Computer assisted surgery
Computer assisted surgery (CAS) is a new surgical concept that refers to preoperative planning, guiding or assisting surgery using computer technology. It's generally acknowledged that CAS includes: 1) creating virtual images of patients; 2) Analysis and deep processing of patient images; 3) diagnosis, preoperative planning and simulation of operation steps; 4) surgical navigation and 5) robotic surgery.
In traditional process of surgery, surgeons formulate the surgical plan according to different conditions based on their clinical experience, and modify it in actual operation until the operation is completed. Since the surgical plan relies significantly on personal experience and skills, the operation effect is much random and uncertain under the effect of anatomical changes or other unexpected events. With the development of medical image equipment, the diagnosis of disease has been digitized. In order to associate the information provided by these equipment with the initiative of surgeons, navigation equipment consisting of interactive two dimensional CT was developed almost simultaneously in 1986 in Japan, the United States and Switzerland, which was an early form of CAS. Development of stereotactic technology and imaging technology, and the attempt to combine them contribute to the appearance of CAS.
Extension of digital medical technology in the field of clinical medicine and the application of medical image acquisition equipment, such as CT, MRI and PET-CT contribute to the formation of a new mode of operation, the precise surgical operation. Individual models of human pathological structure and virtual surgery model for evaluation of specific surgical procedures are developed with the application of virtual reality technology of modern computer technology in the mode surgical operation.
The surgeon firstly inputs the preliminary surgery program into computer, then the 3D image could be produced using the computer system with the preoperative medical image information considered. Then the individualized precise surgical plan is determined using the virtual surgery system, which is beneficial to optimize surgical approach, to reduce surgical injury, to avoid damage to nearby tissues, to improve the location accuracy of lesion, to carry out complicated surgical operations and enhance operation success ratio. The precision surgery has the characters of accurate preoperative decision, precise operation plan, accurate simulation of operation and precise surgical procedures, which can achieve the purpose of operation safely, accurately and thoroughly and achieve perfect effect of the operation. Apart from related medical image equipment and computer system used for carrying out virtual reality human-computer interaction, perform of surgical operation also needs equipment of intraoperative navigation and intraoperative monitoring to match the 3D model processed by computer with the actual operation. The real-time observation images are supposed to match and fuse with the preoperative medical images to guide the surgeon for surgery if other imaging methods (such as endoscopes, B Ultrasound or bedside CT etc.) are used in the surgery.
Stereo positioning system is the system used for determining spatial position and is capable of acquiring the three-dimensional coordinates of the target in its measurement range quickly and connecting the image information and surgical target, which is the bridge between virtual image and reality, and has significant influence on the accuracy of the CAS system and the success of the operation.
Computer assisted surgery system has attracted considerable attentions in the field of digital medicine all over the world. So far, many powerful IT companies in the world have been involved in the field of digital medicine recently. For example, fuji company of Japan has regarded “medical / Life Sciences” as the key development field in the future and devotes to become an integrated health care enterprise covering all areas of “prevention-diagnosis-treatment”. On the aspect of medical imaging information, Fujifilm put forward firstly the Picture Archiving and Communication System (PACS) based on Web Technology and developed the FUJ ISYNAPSE which is capable of saving electronically and analyzing the image information from diverse digital medical image diagnostic equipment, such as: CT, MRI and Cr etc. and guiding operations. Philips provides detailed information about the brain for the doctors using 3D maps, which is beneficial for the doctors to make the correct judgment. 3D Slicert, an Image guided surgery software system, developed by David of Massachusetts Institute of Technology, has been approved by FDA of the United States. Germany Leipzig Falk et al. applied 3D image overlapping technology in overlapping the preoperative coronary artery model reconstructed by tridimensional image reconstruction technology and the visual image of robot assisted coronary artery bypass surgery. This technology could not only provide preoperative planning but also provide navigation during surgery and adjust the preoperative planning program to obtain the best surgical results. In addition, Computer assisted surgery software developed by Edda (American), Julius (German) and Intrasense SAS Company (French) are also widely used in clinic.
The application of the computer assisted surgery system is also explored in department of hepatobiliary surgery and orthopedics in China. Professor Chihua Fang of Southern Medical University and Professor Dong Jiahong of PLA General Hospital cooperated with imaging specialists and computer experts and developed 3D stomach visualization system. The system has been adopted to segment the individual CT data of the liver, pancreas and other organs automatically and rapidly and to reconstruct 3D real-time images. Surgeon can not only observe lesions of patients and detailed adjacency of tumor and internal artery, venous and biliary duct system but also perform surgery simulation through 3D reconstruction model. In the visual virtual environment, preoperative guidance and intraoperative guidance could be conducted by surgeon. The research team led by Professor Yin Qingshui of General Hospital of Guangzhou Military Region has applied computer aided rapid prototyping technology to the difficult and complicated orthopedics operation to improve the success rate of operation and make the operation more accurate and safer.
Application of digital medicine in the field of surgical exercises and anatomy teaching: the virtual surgery system provides a virtual surgery environment for young surgeons and medical students to practice, observe or imitate expert’s surgical procedure repeatedly and design, preview and revise surgery to avoid surgical errors caused by human factors.
At present, development of digital anatomical model software has the following characteristics: from single structural organ identification to the system anatomy, from the plane display to the three-dimensional display, from static image to dynamic virtual anatomy. With the development and improvement of force feedback devices, surgeons and medical students can carry out virtual anatomy and exercise of human or surgical sites at any time through digital anatomical model software and force feedback devices without effect of ethical constraints and lack of specimens.
In addition to clinical applications, CAS system can also be used for teaching. With Virtual Reality and Augmented Reality technology, surgeons or medical students can perform simulative operation. With the surgical instruments installed with feedback device, trainees can not only see the surgical site through the virtual glasses, but also feel the virtual patient's limbs and organs. Through training, doctors can improve surgical skills, and accumulate surgical experience. Medical students do not have to worry about making mistakes in virtual surgery and can practice repeatedly until they master the surgery very well. All of these reduce the costs and improve medical quality. At present, the input images for CAS are mainly CT, MRI and PET-CT images, instead of the ultrasound image which is widely used in medical. The registration of ultrasound images and the interpolation of other low-resolution images will effectively promote the development of CAS.
