ABSTRACT

INTRODUCTION

Advances in computers, diagnostic imaging, medical physics, biomedical engineering, and applied mathematics have enabled continual growth in minimally invasive surgical techniques. Computer-aided surgical systems enable surgeons to treat patients faster, with greater precision and without the significant trauma formerly experienced. In addition, the advent, growth, and development of computer-aided technologies as adjunctive educational, training, and certification methods in surgery will likely affect the surgical practice in ways that are difficult to predict. The advances impact also orbital surgery as well and open new avenues.

This review gives a short overview of the state-of-the-art in technological advances in surgery, including Internet use, visualization, registration, modeling, stereoscopic perception, three-dimensional (3D) interaction, virtual reality, surgical simulators, and surgical robotics.

TECHNOLOGICAL ADVANCEMENTS

In diagnosis and treatment in particular, the patient-specific data have to be easily accessed, visualized, quantified and, most importantly, interacted with. The Internet allows the data to be accessed from anywhere at anytime by anyone authorized. In addition to the multimodal scan transfer, video, audio, human body models, model manipulation parameters, and control data can be transmitted. The wide acceptance of Internet standards and technologies, such as HTML, XML and Java, is instrumental in building global computer networks which, within the next few years, will penetrate our society more than any previous network. High-speed networks combined with medical imaging, surgical simulation, and surgical robotics enable tele-consultation, tele-presence, tele-monitoring, tele-education, and remote collaboration.

Advances in Medical Imaging

Traditionally, radiological scans have been displayed as crosssectional images; however, their effective interpretation

Figure 2 Surgery simulation. (a) Catheter navigation within a 3D cerebral model. (b) Picking a structure of interest (the dorso-medial thalamic nuclei). (c) Removing a skull base tumor. (d) Performing CT craniotomy.

components homogeneous with respect to some feature(s). Segmentation is an important initial step also in image analysis, registration, compression, and computer-aided surgery. As therapy evolves toward minimally invasive approaches, visualization of multimodal volumetric datasets is becoming a critical step in planning and performing therapeutic procedures. Multiple imaging modalities, in order to be displayed together, have to be registered first.

Registration (or matching or alignment) (6) is finding a spatial transformation mapping location in one image to their corresponding locations in another image or model (Fig. 3a and b). Registration in its simpler form is rigid and in a more complex form deformable. Registration techniques also allow human body models to be adapted to the individual anatomy of the patient. Then, information inherent in these models is automatically mapped to the patient-specific data (Fig. 3c).

Multimodal imaging has proved extremely useful in orbital surgery. Computed tomography (CT) and magnetic reso-

Figure 3 Registration. (a) Multimodal in two dimensions—CT and MRI axial images are fused together. (b) Multimodal in three dimensions—cadaveric section images and CT of the Visible Human Data are registered. (c) Model-to-data—a brain atlas in contour representation is superimposed on a coronal brain scan.

nance imaging (MRI) provide excellent morphological detail of the eye and orbit. These modalities are used to diagnose and determine the extent of ocular or periocular tumors, diagnose inflammatory conditions of the orbital region, and determine the severity and extent of ocular trauma. Magnetic resonance angiography (MRA) and color Doppler ultrasonography provide detailed information regarding vascular lesions and flow. To diagnose corneal disorders, various types of microscopy are used, such as specular, confocal, and ultrasound biomicroscopy. Other forms of multimodal registration in ophthalmology exist, such as the development of computeraided geometric models of the eye, which we describe later in this review (7,8).

Modeling focuses on the construction and use of human body models. These models encapsulate anatomical knowledge and provide means to predict, simulate, validate, and enhance the outcomes of diagnostic and surgical procedures. The models can also incorporate certain age, gender, or racial characteristics that may affect surgical decision making.

Geometric modeling deals with geometrical properties of structures to be rendered and manipulated. Physical modeling captures physical properties of modeled structures, which usually requires complicated mathematical and numerical models. By changing the parameters of a biomedical model, various physiological and pathological situations can be simulated.