the ex vivo tissue suggests that Cy5 and ICG are good candidates for deep tissue imaging. In addition, the tumor-specific amplification process was visualized using cancer cells incubated with probiotics that had been labeled with a fluorescent protein. Our approach indicates the potential for in vivo screening of tumors in rodent tumor models.

A Skin-Conformal, Stretchable, and Breathable Fiducial Marker Patch for Surgical Navigation Systems.

Augmented reality (AR) surgical navigation systems have attracted considerable attention as they assist medical professionals in visualizing the location of ailments within the human body that are not readily seen with the naked eye. Taking medical imaging with a parallel C-shaped arm (C-arm) as an example, surgical sites are typically targeted using an optical tracking device and a fiducial marker in real-time. These markers then guide operators who are using a multifunctional endoscope apparatus by signaling the direction or distance needed to reach the affected parts of the body. In this way, fiducial markers are used to accurately protect the vessels and nerves exposed during the surgical process. Although these systems have already shown potential for precision implantation, delamination of the fiducial marker, which is a critical component of the system, from human skin remains a challenge due to a mechanical mismatch between the marker and skin, causing registration problems that lead to poor position alignments and surgical degradation. To overcome this challenge, the mechanical modulus and stiffness of the marker patch should be lowered to approximately 150 kPa, which is comparable to that of the epidermis, while improving functionality. Herein, we present a skin-conformal, stretchable yet breathable fiducial marker for the application in AR-based surgical navigation systems. By adopting pore patterns, we were able to create a fiducial marker with a skin-like low modulus and breathability. When attached to the skin, the fiducial marker was easily identified using optical recognition equipment and showed skin-conformal adhesion when stretched and shrunk repeatedly. As such, we believe the marker would be a good fiducial marker candidate for patients under surgical navigation systems.

Erratum: Multicolor fluorescence imaging using a single RGB-IR CMOS sensor for cancer detection with smURFP-labeled probiotics: publisher's note.

[This corrects the article on p. 2951 in vol. 11, PMID: 32637234.].

Three-Dimensional Evaluation of Similarity of Right and Left Knee Joints.

PURPOSE: The purpose of this study was to evaluate the anatomical similarity of three-dimensional (3D) morphometric parameters between right and left knees. MATERIALS AND METHODS: Ten fresh-frozen paired cadaveric knees were tested. Following dissection, footprint areas of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) were measured. Surface scanning was performed using a 3D scanner. Scanned data were reproduced and morphometric parameters were measured on specialized software. After making mirror models, we compared footprint center positions of the ACL and PCL of both sides and calculated the average deviation of 3D alignment between the right- and left-side models. RESULTS: No significant side-to-side differences were found in any morphometric parameters. Bony shapes displayed a side-to-side difference of 〈1 mm. Distal femoral and proximal tibial volumes did not present side-to-side differences, either; the average 3D deviations of alignment between the right and left sides were 0.8±0.4/1.1±0.6 mm (distal femur/proximal tibia). Center-to-center distances between the right and left ACL footprints were 2.6/2.7 mm (femur/tibia) for the anteromedial bundle and 2.4/2.8 mm for the posterolateral bundle. They were 1.9/1.5 mm for the anterolateral bundle and 2.2/1.8 mm for the posteromedial bundle of the PCL. CONCLUSIONS: There was a remarkable 3D morphometric similarity between right and left knees. Our results might support the concept of obtaining morphologic reference data from the uninvolved contralateral knee.

Automatic segmentation of supraspinatus from MRI by internal shape fitting and autocorrection.

BACKGROUND AND OBJECTIVES: With significant increase in the number of people suffering from shoulder problems, the automatic image segmentation of the supraspinatus (one of the shoulder muscles) has become necessary for efficient and deliberate diagnosis and surgery. In this study, we developed an automatic segmentation method to extract the three-dimensional (3D) configuration of the supraspinatus, and we compared our segmentation results with reference segmentations obtained by experts. METHODS: We developed a two-stage active contour segmentation method using the level sets approach to automatically extract the supraspinatus configuration. In the first stage, a trial segmentation based on intensity and an internal shape fitting technique were performed. In the second stage, the undesired image portions of the trial segmentation were automatically identified by comparing the trial segmentation with the fitted shape, and then corrected by forcing the contour to stop evolution in the over-segmented region and pass through undesired edges in the under-segmented region. RESULTS: The proposed method was found to provide highly accurate results when compared with the reference segmentations. This comparison was made on the basis of four measurements: accuracy (0.995 ± 0.001), Dice similarity coefficients (0.951 ± 0.011), average distance (0.440 ± 0.086mm), and maximal distance (3.045 ± 0.433mm). The proposed method could generate regular surfaces of the 3D supraspinatus. CONCLUSIONS: The proposed automatic segmentation method provides a patient-specific tool to accurately extract the 3D configuration of the supraspinatus.

Registration accuracy enhancement of a surgical navigation system for anterior cruciate ligament reconstruction: A phantom and cadaveric study.

BACKGROUND: Recently, surgical navigation systems have been widely used to improve the results of various orthopaedic surgeries. However, surgical navigation has not been successful in anterior cruciate ligament reconstruction, owing to its inaccuracy and inconvenience. This study investigated the registration of preoperative and intraoperative data, which are the key components in improving accuracy of the navigation system. METHODS: An accurate registration method was proposed using new optical tracking markers and landmark retake. A surgical planning and navigation system for anterior cruciate ligament reconstruction was developed and implemented. The accuracy of the proposed system has been evaluated using phantoms and eight cadaveric knees. The present study investigated only the registration accuracy excluding the errors of optical tracking hardware and surgeon. RESULTS: The target registration errors of femoral tunnelling for anterior cruciate ligament reconstruction in phantoms were found to be 0.24±0.03mm and 0.19±0.10° for the tunnel entry position and tunnel direction, respectively. The target registration errors measured using cadavers were 0.9mm and 1.94°, respectively. CONCLUSIONS: The preclinical experimental results showed that the proposed methods enhanced the registration accuracy of the developed system. As the system becomes more accurate, surgeons could more precisely position and orient the femoral and tibial tunnels to their original anatomical locations.

Preliminary Study for Designing a Novel Vein-Visualizing Device.

Venipuncture is an important health diagnosis process. Although venipuncture is one of the most commonly performed procedures in medical environments, locating the veins of infants, obese, anemic, or colored patients is still an arduous task even for skilled practitioners. To solve this problem, several devices using infrared light have recently become commercially available. However, such devices for venipuncture share a common drawback, especially when visualizing deep veins or veins of a thick part of the body like the cubital fossa. This paper proposes a new vein-visualizing device applying a new penetration method using near-infrared (NIR) light. The light module is attached directly on to the declared area of the skin. Then, NIR beam is rayed from two sides of the light module to the vein with a specific angle. This gives a penetration effect. In addition, through an image processing procedure, the vein structure is enhanced to show it more accurately. Through a phantom study, the most effective penetration angle of the NIR module is decided. Additionally, the feasibility of the device is verified through experiments in vivo. The prototype allows us to visualize the vein patterns of thicker body parts, such as arms.

Arthroscopically blind anatomical anterior cruciate ligament reconstruction using only navigation guidance: a cadaveric study.

BACKGROUND: To develop a preoperative planning and navigation system for anatomic anterior cruciate ligament (ACL) reconstruction and to evaluate the accuracy and the efficacy of anatomical ACL reconstruction using only navigation guidance. METHODS: A three-dimensional (3D) preoperative planning and navigation system was developed from open source libraries. Twenty knees from 10 fresh-frozen human cadavers underwent navigation-only guided double-bundle ACL reconstruction using the transportal technique. A computed tomography (CT) scan was performed after ACL reconstruction to create a 3D surface model of the distal femur. We evaluated the tunnel position by Bernard's quadrant method, the tunnel orientation by measuring the tunnel angle in three projected planes, and the incidence of posterior cortical damage. Then, we compared preoperative planning with the postoperative results. RESULTS: The difference in tunnel position between preoperative planning and the postoperative results was a mean of 2.50±1.75mm (range, 0.77 to 5.85mm) in the anteromedial (AM) tunnel and a mean of 3.53±2.20mm (range, 0.39 to 7.92mm) in the posterolateral (PL) tunnel. The difference in tunnel orientation was a mean of 6.74±6.70° (range, 0.35 to 25.6°) in the AM tunnel and a mean of 5.73±3.51° (range, 1.58 to 15.04°) in the PL tunnel. No statically significant difference was observed. Posterior cortical damage developed in seven cases (35%). CONCLUSIONS: Our navigation-only guided ACL reconstruction produced consistent femoral tunnel position and orientation results. The accuracy and consistency of femoral tunneling were improved by using the preoperative planning and navigation system.

The Effect of Optical Marker Configuration on Tracking Accuracy in Image Guided Surgery.

In this study, the effect of the geometrical configuration of retroreflective markers on the maximum tracking uncertainty of target points during a medical navigation is analyzed. Methods that help users select and set up an optimal configuration for minimizing the navigation uncertainty are proposed. The methods are evaluated by simulating surgical navigation environment using an optical tracking system. The result shows that the maximum uncertainty of tracking the target points lying outside the marker region is a function of the configuration of some of the associated markers and the precision of the optical tracking system used. We also show that the use of flexible rigid bodies minimizes target tracking uncertainty by enabling a customized reconfiguration of markers for optimal pose with respect to individual surgical target position during preoperative planning phase.

Active contour segmentation using level set function with enhanced image from prior intensity.

This paper presents a new active contour segmentation model using a level set function that can correctly capture both the strong and the weak boundaries of a target enclosed by bright and dark regions at the same time. We introduce an enhanced image obtained from prior information about the intensity of the target. The enhanced image emphasizes the regions where pixels have intensities close to the prior intensity. This enables a desirable segmentation of an image having a partially low contrast with the target surrounded by regions that are brighter or darker than the target. We define an edge indicator function on an original image, and local and regularization forces on an enhanced image. An edge indicator function and two forces are incorporated in order to identify the strong and weak boundaries, respectively. We established an evolution equation of contours in the level set formulation and experimented with several medical images to show the performance of the proposed method.