Page 420 - Biomedical Engineering and Design Handbook Volume 2, Applications

398 SURGERY

model and plan may be further updated, based on the images. The computer then uses a variety
of interface devices to assist the surgeon in executing the surgical plan. Depending on what is
most appropriate for the application these interfaces may include active devices such as robots,
“smart” hand tools, and information displays. As the surgery proceeds, additional images or other
measurements may be taken to assess progress and provide feedback for controlling tools and
therapy delivery. On the basis of this feedback, the patient model may be updated during the pro-
cedure. This updated model may be used to refine or update the surgical plan to ensure that the
desired goals are met. Ideally, intraoperative imaging and other feedback can ensure that the tech-
nical goals of the surgical intervention have been achieved before the patient leaves the operating
room. Further, the computer can identify and record a complete record of pertinent information
about the procedure without significant additional cost or overhead.
• Postoperative phase. The preoperative and intraoperative information are combined with addi-
tional images and tests, both to verify the technical results of the procedure and to assess the
longer-term clinical results for the patient. Further, the results of many procedures may be regis-
tered back to an anatomical atlas to facilitate statistical studies relating surgical technique to clin-
ical outcomes.
Note that the above description is of an idealized CIS system: specific systems do not neces-
sarily require all these capabilities, and some of them are beyond the current state of the art.
However, we will use this generic description to organize the technical discussion in the follow-
ing section.
From a surgeon’s perspective, the key difference between advanced medical equipment and a CIS
system is the information integration, both between phases and within each phase. This new capa-
bility requires in most cases modifications to existing surgical protocols, and in a few cases radically
new protocols. It could also enable more surgeons to perform certain difficult procedures that require
much coordination and knowledge available to only a few experienced specialists, or perform pro-
cedures that are currently not feasible.

14.3 THE TECHNOLOGY OF CIS SYSTEMS

This section describes the main technical elements of CIS systems. We begin with a brief summary
of medical imaging devices, and then present methods for image processing, visualization, and mod-
eling. We describe next preoperative planning and analysis, followed by registration of data from
various sources. Then we discuss tracking and sensing, robotics, man-machine interfaces, and sys-
tems integration technology.

14.3.1 Medical Imaging
Medical images, both preoperative and intraoperative, are the main sources of information for CIS
systems.
Since they are used in all CIS systems, we briefly discuss their technical characteristics and typ-
ical uses.
We distinguish between preoperative and intraoperative imaging devices. Preoperative imaging
devices, such as film and digital x-rays, computed tomography (CT), magnetic resonance imaging
(MRI), and nuclear magnetic tomography (NMT), in various forms, are used to obtain images for
diagnosis and surgical planning. In most cases, the imaging devices are large and are located out-
side the surgical suite. Two-dimensional film x-ray images are the most common, with superb spa-
tial resolution, gray-value range, and contrast, and negligible noise and geometric distortion. However,
they are two-dimensional projections of spatial structures, and are not amenable to processing for