Abstract: Virtual reality technology provides a realistic, three-dimensional, fully reproducible and repeatable learning environment for anatomy teaching and surgical training. It has shown great advantages in reducing practical costs, improving training quality and efficiency, and improving the success rate of surgery. This paper introduces the application of virtual reality technology in medical training, analyzes its characteristics, including functional requirements, selection of hardware and software platform, key development technologies and implementation results. The problems in the field of virtual human anatomy and surgical training are analyzed, and the future development of virtual human anatomy and surgical training is prospected.

Key words: virtual reality; Medical training; Anatomy teaching

One, the introduction

Virtual reality technology can be defined as "the sum of hardware and software systems that try to perfect the omnidirectional and sensory illusion existing in another environment" [1]. The environment referred to here is the virtual environment artificially built with the help of computer technology. The concept of virtual reality technology was proposed in the 1960s and 1970s, and began to form and develop in the 1990s [2]. Virtual reality technology has been applied in many fields, such as technical training, production and assembly, video and audio entertainment, and has solved some problems.

Anatomy is an important course for students in medical colleges and universities, but many medical colleges and universities are limited by such problems as weak teaching staff, lack of experimental sites, lack of equipment and experimental subjects, and lack of funds, which greatly reduces the quality and effect of anatomical teaching time [3]. In many colleges and universities, anatomy courses are taught with the aid of atlas and human body models, but this method lacks realistic three-dimensional sense and interaction, which reduces the accuracy of students' understanding of human body and is difficult to stimulate students' interest in learning. Virtual reality technology for medical training, medical science provides a new technology and means. VR and AR technology can be used for human body Computed Tomography (CT), Magnetic Resonance Imaging (MRI), CT angiography (CT angiography), CTA, Magnetic Resonance Angiography (MRA) and other image data are input into the workstation of the virtual reality system for fusion, and three-dimensional human anatomy model is constructed accurately and efficiently. To provide medical students with an intuitive, vivid and repeatable virtual reality anatomy environment, greatly reducing the cost of experimental practice and training costs. And VR and AR technology can without breaking the surface anatomy shows under the condition of deep anatomy, and the Angle of the anatomical structure of arbitrary spin, facilitate students to observe from different point of view, this will help medical students understanding human anatomy of the three-dimensional complex relations, greatly saves the teaching time, ease and shortages of the traditional anatomy teaching specimen loss problem, Enhance the enthusiasm of students to learn and improve the teaching effect. In order to improve the success rate of the actual operation, medical staff can simulate the operation to be performed in the virtual reality system before performing the operation with high risk, complexity and unpredictability. In addition, the VR and AR technology also can break through time and space constraints, the experienced multiple people joint consultation between foreign experts and scholars, the surgery live learning, provides a valuable medical students study "the butcher" perspective of telepresence, interns will be decreased and the operation errors, improve efficiency and quality of education and training of medical science [4].

Ii. Research Status

The research on human anatomy teaching in medical colleges and enterprises at home and abroad can be mainly divided into two stages: The first stage is the construction stage of teaching model of human anatomy (1990-2010). In this stage, virtual three-dimensional teaching model of human anatomy is built by software, and the structure and function of various tissues and organs of human body are understood and learned by computer, helmet display and other equipment, so as to make up for the deficiency of traditional teaching methods and teaching means. The second stage for the application of human anatomy teaching system stage (2010 - present), the stage mainly based on the mature model of human anatomy, by establishing a special system of human anatomy, teaching software and the App or holographic navigation platform, with the help of VR equipment systematically teaching, simulated surgery, surgery live to learn, etc.

2.1 Hardware Development

Currently, the VR systems that have been released all need to use wearable augmented reality devices to help users create a sense of immersion. Wearable augmented reality devices are usually head-mounted display (HMD). Head-mounted digital helmets can be divided into optical see-through (OST) helmets and video see-through (VST) helmets. Optical see-through helmets are commonly used in augmented reality (AR) systems, notably Google Glass. By displaying a high frame rate and high resolution virtual environment in a closed environment isolated from external light, the video perspective helmet enables the user subject to get an immersive and immersive experience in the virtual environment. At present, compared with optical perspective helmet, video perspective helmet has a lower technical threshold and a wider range of applications. As a result, there are a large number of manufacturers launched video perspective type helmet products, such as HTC as the first to enter the realm of VR equipment manufacturing manufacturers, has launched a vive VR glasses series, its characteristic is to provide form a complete set of headphones for the helmet and handle, but vive series is an external device, its operation ability is insufficient, need external host to be used by the user; Pico has unveiled its Neo series of VR glasses, which feature a Snapdragon 845 processor embedded in the device itself and are capable of running some large VR software without an external console. In addition to traditional mobile device manufacturers, some Internet enterprises have also launched VR devices, such as "Adventure 2Pro" launched by iQiyi. As a product launched by the video website itself, it has specially adapted VR resources provided by iQiyi.

For example, HTC Vive Pro weighs 500g and Pico Neo 2 weighs 320g. For reference, glasses for daily wear weigh between 20 and 80G. Therefore, the weight of VR display devices is one of the important factors affecting user immersion, and how to achieve lightweight and miniaturization of VR display devices is still a problem to be solved.

2.2 Software Development

The development platform of human anatomy teaching software can be divided into two categories: system platform and development platform. System platform mainly refers to operating system (OS); The technology development platform mainly includes 3D modeling, content development engine and image recognition software development kit (SDK).

Currently, VR applications are mostly developed on Windows and Mac OS. With the development of VR application technology, the third generation operating system developed for VR/AR will become the mainstream OS. Current third-generation operating systems include Microsoft's (MSFT) Synaptics and Windows Core OS, Google's (GOOG) Fuchsia and Magic Leap's Lumin OS. Synaptics operating system was jointly developed by Synaptics, Microsoft and AMD in July 2018, and uses fingerprint recognition and facial recognition biotechnology to support HoloLens2 devices [5]. Lumin OS is an operating system developed by Magic Leap to support Magic Leap One devices.

3D modeling is the technical core of human anatomy teaching system. Commonly used modeling software includes Poser, 3D Max, Maya, etc. In addition, there are software that can use off-the-shelf human Anatomy maps or models to aid the modeling process, such as the Human Anatomy 3D Interactive Atlas, The AnyBody Human Anatomy Simulation software, Complete Anatomy, etc.

Content development engine (mainly refers to 3D engine) is a very important middleware to build virtual environment, especially for cross-platform development, generally with data management, graphics rendering, interactive editing, platform publishing and other functions. Mainstream 3D engines include Unity3D, Unreal, CryEngine, OpenVR, etc. Unity3D is a popular interactive graphics development engine with an editor that runs on Windows and Mac OS X and supports Oculus Rift devices. Unreal Engine (Unreal engine) is one of the world's most widely licensed development engines, developed by US game development company Epic. OpenVR is a set of UNIVERSAL APIS for VR devices developed by Valve, an American game development company. It allows users to develop apps that support Oculus Rift, HTC Vive and other VR devices without using the SDK provided by the manufacturer.

Image recognition SDK is an important underlying basic software connecting hardware and content. A good SDK has small memory occupation, wide support models and high stability. Foreign mainstream SDKS are Vuforia, Wikitude, Void AR, etc. Considered one of the most widely used AR platforms in the world, Vuforia can easily add advanced computer vision capabilities to any application, enabling it to recognize images and objects, or reconstruct real-world environments, but the Vuforia solution needs to be bundled with Unity. Representative manufacturers of domestic SDK include Baidu, Vision +(Vision Chen), Liangfengtai, Tapp Intelligence, 0Glass, Tencent, etc.

3. Practical application

3.1 Anatomy Teaching

The use of VR or AR technology in anatomy teaching can not only help students to understand the complex human body structure in an all-round and three-dimensional way, but also allow students to conduct repeated simulation training independently, greatly improving the effect of anatomy teaching. AnatomyX, a holographic immersive anatomy education platform from MediVis (USA) that supports HoloLens and Magic Leap One devices, provides over 5,000 3D anatomical models of CT and MRI derived from real cases. It's been used at colleges and universities on the West Coast of the United States and has led to a 15 percent increase in standardized test scores. Taipei Medical University's Virtual reality teaching software Anatomy Classroom (using Vive Pro professional headset) can disassemble and rotate more than 4,000 body structures in A VR environment. In addition, there are also zSpace, an immersive medical platform developed by Infinite Z in the United States, and online VR medical course teaching platform developed by GIBLIB in the United States. In China, there is a human anatomy teaching system based on Kinect developed by Beijing University of Technology in 2014. Sichuan University spent 5 years to build 3D systematic anatomy software compatible with HTC Vive devices [6].

3.2 Preoperative planning

In order to reduce the risk of surgery, multi-sensory experience and practice such as vision and touch can be carried out through the virtual reality preoperative planning system before complicated surgery for patients, so as to understand the difficulty of surgery in advance, assess the risk of surgery, and make an individual surgical plan. Us startup Surgical Theater's Surgery Visualization and planning application Platform, Surgery Rehearsal Platform, supports HTC Vive devices and is currently used in more than 100 hospitals worldwide. SuRgical Planning, the company's SuRgical Planning platform for preoperative neurosurgery, is the first SuRgical Planning(SRP) technology platform to be approved by the FOOD and Drug Administration (FDA). China mainly has THE VR spine surgery planning system mVR independently developed by Miaozhi Technology.

3.3 Surgical training

The construction of a special surgical training center or education platform can help doctors make a reasonable surgical plan, reduce surgical injuries, and improve the accuracy and success rate of surgical positioning. Shorten the time of surgical training and improve doctors' cooperation ability; Strengthen preoperative simulation training to improve surgical proficiency. CAE VimedixAR ultrasound simulator from CAE Healthcare in the United States can liberate human organs from the display screen and, like building blocks, magnify, rotate, rotate, disassemble and install human organs that need to be disassembled. Similar capabilities include Surgical Theater's VR kit for training complex Surgical procedures, the University of Huddersfield's VR system for training surgeons, and the University of Nebraska's 3D Clinical and Surgical Training Center (UNMC). In China, there are few VR platforms used for surgery training, such as surgeiek, a surgical education service platform by Shanghai Medical Weinews Company, and surgical simulation training system by Beijing Liming Vision Company.

3.4 Live broadcast of surgery

Due to the requirement of sterile environment in operating room and the limitation of observation Angle, medical students often cannot see the operation area clearly when observing surgery. In order to reduce pain and promote rapid recovery, physicians often perform minimally invasive surgery with small incision, which further limits the learning of medical students. With the progress of technology, live surgery based on VR/AR technology has become a very good means of surgical learning. VR/AR technology through special panoramic camera set up at the top of the leading physicians in the operating room, the first 360 ° completely filmed the scene of the scene, and then specially fusion splicing transmission to the cloud, medical graduates can through VR/AR device, as it were, to see the operation, and through the visual focus to switch, the Angle of the freedom to choose to watch, You can also see the details of the operation from a "solo" perspective. This new form of surgical live broadcast makes the originally passive audience more active and enables them to learn immersively, which is of great significance for surgical teaching. In April 2016, the Royal London Hospital broadcast a 360° panoramic view of a colon cancer tumor resection operation through VR technology for the first time in the world.

3.5 Remote consultation

Tele-consultation enables a surgeon in the operating room to interact with a remote specialist in real time based on the patient's information, regardless of spatial distance. RoomOne's Remote VR surgical system, which controls a robot arm remotely to perform virtual surgery, is ideal for special occasions such as when a doctor is unavailable or when a patient is suffering from a serious infectious disease. In January 2018, Wuhan Union Hospital and Virginia Tech University used HoloLens equipment to guide doctors in Bozhou People's Hospital of Xinjiang province and successfully carried out the world's first mixed reality (MR) three-place tele-consultation surgery. In March 2019, Changgung Hospital of Tsinghua University and Shenzhen People's Hospital jointly completed a case of AR/VR+5G collaborative remote surgery for hepatopiliary surgery. The use of virtual reality technology for remote consultation has large visual field, clear vision and no sound delay, which not only improves the safety of surgery and promotes the rapid growth of young surgeons, but also makes it possible to relay the teaching of uHD laparoscopic technology and realize remote surgery.

Four, conclusion

VR and AR technology of anatomy teaching and training provides a vivid, three-dimensional, fully scene reappearance type repeatedly learning environment, but also for the real implementation of "perspective" surgery navigation and telepresence live to study, in practice to reduce costs, improve the training quality and efficiency, and improve the success rate of surgery showed great advantage, Is gradually become the medical teaching and surgical training field "new favor". However, this approach cannot completely replace traditional teaching, and the experience gained from VR and AR training must go through practical operation before it can be truly applied to clinical surgery. At present, imaging resolution is insufficient, which makes it difficult for virtual teaching system to display small anatomical structures, and the tactile experience technology of virtual reality is still in the development stage. Therefore, China's research on virtual reality anatomy teaching and surgical simulation is still in the stage of experiment and exploration, and there are mainly the following problems:

1) Lack of VR/AR medical personnel training system. With the development of VR and AR technologies, there is a shortage of software development talents in the medical field, and it is difficult to effectively support the innovative development of VR/AR medical education. The development of VR/AR medical software needs interdisciplinary talents in the fields of computer technology and medicine. However, colleges and universities are still in the initial stage of VR discipline construction, and lack a talent training system for interdisciplinary disciplines in the fields of computer and medicine. Some top foreign design universities opened VR courses in 2016, and a large number of universities have opened VR human anatomy teaching. In 2019 and 2020, China successively added VR application technology majors in vocational and technical colleges and universities. Due to the interdisciplinary and innovative nature of the new majors, the school lags behind in the major setting, teacher introduction, hardware and software equipment to varying degrees.

2) The research and development force of key technologies and products is insufficient, the conversion rate of results is low, the price is expensive, and it cannot be popularized on a large scale. In China's existing virtual medical teaching software development enterprises, most of them are start-up technology teams or small and micro enterprises composed of a large number of computer professionals, while medical professionals account for few or almost no. The few existing medical education VR development talents mainly come from the industry of game, animation, 3D simulation, model, etc., and there is a shortage of technical talents for medical education software development. Therefore, at present, the development of VR medical software is usually jointly developed by companies and hospitals, resulting in a lack of research and development strength of key technologies and products, resulting in a long time for software development. In addition, there are far fewer companies or institutions developing VR anatomy teaching and training software in China than in foreign countries. Most of the self-developed software is not practical enough, and the price of the software is relatively expensive. Some of the software used in China also has intellectual property problems such as crack or piracy, so the conversion rate of software development results is low.

3) Medical teaching software products and system evaluation system need to be established, and relevant laws and regulations, industrial chain and ecosystem need to be improved. The existing STANDARD system of VR equipment is not perfect, the compatibility between hardware, system and content is poor, hardware standards, data exchange, secure communication, standards between equipment and applications have not been published, and there is no standard specification for product performance and quality. Problems such as software development tools, data interfaces and human health applicability are not clear, and industrial users lack trust in the large-scale use of virtual medical education products. Medical teaching software products and system evaluation indicators need to be established, and relevant laws and regulations such as privacy law, industrial chain and ecosystem need to be improved.

reference

[1] XIAO J, ZHOU Y,  ZHOU Z. Survey on Augmented Virtual Environment and Augmented Reality[J]. SCIENTIA SINICA Informationis, 2015, 45(2):  157-180.

[2] BIOCCA F, DELANEY B. Immersive Virtual Reality Technology[J]. Communication in the age of virtual reality, 1995.

[3] China Youth Network. Sichuan university VR five-year "anatomy class" into teaching [EB/OL]. (2016-11-06) [2019-07-01]. HTTP: / / http://news.youth.cn/kj/201611/t20161106_8818862.htm.

[4] Li Jia, Yuan Na. [J]. Chinese Journal of Medical Education technology, 2017, 8(4): 392-395.

[5] Chen J. FIDO authentication for four fingerprint recognition schemes of Synaptics [J]. Computers and Networks, 2015, 41(17): 79

[6] Yan Y HUA. VRCore series: Best application work "3D Systematic Anatomy of Human Health" [EB/OL]. (2016-11-09)[2019-07-25]. https://yivi⁃ an.com/news/23636.html.