Augmented Reality Procedure Assistance System for Operator Training and Simulation

Extended-Reality Technologies: An Overview of Emerging Applications in Medical Education and Clinical Care.

The combination of health and entertainment becomes possible due to the development of wearable augmented reality equipment and corresponding application software. In this paper, we implemented a fast calibration extended from SPAAM for an optical see-through head-mounted display (OSTHMD) which was made in our lab. During the calibration, the tracking and recognition techniques upon natural targets were used, and the spatial corresponding points had been set in dispersed and well-distributed positions. We evaluated the precision of this calibration, in which the view angle ranged from 0 degree to 70 degrees. Relying on the results above, we calculated the position of human eyes relative to the world coordinate system and rendered 3D objects in real time with arbitrary complexity on OSTHMD, which accurately matched the real world. Finally, we gave the degree of satisfaction about our device in the combination of entertainment and prevention of cervical vertebra diseases through user feedbacks.

In Augmented Reality (AR) with an Optical See-Through Head-Mounted Display (OST-HMD), the spatial calibration between a user's eye and the display screen is a crucial issue in realizing seamless AR experiences. A successful calibration hinges upon proper modeling of the display system which is conceptually broken down into an eye part and an HMD part. This paper breaks the HMD part down even further to investigate optical aberration issues. The display optics causes two different optical aberrations that degrade the calibration quality: the distortion of incoming light from the physical world, and that of light from the image source of the HMD. While methods exist for correcting either of the two distortions independently, there is, to our knowledge, no method which corrects for both simultaneously. This paper proposes a calibration method that corrects both of the two distortions simultaneously for an arbitrary eye position given an OST-HMD system. We expand a light-field (LF) correction approach [8] originally designed for the former distortion. Our method is camera-based and has an offline learning and an online correction step. We verify our method in exemplary calibrations of two different OST-HMDs: a professional and a consumer OST-HMD. The results show that our method significantly improves the calibration quality compared to a conventional method with the accuracy comparable to 20/50 visual acuity. The results also indicate that only by correcting both the distortions simultaneously can improve the quality.

Optical see-through head-mounted displays (OST HMDs) are a major output medium for Augmented Reality, which have seen significant growth in popularity and usage among the general public due to the growing release of consumer-oriented models, such as the Microsoft Hololens. Unlike Virtual Reality headsets, OST HMDs inherently support the addition of computer-generated graphics directly into the light path between a user's eyes and their view of the physical world. As with most Augmented and Virtual Reality systems, the physical position of an OST HMD is typically determined by an external or embedded 6-Degree-of-Freedom tracking system. However, in order to properly render virtual objects, which are perceived as spatially aligned with the physical environment, it is also necessary to accurately measure the position of the user's eyes within the tracking system's coordinate frame. For over 20 years, researchers have proposed various calibration methods to determine this needed eye position. However, to date, there has not been a comprehensive overview of these procedures and their requirements. Hence, this paper surveys the field of calibration methods for OST HMDs. Specifically, it provides insights into the fundamentals of calibration techniques, and presents an overview of both manual and automatic approaches, as well as evaluation methods and metrics. Finally, it also identifies opportunities for future research.

We propose a varifocal occlusion technique for optical see-through head-mounted displays (OST-HMDs). Occlusion in OST-HMDs is a powerful visual cue that enables depth perception in augmented reality (AR). Without occlusion, virtual objects rendered by an OST-HMD appear semi-transparent and less realistic. A common occlusion technique is to use spatial light modulators (SLMs) to block incoming light rays at each pixel on the SLM selectively. However, most of the existing methods create an occlusion mask only at a single, fixed depth-typically at infinity. With recent advances in varifocal OST-HMDs, such traditional fixed-focus occlusion causes a mismatch in depth between the occlusion mask plane and the virtual object to be occluded, leading to an uncomfortable user experience with blurred occlusion masks. In this paper, we thus propose an OST-HMD system with varifocal occlusion capability: we physically slide a transmissive liquid crystal display (LCD) to optically shift the occlusion plane along the optical path so that the mask appears sharp and aligns to a virtual image at a given depth. Our solution has several benefits over existing varifocal occlusion methods: it is computationally less demanding and, more importantly, it is optically consistent, i.e., when a user loses focus on the corresponding virtual image, the mask again gets blurred consistently as the virtual image does. In the experiment, we build a proof-of-concept varifocal occlusion system implemented with a custom retinal projection display and demonstrate that the system can shift the occlusion plane to depths ranging from 25 cm to infinity.

We conducted a systematic review of recent literature to understand the current challenges in the use of optical see-through head-mounted displays (OST-HMDs) for augmented reality (AR) assisted surgery. Using Google Scholar, 57 relevant articles from 1 January 2021 through 18 March 2022 were identified. Selected articles were then categorized based on a taxonomy that described the required components of an effective AR-based navigation system: data, processing, overlay, view, and validation. Our findings indicated a focus on orthopedic () and maxillofacial surgeries (). For preoperative input data, computed tomography (CT) (), and surface rendered models () were most commonly used to represent image information. Virtual content was commonly directly superimposed with the target site (); this was achieved by surface tracking of fiducials (), external tracking (), or manual placement (). Microsoft HoloLens devices ( in 2021, in 2022) were the most frequently used OST-HMDs; gestures and/or voice () served as the preferred interaction paradigm. Though promising system accuracy in the order of 2–5 mm has been demonstrated in phantom models, several human factors and technical challenges—perception, ease of use, context, interaction, and occlusion—remain to be addressed prior to widespread adoption of OST-HMD led surgical navigation.

Augmented reality (AR) systems can be effectively used to enhance manufacturing and industrial processes. However, not all the existing prototypes of AR systems can be used in an industrial environment due to heavy constraints such as low robustness or cumbersome equipment. Our AR system relies purely on passive techniques to solve the real-time registration problem, and it can run on a portable computer. We combined a powerful virtual reality (VR) component-based simulation framework with computer vision techniques, turning it into an AR system. The resulting system allows us to produce complex rendering and animation of avatars, and blend them into the real world. The system tracks the 3D camera position by means of a natural features tracker, which, given a rough CAD model, can deal with complex 3D objects. The tracking method is robust and can handle large camera displacements and aspect changes. The target applications of our AR system are industrial maintenance, repair and training. The tracking robustness makes the AR system able to work in real environments, such as industrial facilities, and not only in the laboratory.

An optical see-through head-mounted display (OST-HMD) can potentially improve the safety and accuracy of ultrasonography (US)-guided fine-needle aspiration. We aimed to evaluate the usefulness of an OST-HMD in US-guided needle-puncture procedures. We conducted a prospective randomized controlled study in which we compared the accuracy and safety of the US-guided needle puncture procedure and the stress on the practitioner when using OST-HMD versus standard US display (SUD). Inexperienced medical students were enrolled and randomly divided into two groups. A breast phantom was used to evaluate the required time and accuracy of the US-guided needle puncture. Practitioner stress was quantified using a visual analog scale (VAS). When the procedure was performed for the first time, the time required to reach the target lesion at a shallow depth was significantly shorter in the OST-HMD group (39.8 ± 39.9 s) than in the SUD group (71.0 ± 81.0 s) (p = 0.01). Using the OST-HMD significantly reduced the unintentional puncture of a non-target lesion (p = 0.01). Furthermore, the stress felt by the practitioners when capturing the image of the target lesion (p < 0.001), inserting and advancing the needle more deeply (p < 0.001), and puncturing the target lesion (p < 0.001) was significantly reduced in the OST-HMD group compared with that in the SUD group. Use of OST-HMD may improve the accuracy and safety of US-guided needle puncture procedures and may reduce practitioner stress during the procedure.

ObjectiveThe aim of this study was to investigate the feasibility of using augmented reality (AR) glasses in central line simulation by novice operators and compare its efficacy to standard central line simulation/teaching.DesignThis was a prospective randomized controlled study enrolling 32 novice operators. Subjects were randomized on a 1:1 basis to either simulation using the augmented virtual reality glasses or simulation using conventional instruction.SettingThe study was conducted in tertiary-care urban teaching hospital.SubjectsA total of 32 adult novice central line operators with no visual or auditory impairments were enrolled. Medical doctors, respiratory therapists, and sleep technicians were recruited from the medical field.Measurements and main resultsThe mean time for AR placement in the AR group was 71±43 s, and the time to internal jugular (IJ) cannulation was 316±112 s. There was no significant difference in median (minimum, maximum) time (seconds) to IJ cannulation for those who were in the AR group and those who were not (339 [130, 550] vs 287 [35, 475], p=0.09), respectively. There was also no significant difference between the two groups in median total procedure time (524 [329, 792] vs 469 [198, 781], p=0.29), respectively. There was a significant difference in the adherence level between the two groups favoring the AR group (p=0.003).ConclusionAR simulation of central venous catheters in manikins is feasible and efficacious in novice operators as an educational tool. Future studies are recommended in this area as it is a promising area of medical education.

Virtual reality (VR) and augmented reality (AR) systems are increasingly available to neurosurgeons. These systems may provide opportunities for technical rehearsal and assessments of surgeon performance. The assessment of neurosurgeon skill in VR and AR environments and the validity of VR and AR feedback has not been systematically reviewed. A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted through MEDLINE and PubMed. Studies published in English between January 1990 and February 2021 describing the use of VR or AR to quantify surgical technical performance of neurosurgeons without the use of human raters were included. The types and categories of automated performance metrics (APMs) from each of these studies were recorded. Thirty-three VR studies were included in the review; no AR studies met inclusion criteria. VR APMs were categorized as either distance to target, force, kinematics, time, blood loss, or volume of resection. Distance and time were the most well-studied APM domains, although all domains were effective at differentiating surgeon experience levels. Distance was successfully used to track improvements with practice. Examining volume of resection demonstrated that attending surgeons removed less simulated tumor but preserved more normal tissue than trainees. More recently, APMs have been used in machine learning algorithms to predict level of training with a high degree of accuracy. Key limitations to enhanced-reality systems include limited AR usage for automated surgical assessment and lack of external and longitudinal validation of VR systems. VR has been used to assess surgeon performance across a wide spectrum of domains. The VR environment can be used to quantify surgeon performance, assess surgeon proficiency, and track training progression. AR systems have not yet been used to provide metrics for surgeon performance assessment despite potential for intraoperative integration. VR-based APMs may be especially useful for metrics that are difficult to assess intraoperatively, including blood loss and extent of resection.

Introduction: Augmented Reality (AR) systems are systems in which users view and interact with virtual objects overlaying the real world. AR systems are used across a variety of disciplines, i.e., games, medicine, and education to name a few. Optical See-Through (OST) AR displays allow users to perceive the real world directly by combining computer-generated imagery overlaying the real world. While perception of depth and visibility of objects is a widely studied field, we wanted to observe how color, luminance, and movement of an object interacted with each other as well as external luminance in OST AR devices. Little research has been done regarding the issues around the effect of virtual objects’ parameters on depth perception, external lighting, and the effect of an object’s mobility on this depth perception.Methods: We aim to perform an analysis of the effects of motion cues, color, and luminance on depth estimation of AR objects overlaying the real world with OST displays. We perform two experiments, differing in environmental lighting conditions (287 lux and 156 lux), and analyze the effects and differences on depth and speed perceptions.Results: We have found that while stationary objects follow previous research with regards to depth perception, motion and both object and environmental luminance play a factor in this perception.Discussion: These results will be significantly useful for developers to account for depth estimation issues that may arise in AR environments. Awareness of the different effects of speed and environmental illuminance on depth perception can be utilized when performing AR or MR applications where precision matters.

Endoscopic surgery causes less tissue injury compared to open surgical techniques, thus promoting more rapid recuperation and reduced post-operative pain. Endoscopy, however, allows the surgeon to visualise only the anatomical surface of the surgical site, with a relatively narrow field of view. Moreover, the 2D video captured by the conventional endoscope does not provide depth perception of the surgical scene. In this study, these limitations have been addressed with the development of an augmented reality (AR) system with stereoscopic visualisation. A phantom and its 3D CT model were used, respectively, to form the real and virtual parts of the AR. The virtual environment camera pose was tracked using algorithms for image feature detection, feature matching and Perspective-n-Point applied on the endoscopic image and the 3D virtual model-rendered image. The endoscope video frame- and the virtual model-rendered images were superimposed to form the AR composite view. The depth buffer (z-buffer) of the rendering window was further used to make a stereo pair of the AR image. The AR system produced a stereo composite view having well-aligned real and virtual components. The RMS error of the real and virtual image contours registration was 9.6 ± 6.7 mm. Correlation coefficients between the depth map from z-buffer and a depth camera was between 0.60 and 0.96 (p < 0.05). The AR system requires further improvement to be applicable at a higher frame rate of endoscope image acquisition. It also needs to include motion and deformation models when applied to animals or patients.

Real-time visualization of imaging data constitutes a critical part of surgical workflow. Augmented reality (AR) is a promising tool to assist in conventional surgical navigation systems. We have been developing an AR framework for clinical imaging and guidance using an optical see-through head-mounted display (OST-HMD) and fluorescence lifetime imaging (FLIm) instrumentation. This framework supports in vivo scanning of FLIm data and the real-time visualization of diagnostic information overlaid on the interrogated tissue area. With the high discriminative power of FLIm, our FLIm-AR concept has the potential for indicating tumor margins and assisting with tumor excision surgery.

The human visual system always focuses at a distinct depth. Therefore, objects that lie at different depths appear blurred, a phenomenon known as Depth of Field (DoF); as the user's focus depth changes, different objects come in and out of focus. Augmented Reality (AR) is a technology that superimposes computer graphics (CG) images onto a user's view of the real world. A commonly used AR display device is an Optical See-Through Head-Mounted Display (OST-HMD), enabling users to observe the real-world directly, with CG added to it. A common problem in such systems is the mismatch between the DoF properties of the user's eyes and the virtual camera used to generate CG.In this demonstration, we present an improved version of the system presented in [11] as two implementations: The first as a high quality tabletop system, the second as a component which has been integrated into the Microsoft Hololens [18].

This paper describes the design of an optical see-through head-mounted display (HMD) system for Augmented Reality (AR). Our goals were to make virtual objects perfectly indistinguishable from real objects, wherever the user roams, and to find out to which extent imperfections are hindering applications in art and design. For AR, fast and accurate measuring of head motions is crucial. We made a head-pose tracker for the HMD that uses error-state Kalman filters to fuse data from an inertia tracker with data from a camera that tracks visual markers. This makes on-line head-pose based rendering of dynamic virtual content possible.We measured our system, and found that with an A4-sized marker viewed from > 20° at 5 m distance with an SXGA camera (FOV 108°), the RMS error in the tracker angle was < 0.5° when moving the head slowly. Our Kalman filters suppressed the pose error due to camera delay, which is proportional to the angular and linear velocities, and the dynamic misalignment was comparable to the static misalignment. Applications of artists and designers lead to observations on the profitable use of our AR system. Their exhibitions at world-class museums showed that AR is a powerful tool for disclosing cultural heritage.